EXHIBIT 4.1





                                                             EXECUTION VERSION


                  WASHINGTON MUTUAL MORTGAGE SECURITIES CORP.,

                        as Depositor and Master Servicer

                                       and

                                 CITIBANK, N.A.,

                                   as Trustee

                                       and

                        CHRISTIANA BANK & TRUST COMPANY,

                               as Delaware Trustee



                         POOLING AND SERVICING AGREEMENT

                                 $375,385,345.35

                   Washington Mutual Mortgage Securities Corp.

                     WaMu Mortgage Pass-Through Certificates

                                 Series 2004-S1

                         Cut-Off Date: February 1, 2004

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                                Table of Contents
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                                                                                                                 Page


ARTICLE I........................................................................................................7

         SECTION 1.01
                  Definitions....................................................................................7

                  Aggregate Certificate Principal Balance........................................................7

                  Appraised Value................................................................................7

                  Assignment of Proprietary Lease................................................................7

                  Authenticating Agent...........................................................................7

                  Authorized Denomination........................................................................7

                  Bankruptcy Coverage............................................................................8

                  Bankruptcy Loss................................................................................8

                  Beneficial Holder..............................................................................8

                  Benefit Plan Opinion...........................................................................8

                  Book-Entry Certificates........................................................................8

                  Business Day...................................................................................8

                  Buydown Agreement..............................................................................8

                  Buydown Fund...................................................................................8

                  Buydown Fund Account...........................................................................9

                  Buydown Loan...................................................................................9

                  Carry-Forward Subsequent Recoveries Amount.....................................................9

                  Certificate....................................................................................9

                  Certificate Account............................................................................9

                  Certificateholder or Holder....................................................................9

                  Certificate Interest Rate.....................................................................10

                  Certificate of Trust..........................................................................10

                  Certificate Principal Balance.................................................................10

                  Certificate Register and Certificate Registrar................................................10

                  Class.........................................................................................10

                  Class A Certificates..........................................................................11

                  Class A-L Regular Interests...................................................................11

                  Class 1-A-1 Certificates......................................................................11

                  Class 1-A-1-L Regular Interest................................................................11


                                                     i
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                  Class 1-A-2 Certificates......................................................................11

                  Class 1-A-2-L Regular Interest................................................................11

                  Class 1-A-3 Certificates......................................................................11

                  Class 1-A-3-L Regular Interest................................................................11

                  Class 1-A-4 Certificates......................................................................11

                  Class 1-A-4 Notional Amount...................................................................11

                  Class 1-A-5 Certificates......................................................................11

                  Class 1-A-5-L Regular Interest................................................................11

                  Class 1-A-6 Certificates......................................................................11

                  Class 1-A-6-L Regular Interest................................................................11

                  Class 1-A-7 Certificates......................................................................11

                  Class 1-A-7-L Regular Interest................................................................12

                  Class 1-A-8 Certificates......................................................................12

                  Class 1-A-8-L Regular Interest................................................................12

                  Class 1-A-9 Certificates......................................................................12

                  Class 1-A-9-L Regular Interest................................................................12

                  Class 1-A-10 Certificates.....................................................................12

                  Class 1-A-10-L Regular Interest...............................................................12

                  Class 1-A-11 Certificates.....................................................................12

                  Class 1-A-11-L Regular Interest...............................................................12

                  Class 1-A-12 Certificates.....................................................................12

                  Class 1-A-12-L Regular Interest...............................................................12

                  Class 2-A-1 Certificates......................................................................12

                  Class 2-A-1-L Regular Interest................................................................12

                  Class 2-A-2 Certificates......................................................................12

                  Class 2-A-2 Notional Amount...................................................................13

                  Class B Certificates..........................................................................13

                  Class B Percentage............................................................................13

                  Class B-L Regular Interests...................................................................13

                  Class B-1 Certificates........................................................................13

                                                             ii
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                  Class B-1-L Regular Interest..................................................................13

                  Class B-2 Certificates........................................................................13

                  Class B-2-L Regular Interest..................................................................13

                  Class B-3 Certificates........................................................................13

                  Class B-3-L Regular Interest..................................................................13

                  Class B-4 Certificates........................................................................13

                  Class B-4-L Regular Interest..................................................................13

                  Class B-5 Certificates........................................................................13

                  Class B-5-L Regular Interest..................................................................13

                  Class B-6 Certificates........................................................................14

                  Class B-6-L Regular Interest..................................................................14

                  Class C-Y Principal Reduction Amounts.........................................................14

                  Class C-Y Regular Interests...................................................................14

                  Class C-Y-1 Principal Distribution Amount.....................................................14

                  Class C-Y-1 Regular Interest..................................................................14

                  Class C-Y-2 Principal Distribution Amount.....................................................14

                  Class C-Y-2 Regular Interest..................................................................14

                  Class C-Z Principal Reduction Amounts.........................................................14

                  Class C-Z Regular Interests...................................................................15

                  Class C-Z-1 Principal Distribution Amount.....................................................15

                  Class C-Z-1 Regular Interest..................................................................15

                  Class C-Z-2 Principal Distribution Amount.....................................................15

                  Class C-Z-2 Regular Interest..................................................................15

                  Class Notional Amount.........................................................................15

                  Class P Certificates..........................................................................15

                  Class P Fraction..............................................................................15

                  Class P Mortgage Loan.........................................................................15

                  Class P-L Regular Interest....................................................................16

                  Class P-M Regular Interest....................................................................16

                  Class Principal Balance.......................................................................16

                                                           iii
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                  Class R Certificates..........................................................................17

                  Class R Residual Interests....................................................................17

                  Class R-1 Residual Interest...................................................................17

                  Class R-2 Residual Interest...................................................................17

                  Clearing Agency...............................................................................17

                  Closing Date..................................................................................17

                  Code..........................................................................................17

                  Company.......................................................................................17

                  Compensating Interest.........................................................................17

                  Cooperative...................................................................................18

                  Cooperative Apartment.........................................................................18

                  Cooperative Lease.............................................................................18

                  Cooperative Loans.............................................................................18

                  Cooperative Stock.............................................................................18

                  Cooperative Stock Certificate.................................................................18

                  Corporate Trust Office........................................................................18

                  Corporation...................................................................................18

                  Corresponding Class...........................................................................18

                  Credit Support Depletion Date.................................................................19

                  Cumulative Carry-Forward Subsequent Recoveries Amount.........................................19

                  Curtailment...................................................................................19

                  Curtailment Shortfall.........................................................................19

                  Custodial Account for P&I.....................................................................19

                  Custodial Account for Reserves................................................................20

                  Custodial Agreement...........................................................................20

                  Custodian.....................................................................................20

                  Cut-Off Date..................................................................................20

                  Definitive Certificates.......................................................................20

                  Delaware Trustee..............................................................................20

                  Depositary Agreement..........................................................................20

                                                           iv
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                  Destroyed Mortgage Note.......................................................................20

                  Determination Date............................................................................20

                  Disqualified Organization.....................................................................21

                  Distribution Date.............................................................................21

                  DTC...........................................................................................21

                  DTC Participant...............................................................................21

                  Due Date......................................................................................21

                  Eligible Institution..........................................................................21

                  Eligible Investments..........................................................................21

                  ERISA.........................................................................................23

                  ERISA Restricted Certificate..................................................................23

                  Event of Default..............................................................................23

                  Excess Liquidation Proceeds...................................................................23

                  Excess Subsequent Recoveries..................................................................23

                  FDIC..........................................................................................23

                  FHA...........................................................................................23

                  Fannie Mae....................................................................................23

                  Final Maturity Date...........................................................................23

                  Fitch.........................................................................................23

                  Fraud Coverage................................................................................23

                  Fraud Loss....................................................................................24

                  Freddie Mac...................................................................................24

                  Indirect DTC Participants.....................................................................24

                  Initial Custodial Agreement...................................................................24

                  Initial Custodian.............................................................................24

                  Insurance Proceeds............................................................................24

                  Interest Distribution Amount..................................................................24

                  Interest Transfer Amount......................................................................25

                  Investment Account............................................................................25

                  Investment Depository.........................................................................25

                                                           v
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                  Junior Subordinate Certificates...............................................................25

                  Last Scheduled Distribution Date..............................................................25

                  Lender........................................................................................25

                  LIBOR.........................................................................................25

                  LIBOR Determination Date......................................................................26

                  Liquidated Mortgage Loan......................................................................26

                  Liquidation Principal.........................................................................26

                  Liquidation Proceeds..........................................................................26

                  Loan-to-Value Ratio...........................................................................26

                  Lockout Liquidation Amount....................................................................27

                  Lockout Percentage............................................................................27

                  Lockout Priority Amount.......................................................................27

                  Lowest Class B Owner..........................................................................27

                  Master Servicer...............................................................................27

                  Master Servicer Business Day..................................................................27

                  Master Servicing Fee..........................................................................27

                  MERS..........................................................................................27

                  MERS Loan.....................................................................................27

                  MERS(R)System..................................................................................28

                  MIN...........................................................................................28

                  MOM Loan......................................................................................28

                  Monthly P&I Advance...........................................................................28

                  Monthly Payment...............................................................................28

                  Moody's.......................................................................................28

                  Mortgage......................................................................................28

                  Mortgage File.................................................................................28

                  Mortgage Interest Rate........................................................................31

                  Mortgage Loan Schedule........................................................................31

                  Mortgage Loans................................................................................31

                  Mortgage Note.................................................................................32


                                                              vi
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                  Mortgage Pool.................................................................................32

                  Mortgage Pool Assets..........................................................................32

                  Mortgaged Property............................................................................32

                  Mortgagor.....................................................................................32

                  Nonrecoverable Advance........................................................................32

                  Non-U.S. Person...............................................................................32

                  Notice Addresses..............................................................................32

                  OTS...........................................................................................33

                  Officer's Certificate.........................................................................33

                  Opinion of Counsel............................................................................33

                  Original Trust Agreement......................................................................33

                  Original Value................................................................................33

                  Overcollateralized Subgroup...................................................................33

                  Ownership Interest............................................................................33

                  Pass-Through Entity...........................................................................33

                  Pass-Through Rate.............................................................................33

                  Paying Agent..................................................................................34

                  Payoff........................................................................................34

                  Payoff Earnings...............................................................................34

                  Payoff Interest...............................................................................34

                  Payoff Period.................................................................................34

                  Percentage Interest...........................................................................34

                  Permitted Transferee..........................................................................35

                  Person........................................................................................35

                  Planned Principal Balance.....................................................................35

                  Prepaid Monthly Payment.......................................................................35

                  Primary Insurance Policy......................................................................36

                  Principal Balance.............................................................................36

                  Principal Payment.............................................................................36

                  Principal Payment Amount......................................................................36


                                                        vii
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                  Principal Prepayment..........................................................................37

                  Principal Prepayment Amount...................................................................37

                  Principal Transfer Amount.....................................................................37

                  Prior Period..................................................................................37

                  Pro Rata Allocation...........................................................................37

                  Prospectus....................................................................................38

                  Purchase Obligation...........................................................................38

                  Purchase Price................................................................................38

                  Qualified Insurer.............................................................................38

                  Rating Agency.................................................................................38

                  Ratings.......................................................................................38

                  Realized Loss.................................................................................38

                  Recognition Agreement.........................................................................41

                  Record Date...................................................................................41

                  Reference Banks...............................................................................41

                  Regular Interest Group........................................................................41

                  Regular Interests.............................................................................41

                  Relief Act Shortfall..........................................................................41

                  REMIC.........................................................................................41

                  REMIC Provisions..............................................................................41

                  REMIC I.......................................................................................42

                  REMIC I Assets................................................................................42

                  REMIC I Available Distribution Amount.........................................................42

                  REMIC I Distribution Amount...................................................................43

                  REMIC I Regular Interests.....................................................................45

                  REMIC II......................................................................................45

                  REMIC II Assets...............................................................................45

                  REMIC II Available Distribution Amount........................................................45

                  REMIC II Distribution Amount..................................................................45

                  REMIC II Regular Interests....................................................................53


                                                           viii
<PAGE>

                  REMIC III.....................................................................................53

                  REMIC III Assets..............................................................................53

                  REMIC III Available Distribution Amount.......................................................53

                  REMIC III Distribution Amount.................................................................53

                  REMIC III Regular Interests...................................................................54

                  Residual Certificates.........................................................................55

                  Residual Distribution Amount..................................................................55

                  Responsible Officer...........................................................................55

                  Secretary of State............................................................................55

                  Securities Act................................................................................55

                  Security Agreement............................................................................55

                  Selling and Servicing Contrac.................................................................55

                  Senior Certificates...........................................................................56

                  Senior Subordinate Certificates...............................................................56

                  Servicer......................................................................................56

                  Servicing Fee.................................................................................56

                  Servicing Officer.............................................................................56

                  Special Hazard Coverage.......................................................................56

                  Special Hazard Loss...........................................................................56

                  Special Primary Insurance Policy..............................................................57

                  Special Primary Insurance Premium.............................................................57

                  Statutory Trust Statute.......................................................................57

                  Step Down Percentage..........................................................................57

                  Subgroup......................................................................................57

                  Subgroup 1....................................................................................57

                  Subgroup 1 Certificates.......................................................................58

                  Subgroup 1 Loans..............................................................................58

                  Subgroup 1 Senior Principal Distribution Amount...............................................58

                  Subgroup 1 Senior Liquidation Amount..........................................................58

                  Subgroup 1 Senior Percentage..................................................................58


                                                           ix
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                  Subgroup 1 Senior Prepayment Percentage or Subgroup 2 Senior Prepayment Percentage............58

                  Subgroup 1 Subordinate Balance................................................................60

                  Subgroup 1 Subordinate Percentage.............................................................60

                  Subgroup 1 Subordinate Prepayment Percentage..................................................60

                  Subgroup 1-L Regular Interests................................................................60

                  Subgroup 2....................................................................................60

                  Subgroup 2 Certificates.......................................................................60

                  Subgroup 2 Loans..............................................................................60

                  Subgroup 2 Senior Principal Distribution Amount...............................................60

                  Subgroup 2 Senior Liquidation Amount..........................................................61

                  Subgroup 2 Senior Percentage..................................................................61

                  Subgroup 2 Senior Prepayment Percentage.......................................................61

                  Subgroup 2 Subordinate Balance................................................................61

                  Subgroup 2 Subordinate Percentage.............................................................61

                  Subgroup 2 Subordinate Prepayment Percentage..................................................61

                  Subgroup 2-L Regular Interests................................................................61

                  Subordinate Certificates......................................................................61

                  Subordinate Component Balance.................................................................61

                  Subordinate Liquidation Amount................................................................61

                  Subordinate Percentage........................................................................61

                  Subordinate Principal Distribution Amount.....................................................62

                  Subordinate Principal Prepayments Distribution Amount.........................................62

                  Subordination Level...........................................................................62

                  Subsequent Recoveries.........................................................................63

                  Substitute Mortgage Loan......................................................................63

                  Targeted Principal Balance....................................................................63

                  Tax Matters Person............................................................................63

                  Termination Date..............................................................................63

                  Termination Payment...........................................................................63


                                                                x
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                  Total Transfer Amount.........................................................................64

                  Transfer......................................................................................64

                  Transferee....................................................................................64

                  Transferee Affidavit and Agreement............................................................64

                  Trust.........................................................................................64

                  Trustee.......................................................................................64

                  Uncollected Interest..........................................................................64

                  Uncompensated Interest Shortfall..............................................................64

                  Undercollateralized Subgroup..................................................................64

                  Underwriter...................................................................................65

                  Underwriting Standards........................................................................65

                  Uninsured Cause...............................................................................65

                  U.S. Person...................................................................................65

                  VA............................................................................................65

                  Withdrawal Date...............................................................................65

ARTICLE II            Creation of the Trust; Conveyance of the Mortgage Pool Assets, REMIC I Regular Interests and REMIC II
                      Regular Interests; REMIC Election and Designations; Original Issuance of Certificates.....65

         SECTION 2.01               Creation of the Trust.......................................................65

         SECTION 2.02               Restrictions on Activities of the Trust.....................................66

         SECTION 2.03               Separateness Requirements...................................................67

         SECTION 2.04               Conveyance of Mortgage Pool Assets; Security Interest.......................68

         SECTION 2.05               Delivery of Mortgage Files..................................................70

         SECTION 2.06               REMIC Election for REMIC I..................................................71

         SECTION 2.07               Acceptance by Trustee.......................................................73

         SECTION 2.08               Representations and Warranties of the Company Concerning the Mortgage Loans.75

         SECTION 2.09               Acknowledgment of Transfer of Mortgage Pool Assets..........................79

         SECTION 2.10               Conveyance of REMIC I Regular Interests; Security Interest..................79

         SECTION 2.11               REMIC Election for REMIC II.................................................81

                                                         xi

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         SECTION 2.12               Acknowledgement of Transfer of REMIC II Assets..............................82

         SECTION 2.13               Conveyance of REMIC II Regular Interests; Security Interest.................82

         SECTION 2.14               REMIC Election for REMIC III................................................84

         SECTION 2.15               Acknowledgement of Transfer of REMIC III Assets; Authentication of Certificates85

         SECTION 2.16               Legal Title.................................................................85

         SECTION 2.17               Compliance with ERISA Requirements..........................................85

         SECTION 2.18               Additional Representation of the Company Concerning the Mortgage Loans......85

ARTICLE III           Administration and Servicing of Mortgage Loans............................................86

         SECTION 3.01               The Company to Act as Master Servicer.......................................86

         SECTION 3.02               Custodial Accounts and Buydown Fund Accounts................................88

         SECTION 3.03               The Investment Account; Eligible Investments................................89

         SECTION 3.04               The Certificate Account.....................................................90

         SECTION 3.05               Permitted Withdrawals from the Certificate Account, the Investment Account and Custodial
                                    Accounts for P&I and of Buydown Funds from the Buydown Fund Accounts........91

         SECTION 3.06               Maintenance of Primary Insurance Policies; Collections Thereunder...........93

         SECTION 3.07               Maintenance of Hazard Insurance.............................................93

         SECTION 3.08               Enforcement of Due-on-Sale Clauses; Assumption Agreements...................94

         SECTION 3.09               Realization Upon Defaulted Mortgage Loans...................................95

         SECTION 3.10               Trustee to Cooperate; Release of Mortgage Files.............................97

         SECTION 3.11               Compensation to the Master Servicer and the Servicers.......................97

         SECTION 3.12               Reports to the Trustee; Certificate Account Statement.......................98

         SECTION 3.13               Annual Statement as to Compliance...........................................98

         SECTION 3.14               Access to Certain Documentation and Information Regarding
                                    the Mortgage Loans..........................................................98

         SECTION 3.15               Annual Independent Public Accountants' Servicing Report.....................99

         SECTION 3.16               [Reserved.].................................................................99


                                                   xii
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         SECTION 3.17               [Reserved.].................................................................99

         SECTION 3.18               [Reserved.].................................................................99

         SECTION 3.19               [Reserved.].................................................................99

         SECTION 3.20               Assumption or Termination of Selling and Servicing Contracts by Trustee.....99

ARTICLE IV            Payments to Certificateholders; Payment of Expenses......................................100

         SECTION 4.01               Distributions to Holders of REMIC I Regular Interests and
                                    Class R-1 Residual Interest................................................100

         SECTION 4.02               Advances by the Master Servicer; Distribution Reports to the Trustee.......100

         SECTION 4.03               Nonrecoverable Advances....................................................102

         SECTION 4.04               Distributions to Holders of REMIC II Regular Interests and
                                    Class R-2 Residual Interest................................................102

         SECTION 4.05               Distributions to Certificateholders; Payment of
                                    Special Primary Insurance Premiums.........................................102

         SECTION 4.06               Statements to Certificateholders...........................................103

ARTICLE V             The Certificates.........................................................................104

         SECTION 5.01               The Certificates...........................................................104

         SECTION 5.02               Certificates Issuable in Classes; Distributions of Principal and
                                    Interest; Authorized Denominations.........................................111

         SECTION 5.03               Registration of Transfer and Exchange of Certificates......................111

         SECTION 5.04               Mutilated, Destroyed, Lost or Stolen Certificates..........................112

         SECTION 5.05               Persons Deemed Owners......................................................112

         SECTION 5.06               Temporary Certificates.....................................................112

         SECTION 5.07               Book-Entry for Book-Entry Certificates.....................................113

         SECTION 5.08               Notices to Clearing Agency.................................................114

         SECTION 5.09               Definitive Certificates....................................................114

         SECTION 5.10               Office for Transfer of Certificates........................................114

         SECTION 5.11               Nature of Certificates.....................................................114

ARTICLE VI            The Company and the Master Servicer......................................................115

         SECTION 6.01               Liability of the Company and the Master Servicer...........................115

         SECTION 6.02               Merger or Consolidation of the Company, or the Master Servicer.............115


                                             xiii
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         SECTION 6.03               Limitation on Liability of the Company, the Master Servicer and Others.....115

         SECTION 6.04               The Company and the Master Servicer not to Resign..........................116

         SECTION 6.05               Trustee Access.............................................................116

ARTICLE VII           Default..................................................................................117

         SECTION 7.01               Events of Default..........................................................117

         SECTION 7.02               Trustee to Act; Appointment of Successor...................................119

         SECTION 7.03               Notification to Certificateholders.........................................120

ARTICLE VIII          Concerning the Trustees..................................................................120

         SECTION 8.01               Duties of Trustees.........................................................120

         SECTION 8.02               Certain Matters Affecting the Trustees.....................................122

         SECTION 8.03               Trustees Not Liable for Certificates or Mortgage Loans.....................123

         SECTION 8.04               Trustees May Own Certificates..............................................124

         SECTION 8.05               The Master Servicer to Pay Trustees' Fees and Expenses.....................124

         SECTION 8.06               Eligibility Requirements for Trustees......................................124

         SECTION 8.07               Resignation and Removal of Trustees........................................124

         SECTION 8.08               Successor Trustee..........................................................125

         SECTION 8.09               Merger or Consolidation of Trustee.........................................126

         SECTION 8.10               Appointment of Co-Trustee or Separate Trustee..............................126

         SECTION 8.11               Authenticating Agents......................................................127

         SECTION 8.12               Paying Agents..............................................................128

         SECTION 8.13               Duties of Delaware Trustee.................................................128

         SECTION 8.14               Amendment to Certificate of Trust..........................................129

         SECTION 8.15               Limitation of Liability....................................................129

ARTICLE IX            Termination..............................................................................129

         SECTION 9.01               Termination Upon Purchase by the Master Servicer or
                                    Liquidation of All Mortgage Loans..........................................129

         SECTION 9.02               Additional Termination Requirements........................................131

         SECTION 9.03               Trust Irrevocable..........................................................132

ARTICLE X             Miscellaneous Provisions.................................................................132

         SECTION 10.01              Amendment..................................................................132


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         SECTION 10.02              Recordation of Agreement...................................................133

         SECTION 10.03              Limitation on Rights of Certificateholders.................................134

         SECTION 10.04              Access to List of Certificateholders.......................................134

         SECTION 10.05              Governing Law..............................................................135

         SECTION 10.06              Notices....................................................................135

         SECTION 10.07              Severability of Provisions.................................................135

         SECTION 10.08              Counterpart Signatures.....................................................135

         SECTION 10.09              Benefits of Agreement......................................................135

         SECTION 10.10              Notices and Copies to Rating Agencies......................................136




Appendix 1              Definition of "Class C-Y Principal Reduction Amounts"
Exhibit A               Form of Certificates (other than Class R Certificates)
Exhibit B               Form of Class R Certificates
Exhibit C               [Reserved]
Exhibit D               Mortgage Loan Schedule
Exhibit E               Selling And Servicing Contract
Exhibit F               Form of Transferor Certificate For Junior Subordinate Certificates
Exhibit G               Form of Transferee's Agreement For Junior Subordinate Certificates
Exhibit H               Form of Additional Matter Incorporated Into The Certificates
Exhibit I               Transferor Certificate
Exhibit J               Transferee Affidavit And Agreement
Exhibit K               [Reserved]
Exhibit L               Form of Investment Letter
Exhibit M               Form of Trustee's Certification Pursuant to Section 2.02
Exhibit N               Officer's Certificate With Respect to ERISA Matters Pursuant to Section 5.01(d)
Exhibit O               Officer's Certificate With Respect to ERISA Matters Pursuant to Section 5.01(g)
</Table>



                                            xv

<PAGE>

         This Pooling and Servicing Agreement, dated and effective as of
February 1, 2004 (this "Agreement"), is executed by and among Washington Mutual
Mortgage Securities Corp., as depositor and Master Servicer (the "Company"),
Citibank, N.A., a national banking association with a corporate trust office at
111 Wall Street, 14th Floor, Zone 3, New York, New York 10005, as Trustee (the
"Trustee"), and Christiana Bank & Trust Company, as Delaware Trustee (the
"Delaware Trustee"). Capitalized terms used in this Agreement and not otherwise
defined have the meanings ascribed to such terms in Article I hereof.

                              PRELIMINARY STATEMENT

         The Company at the Closing Date is the owner of the Mortgage Loans and
the other property being conveyed by it to the Trust. On the Closing Date, the
Company will acquire the REMIC I Regular Interests and the Class R-1 Residual
Interest from the Trust as consideration for its transfer to the Trust of the
Mortgage Loans and certain other assets and will be the owner of the REMIC I
Regular Interests and the Class R-1 Residual Interest. Thereafter on the Closing
Date, the Company will acquire the REMIC II Regular Interests and the Class R-2
Residual Interest from the Trust as consideration for its transfer to the Trust
of the REMIC I Regular Interests and will be the owner of the REMIC II Regular
Interests. Thereafter on the Closing Date, the Company will acquire the
Certificates (other than the Class R-1 and Class R-2 Residual Interests) and the
Class R-3 Residual Interest from the Trust as consideration for its transfer to
the Trust of the REMIC II Regular Interests and will be the owner of the
Certificates. The Company has duly authorized the execution and delivery of this
Agreement to provide for (i) the conveyance to the Trust of the Mortgage Loans
and certain other assets, (ii) the issuance to the Company of the REMIC I
Regular Interests and the Class R-1 Residual Interest representing in the
aggregate the entire beneficial interest in REMIC I, (iii) the conveyance to the
Trust of the REMIC I Regular Interests, (iv) the issuance to the Company of the
REMIC II Regular Interests and the Class R-2 Residual Interest representing in
the aggregate the entire beneficial interest in REMIC II, (v) the conveyance to
the Trust of the REMIC II Regular Interests and (vi) the issuance to the Company
of the Certificates, such Certificates (other than the portion of the Class R
Certificates representing ownership of the Class R-1 and Class R-2 Residual
Interests) representing in the aggregate the entire beneficial interest in REMIC
III. The Company is entering into this Agreement, and the Trustee and the
Delaware Trustee are each accepting the trust created hereby, for good and
valuable consideration, the receipt and sufficiency of which are hereby
acknowledged.

         The Certificates issued hereunder, other than the Junior Subordinate
Certificates, have been offered for sale pursuant to a Prospectus, dated
February 10, 2004, and a Prospectus Supplement, dated February 20, 2004, of the
Company (together, the "Prospectus"). The Junior Subordinate Certificates have
been offered for sale pursuant to a Private Placement Memorandum, dated February
24, 2004. The Trust created hereunder is intended to be the "Trust" described in
the Prospectus and the Private Placement Memorandum and the Certificates are
intended to be the "Certificates" described therein. The following tables set
forth the designation, type of interest, Certificate Interest Rate, initial
Class Principal Balance and Final Maturity Date for the REMIC I Regular
Interests, the REMIC II Regular Interests, the Class R Residual Interests and
the Certificates:

                                       1
<PAGE>

<TABLE>
<CAPTION>
                                                 REMIC I Interests

  Class Designation for
   each REMIC I Regular                           Certificate           Initial Class
 Interest and the Class       Type of                Interest               Principal
  R-1 Residual Interest      Interest                Rate (1)                 Balance         Final Maturity Date*
----------------------    ------------    --------------------    --------------------     ------------------------
<S>                       <C>             <C>                     <C>                      <C>
      Class C-Y-1         Regular                  5.500%            $    163,082.40               March 2034
      Class C-Y-2         Regular                  8.000%                  23,391.22               March 2034
      Class C-Z-1         Regular                  5.500%             326,001,709.23               March 2034
      Class C-Z-2         Regular                  8.000%              46,759,044.50               March 2034
      Class P-M           Regular                     (2)               2,438,018.62               March 2034
      Class R-1+          Residual                 5.500%                     100.00               March 2034
</TABLE>

*        The Distribution Date in the specified month, which is the month
         following the month the latest maturing Mortgage Loan in the related
         Subgroup matures. For federal income tax purposes, for each Class of
         REMIC I Regular and Residual Interests, the "latest possible maturity
         date" shall be the Final Maturity Date.

+        The Class R-1 Residual Interest is entitled to receive the applicable
         Residual Distribution Amount and any Excess Liquidation Proceeds.

(1)      Interest distributed to the REMIC I Regular Interests (other than the
         Class P-M Regular Interest, which shall not be entitled to receive any
         distributions of interest) and the Class R-1 Residual Interest on each
         Distribution Date will have accrued at the applicable per annum
         Certificate Interest Rate on the applicable Class Principal Balance
         outstanding immediately before such Distribution Date.

(2)      The Class P-M Regular Interest shall not be entitled to receive any
         distributions of interest.

         As provided herein, with respect to REMIC I, the Company will cause an
election to be made on behalf of REMIC I to be treated for federal income tax
purposes as a REMIC. The REMIC I Regular Interests will be designated regular
interests in REMIC I and the Class R-1 Residual Interest will be designated the
sole class of residual interest in REMIC I, for purposes of the REMIC
Provisions.




                                       2
<PAGE>

<TABLE>
<CAPTION>
                                                       REMIC II Interests


    Class Designation for       Type of           Certificate            Initial Class             Final Maturity
    each REMIC II Regular      Interest            Interest                Principal                    Date*
   Interest and the Class                          Rate (1)                 Balance
    R-2 Residual Interest
  ------------------------    ------------    --------------------    --------------------     ------------------------
  <S>                         <C>             <C>                     <C>                      <C>
  Class 1-A-1-L                Regular             4.050%             $ 99,827,849.00             March 2034
  Class 1-A-2-L                Regular             4.050%             13,000,000.00               March 2034
  Class 1-A-3-L                Regular             8.000%             65,440,151.00               March 2034
  Class 1-A-5-L                Regular             5.500%             56,668,000.00               March 2034
  Class 1-A-6-L                Regular             5.500%             7,747,663.00                March 2034
  Class 1-A-7-L                Regular             (2)                19,800,000.00               March 2034
  Class 1-A-8-L                Regular             (3)                7,200,000.00                March 2034
  Class 1-A-9-L                Regular             5.500%             15,000,000.00               March 2034
  Class 1-A-10-L               Regular             5.500%             20,000,000.00               March 2034
  Class 1-A-11-L               Regular             5.500%             600,000.00                  March 2034
  Class 1-A-12-L               Regular             5.500%             11,031,529.00               March 2034
  Class 2-A-1-L                Regular             8.000%             45,369,689.00               March 2034
  Class P-L                    Regular             (4)                2,438,018.62                March 2034
  Class B-1-L                  Regular            Variable(5)         5,256,000.00                March 2034
  Class B-2-L                  Regular            Variable(5)         2,252,000.00                March 2034
  Class B-3-L                  Regular            Variable(5)         1,502,000.00                March 2034
  Class B-4-L                  Regular            Variable(5)         750,000.00                  March 2034
  Class B-5-L                  Regular            Variable(5)         751,000.00                  March 2034
  Class B-6-L                  Regular            Variable(5)         751,346.35                  March 2034
  Class R-2 (6)                Residual           -----               -----                       March 2034
</TABLE>

*        The Distribution Date in the specified month, which is the month
         following the month the latest maturing Mortgage Loan in the related
         Subgroup (or Subgroups, as applicable) matures. For federal income tax
         purposes, for each Class of REMIC II Regular and Residual Interests,
         the "latest possible maturity date" shall be the Final Maturity Date.
(1)      Interest distributed to the REMIC II Regular Interests (other than the
         Class P-L Regular Interest, which shall not be entitled to receive any
         distributions of interest) on each Distribution Date will have accrued
         at the applicable per annum Certificate Interest Rate on the applicable
         Class Principal Balance outstanding immediately before such
         Distribution Date.
(2)      The Certificate Interest Rate for the Class 1-A-7-L Regular Interest
         shall equal LIBOR plus 1.500%, subject to a minimum and maximum
         Certificate Interest Rate of 1.500% and 7.500% per annum, respectively.
(3)      The Certificate Interest Rate for the Class 1-A-8-L Regular Interest
         shall equal 16.500% minus the product of LIBOR and 2.750, subject to a
         minimum and maximum Certificate Interest Rate of 0.000% and 16.500% per
         annum, respectively.
(4)      The Class P-L Regular Interest shall not be entitled to receive any
         distributions of interest. (5) The Certificate Interest Rate for each
         Class of the Class B-L Regular Interests shall equal, on any
         Distribution Date, the weighted average of the Certificate Interest
         Rates for the Class C-Y-1 and Class C-Y-2 Regular Interests.
(6)      The Class R-2 Residual Interest shall be entitled to receive the
         applicable Residual Distribution Amount. The Class R-2 Residual
         Interest shall not be entitled to receive any distributions of interest
         or principal.

                                       3
<PAGE>

         As provided herein, with respect to REMIC II, the Company will cause an
election to be made on behalf of REMIC II to be treated for federal income tax
purposes as a REMIC. The REMIC II Regular Interests will be designated regular
interests in REMIC II and the Class R-2 Residual Interest will be designated the
sole class of residual interest in REMIC II, for purposes of the REMIC
Provisions.




                                       4
<PAGE>

<TABLE>
<CAPTION>
                                                              REMIC III Interests


    Class Designation for       Type of           Certificate            Initial Class             Final Maturity
        each Class of          Interest            Interest                Principal                    Date*
    Certificates and the                           Rate (1)                 Balance
     Class R-3 Residual
          Interest
------------------------    ------------    --------------------    --------------------     ------------------------
<S>                         <C>             <C>                     <C>                      <C>
  Class 1-A-1                  Regular             4.050%             $ 99,827,849.00             March 2034
  Class 1-A-2                  Regular             4.050%             13,000,000.00               March 2034
  Class 1-A-3                  Regular             (2)                65,440,151.00               March 2034
  Class 1-A-4                  Regular             (3)                -----                       March 2034
  Class 1-A-5                  Regular             5.500%             56,668,000.00               March 2034
  Class 1-A-6                  Regular             5.500%             7,747,663.00                March 2034
  Class 1-A-7                  Regular             (4)                19,800,000.00               March 2034
  Class 1-A-8                  Regular             (5)                7,200,000.00                March 2034
  Class 1-A-9                  Regular             5.500%             15,000,000.00               March 2034
  Class 1-A-10                 Regular             5.500%             20,000,000.00               March 2034
  Class 1-A-11                 Regular             5.500%             600,000.00                  March 2034
  Class 1-A-12                 Regular             5.500%             11,031,529.00               March 2034
  Class 2-A-1                  Regular             (6)                45,369,689.00               March 2034
  Class 2-A-2                  Regular             (7)                -----                       March 2034
  Class P                      Regular             (8)                2,438,018.62                March 2034
  Class B-1                    Regular            Variable(9)         5,256,000.00                March 2034
  Class B-2                    Regular            Variable(9)         2,252,000.00                March 2034
  Class B-3                    Regular            Variable(9)         1,502,000.00                March 2034
  Class B-4                    Regular            Variable(9)         750,000.00                  March 2034
  Class B-5                    Regular            Variable(9)         751,000.00                  March 2034
  Class B-6                    Regular            Variable(9)         751,346.35                  March 2034
  Class R-3 (10)               Residual           -----                   -----                   March 2034
</TABLE>

*        The Distribution Date in the specified month, which is the month
         following the month the latest maturing Mortgage Loan in the related
         Subgroup (or Subgroups, as applicable) matures. For federal income tax
         purposes, for each Class of REMIC III Regular and Residual Interests,
         the "latest possible maturity date" shall be the Final Maturity Date.
(1)      Interest distributed on each Distribution Date to the Certificates
         (other than the Class P Certificates, which shall not be entitled to
         receive any distributions of interest) will have accrued at the
         applicable per annum Certificate Interest Rate on the applicable Class
         Principal Balance or Class Notional Amount outstanding immediately
         before such Distribution Date.
(2)      The Certificate Interest Rate for the Class 1-A-3 Certificates shall
         equal LIBOR plus 0.400%, subject to a minimum and maximum Certificate
         Interest Rate of 0.400% and 8.000% per annum, respectively.
(3)      The Certificate Interest Rate for the Class 1-A-4 Certificates shall
         equal 7.600% minus LIBOR, subject to a minimum and maximum Certificate
         Interest Rate of 0.000% and 7.600% per annum, respectively. The Class
         1-A-4 Certificates shall accrue interest on the Class 1-A-4 Notional
         Amount. The Class 1-A-4 Certificates shall not be entitled to receive
         any distributions of principal.
(4)      The Certificate Interest Rate for the Class 1-A-7 Certificates shall
         equal LIBOR plus 1.500%, subject to a minimum and maximum Certificate
         Interest Rate of 1.500% and 7.500% per annum, respectively.
(5)      The Certificate Interest Rate for the Class 1-A-8 Certificates shall
         equal 16.500% minus the product of LIBOR and 2.750, subject to a
         minimum and maximum Certificate Interest Rate of 0.000% and 16.500% per
         annum, respectively.
(6)      The Certificate Interest Rate for the Class 2-A-1 Certificates shall
         equal LIBOR plus 0.550%, subject to a minimum and maximum Certificate
         Interest Rate of 0.550% and 8.000% per annum, respectively.
(7)      The Certificate Interest Rate for the Class 2-A-2 Certificates shall
         equal 7.450% minus LIBOR, subject to a minimum and maximum Certificate
         Interest Rate of 0.000% and 7.450% per annum, respectively. The Class
         2-A-2 Certificates shall accrue interest on the Class 2-A-2 Notional
         Amount. The Class 2-A-2 Certificates shall not be entitled to receive
         any distributions of principal.


                                       5
<PAGE>

(8)      The Class P Certificates shall not be entitled to receive any
         distributions of interest. (9) The Certificate Interest Rate for each
         Class of the Class B Certificates shall equal, on any Distribution
         Date, the weighted average of the Certificate Interest Rates for the
         Class C-Y-1and Class C-Y-2 Regular Interests.
(10)     The Class R-3 Residual Interest shall be entitled to receive the
         applicable Residual Distribution Amount. The Class R-3 Residual
         Interest shall not be entitled to receive any distributions of interest
         or principal.

         As provided herein, with respect to REMIC III, the Company will cause
an election to be made on behalf of REMIC III to be treated for federal income
tax purposes as a REMIC. The Certificates (other than the Class R Certificates)
will be designated regular interests in REMIC III, and the Class R-3 Residual
Interest will be designated the sole class of residual interest in REMIC III,
for purposes of the REMIC Provisions. As of the Cut-Off Date, the Mortgage Loans
have an aggregate Principal Balance of $375,385,346.35 and the Certificates have
an Aggregate Certificate Principal Balance of $375,385,345.35.

         In addition, the Trust will issue the Class R Certificates, which will
represent ownership of the Class R-1, Class R-2 and Class R-3 Residual
Interests.

                              W I T N E S S E T H :

         WHEREAS, the Company is a corporation duly organized and existing under
and by virtue of the laws of the State of Delaware and has full corporate power
and authority to enter into this Agreement and to undertake the obligations
undertaken by it herein;

         WHEREAS, the Trustee is a national banking association duly organized
and existing under the laws of the United States of America and has full power
and authority to enter into this Agreement;

         WHEREAS, the Delaware Trustee is a banking corporation duly organized
and existing under the laws of the State of Delaware and has full power and
authority to enter into this Agreement;

         WHEREAS, prior to the execution and delivery hereof, the Company and
the Delaware Trustee have entered into the Original Trust Agreement, and the
Delaware Trustee has filed the Certificate of Trust;

         WHEREAS, it is the intention of the Company, the Trustee and the
Delaware Trustee that the Trust created by this Agreement constitute a statutory
trust under the Statutory Trust Statute, that this Agreement constitute the
governing instrument of the Trust, and that this Agreement amend and restate the
Original Trust Agreement;

         WHEREAS, the Company is the owner of the Mortgage Loans identified in
the Mortgage Loan Schedule hereto having unpaid Principal Balances on the
Cut-Off Date as stated therein; and

         WHEREAS, the Company has been duly authorized to create the Trust to
(i) hold the Mortgage Loans and certain other property, (ii) issue the REMIC I
Regular Interests and the Class R-1 Residual Interest, (iii) hold the REMIC I
Regular Interests, (iv) issue the REMIC II Regular Interests and the Class R-2
Residual Interest, (v) hold the REMIC II Regular Interests and (vi) issue the
Certificates.

                                       6
<PAGE>

         NOW, THEREFORE, in order to declare the terms and conditions upon which
the REMIC I Regular Interests, the REMIC II Regular Interests, the Class R
Residual Interests and the Certificates are to be issued, and in consideration
of the premises and of the purchase and acceptance of the Certificates by the
Holders thereof, the Company covenants and agrees with the Trustee and the
Delaware Trustee, for the equal and proportionate benefit of the respective
Holders from time to time of the REMIC I Regular Interests, the REMIC II Regular
Interests and the Certificates, as applicable, as follows:



                                   ARTICLE I



SECTION 1.01      Definitions.

         Whenever used in this Agreement, the following words and phrases,
unless the context otherwise requires, shall have the following meanings:

         Aggregate Certificate Principal Balance: At any given time, the sum of
the then current Class Principal Balances of the Certificates.

         Appraised Value: The amount set forth in an appraisal made by or for
(a) the mortgage originator in connection with its origination of each Mortgage
Loan (including a Mortgage Loan originated to refinance mortgage debt), (b) with
respect to a Mortgage Loan originated to refinance mortgage debt, the originator
of the mortgage debt that was refinanced or (c) the Servicer, at any time, in
accordance with the Selling and Servicing Contract.

         Assignment of Proprietary Lease: With respect to a Cooperative Loan,
the assignment or mortgage of the related Cooperative Lease from the Mortgagor
to the originator of the Cooperative Loan.

         Authenticating Agent: Any authenticating agent appointed by the Trustee
pursuant to Section 8.11.

         Authorized Denomination: With respect to the Certificates (other than
the Class 1-A-4, Class 2-A-2 and Class R Certificates), an initial Certificate
Principal Balance equal to $25,000 and multiples of $1 in excess thereof, except
that one Certificate of each Class of the Junior Subordinate Certificates may be
issued in an amount that is not an integral multiple of $1. With respect to the
Class 1-A-4 and Class 2-A-2 Certificates, a Class Notional Amount as of the
Cut-Off Date equal to $100,000 and multiples of $1 in excess thereof. With
respect to the Class R Certificates, one Certificate with a Percentage Interest
equal to 0.01% and one Certificate with a Percentage Interest equal to 99.99%.

                                       7
<PAGE>

         Bankruptcy Coverage: $100,000 less (a) any scheduled or permissible
reduction in the amount of Bankruptcy Coverage pursuant to the second paragraph
of this definition and (b) Bankruptcy Losses allocated to the Certificates.

         The Bankruptcy Coverage may be reduced upon written confirmation from
the Rating Agencies that such reduction will not adversely affect the then
current ratings assigned to the Certificates by the Rating Agencies.

         Bankruptcy Loss: A loss on a Mortgage Loan arising out of (i) a
reduction in the scheduled Monthly Payment for such Mortgage Loan by a court of
competent jurisdiction in a case under the United States Bankruptcy Code, other
than any such reduction that arises out of clause (ii) of this definition of
"Bankruptcy Loss," including, without limitation, any such reduction that
results in a permanent forgiveness of principal, or (ii) with respect to any
Mortgage Loan, a valuation, by a court of competent jurisdiction in a case under
such Bankruptcy Code, of the related Mortgaged Property in an amount less than
the then outstanding Principal Balance of such Mortgage Loan.

         Beneficial Holder: A Person holding a beneficial interest in any
Book-Entry Certificate as or through a DTC Participant or an Indirect DTC
Participant or a Person holding a beneficial interest in any Definitive
Certificate.

         Benefit Plan Opinion: With respect to any Certificate presented for
registration in the name of any Person, an Opinion of Counsel acceptable to and
in form and substance satisfactory to the Trustee and the Company to the effect
that the purchase or holding of such Certificate is permissible under applicable
law, will not constitute or result in a non-exempt prohibited transaction under
Section 406 of ERISA or Section 4975 of the Code, and will not subject the
Trust, the Trustee, the Delaware Trustee, the Master Servicer or the Company to
any obligation or liability (including obligations or liabilities under Section
406 of ERISA or Section 4975 of the Code) in addition to those undertaken in
this Agreement, which Opinion of Counsel shall not be an expense of the Trust,
the Trustee, the Delaware Trustee, the Master Servicer or the Company.

         Book-Entry Certificates: The Class A, Class P and Senior Subordinate
Certificates, beneficial ownership and transfers of which shall be made through
book entries as described in Section 5.07.

         Business Day: Any day other than a Saturday, a Sunday, or a day on
which banking institutions in Stockton, California, Chicago, Illinois, New York,
New York, Seattle, Washington or any city in which the Corporate Trust Office is
located are authorized or obligated by law or executive order to be closed.

         Buydown Agreement: An agreement between a Person and a Mortgagor
pursuant to which such Person has provided a Buydown Fund.

         Buydown Fund: A fund provided by the originator of a Mortgage Loan or
another Person with respect to a Buydown Loan which provides an amount
sufficient to subsidize regularly scheduled principal and interest payments due
on such Buydown Loan for a period. Buydown Funds may be (i) funded at the par
values of future payment subsidies, or (ii) funded in an amount less than the
par values of future payment subsidies, and determined by discounting such par


                                       8
<PAGE>

values in accordance with interest accruing on such amounts, in which event they
will be deposited in an account bearing interest. Buydown Funds may be held in a
separate Buydown Fund Account or may be held in a Custodial Account for P&I or a
Custodial Account for Reserves and monitored by a Servicer.

         Buydown Fund Account: A separate account or accounts created and
maintained pursuant to Section 3.02 (a) with the corporate trust department of
the Trustee or another financial institution approved by the Master Servicer,
(b) within FDIC insured accounts (or other accounts with comparable insurance
coverage acceptable to the Rating Agencies) created, maintained and monitored by
a Servicer or (c) in a separate non-trust account without FDIC or other
insurance in an Eligible Institution. Such account or accounts may be
non-interest bearing or may bear interest. In the event that a Buydown Fund
Account is established pursuant to clause (b) of the preceding sentence, amounts
held in such Buydown Fund Account shall not exceed the level of deposit
insurance coverage on such account; accordingly, more than one Buydown Fund
Account may be established.

         Buydown Loan: A Mortgage Loan for which the Mortgage Interest Rate has
been subsidized through a Buydown Fund provided at the time of origination of
such Mortgage Loan.

         Carry-Forward Subsequent Recoveries Amount: For any Distribution Date
and any Subgroup, the excess, if any, of (i) the Subsequent Recoveries for such
Distribution Date for such Subgroup over (ii) the amount by which the Class
Principal Balance of the Class of Subordinate Certificates with the lowest
priority is increased in respect of Subsequent Recoveries for such Subgroup on
such Distribution Date pursuant to the definition of "Class Principal Balance"
herein.

         Certificate: Any one of the Certificates issued pursuant to this
Agreement, executed by the Trustee and authenticated by or on behalf of the
Trustee hereunder in substantially one of the forms set forth in Exhibit A and B
hereto. The additional matter appearing in Exhibit H shall be deemed
incorporated into Exhibit A as though set forth at the end of such Exhibit.

         Certificate Account: The separate trust account created and maintained
with the Trustee, the Investment Depository or any other bank or trust company
acceptable to the Rating Agencies which is incorporated under the laws of the
United States or any state thereof pursuant to Section 3.04, which account shall
bear a designation clearly indicating that the funds deposited therein are held
in trust for the benefit of the Trust or any other account serving a similar
function acceptable to the Rating Agencies. Funds in the Certificate Account may
be invested in Eligible Investments pursuant to Section 3.04(b) and reinvestment
earnings thereon shall be paid to the Master Servicer as additional servicing
compensation. Funds deposited in the Certificate Account (exclusive of the
Master Servicing Fee) shall be held in trust for the Certificateholders and for
the uses and purposes set forth in Section 2.01, Section 3.04, Section 3.05,
Section 4.01, Section 4.04 and Section 4.05.

         Certificateholder or Holder: With respect to the Certificates, the
person in whose name a Certificate is registered in the Certificate Register,
except that, solely for the purposes of giving any consent pursuant to this
Agreement, any Certificate registered in the name of the Company, the Master


                                       9
<PAGE>

Servicer or any affiliate thereof shall be deemed not to be outstanding and the
Percentage Interest evidenced thereby shall not be taken into account in
determining whether the requisite percentage of Percentage Interests necessary
to effect any such consent has been obtained; provided, that the Trustee may
conclusively rely upon an Officer's Certificate to determine whether any Person
is an affiliate of the Company or the Master Servicer. With respect to the REMIC
I Regular Interests, the owner of the REMIC I Regular Interests, which as of the
Closing Date shall be the Trust. With respect to the REMIC II Regular Interests,
the owner of the REMIC II Regular Interests, which as of the Closing Date shall
be the Trust.

         Certificate Interest Rate: For each Class of Certificates and REMIC I
and REMIC II Regular Interests, the per annum rate set forth as the Certificate
Interest Rate for such Class in the Preliminary Statement hereto.

         Certificate of Trust: The certificate of trust filed with respect to
the Trust with the Secretary of State in accordance with Section 3810(a) of the
Statutory Trust Statute.

         Certificate Principal Balance: For each Certificate of any Class, the
portion of the related Class Principal Balance, if any, represented by such
Certificate.

         Certificate Register and Certificate Registrar: The register maintained
and the registrar appointed, respectively, pursuant to Section 5.03.

         Class: All REMIC I Regular Interests or the Class R-1 Residual Interest
having the same priority and rights to payments on the Mortgage Loans from the
REMIC I Available Distribution Amount, all REMIC II Regular Interests or the
Class R-2 Residual Interest having the same priority and rights to payments on
the REMIC I Regular Interests from the REMIC II Available Distribution Amount,
and all REMIC III Regular Interests or the Class R-3 Residual Interest having
the same priority and rights to payments on the REMIC II Regular Interests from
the REMIC III Available Distribution Amount, as applicable, which REMIC I
Regular Interests, REMIC II Regular Interests, REMIC III Regular Interests and
Class R Residual Interests, as applicable, shall be designated as a separate
Class, and which, in the case of the Certificates (including the Class R
Certificates representing ownership of the Class R Residual Interests), shall be
set forth in the applicable forms of Certificates attached hereto as Exhibits A
and B. Each Class of REMIC I Regular Interests and the Class R-1 Residual
Interest shall be entitled to receive the amounts allocated to such Class
pursuant to the definition of "REMIC I Distribution Amount" only to the extent
of the REMIC I Available Distribution Amount for such Distribution Date
remaining after distributions in accordance with prior clauses of the definition
of "REMIC I Distribution Amount," each Class of REMIC II Regular Interests and
the Class R-2 Residual Interest shall be entitled to receive the amounts
allocated to such Class pursuant to the definition of "REMIC II Distribution
Amount" only to the extent of the REMIC II Available Distribution Amount for
such Distribution Date remaining after distributions in accordance with prior
clauses of the definition of "REMIC II Distribution Amount" and each Class of
REMIC III Regular Interests and the Class R-3 Residual Interest shall be
entitled to receive the amounts allocated to such Class pursuant to the
definition of "REMIC III Distribution Amount" only to the extent of the REMIC
III Available Distribution Amount for such Distribution Date remaining after
distributions in accordance with prior clauses of the definition of "REMIC III
Distribution Amount."



                                       10
<PAGE>

         Class A Certificates: The Subgroup 1 and Subgroup 2 Certificates.

         Class A-L Regular Interests: The Subgroup 1-L and Subgroup 2-L Regular
Interests.

         Class 1-A-1 Certificates: The Certificates designated as "Class 1-A-1"
on the face thereof in substantially the form attached hereto as Exhibit A.

         Class 1-A-1-L Regular Interest: The uncertificated undivided beneficial
interest in REMIC II which constitutes a REMIC II Regular Interest and is
entitled to distributions as set forth herein.

         Class 1-A-2 Certificates: The Certificates designated as "Class 1-A-2"
on the face thereof in substantially the form attached hereto as Exhibit A.

         Class 1-A-2-L Regular Interest: The uncertificated undivided beneficial
interest in REMIC II which constitutes a REMIC II Regular Interest and is
entitled to distributions as set forth herein.

         Class 1-A-3 Certificates: The Certificates designated as "Class 1-A-3"
on the face thereof in substantially the form attached hereto as Exhibit A.

         Class 1-A-3-L Regular Interest: The uncertificated undivided beneficial
interest in REMIC II which constitutes a REMIC II Regular Interest and is
entitled to distributions as set forth herein.

         Class 1-A-4 Certificates: The Certificates designated as "Class 1-A-4"
on the face thereof in substantially the form attached hereto as Exhibit A.

         Class 1-A-4 Notional Amount: For any Distribution Date, the Class 1-A-3
Principal Balance immediately before that Distribution Date.

         Class 1-A-5 Certificates: The Certificates designated as "Class 1-A-5"
on the face thereof in substantially the form attached hereto as Exhibit A.

         Class 1-A-5-L Regular Interest: The uncertificated undivided beneficial
interest in REMIC II which constitutes a REMIC II Regular Interest and is
entitled to distributions as set forth herein.

         Class 1-A-6 Certificates: The Certificates designated as "Class 1-A-6"
on the face thereof in substantially the form attached hereto as Exhibit A.

         Class 1-A-6-L Regular Interest: The uncertificated undivided beneficial
interest in REMIC II which constitutes a REMIC II Regular Interest and is
entitled to distributions as set forth herein.

         Class 1-A-7 Certificates: The Certificates designated as "Class 1-A-7"
on the face thereof in substantially the form attached hereto as Exhibit A.

                                       11
<PAGE>

         Class 1-A-7-L Regular Interest: The uncertificated undivided beneficial
interest in REMIC II which constitutes a REMIC II Regular Interest and is
entitled to distributions as set forth herein.

         Class 1-A-8 Certificates: The Certificates designated as "Class 1-A-8"
on the face thereof in substantially the form attached hereto as Exhibit A.

         Class 1-A-8-L Regular Interest: The uncertificated undivided beneficial
interest in REMIC II which constitutes a REMIC II Regular Interest and is
entitled to distributions as set forth herein.

         Class 1-A-9 Certificates: The Certificates designated as "Class 1-A-9"
on the face thereof in substantially the form attached hereto as Exhibit A.

         Class 1-A-9-L Regular Interest: The uncertificated undivided beneficial
interest in REMIC II which constitutes a REMIC II Regular Interest and is
entitled to distributions as set forth herein.

         Class 1-A-10 Certificates: The Certificates designated as "Class
1-A-10" on the face thereof in substantially the form attached hereto as Exhibit
A.

         Class 1-A-10-L Regular Interest: The uncertificated undivided
beneficial interest in REMIC II which constitutes a REMIC II Regular Interest
and is entitled to distributions as set forth herein.

         Class 1-A-11 Certificates: The Certificates designated as "Class
1-A-11" on the face thereof in substantially the form attached hereto as Exhibit
A.

         Class 1-A-11-L Regular Interest: The uncertificated undivided
beneficial interest in REMIC II which constitutes a REMIC II Regular Interest
and is entitled to distributions as set forth herein.

         Class 1-A-12 Certificates: The Certificates designated as "Class
1-A-12" on the face thereof in substantially the form attached hereto as Exhibit
A.

         Class 1-A-12-L Regular Interest: The uncertificated undivided
beneficial interest in REMIC II which constitutes a REMIC II Regular Interest
and is entitled to distributions as set forth herein.

         Class 2-A-1 Certificates: The Certificates designated as "Class 2-A-1"
on the face thereof in substantially the form attached hereto as Exhibit A.

         Class 2-A-1-L Regular Interest: The uncertificated undivided beneficial
interest in REMIC II which constitutes a REMIC II Regular Interest and is
entitled to distributions as set forth herein.

         Class 2-A-2 Certificates: The Certificates designated as "Class 2-A-2"
on the face thereof in substantially the form attached hereto as Exhibit A.



                                       12
<PAGE>

         Class 2-A-2 Notional Amount: For any Distribution Date, the Class 2-A-1
Principal Balance immediately before that Distribution Date.

         Class B Certificates: The Class B-1, Class B-2, Class B-3, Class B-4,
Class B-5 and Class B-6 Certificates.

         Class B Percentage: For any date of determination, the aggregate Class
Principal Balance of the Class B Certificates divided by the then outstanding
aggregate Principal Balance of the Mortgage Loans.

         Class B-L Regular Interests: The Class B-1-L, Class B-2-L, Class B-3-L,
Class B-4-L, Class B-5-L and Class B-6-L Regular Interests.

         Class B-1 Certificates: The Certificates designated as "Class B-1" on
the face thereof in substantially the form attached hereto as Exhibit A.

         Class B-1-L Regular Interest: The uncertificated undivided beneficial
interest in REMIC II which constitutes a REMIC II Regular Interest and is
entitled to distributions as set forth herein.

         Class B-2 Certificates: The Certificates designated as "Class B-2" on
the face thereof in substantially the form attached hereto as Exhibit A.

         Class B-2-L Regular Interest: The uncertificated undivided beneficial
interest in REMIC II which constitutes a REMIC II Regular Interest and is
entitled to distributions as set forth herein.

         Class B-3 Certificates: The Certificates designated as "Class B-3" on
the face thereof in substantially the form attached hereto as Exhibit A.

         Class B-3-L Regular Interest: The uncertificated undivided beneficial
interest in REMIC II which constitutes a REMIC II Regular Interest and is
entitled to distributions as set forth herein.

         Class B-4 Certificates: The Certificates designated as "Class B-4" on
the face thereof in substantially the form attached hereto as Exhibit A.

         Class B-4-L Regular Interest: The uncertificated undivided beneficial
interest in REMIC II which constitutes a REMIC II Regular Interest and is
entitled to distributions as set forth herein.

         Class B-5 Certificates: The Certificates designated as "Class B-5" on
the face thereof in substantially the form attached hereto as Exhibit A.

         Class B-5-L Regular Interest: The uncertificated undivided beneficial
interest in REMIC II which constitutes a REMIC II Regular Interest and is
entitled to distributions as set forth herein.



                                       13
<PAGE>

         Class B-6 Certificates: The Certificates designated as "Class B-6" on
the face thereof in substantially the form attached hereto as Exhibit A.

         Class B-6-L Regular Interest: The uncertificated undivided beneficial
interest in REMIC II which constitutes a REMIC II Regular Interest and is
entitled to distributions as set forth herein.

         Class C-Y Principal Reduction Amounts: For any Distribution Date, the
amounts by which the Class Principal Balances of the Class C-Y-1 and Class C-Y-2
Regular Interests, respectively, will be reduced on such Distribution Date by
the allocation of Realized Losses and the distribution of principal, determined
as described in Appendix 1.

         Class C-Y Regular Interests: The Class C-Y-1 and Class C-Y-2 Regular
Interests.

         Class C-Y-1 Principal Distribution Amount: For any Distribution Date,
the sum of (A) the excess, if any, of the Class C-Y-1 Principal Reduction Amount
for such Distribution Date over the principal portion of Realized Losses
allocated to the Class C-Y-1 Regular Interest on such Distribution Date and (B)
an amount equal to the lesser of (i) the portion, if any, of the Subsequent
Recoveries for Subgroup 1 for such Distribution Date not included in the Class
C-Z-1 Principal Distribution Amount pursuant to clause (B) of the definition
thereof and (ii) the amount of Realized Losses allocated to the Class C-Y-1
Regular Interest on previous Distribution Dates (the amount in this clause
(B)(ii) reduced by the amount, if any, calculated pursuant to this clause (B)
for prior Distribution Dates).

         Class C-Y-1 Regular Interest: The uncertificated undivided beneficial
interest in REMIC I which constitutes a REMIC I Regular Interest and is entitled
to distributions as set forth herein.

         Class C-Y-2 Principal Distribution Amount: For any Distribution Date,
the sum of (A) the excess, if any, of the Class C-Y-2 Principal Reduction Amount
for such Distribution Date over the principal portion of Realized Losses
allocated to the Class C-Y-2 Regular Interest on such Distribution Date and (B)
an amount equal to the lesser of (i) the portion, if any, of the Subsequent
Recoveries for Subgroup 2 for such Distribution Date not included in the Class
C-Z-2 Principal Distribution Amount pursuant to clause (B) of the definition
thereof and (ii) the amount of Realized Losses allocated to the Class C-Y-2
Regular Interest on previous Distribution Dates (the amount in this clause
(B)(ii) reduced by the amount, if any, calculated pursuant to this clause (B)
for prior Distribution Dates).

         Class C-Y-2 Regular Interest: The uncertificated undivided beneficial
interest in REMIC I which constitutes a REMIC I Regular Interest and is entitled
to distributions as set forth herein.

         Class C-Z Principal Reduction Amounts: For any Distribution Date, the
amounts by which the Class Principal Balances of the Class C-Z-1 and Class C-Z-2
Regular Interests, respectively, will be reduced on such Distribution Date by
the allocation of Realized Losses and the distribution of principal, which shall
be in each case the excess of (A) the sum of (x) the excess of the REMIC I
Available Distribution Amount for the related Subgroup (i.e. the "related
Subgroup" for the Class C-Z-1 Regular Interest is Subgroup 1 and the "related
Subgroup" for the Class C-Z-2 Regular Interest is Subgroup 2) over the sum of
the amounts thereof distributable (i) in the case of Subgroup 1, to the Class
P-M Regular Interest, (ii) in respect of interest on such Class C-Z Regular
Interest and the related Class C-Y Regular Interest, (iii) to such Class C-Z
Regular Interest and the related Class C-Y Regular Interest pursuant to clause
(c)(ii) of the definition of "REMIC I Distribution Amount" and (iv) in the case


                                       14
<PAGE>

of Subgroup 1, to the Class R-1 Residual Interest and (y) the amount of Realized
Losses allocable to principal for the related Subgroup (reduced, in the case of
Subgroup 1, by the portion of such amount allocable to the Class P-M Regular
Interest) over (B) the Class C-Y Principal Reduction Amount for the related
Subgroup.

         Class C-Z Regular Interests: The Class C-Z-1 and Class C-Z-2 Regular
Interests.

         Class C-Z-1 Principal Distribution Amount: For any Distribution Date,
the sum of (A) the excess, if any, of the Class C-Z-1 Principal Reduction Amount
for such Distribution Date over the principal portion of Realized Losses
allocated to the Class C-Z-1 Regular Interest on such Distribution Date and (B)
an amount equal to the lesser of (i) the Subsequent Recoveries for Subgroup 1
for such Distribution Date and (ii) the amount of Realized Losses allocated to
the Class C-Z-1 Regular Interest on previous Distribution Dates (the amount in
this clause (B)(ii) reduced by the amount, if any, calculated pursuant to this
clause (B) for prior Distribution Dates).

         Class C-Z-1 Regular Interest: The uncertificated undivided beneficial
interest in REMIC I which constitutes a REMIC I Regular Interest and is entitled
to distributions as set forth herein.

         Class C-Z-2 Principal Distribution Amount: For any Distribution Date,
the sum of (A) the excess, if any, of the Class C-Z-2 Principal Reduction Amount
for such Distribution Date over the principal portion of Realized Losses
allocated to the Class C-Z-2 Regular Interest on such Distribution Date and (B)
an amount equal to the lesser of (i) the Subsequent Recoveries for Subgroup 2
for such Distribution Date and (ii) the amount of Realized Losses allocated to
the Class C-Z-2 Regular Interest on previous Distribution Dates (the amount in
this clause (B)(ii) reduced by the amount, if any, calculated pursuant to this
clause (B) for prior Distribution Dates).

         Class C-Z-2 Regular Interest: The uncertificated undivided beneficial
interest in REMIC I which constitutes a REMIC I Regular Interest and is entitled
to distributions as set forth herein.

         Class Notional Amount: With respect to the Class 1-A-4 and Class 2-A-2
Certificates, the related notional amount for such Class, as specified herein
(e.g., the "Class Notional Amount" for the Class 1-A-4 Certificates, is the
Class 1-A-4 Notional Amount).

         Class P Certificates: The Certificates designated as "Class P" on the
face thereof in substantially the form attached hereto as Exhibit A.

         Class P Fraction: For each Class P Mortgage Loan, a fraction, the
numerator of which is 5.500% less the Pass-Through Rate on such Class P Mortgage
Loan and the denominator of which is 5.500%.

         Class P Mortgage Loan: Any Subgroup 1 Loan with a Pass-Through Rate of
less than 5.500% per annum.

                                       15
<PAGE>

         Class P-L Regular Interest: The uncertificated undivided beneficial
interest in REMIC II which constitutes a REMIC II Regular Interest and is
entitled to distributions as set forth herein.

         Class P-M Regular Interest: The uncertificated undivided beneficial
interest in REMIC I which constitutes a REMIC I Regular Interest and is entitled
to distributions as set forth herein.

         Class Principal Balance: For any Class of Certificates, or Class of
REMIC I or REMIC II Regular Interests and for the Class R-1 Residual Interest,
the applicable initial Class Principal Balance therefor set forth in the
Preliminary Statement hereto (or, in the case of the Class R Certificates, the
Class Principal Balance of the Class R-1 Residual Interest), corresponding to
the rights of such Class in payments of principal due to be passed through to
the Certificateholders or the Holders of the Regular Interests from principal
payments on the Mortgage Loans, the REMIC I Regular Interests or the REMIC II
Regular Interests, as applicable, as reduced from time to time by (x)
distributions of principal to the Certificateholders or the Holders of the REMIC
I or REMIC II Regular Interests of such Class and (y) the portion of Realized
Losses allocated to the Class Principal Balance of such Class pursuant to the
definition of "Realized Loss" (including amounts allocated as losses to the
Class B Certificates and the Class B-L Regular Interests pursuant to the fourth
paragraph of the definition of "Realized Loss") with respect to a given
Distribution Date. For any Distribution Date, the reduction of the Class
Principal Balance of any Class of Certificates and REMIC I or REMIC II Regular
Interests pursuant to the definition of "Realized Loss" shall be deemed
effective after the determination and distribution of principal on such Class
pursuant to the definitions of "REMIC I Distribution Amount," "REMIC II
Distribution Amount" and "REMIC III Distribution Amount."

         Notwithstanding the foregoing, (A) any amounts distributed in respect
of losses pursuant to paragraph (I)(c)(i) or (I)(c)(ii) of the definition of
"REMIC II Distribution Amount" shall not cause a reduction in the Class
Principal Balance of the Class P Certificates or the Class P-L Regular Interest,
(B) any amounts distributed in respect of principal losses pursuant to paragraph
(I)(c)(xxi) of the definition of "REMIC II Distribution Amount" shall not cause
a reduction in the Class Principal Balances of the REMIC II Regular Interests or
their Corresponding Classes, (C) any amounts distributed in respect of principal
losses pursuant to clause (c)(i) of the definition of "REMIC I Distribution
Amount" shall not cause a reduction in the Class Principal Balance of the Class
P-M Regular Interest, (D) any amounts distributed in respect of principal losses
pursuant to clause (c)(ii) of the definition of "REMIC I Distribution Amount"
shall not cause a reduction in the Class Principal Balances of the REMIC I
Regular Interests and (E) any amounts distributed to the REMIC I Regular
Interests in respect of Subsequent Recoveries shall not cause a reduction in the
Class Principal Balances of the REMIC I Regular Interests.

         In addition to the foregoing, on each Distribution Date, the Class
Principal Balance of the Class of Subordinate Certificates with the lowest
priority then outstanding shall be increased by an amount, for each Subgroup,
equal to the lesser of (i) the Subsequent Recoveries for such Distribution Date
for such Subgroup and (ii) the amount of Realized Losses for Mortgage Loans (or
portions of Mortgage Loans) in such Subgroup allocated to such Class on previous
Distribution Dates (the amount in this clause (ii) reduced by the amount, if
any, by which such Class Principal Balance has been increased on prior
Distribution Dates pursuant to this paragraph in respect of Subsequent
Recoveries for such Subgroup).

                                       16
<PAGE>

         The Class Principal Balance for the Class 1-A-1 Certificates shall be
referred to as the "Class 1-A-1 Principal Balance," the Class Principal Balance
for the Class 1-A-1-L Regular Interest shall be referred to as the "Class
1-A-1-L Principal Balance" and so on. The Class Principal Balances for the Class
1-A-4 and Class Class 2-A-2 Certificates shall each be zero.

         Class R Certificates: The Certificates designated as "Class R" on the
face thereof in substantially the form attached hereto as Exhibit B,
representing ownership of the Class R-1, Class R-2 and Class R-3 Residual
Interests, each of which Class of Residual Interests has been designated as the
sole class of "residual interest" in REMIC I, REMIC II and REMIC III,
respectively, pursuant to Section 2.06, Section 2.11 and Section 2.14,
respectively, for purposes of Section 860G(a)(2) of the Code.

         Class R Residual Interests: The Class R-1, Class R-2 and Class R-3
Residual Interests (which shall be transferable only as a unit evidenced by the
Class R Certificates, in accordance with the applicable provisions of Section
5.01).

         Class R-1 Residual Interest: The uncertificated undivided beneficial
interest in REMIC I which has been designated as the single class of "residual
interest" in REMIC I pursuant to Section 2.06. The Class R-1 Residual Interest,
together with the REMIC I Regular Interests, shall be deemed to be a separate
series of beneficial interests in the assets of the Trust consisting of the
REMIC I Assets pursuant to Section 3806(b)(2) of the Statutory Trust Statute.

         Class R-2 Residual Interest: The uncertificated undivided beneficial
interest in REMIC II which has been designated as the single class of "residual
interest" in REMIC II pursuant to Section 2.11. The Class R-2 Residual Interest,
together with the REMIC II Regular Interests, shall be deemed to be a separate
series of beneficial interests in the assets of the Trust consisting of the
REMIC II Assets pursuant to Section 3806(b)(2) of the Statutory Trust Statute.

         Clean-Up Call Percentage: 5%.

         Clearing Agency: An organization registered as a "clearing agency"
pursuant to Section 17A of the Securities Exchange Act of 1934, as amended,
which initially shall be DTC.

         Closing Date: February 24, 2004, which is the date of settlement of the
sale of the Certificates to the original purchasers thereof.

         Code: The Internal Revenue Code of 1986, as amended.

         Company: Washington Mutual Mortgage Securities Corp., a Delaware
corporation, or its successor-in-interest.

         Compensating Interest: For any Distribution Date, the lesser of (i) the
sum of (a) the aggregate Master Servicing Fee payable with respect to the
Mortgage Loans on such Distribution Date, (b) the aggregate Payoff Earnings with
respect to the Mortgage Loans for such Distribution Date and (c) the aggregate
Payoff Interest with respect to the Mortgage Loans for such Distribution Date
and (ii) the aggregate Uncollected Interest with respect to the Mortgage Loans
for such Distribution Date.

                                       17
<PAGE>

         Cooperative: A private, cooperative housing corporation which owns or
leases land and all or part of a building or buildings, including apartments,
spaces used for commercial purposes and common areas therein and whose board of
directors authorizes, among other things, the sale of Cooperative Stock.

         Cooperative Apartment: A dwelling unit in a multi-dwelling building
owned or leased by a Cooperative, which unit the Mortgagor has an exclusive
right to occupy pursuant to the terms of a proprietary lease or occupancy
agreement.

         Cooperative Lease: With respect to a Cooperative Loan, the proprietary
lease or occupancy agreement with respect to the Cooperative Apartment occupied
by the Mortgagor and relating to the related Cooperative Stock, which lease or
agreement confers an exclusive right to the holder of such Cooperative Stock to
occupy such apartment.

         Cooperative Loans: Any of the Mortgage Loans made in respect of a
Cooperative Apartment, evidenced by a Mortgage Note and secured by (i) a
Security Agreement, (ii) the related Cooperative Stock Certificate, (iii) an
assignment or mortgage of the Cooperative Lease, (iv) financing statements and
(v) a stock power (or other similar instrument), and ancillary thereto, a
Recognition Agreement, each of which was transferred and assigned to the Trust
pursuant to Section 2.04.

         Cooperative Stock: With respect to a Cooperative Loan, the single
outstanding class of stock, partnership interest or other ownership instrument
in the related Cooperative.

         Cooperative Stock Certificate: With respect to a Cooperative Loan, the
stock certificate or other instrument evidencing the related Cooperative Stock.

         Corporate Trust Office: The corporate trust office of the Trustee, at
which at any particular time its corporate trust business with respect to this
Agreement shall be administered, which office at the date of the execution of
this Agreement is located at 111 Wall Street, 14th Floor, Zone 3, New York, New
York 10005, Attention: Structured Finance Group, Washington Mutual 2004-S1.

         Corporation: Any Person (other than an individual, partnership, joint
venture or unincorporated organization) incorporated, associated, organized,
chartered or existing under the laws of any state or under the federal laws of
the United States of America; provided, that such Person have indefinite
existence under the law of its domicile.

         Corresponding Class: With respect to the Certificates and the REMIC II
Regular Interests, the "Corresponding Class" shall be as indicated in the
following table:

Class 1-A-1-L                Class 1-A-1
Class 1-A-2-L                Class 1-A-2
Class 1-A-3-L                Class 1-A-3
Class 1-A-5-L                Class 1-A-5
Class 1-A-6-L                Class 1-A-6
Class 1-A-7-L                Class 1-A-7
Class 1-A-8-L                Class 1-A-8
Class 1-A-9-L                Class 1-A-9


                                       18
<PAGE>

Class 1-A-10-L               Class 1-A-10
Class 1-A-11-L               Class 1-A-11
Class 1-A-12-L               Class 1-A-12
Class 2-A-1-L                Class 2-A-1
Class P-L                    Class P
Class B-1-L                  Class B-1
Class B-2-L                  Class B-2
Class B-3-L                  Class B-3
Class B-4-L                  Class B-4
Class B-5-L                  Class B-5
Class B-6-L                  Class B-6

         Credit Support Depletion Date: The first Distribution Date on which the
aggregate Class Principal Balance of the Class B Certificates has been or will
be reduced to zero as a result of principal distributions thereon and the
allocation of Realized Losses on such Distribution Date.

         Cumulative Carry-Forward Subsequent Recoveries Amount: For any
Distribution Date and any Subgroup, the sum of (i) the Carry-Forward Subsequent
Recoveries Amount for such Distribution Date for such Subgroup and (ii) the
Carry-Forward Subsequent Recoveries Amounts for prior Distribution Dates for
such Subgroup to the extent such Carry-Forward Subsequent Recoveries Amounts
have not been applied in reduction of Realized Losses on prior Distribution
Dates pursuant to the first paragraph of the definition of "Realized Loss"
herein.

         Curtailment: Any payment of principal on a Mortgage Loan, made by or on
behalf of the related Mortgagor, other than a Monthly Payment, a Prepaid Monthly
Payment or a Payoff, which is applied to reduce the outstanding principal
balance of the Mortgage Loan. (Prepayment penalties are not payments of
principal and hence Curtailments do not include prepayment penalties.)

         Curtailment Shortfall: For any Distribution Date and for any
Curtailment applied with a Monthly Payment in the Prior Period other than a
Prepaid Monthly Payment, an amount equal to one month's interest on such
Curtailment at the applicable Pass-Through Rate on such Mortgage Loan.

         Custodial Account for P&I: The Custodial Account for principal and
interest established and maintained by each Servicer pursuant to its Selling and
Servicing Contract and caused by the Master Servicer to be established and
maintained pursuant to Section 3.02 (a) with the corporate trust department of
the Trustee or another financial institution approved by the Master Servicer
such that the rights of the Master Servicer, the Trustee, the Trust, the
Delaware Trustee and the Certificateholders thereto shall be fully protected
against the claims of any creditors of the applicable Servicer and of any
creditors or depositors of the institution in which such account is maintained,
(b) within FDIC insured accounts (or other accounts with comparable insurance
coverage acceptable to the Rating Agencies) created, maintained and monitored by
a Servicer or (c) in a separate non-trust account without FDIC or other
insurance in an Eligible Institution. In the event that a Custodial Account for
P&I is established pursuant to clause (b) of the preceding sentence, amounts
held in such Custodial Account for P&I shall not exceed the level of deposit
insurance coverage on such account; accordingly, more than one Custodial Account


                                       19
<PAGE>

for P&I may be established. Any amount that is at any time not protected or
insured in accordance with the first sentence of this definition of "Custodial
Account for P&I" shall promptly be withdrawn from such Custodial Account for P&I
and be remitted to the Investment Account.

         Custodial Account for Reserves: The Custodial Account for Reserves
established and maintained by each Servicer pursuant to its Selling and
Servicing Contract and caused by the Master Servicer to be established and
maintained pursuant to Section 3.02 (a) with the corporate trust department of
the Trustee or another financial institution approved by the Master Servicer
such that the rights of the Master Servicer, the Trustee, the Trust, the
Delaware Trustee and the Certificateholders thereto shall be fully protected
against the claims of any creditors of the applicable Servicer and of any
creditors or depositors of the institution in which such account is maintained,
(b) within FDIC insured accounts (or other accounts with comparable insurance
coverage acceptable to the Rating Agencies) created, maintained and monitored by
a Servicer or (c) in a separate non-trust account without FDIC or other
insurance in an Eligible Institution. In the event that a Custodial Account for
Reserves is established pursuant to clause (b) of the preceding sentence,
amounts held in such Custodial Account for Reserves shall not exceed the level
of deposit insurance coverage on such account; accordingly, more than one
Custodial Account for Reserves may be established. Any amount that is at any
time not protected or insured in accordance with the first sentence of this
definition of "Custodial Account for Reserves" shall promptly be withdrawn from
such Custodial Account for Reserves and be remitted to the Investment Account.

         Custodial Agreement: The agreement, if any, between the Trustee and a
Custodian (or the Trustee, a Custodian and the Master Servicer) providing for
the safekeeping of the Mortgage Files on behalf of the Trust.

         Custodian: A custodian which is appointed by the Trustee with the
consent of the Master Servicer, as provided in Article II hereof, pursuant to a
Custodial Agreement. Any Custodian so appointed shall act as agent on behalf of
the Trustee. The reasonable fees and expenses of the Custodian shall be paid by
the Master Servicer. The Trustee shall remain at all times responsible under the
terms of this Agreement, notwithstanding the fact that certain duties have been
assigned to a Custodian.

         Cut-Off Date: February 1, 2004.

         Definitive Certificates: Certificates in definitive, fully registered
and certificated form.

         Delaware Trustee: Christiana Bank & Trust Company, or its
successor-in-interest as provided in Section 8.09, or any successor trustee
appointed as herein provided.

         Depositary Agreement: The Letter of Representations, dated February 23,
2004 by and among DTC, the Trust and the Trustee. The Trustee is authorized to
enter into the Depositary Agreement on behalf of the Trust.

         Destroyed Mortgage Note: A Mortgage Note the original of which (or a
portion of the original of which) was permanently lost or destroyed and has not
been replaced.

         Determination Date: A day not later than the 10th day preceding a
related Distribution Date, as determined by the Master Servicer.

                                       20
<PAGE>

         Disqualified Organization: Any Person which is not a Permitted
Transferee, but does not include any Pass-Through Entity which owns or holds a
Residual Certificate and of which a Disqualified Organization, directly or
indirectly, may be a stockholder, partner or beneficiary.

         Distribution Date: With respect to distributions on the REMIC I Regular
Interests, the REMIC II Regular Interests and the Certificates, the 25th day
(or, if such 25th day is not a Business Day, the Business Day immediately
succeeding such 25th day) of each month, with the first such date being March
25, 2004. The "related Due Date" for any Distribution Date is the Due Date
immediately preceding such Distribution Date.

         DTC: The Depository Trust Company.

         DTC Participant: A broker, dealer, bank, other financial institution or
other Person for whom DTC effects book-entry transfers and pledges of securities
deposited with DTC.

         Due Date: The day on which the Monthly Payment for each Mortgage Loan
is due.

         Eligible Institution: An institution having (i) the highest short-term
debt rating, and one of the two highest long-term debt ratings of the Rating
Agencies, (ii) with respect to any Custodial Account for P&I and special
Custodial Account for Reserves, an unsecured long-term debt rating of at least
one of the two highest unsecured long-term debt ratings of the Rating Agencies,
(iii) with respect to any Buydown Fund Account or Custodial Account which also
serves as a Buydown Fund Account, the highest unsecured long-term debt rating by
the Rating Agencies, or (iv) the approval of the Rating Agencies. Such
institution may be the Servicer if the applicable Selling and Servicing Contract
requires the Servicer to provide the Master Servicer with written notice on the
Business Day following the date on which the Servicer determines that such
Servicer's short-term debt and unsecured long-term debt ratings fail to meet the
requirements of the prior sentence. Notwithstanding the foregoing, Washington
Mutual Bank, FA shall be an "Eligible Institution" if the following conditions
are satisfied: (i) Washington Mutual Bank, FA is acting as Servicer, (ii) if S&P
is a Rating Agency as defined herein, the long-term unsecured debt obligations
of Washington Mutual Bank, FA are rated no lower than "A-" by S&P and the
short-term unsecured debt obligations of Washington Mutual Bank, FA are rated no
lower than "A-2" by S&P, (iii) if Fitch is a Rating Agency as defined herein,
the long-term unsecured debt obligations of Washington Mutual Bank, FA are rated
no lower than "A" by Fitch and the short-term unsecured debt obligations of
Washington Mutual Bank, FA are rated no lower than "F1" by Fitch and (iv) if
Moody's is a Rating Agency as defined herein, the long-term unsecured debt
obligations of Washington Mutual Bank, FA are rated no lower than "A2" by
Moody's and the short-term unsecured debt obligations of Washington Mutual Bank,
FA are rated no lower than "P-1" by Moody's; provided, that if the long-term or
short-term unsecured debt obligations of Washington Mutual Bank, FA are
downgraded by any of the Rating Agencies to a rating lower than the applicable
rating specified in this sentence, Washington Mutual Bank, FA shall cease to be
an "Eligible Institution" ten Business Days after notification of such
downgrade.

         Eligible Investments: Any one or more of the obligations or securities
listed below in which funds deposited in the Investment Account, the Certificate
Account, the Custodial Account for P&I and the Custodial Account for Reserves
may be invested:

                                       21
<PAGE>

         (i) Obligations of, or guaranteed as to principal and interest by, the
United States or any agency or instrumentality thereof when such obligations are
backed by the full faith and credit of the United States;

         (ii) Repurchase agreements on obligations described in clause (i) of
this definition of "Eligible Investments," provided that the unsecured
obligations of the party (including the Trustee in its commercial capacity)
agreeing to repurchase such obligations have at the time one of the two highest
short term debt ratings of the Rating Agencies and provided that such
repurchaser's unsecured long term debt has one of the two highest unsecured long
term debt ratings of the Rating Agencies;

         (iii) Federal funds, certificates of deposit, time deposits and
bankers' acceptances of any U.S. bank or trust company incorporated under the
laws of the United States or any state (including the Trustee in its commercial
capacity), provided that the debt obligations of such bank or trust company (or,
in the case of the principal bank in a bank holding company system, debt
obligations of the bank holding company) at the date of acquisition thereof have
one of the two highest short term debt ratings of the Rating Agencies and
unsecured long term debt has one of the two highest unsecured long term debt
ratings of the Rating Agencies;

         (iv) Obligations of, or obligations guaranteed by, any state of the
United States or the District of Columbia, provided that such obligations at the
date of acquisition thereof shall have the highest long-term debt ratings
available for such securities from the Rating Agencies;

         (v) Commercial paper of any corporation incorporated under the laws of
the United States or any state thereof, which on the date of acquisition has the
highest commercial paper rating of the Rating Agencies, provided that the
corporation has unsecured long term debt that has one of the two highest
unsecured long term debt ratings of the Rating Agencies;

         (vi) Securities (other than stripped bonds or stripped coupons) bearing
interest or sold at a discount that are issued by any corporation incorporated
under the laws of the United States or any state thereof and have the highest
long-term unsecured rating available for such securities from the Rating
Agencies; provided, however, that securities issued by any such corporation will
not be investments to the extent that investment therein would cause the
outstanding principal amount of securities issued by such corporation that are
then held as part of the Investment Account or the Certificate Account to exceed
20% of the aggregate principal amount of all Eligible Investments then held in
the Investment Account and the Certificate Account; and

         (vii) Units of taxable money market funds (which may be 12b-1 funds, as
contemplated under the rules promulgated by the Securities and Exchange
Commission under the Investment Company Act of 1940), which funds have the
highest rating available for such securities from the Rating Agencies or which
have been designated in writing by the Rating Agencies as Eligible Investments;



                                       22
<PAGE>

provided, however, that such obligation or security is held for a temporary
period pursuant to Section 1.860G-2(g)(1) of the Treasury Regulations, and that
such period can in no event exceed thirteen months.

         In no event shall an instrument be an Eligible Investment if such
instrument (a) evidences a right to receive only interest payments with respect
to the obligations underlying such instrument or (b) has been purchased at a
price greater than the outstanding principal balance of such instrument.

         ERISA: The Employee Retirement Income Security Act of 1974, as amended.

         ERISA Restricted Certificate: Any Senior Subordinate Certificate.

         Event of Default: Any event of default as specified in Section 7.01.

         Excess Liquidation Proceeds: With respect to any Distribution Date, the
sum of (i) the excess, if any, of aggregate Liquidation Proceeds received during
the Prior Period over the amount that would have been received if Payoffs had
been made with respect to such Mortgage Loans on the date such Liquidation
Proceeds were received and (ii) any Excess Subsequent Recoveries for any
Subgroup for such Distribution Date.

         Excess Subsequent Recoveries: For any Distribution Date and any
Subgroup, the excess, if any, of (i) amounts received by the Master Servicer
during the Prior Period (after deduction of amounts reimbursable under Section
3.05(a)(i) and (ii)) in connection with the liquidation of defaulted Mortgage
Loans in such Subgroup after such Mortgage Loans became Liquidated Mortgage
Loans over (ii) the Subsequent Recoveries for such Distribution Date for such
Subgroup.

         FDIC: Federal Deposit Insurance Corporation, or any successor thereto.

         FHA: Federal Housing Administration, or any successor thereto.

         Fannie Mae: The entity formerly known as the Federal National Mortgage
Association, or any successor thereto.

         Final Maturity Date: With respect to each Class of the REMIC I Regular
Interests, the REMIC II Regular Interests and the Certificates, the date set
forth in the applicable table contained in the Preliminary Statement hereto.

         Fitch: Fitch Ratings, provided that at any time it be a Rating Agency.

         Fraud Coverage: During the period prior to the first anniversary of the
Cut-Off Date, 2.00% of the aggregate principal balance of the Mortgage Loans as
of the Cut-Off Date (the "Initial Fraud Coverage"), reduced by Fraud Losses
allocated to the Certificates since the Cut-Off Date; during the period from the


                                       23
<PAGE>

first anniversary of the Cut-Off Date to (but not including) the fifth
anniversary of the Cut-Off Date, the amount of the Fraud Coverage on the most
recent previous anniversary of the Cut-Off Date (calculated in accordance with
the second sentence of this paragraph) reduced by Fraud Losses allocated to the
Certificates since such anniversary; and during the period on and after the
fifth anniversary of the Cut-Off Date, zero. On each anniversary of the Cut-Off
Date, the Fraud Coverage shall be reduced to the lesser of (i) on the first,
second, third and fourth anniversaries of the Cut-Off Date, 1.00% of the
aggregate principal balance of the Mortgage Loans as of the Due Date in the
preceding month and (ii) the excess of the Initial Fraud Coverage over
cumulative Fraud Losses allocated to the Certificates since the Cut-Off Date.

         The Fraud Coverage may be reduced upon written confirmation from the
Rating Agencies that such reduction will not adversely affect the then current
ratings assigned to the Certificates by the Rating Agencies.

         Fraud Loss: A Realized Loss (or portion thereof) with respect to a
Mortgage Loan arising from any action, event or state of facts with respect to
such Mortgage Loan which, because it involved or arose out of any dishonest,
fraudulent, criminal, negligent or knowingly wrongful act, error or omission by
the Mortgagor, originator (or assignee thereof) of such Mortgage Loan, Lender, a
Servicer or the Master Servicer, would result in an exclusion from, denial of,
or defense to coverage which otherwise would be provided by a Primary Insurance
Policy previously issued with respect to such Mortgage Loan.

         Freddie Mac: The entity formerly known as the Federal Home Loan
Mortgage Corporation, or any successor thereto.

         Indirect DTC Participants: Entities such as banks, brokers, dealers or
trust companies, that clear through or maintain a custodial relationship with a
DTC Participant, either directly or indirectly.

         Initial Custodial Agreement: The Custodial Agreement, dated the date
hereof, among the Trustee, the Master Servicer and the Initial Custodian.

         Initial Custodian: Washington Mutual Bank fsb, which has been
designated by the Company to be appointed by the Trustee to act as Custodian,
and whose appointment has been approved by the Master Servicer.

         Insurance Proceeds: Amounts paid or payable by the insurer under any
Primary Insurance Policy or any other insurance policy (including any
replacement policy permitted under this Agreement) covering any Mortgage Loan or
Mortgaged Property, including, without limitation, any hazard insurance policy
required pursuant to Section 3.07, any title insurance policy required pursuant
to Section 2.08 and any FHA insurance policy or VA guaranty.

         Interest Distribution Amount: For any Distribution Date, for any Class
of REMIC I Regular Interests, REMIC II Regular Interests and for the Class R-1
Residual Interest, the amount of interest accrued during the Prior Period (or,
in the case of the Class 1-A-3-L and Class 2-A-1-L Regular Interests, during the


                                       24
<PAGE>

period beginning on the 25th day of the preceding calendar month and ending on
the 24th day of the month of the Distribution Date), at the related Certificate
Interest Rate for such Class for such Distribution Date, on the respective Class
Principal Balance or Class Notional Amount immediately before such Distribution
Date, reduced by Uncompensated Interest Shortfall and the interest portion of
Realized Losses allocated to such Class pursuant to the definitions of
"Uncompensated Interest Shortfall" and "Realized Loss," respectively. The
computation of interest accrued shall be made on the basis of a 360-day year of
twelve 30-day months. The Interest Distribution Amounts for the Class P-L and
Class P-M Regular Interests shall equal zero.

         Interest Transfer Amount: On any Distribution Date for an
Undercollateralized Subgroup, an amount equal to one month's interest on the
applicable Principal Transfer Amount at 5.500% per annum if the
Undercollateralized Subgroup is Subgroup 1 and at 8.000% if the
Undercollateralized Subgroup is Subgroup 2, plus any interest accrued on the
Senior Certificates related to such Undercollateralized Subgroup remaining
unpaid from prior Distribution Dates.

         Investment Account: The commingled account (which shall be commingled
only with investment accounts related to series of pass-through certificates
with a class of certificates which has a rating equal to the highest of the
Ratings of the Certificates) maintained by the Master Servicer in the trust
department of the Investment Depository pursuant to Section 3.03 and which bears
a designation acceptable to the Rating Agencies.

         Investment Depository: JPMorgan Chase Bank, or another bank or trust
company designated from time to time by the Master Servicer. The Investment
Depository shall at all times be an Eligible Institution.

         Junior Subordinate Certificates: The Class B-4, Class B-5 and Class B-6
Certificates.

         Last Scheduled Distribution Date: With respect to any Class of
Certificates, the Final Maturity Date for such Class.

         Lender: An institution from which the Company purchased any Mortgage
Loans pursuant to a Selling and Servicing Contract.

         LIBOR: With respect to the first Distribution Date, 1.100%; and with
respect to each Distribution Date thereafter, the London Interbank Offered Rate
for one-month United States dollar deposits determined by the Master Servicer on
the LIBOR Determination Date on the basis of quotations provided by each of the
Reference Banks as of approximately 11:00 a.m. (London time) on the LIBOR
Determination Date as such quotations appear on The Bloomberg Professional
Service, as follows:

         (A) in the event that only one or none of the Reference Banks provides
such quotations, the higher of:

         (i) LIBOR as determined on the immediately preceding LIBOR
Determination Date (or, in the case of the first LIBOR Determination Date,
1.100%), and

         (ii) the Reserve Rate. The "Reserve Rate" will be the rate per annum
(rounded upward, if necessary, to the nearest multiple of 1/16th of 1%) that the
Master Servicer determines to be either

                                       25
<PAGE>

         (x) the arithmetic mean of the offered quotations that the leading
banks in New York City selected by the Master Servicer in its sole discretion
are then quoting on the relevant LIBOR Determination Date for one-month United
States dollar deposits to the principal London office of each of the Reference
Banks or those of them (being at least two in number) to which such offered
quotations are, in the opinion of the Master Servicer, being so made, or

         (y) in the event that the Master Servicer can determine no such
arithmetic mean, the arithmetic mean of the offered quotations that the leading
banks in New York City selected by the Master Servicer in its sole discretion
are quoting on such LIBOR Determination Date to leading European banks for
one-month United States dollar deposits, provided, however, that if the banks
selected by the Master Servicer are not then so quoting, LIBOR shall be as
determined on the immediately preceding LIBOR Determination Date (or, in the
case of the first LIBOR Determination Date, 1.100%);

         (B) otherwise, the arithmetic mean (rounded upward, if necessary, to
the nearest multiple of 1/16th of 1%) of such offered quotations

         the establishment of which, in each case, shall be final and binding in
the absence of manifest error.

         LIBOR Determination Date: With respect to interest paid on any
Distribution Date, the second day on which banks in London and New York City are
open for the transaction of international business prior to the 25th day of the
month preceding the Distribution Date.

         Liquidated Mortgage Loan: A Mortgage Loan (other than a Mortgage Loan
with respect to which a Payoff has been made) for which the Master Servicer or
the applicable Servicer has determined in accordance with its customary
servicing practices that it has received all amounts which it expects to recover
from or on account of such Mortgage Loan, whether from Insurance Proceeds,
Liquidation Proceeds or otherwise. For purposes of this definition, acquisition
of a Mortgaged Property by the Trust shall not constitute final liquidation of
the related Mortgage Loan.

         Liquidation Principal: The principal portion of Liquidation Proceeds
received (exclusive of the portion thereof attributable to distributions to the
Class P-L Regular Interest pursuant to clauses (I)(a)(i) and (II)(a)(i) of the
definition of "REMIC II Distribution Amount") with respect to each Mortgage Loan
which became a Liquidated Mortgage Loan (but not in excess of the principal
balance thereof) during the Prior Period.

         Liquidation Proceeds: Amounts after deduction of amounts reimbursable
under Section 3.05(a)(i) and (ii) received and retained in connection with the
liquidation of defaulted Mortgage Loans, whether through foreclosure or
otherwise, other than any Subsequent Recoveries.

         Loan-to-Value Ratio: The original principal amount of a Mortgage Loan
divided by the Original Value; provided, however, that references to "current


                                       26
<PAGE>

Loan-to-Value Ratio" or "Loan-to-Value Ratio as of the Cut-Off Date" in Section
2.08 shall be deemed to mean the then current Principal Balance of a Mortgage
Loan divided by the Original Value.

         Lockout Liquidation Amount: For any Distribution Date, the aggregate,
for each Subgroup 1 Loan which became a Liquidated Mortgage Loan during the
Prior Period, of the lesser of (i) the Lockout Percentage of the Principal
Balance of such Mortgage Loan (exclusive of the Class P Fraction of such balance
for any Class P Mortgage Loan) and (ii) the Lockout Percentage of the
Liquidation Principal with respect to such Mortgage Loan.

         Lockout Percentage: For any Distribution Date, the product of (i) the
aggregate Class Principal Balance of the Class 1-A-10, Class 1-A-11 and Class
1-A-12 Certificates, divided by the aggregate Principal Balance of the Subgroup
1 Loans (exclusive of the Class P Fraction of such balance for any Class P
Mortgage Loan), in each case immediately before such Distribution Date and (ii)
the Step Down Percentage.

         Lockout Priority Amount: For any Distribution Date, the sum of (i) the
Lockout Percentage of the Principal Payment Amount for Subgroup 1 (exclusive of
the portion thereof attributable to principal distributions to the Class P-L
Regular Interest pursuant to clause (I)(a)(i) and (II)(a)(i) of the definition
of "REMIC II Distribution Amount"), (ii) the Lockout Percentage of the Principal
Prepayment Amount for Subgroup 1 (exclusive of the portion thereof attributable
to principal distributions to the Class P-L Regular Interest pursuant to clause
(I)(a)(i) and (II)(a)(i) of the definition of "REMIC II Distribution Amount")
and (iii) the Lockout Liquidation Amount. The Lockout Priority Amount shall
equal zero until the Distribution Date in March 2009.

         Lowest Class B Owner: An owner unaffiliated with the Company or the
Master Servicer of (i) a 100% interest in the Class of Class B Certificates with
the lowest priority or (ii) a 100% interest in a class of securities
representing such interest in such Class specified in clause (i) above.

         Master Servicer: The Company, or any successor thereto appointed as
provided pursuant to Section 7.02, acting to service and administer the Mortgage
Loans pursuant to Section 3.01.

         Master Servicer Business Day: Any day other than a Saturday, a Sunday,
or a day on which banking institutions in Chicago, Illinois are authorized or
obligated by law or executive order to be closed.

         Master Servicing Fee: The fee charged by the Master Servicer for
supervising the mortgage servicing and advancing certain expenses, equal to a
per annum rate set forth for each Mortgage Loan in Exhibit D on the outstanding
Principal Balance of such Mortgage Loan, payable monthly from the Certificate
Account, the Investment Account or the Custodial Account for P&I.

         MERS: Mortgage Electronic Registration Systems, Inc., a Delaware
corporation, or any successor thereto.

         MERS Loan: Any Mortgage Loan registered on the MERS(R) System for which
MERS appears as the mortgagee of record on the Mortgage or on an assignment
thereof.



                                       27
<PAGE>

         MERS(R) System: The system of electronically recording transfers of
Mortgages maintained by MERS.

         MIN: The Mortgage Identification Number for a MERS Loan.

         MOM Loan: A Mortgage Loan that was registered on the MERS(R) System at
the time of origination thereof and for which MERS appears as the mortgagee of
record on the Mortgage.

         Monthly P&I Advance: An advance of funds by the Master Servicer
pursuant to Section 4.02 or a Servicer pursuant to its Selling and Servicing
Contract to cover delinquent principal and interest installments.

         Monthly Payment: The scheduled payment of principal and interest on a
Mortgage Loan (including any amounts due from a Buydown Fund, if any) which is
due on the related Due Date for such Mortgage Loan.

         Moody's: Moody's Investors Service, Inc., provided that at any time it
be a Rating Agency.

         Mortgage: The mortgage, deed of trust or other instrument securing a
Mortgage Note.

         Mortgage File: The following documents or instruments with respect to
each Mortgage Loan transferred and assigned by the Company pursuant to Section
2.04, (X) with respect to each Mortgage Loan that is not a Cooperative Loan:

         (i) The original Mortgage Note endorsed (A) in blank, without recourse,
or (B) to "Citibank, N.A., as Custodian/Trustee, without recourse" or to "WaMu
Mortgage Pass-Through Certificates Series 2004-S1 Trust, without recourse" and
all intervening endorsements evidencing a complete chain of endorsements from
the originator to the Trustee or the Trust, as applicable, or, in the event of
any Destroyed Mortgage Note, a copy or a duplicate original of the Mortgage Note
(or portion thereof, as applicable), together with an original lost note
affidavit from the originator of the Mortgage Loan or the Company (or any
affiliate of the Company from which the Company acquired the Mortgage Loan), as
applicable, stating that the original Mortgage Note (or portion thereof, as
applicable) was lost, misplaced or destroyed, together with a copy of the
Mortgage Note (or portion thereof, as applicable); provided, however, that in
the event the Company acquired the Mortgage Loan from an affiliate of the
Company, then the Mortgage Note (or portion thereof, as applicable) need not be
endorsed in blank or to Citibank, N.A. or the Trust as provided above (but, if
not so endorsed, shall be made payable to, or endorsed by the mortgagee named
therein to, such affiliate of the Company);

         (ii) The Buydown Agreement, if applicable;

         (iii) A Mortgage that is either

                                       28
<PAGE>

         (1) (x) the original recorded Mortgage with evidence of recording
thereon for the jurisdiction in which the Mortgaged Property is located (which
original recorded Mortgage, in the case of a MOM Loan, shall set forth the MIN
and shall indicate that the Mortgage Loan is a MOM Loan), (y) unless the
Mortgage Loan is a MERS Loan, an original Mortgage assignment thereof duly
executed and acknowledged in recordable form (A) in blank or (B) to "Citibank,
N.A., as Custodian/Trustee," or to "WaMu Mortgage Pass-Through Certificates
Series 2004-S1 Trust," and (z) unless the Mortgage Loan is a MOM Loan, recorded
originals of all intervening assignments evidencing a complete chain of
assignment, from the originator to the name holder or the payee endorsing the
related Mortgage Note (or, in the case of a MERS Loan other than a MOM Loan,
from the originator to MERS); or

         (2) (x) a copy (which may be in electronic form) of the Mortgage (which
Mortgage, in the case of a MOM Loan, shall set forth the MIN and shall indicate
that the Mortgage Loan is a MOM Loan) which represents a true and correct
reproduction of the original Mortgage and which has either been certified (i) on
the face thereof by the public recording office in the appropriate jurisdiction
in which the Mortgaged Property is located, or (ii) by the originator, the
related Lender or the escrow or title company which provided closing services in
connection with such Mortgage Loan as a true and correct copy the original of
which has been sent for recordation, (y) unless the Mortgage Loan is a MERS
Loan, an original Mortgage assignment thereof duly executed and acknowledged in
recordable form (A) in blank or (B) to "Citibank, N.A., as Custodian/Trustee,"
or to "WaMu Mortgage Pass-Through Certificates Series 2004-S1 Trust," and (z)
unless the Mortgage Loan is a MOM Loan, true and correct copies, certified by
the applicable county recorder or by the originator or Lender as described
above, of all intervening assignments evidencing a complete chain of assignment
from the originator to the name holder or the payee endorsing the related
Mortgage Note (or, in the case of a MERS Loan other than a MOM Loan, from the
originator to MERS);

         provided, however, that in the event the Company acquired the Mortgage
Loan from an affiliate of the Company, then the Mortgage File need not include a
Mortgage assignment executed in blank or to Citibank, N.A. or the Trust as
provided in clause (X)(iii)(1)(y) or (X)(iii)(2)(y) above, as applicable (but
the Mortgage File shall, unless the Mortgage Loan was originated by such
affiliate of the Company, include an intervening Mortgage assignment to such
affiliate as provided in clause (X)(iii)(1)(z) or (X)(iii)(2)(z) above, as
applicable); and

         (iv) For any Mortgage Loan that has been modified or amended, the
original instrument or instruments effecting such modification or amendment;

         and (Y) with respect to each Cooperative Loan:

         (i) the original Mortgage Note endorsed (A) in blank, without recourse,
or (B) to "Citibank, N.A., as Custodian/Trustee, without recourse" or to "WaMu


                                       29
<PAGE>

Mortgage Pass-Through Certificates Series 2004-S1 Trust, without recourse" and
all intervening endorsements evidencing a complete chain of endorsements, from
the originator to the Trustee or the Trust, as applicable, or, in the event of
any Destroyed Mortgage Note, a copy or a duplicate original of the Mortgage Note
(or portion thereof, as applicable), together with an original lost note
affidavit from the originator of the Cooperative Loan or the Company (or any
affiliate of the Company from which the Company acquired the Mortgage Loan), as
applicable, stating that the original Mortgage Note (or portion thereof, as
applicable) was lost, misplaced or destroyed, together with a copy of the
Mortgage Note (or portion thereof, as applicable); provided, however, that in
the event the Company acquired the Cooperative Loan from an affiliate of the
Company, then the Mortgage Note need not be endorsed in blank or to Citibank,
N.A. or the Trust as provided above (but, if not so endorsed, shall be made
payable to, or endorsed by the originator or successor lender named therein to,
such affiliate of the Company);

         (ii) A counterpart of the Cooperative Lease and the Assignment of
Proprietary Lease to the originator of the Cooperative Loan;

         (iii) The related Cooperative Stock Certificate, representing the
related Cooperative Stock pledged with respect to such Cooperative Loan,
together with an undated stock power (or other similar instrument) executed in
blank;

         (iv) The Recognition Agreement;

         (v) The Security Agreement;

         (vi) Copies of the original UCC financing statement, and any
continuation statements, filed by the originator of such Cooperative Loan as
secured party, each with evidence of recording thereof, evidencing the interest
of the originator under the Security Agreement and the Assignment of Proprietary
Lease;

         (vii) Copies of the filed UCC assignments or amendments of the security
interest referenced in clause (vi) above showing an unbroken chain of title from
the originator to the Trust, each with evidence of recording thereof, evidencing
the interest of the assignee under the Security Agreement and the Assignment of
Proprietary Lease;

         (viii) An executed assignment of the interest of the originator in the
Security Agreement, the Assignment of Proprietary Lease and the Recognition
Agreement, showing an unbroken chain of title from the originator to the Trust;
and

         (ix) For any Cooperative Loan that has been modified or amended, the
original instrument or instruments effecting such modification or amendment;

                                       30
<PAGE>

         provided, however, that in the event the Company acquired the
Cooperative Loan from an affiliate of the Company, then the Mortgage File need
not include (1) a UCC assignment or amendment of the security interest
referenced in clause (Y)(vi) above to the Trust as provided in clause (Y)(vii)
above (but the Mortgage File shall, unless the Cooperative Loan was originated
by such affiliate of the Company, include a UCC assignment or amendment of such
security interest to such affiliate) or (2) an assignment of the interest of the
originator in the Security Agreement, the Assignment of Proprietary Lease and
the Recognition Agreement to the Trust as provided in clause (Y)(viii) above
(but the Mortgage File shall, unless the Cooperative Loan was originated by such
affiliate of the Company, include an assignment of such interest to such
affiliate).

         Mortgage Interest Rate: For any Mortgage Loan, the per annum rate at
which interest accrues on such Mortgage Loan pursuant to the terms of the
related Mortgage Note.

         Mortgage Loan Schedule: The schedule, as amended from time to time, of
Mortgage Loans attached hereto as Exhibit D, which shall set forth as to each
Mortgage Loan the following, among other things:

         (i) its loan number,

         (ii) the address of the Mortgaged Property,

         (iii) the name of the Mortgagor,

         (iv) the Original Value of the property subject to the Mortgage,

         (v) the Principal Balance as of the Cut-Off Date,

         (vi) the Mortgage Interest Rate borne by the Mortgage Note,

         (vii) whether a Primary Insurance Policy is in effect as of the Cut-Off
Date, and, if so, whether such Primary Insurance Policy is a Special Primary
Insurance Policy,

         (viii) the maturity of the Mortgage Note,

         (ix) the Servicing Fee and the Master Servicing Fee, and

         (x) whether it imposes penalties for early prepayments.

         Mortgage Loans: The mortgage loans and cooperative loans (if any)
listed on the Mortgage Loan Schedule and transferred and assigned to the Trust
pursuant hereto. With respect to each Mortgage Loan that is a Cooperative Loan,
"Mortgage Loan" shall include, but not be limited to, the related Mortgage Note,
Security Agreement, Assignment of Proprietary Lease, Recognition Agreement,
Cooperative Stock Certificate and Cooperative Lease and, with respect to each
Mortgage Loan other than a Cooperative Loan, "Mortgage Loan" shall include, but
not be limited to the Mortgages and the related Mortgage Notes.



                                       31
<PAGE>

         Mortgage Note: The note or other evidence of the indebtedness of a
Mortgagor under a Mortgage Loan.

         Mortgage Pool: All of the Mortgage Loans.

         Mortgage Pool Assets: The following assets: (i) the Mortgage Loans and
all rights pertaining thereto; (ii) such assets as from time to time may be held
by the Trust (or its duly appointed agent) in the Certificate Account or the
Investment Account (except amounts representing the Master Servicing Fee or the
Servicing Fee); (iii) such assets as from time to time may be held by Servicers
in a Custodial Account for P&I or Custodial Account for Reserves or a Buydown
Fund Account related to the Mortgage Loans (except amounts representing the
Master Servicing Fee or the Servicing Fee); (iv) property which secured a
Mortgage Loan and which has been acquired by foreclosure or deed in lieu of
foreclosure or, in the case of a Cooperative Loan, a similar form of conversion,
after the Cut-Off Date; and (v) amounts paid or payable by the insurer under any
FHA insurance policy or any Primary Insurance Policy and proceeds of any VA
guaranty and any other insurance policy related to any Mortgage Loan or the
Mortgage Pool.

         Mortgaged Property: With respect to any Mortgage Loan, other than a
Cooperative Loan, the real property, together with improvements thereto, and,
with respect to any Cooperative Loan, the related Cooperative Stock and
Cooperative Lease, securing the indebtedness of the Mortgagor under the related
Mortgage Loan. "Mortgaged Property" shall also refer to property which once
secured the indebtedness of a Mortgagor under the related Mortgage Loan but
which was acquired by the Trust upon foreclosure or other liquidation of such
Mortgage Loan.

         Mortgagor: The obligor on a Mortgage Note.

         Nonrecoverable Advance: With respect to any Mortgage Loan, any advance
which the Master Servicer shall determine to be a Nonrecoverable Advance
pursuant to Section 4.03 and which was, or is proposed to be, made by (i) the
Master Servicer or (ii) a Servicer pursuant to its Selling and Servicing
Contract.

         Non-U.S. Person: A Person that is not a U.S. Person.

         Notice Addresses: (a) In the case of the Company, 75 North Fairway
Drive, Vernon Hills, Illinois 60061, Attention: Master Servicing Department,
with a copy to: Washington Mutual Legal Department, 1201 Third Avenue, WMT 1706,
Seattle, WA 98101, Attention: WMMSC, or such other address as may hereafter be
furnished to the Trustee in writing by the Company, (b) in the case of the
Trustee, at its Corporate Trust Office, or such other address as may hereafter
be furnished to the Master Servicer in writing by the Trustee, (c) in the case
of the Delaware Trustee, 1314 King Street, Wilmington, DE 19801, or such other
address as may hereafter be furnished to the Master Servicer in writing by the
Delaware Trustee, (d) in the case of the Trust, c/o Citibank, N.A., at the
Corporate Trust Office, or such other address as may hereafter be furnished to
the Master Servicer in writing by the Trustee, (e) in the case of the
Certificate Registrar, at its Corporate Trust Office, or such other address as
may hereafter be furnished to the Trustee in writing by the Certificate
Registrar, (f) in the case of Moody's, 99 Church Street, New York, New York
10007, Attention: Monitoring, or such other address as may hereafter be
furnished to the Trustee and Master Servicer in writing by Moody's and (g) in
the case of Fitch, 1 State Street Plaza, New York, New York, 10004, Attention:


                                       32
<PAGE>

Glenn Costello, or such other address as may hereafter be furnished to the
Trustee and Master Servicer in writing by Fitch.

         OTS: The Office of Thrift Supervision, or any successor thereto.

         Officer's Certificate: A certificate signed by the Chairman of the
Board, the President, a Vice President, or the Treasurer of the Master Servicer
and delivered to the Trustee or the Delaware Trustee, as applicable.

         Opinion of Counsel: A written opinion of counsel, who shall be
reasonably acceptable to the Trustee or the Delaware Trustee, as applicable, and
who may be counsel (including in-house counsel) for the Company or the Master
Servicer.

         Original Trust Agreement: The Trust Agreement, dated as of February 1,
2004, between the Company and the Delaware Trustee, providing for the creation
of the Trust.

         Original Value: With respect to any Mortgage Loan other than a Mortgage
Loan originated for the purpose of refinancing an existing mortgage debt, the
lesser of (a) the Appraised Value (if any) of the Mortgaged Property at the time
the Mortgage Loan was originated or (b) the purchase price paid for the
Mortgaged Property by the Mortgagor. With respect to a Mortgage Loan originated
for the purpose of refinancing existing mortgage debt, the Original Value shall
be equal to the Appraised Value of the Mortgaged Property.

         Overcollateralized Subgroup: Either of Subgroup 1 or Subgroup 2, if on
any Distribution Date such Subgroup is not an Undercollateralized Subgroup and
the other Subgroup is an Undercollateralized Subgroup.

         Ownership Interest: With respect to any Residual Certificate, any
ownership or security interest in such Residual Certificate, including any
interest in a Residual Certificate as the Holder thereof and any other interest
therein whether direct or indirect, legal or beneficial, as owner or as pledgee.

         Pass-Through Entity: Any regulated investment company, real estate
investment trust, common trust fund, partnership, trust or estate, and any
organization to which Section 1381 of the Code applies.

         Pass-Through Rate: For each Mortgage Loan, a per annum rate equal to
the Mortgage Interest Rate for such Mortgage Loan less the per annum percentage
rates related to each of (i) the Servicing Fee for such Mortgage Loan, (ii) the
Master Servicing Fee for such Mortgage Loan and (iii) if such Mortgage Loan was
covered by a Special Primary Insurance Policy on the Closing Date (even if no
longer so covered), the applicable Special Primary Insurance Premium. For each
Mortgage Loan, any calculation of monthly interest at such rate shall be based
upon annual interest at such rate (computed on the basis of a 360-day year of
twelve 30-day months) on the unpaid Principal Balance of such Mortgage Loan
divided by twelve, and any calculation of interest at such rate by reason of a
Payoff shall be based upon annual interest at such rate on the outstanding
Principal Balance of such Mortgage Loan multiplied by a fraction, the numerator
of which is the number of days elapsed from the Due Date of the last scheduled


                                       33
<PAGE>

payment of principal and interest to, but not including, the date of such
Payoff, and the denominator of which is (a) for Payoffs received on a Due Date,
360, and (b) for all other Payoffs, 365.

         Paying Agent: Any paying agent appointed by the Trustee pursuant to
Section 8.12.

         Payoff: Any Mortgagor payment of principal on a Mortgage Loan equal to
the entire outstanding Principal Balance of such Mortgage Loan, if received in
advance of the last scheduled Due Date for such Mortgage Loan and accompanied by
an amount of interest equal to accrued unpaid interest on the Mortgage Loan to
the date of such payment-in-full. (Prepayment penalties are not payments of
principal and hence Payoffs do not include prepayment penalties.)

         Payoff Earnings: For any Distribution Date with respect to each
Mortgage Loan on which a Payoff was received by the Master Servicer during the
Payoff Period, the aggregate of the interest earned by the Master Servicer from
investment of each such Payoff from the date of receipt of such Payoff until the
Business Day immediately preceding the related Distribution Date (net of
investment losses).

         Payoff Interest: For any Distribution Date with respect to a Mortgage
Loan for which a Payoff was received on or after the first calendar day of the
month of such Distribution Date and before the 15th calendar day of such month,
an amount of interest thereon at the applicable Pass-Through Rate from the first
day of the month of distribution through the day of receipt thereof; to the
extent (together with Payoff Earnings and the aggregate Master Servicing Fee)
not required to be distributed as Compensating Interest on such Distribution
Date, Payoff Interest shall be payable to the Master Servicer as additional
servicing compensation.

         Payoff Period: For the first Distribution Date, the period from the
Cut-Off Date through March 14, 2004, inclusive; and for any Distribution Date
thereafter, the period from the 15th day of the Prior Period through the 14th
day of the month of such Distribution Date, inclusive.

         Percentage Interest: (a) With respect to the right of each Certificate
of a particular Class in the distributions allocated to such Class, "Percentage
Interest" shall mean the percentage equal to:

         (i) with respect to any Certificate (other than the Residual, Class
1-A-4 and Class 2-A-2 Certificates), its Certificate Principal Balance divided
by the applicable Class Principal Balance;

         (ii) with respect to any Class 1-A-4 and Class 2-A-2 Certificate, the
portion of the respective Class Notional Amount evidenced by such Certificate
divided by the respective Class Notional Amount; and

         (iii) with respect to any Residual Certificate, the percentage set
forth on the face of such Certificate.

         (b) With respect to the rights of each Certificate in connection with
Sections 5.09, 7.01, 8.01(c), 8.02, 8.07, 10.01 and 10.03, "Percentage Interest"
shall mean the percentage equal to:

                                       34
<PAGE>

         (i) with respect to any Certificate (other than the Residual, Class
1-A-4 and Class 2-A-2 Certificates), the product of (x) ninety-eight percent
(98%) and (y) its Certificate Principal Balance divided by the Aggregate
Certificate Principal Balance of the Certificates; provided, however, that the
percentage in clause (x) above shall be increased by one percent (1%) upon the
retirement of each Class of Certificates referenced in the parenthetical above
(other than the Residual Certificates);

         (ii) with respect to any Class 1-A-4 or Class 2-A-2 Certificate, one
percent (1%) of such Certificate's Percentage Interest as calculated by
paragraph (a)(ii) of this definition; and

         (iii) with respect to any Residual Certificate, zero.

         Permitted Transferee: With respect to the holding or ownership of any
Residual Certificate, any Person other than (i) the United States, a State or
any political subdivision thereof, or any agency or instrumentality of any of
the foregoing, (ii) a foreign government, International Organization or any
agency or instrumentality of either of the foregoing, (iii) an organization
(except certain farmers' cooperatives described in Code Section 521) which is
exempt from the taxes imposed by Chapter 1 of the Code (unless such organization
is subject to the tax imposed by Section 511 of the Code on unrelated business
taxable income), (iv) rural electric and telephone cooperatives described in
Code Section 1381(a)(2)(C), (v) any "electing large partnership" as defined in
Section 775(a) of the Code, (vi) any Person from whom the Trustee has not
received an affidavit to the effect that it is not a "disqualified organization"
within the meaning of Section 860E(e)(5) of the Code, and (vii) any other Person
so designated by the Company based upon an Opinion of Counsel that the transfer
of an Ownership Interest in a Residual Certificate to such Person may cause
REMIC I, REMIC II or REMIC III to fail to qualify as a REMIC at any time that
the Certificates are outstanding. The terms "United States," "State" and
"International Organization" shall have the meanings set forth in Code Section
7701 or successor provisions. A corporation shall not be treated as an
instrumentality of the United States or of any State or political subdivision
thereof if all of its activities are subject to tax, and, with the exception of
the Freddie Mac, a majority of its board of directors is not selected by such
governmental unit.

         Person: Any individual, corporation, limited liability company,
partnership, joint venture, association, joint-stock company, trust,
unincorporated organization or government or any agency or political subdivision
thereof.

         Planned Principal Balance: With respect to the Class 1-A-1, Class 1-A-2
and Class 1-A-3 Certificates, the aggregate amount set forth in the table
attached as Appendix D to the Prospectus, for the applicable Distribution Date,
under the heading "Class 1-A-1, Class 1-A-2 and Class 1-A-3 Aggregate Planned
Principal Balance."

         Prepaid Monthly Payment: Any Monthly Payment received prior to its
scheduled Due Date, which is intended to be applied to a Mortgage Loan on its
scheduled Due Date and held in the related Custodial Account for P&I until the
Withdrawal Date following its scheduled Due Date.



                                       35
<PAGE>

         Primary Insurance Policy: A policy of mortgage guaranty insurance, if
any, on an individual Mortgage Loan or on pools of mortgage loans that include
an individual Mortgage Loan, providing coverage as required by Section 2.08(xi)
(including any Special Primary Insurance Policy).

         Principal Balance: Except as used in Sections 2.07, 3.09 and 9.01 and
for purposes of the definition of Purchase Price, at the time of any
determination, the principal balance of a Mortgage Loan remaining to be paid at
the close of business on the Cut-Off Date, after application of all scheduled
principal payments due on or before the Cut-Off Date, whether or not received,
reduced by all amounts distributed or (except when such determination occurs
earlier in the month than the Distribution Date) to be distributed to
Certificateholders through the Distribution Date in the month of determination
that are reported as allocable to principal of such Mortgage Loan.

         For purposes of the definition of Purchase Price and as used in
Sections 2.07, 3.09 and 9.01, at the time of any determination, the principal
balance of a Mortgage Loan remaining to be paid at the close of business on the
Cut-Off Date, after deduction of all scheduled principal payments due on or
before the Cut-Off Date, whether or not received, reduced by all amounts
distributed or to be distributed to Certificateholders through the Distribution
Date in the month of determination that are reported as allocable to principal
of such Mortgage Loan.

         In the case of a Substitute Mortgage Loan, "Principal Balance" shall
mean, at the time of any determination, the principal balance of such Substitute
Mortgage Loan transferred to the Trust, on the date of substitution, reduced by
all amounts distributed or to be distributed to Certificateholders through the
Distribution Date in the month of determination that are reported as allocable
to principal of such Substitute Mortgage Loan.

         The Principal Balance of a Mortgage Loan (including a Substitute
Mortgage Loan) shall not be adjusted solely by reason of any bankruptcy or
similar proceeding or any moratorium or similar waiver or grace period. Whenever
a Realized Loss has been incurred with respect to a Mortgage Loan during a
calendar month, the Principal Balance of such Mortgage Loan shall be reduced by
the amount of such Realized Loss as of the Due Date next following the end of
such calendar month.

         Principal Payment: Any payment of principal on a Mortgage Loan other
than a Principal Prepayment.

         Principal Payment Amount: For any Distribution Date and for either
Subgroup, the sum with respect to the Mortgage Loans (or portions of Mortgage
Loans) in such Subgroup of (i) the scheduled principal payments on such Mortgage
Loans due on the related Due Date, (ii) the principal portion of proceeds
received with respect to any such Mortgage Loan which was purchased or
repurchased pursuant to a Purchase Obligation or as permitted by this Agreement
during the Prior Period and (iii) any other unscheduled payments of principal
which were received with respect to any such Mortgage Loan during the Prior
Period, other than Payoffs, Curtailments, Liquidation Principal and Subsequent
Recoveries.



                                       36
<PAGE>

         Principal Prepayment: Any payment of principal on a Mortgage Loan which
constitutes a Payoff or a Curtailment.

         Principal Prepayment Amount: For any Distribution Date and for either
Subgroup, the sum with respect to the Mortgage Loans (or portions of Mortgage
Loans) in such Subgroup of (i) Curtailments received during the Prior Period
from such Mortgage Loans and (ii) Payoffs received during the Payoff Period from
such Mortgage Loans.

         Principal Transfer Amount: For any Distribution Date for an
Undercollateralized Subgroup, the excess, if any, of the aggregate Class
Principal Balance of the Class A-L Regular Interests related to such
Undercollateralized Subgroup over the aggregate Principal Balance of the
Mortgage Loans (or portions of Mortgage Loans) in such Subgroup (in the case of
Subgroup 1, less the applicable Class P Fraction thereof with respect to any
Class P Mortgage Loans in such Subgroup), in each case immediately prior to such
Distribution Date.

         Prior Period: With respect to any Distribution Date, the calendar month
immediately preceding such Distribution Date.

         Pro Rata Allocation: The allocation of the principal portion of
Realized Losses to all Classes of the Class A-L Regular Interests, on the one
hand, and the Class B-L Regular Interests, on the other hand, pro rata according
to their respective aggregate Class Principal Balances, in reduction thereof, in
the manner provided in the succeeding paragraphs of this definition (except if
the loss is recognized with respect to a Class P Mortgage Loan, in which case
the applicable Class P Fraction of such loss shall first be allocated to the
Class P-L Regular Interest, and the remainder of such loss shall be allocated as
set forth above), and the allocation of the interest portion of Realized Losses
to all Classes of REMIC II Regular Interests (other than the Class P-L Regular
Interest), pro rata according to the amount of interest accrued but unpaid on
each such Class, in reduction thereof, and then to the Class A-L Regular
Interests, on the one hand, and the Class B-L Regular Interests, on the other
hand, pro rata according to their respective aggregate Class Principal Balances,
in reduction thereof, in the manner provided in the succeeding paragraphs of
this definition.

         The principal portion of a Realized Loss on any Mortgage Loan allocated
to the Class A-L Regular Interests pursuant to this definition of "Pro Rata
Allocation" shall be allocated in reduction of the respective Class Principal
Balances of the Subgroup 1-L and Subgroup 2-L Regular Interests as follows:

         (i) with respect to any Realized Loss on a Mortgage Loan with a
Pass-Through Rate of 5.500% or less, to the Subgroup 1-L Regular Interests only;

         (ii) with respect to any Realized Loss on a Mortgage Loan with a
Pass-Through Rate greater than 5.500%, a fraction equal to (a) 8.000 minus the
Pass-Through Rate of that Mortgage Loan, divided by (b) 2.5 to the Subgroup 1-L
Regular Interests and the remainder to the Subgroup 2-L Regular Interests, pro
rata according to their respective Class Principal Balances;

         The total amount of the principal portion of Realized Losses allocated
to the Class B-L Regular Interests pursuant to this definition of "Pro Rata


                                       37
<PAGE>

Allocation" shall be allocated to each Class of Class B-L Regular Interests in
reduction of the respective Class Principal Balances thereof pro rata according
to the Class Principal Balances thereof.

         Prospectus: The Prospectus, dated February 10, 2004, and the Prospectus
Supplement, dated February 20, 2004, of the Company.

         Purchase Obligation: An obligation of the Company to repurchase
Mortgage Loans under the circumstances and in the manner provided in Section
2.07 or Section 2.08.

         Purchase Price: With respect to any Mortgage Loan to be purchased
pursuant to a Purchase Obligation or pursuant to Section 3.01, an amount equal
to the sum of (i) the Principal Balance thereof, (ii) unpaid accrued interest
thereon, if any, during the calendar month in which the date of purchase occurs
to the last day of such month at a rate equal to the applicable Pass-Through
Rate and (iii) with respect to any Mortgage Loan to be purchased pursuant to
Section 2.08, any costs and damages incurred by the Trust in connection with any
violation by such Mortgage Loan of any predatory and abusive lending laws, to
the extent such costs and damages result from a breach of the representation and
warranty made by the Company pursuant to clause (viii) of Section 2.08;
provided, however, that to the extent that such costs and damages constitute a
set-off against the principal balance of the Mortgage Loan, such costs and
damages will not be paid pursuant to this clause (iii), and the amount paid
pursuant to clause (i) above will be calculated without regard to such set-off;
provided, further, that no Mortgage Loan shall be purchased or required to be
purchased pursuant to Section 2.08, or more than two years after the Closing
Date under Section 2.07, unless (a) the Mortgage Loan to be purchased is in
default, or default is in the judgment of the Company reasonably imminent, or
(b) the Company, at its expense, delivers to the Trustee an Opinion of Counsel
addressed to the Trust and the Trustee to the effect that the purchase of such
Mortgage Loan will not give rise to a tax on a prohibited transaction, as
defined in Section 860F(a) of the Code.

         Qualified Insurer: A mortgage guaranty insurance company duly qualified
as such under the laws of the states in which the Mortgaged Properties are
located if such qualification is necessary to issue the applicable insurance
policy or bond, duly authorized and licensed in such states to transact the
applicable insurance business and to write the insurance provided by the Primary
Insurance Policies and approved as an insurer by the Master Servicer. A
Qualified Insurer must have the rating required by the Rating Agencies.

         Rating Agency: Initially, each of Moody's and Fitch and thereafter,
each nationally recognized statistical rating organization that has rated the
Certificates at the request of the Company, or their respective successors in
interest.

         Ratings: As of any date of determination, the ratings, if any, of the
Certificates as assigned by the applicable Rating Agencies.

         Realized Loss: For any Distribution Date, with respect to any Mortgage
Loan which became a Liquidated Mortgage Loan during the related Prior Period,
the sum of (i) the principal balance of such Mortgage Loan remaining outstanding
and the principal portion of Nonrecoverable Advances actually reimbursed with
respect to such Mortgage Loan (the principal portion of such Realized Loss), and
(ii) the accrued interest on such Mortgage Loan remaining unpaid and the


                                       38
<PAGE>

interest portion of Nonrecoverable Advances actually reimbursed with respect to
such Mortgage Loan (the interest portion of such Realized Loss); provided,
however, that for purposes of allocating Realized Losses to the Certificates and
the REMIC II Regular Interests pursuant to this definition of "Realized Loss,"
the aggregate principal portion of Realized Losses for any Distribution Date for
any Subgroup shall be reduced by the Cumulative Carry-Forward Subsequent
Recoveries Amount for such Distribution Date for such Subgroup. For any
Distribution Date, with respect to any Mortgage Loan which is not a Liquidated
Mortgage Loan, the amount of the Bankruptcy Loss incurred with respect to such
Mortgage Loan as of the related Due Date.

         Realized Losses on Subgroup 1 and Subgroup 2 Loans shall be allocated
to the REMIC I Regular Interests as follows: (1) The interest portion of
Realized Losses on Subgroup 1 Loans, if any, shall be allocated among the Class
C-Y-1 and Class C-Z-1 Regular Interests pro rata according to the amount of
interest accrued but unpaid thereon, in reduction thereof; (2) the interest
portion of Realized Losses on Subgroup 2 Loans, if any, shall be allocated among
the Class Class C-Y-2 and Class C-Z-2 Regular Interests pro rata according to
the amount of interest accrued but unpaid thereon, in reduction thereof. Any
interest portion of such Realized Losses in excess of the amount allocated
pursuant to the preceding sentence shall be treated as a principal portion of
Realized Losses not attributable to any specific Mortgage Loan in such Subgroup
and allocated pursuant to the succeeding sentences. The applicable Class P
Fraction of any principal portion of Realized Losses attributable to a Class P
Mortgage Loan shall be allocated to the Class P-M Regular Interest in reduction
of the Class Principal Balance thereof. The remainder of the principal portion
of Realized Losses with respect to Subgroup 1 and Subgroup 2 shall be allocated
to the REMIC I Regular Interests as follows: (1) The principal portion of
Realized Losses on Subgroup 1 Loans shall be allocated, first, to the Class
C-Y-1 Regular Interest to the extent of the Class C-Y-1 Principal Reduction
Amount in reduction of the Class Principal Balance of such Regular Interest and,
second, the remainder, if any, of such principal portion of such Realized Losses
shall be allocated to the Class C-Z-1 Regular Interest in reduction of the Class
Principal Balance thereof; and (2) the principal portion of Realized Losses on
Subgroup 2 Loans shall be allocated, first, to the Class C-Y-2 Regular Interest
to the extent of the Class C-Y-2 Principal Reduction Amount in reduction of the
Class Principal Balance of such Regular Interest and, second, the remainder, if
any, of such principal portion of such Realized Losses shall be allocated to the
Class C-Z-2 Regular Interest in reduction of the Class Principal Balance
thereof.

         Except for Special Hazard Losses in excess of the Special Hazard
Coverage, Fraud Losses in excess of the Fraud Coverage and Bankruptcy Losses in
excess of the Bankruptcy Coverage, Realized Losses on Mortgage Loans in a
Subgroup shall be allocated among the REMIC II Regular Interests (i) for
Realized Losses allocable to principal (a) first, to the Class B-6-L Regular
Interest, until the Class B-6-L Principal Balance has been reduced to zero, (b)
second, to the Class B-5-L Regular Interest, until the Class B-5-L Principal
Balance has been reduced to zero, (c) third, to the Class B-4-L Regular
Interest, until the Class B-4-L Principal Balance has been reduced to zero, (d)
fourth, to the Class B-3-L Regular Interest, until the Class B-3-L Principal
Balance has been reduced to zero, (e) fifth, to the Class B-2-L Regular
Interest, until the Class B-2-L Principal Balance has been reduced to zero, (f)
sixth, to the Class B-1-L Regular Interest, until the Class B-1-L Principal
Balance has been reduced to zero, and (g) seventh, (x) with respect to Realized


                                       39
<PAGE>

Losses on Subgroup 1 Loans, to the Class 1-A-1-L, Class 1-A-2-L, Class 1-A-3-L,
Class 1-A-5-L, Class 1-A-6-L, Class 1-A-7-L, Class 1-A-8-L, Class 1-A-9-L, Class
1-A-10-L, Class 1-A-11-L and Class 1-A-12-L Regular Interests, pro rata,
according to, and in reduction of, the Class Principal Balances thereof and (y)
with respect to Realized Losses on Subgroup 2 Loans, to the Class 2-A-1-L
Regular Interest, in reduction of the Class Principal Balance thereof; provided,
however, that if the loss is recognized with respect to a Class P Mortgage Loan,
the applicable Class P Fraction of such loss shall first be allocated to the
Class P-L Regular Interest and the remainder of such loss shall be allocated as
set forth above in this clause (i); and (ii) for Realized Losses allocable to
interest (a) first, to the Class B-6-L Regular Interest, in reduction of accrued
but unpaid interest thereon and then in reduction of the Class B-6-L Principal
Balance, (b) second, to the Class B-5-L Regular Interest, in reduction of
accrued but unpaid interest thereon and then in reduction of the Class B-5-L
Principal Balance, (c) third, to the Class B-4-L Regular Interest, in reduction
of accrued but unpaid interest thereon and then in reduction of the Class B-4-L
Principal Balance, (d) fourth, to the Class B-3-L Regular Interest, in reduction
of accrued but unpaid interest thereon and then in reduction of the Class B-3-L
Principal Balance, (e) fifth, to the Class B-2-L Regular Interest, in reduction
of accrued but unpaid interest thereon and then in reduction of the Class B-2-L
Principal Balance, (f) sixth, to the Class B-1-L Regular Interest, in reduction
of accrued but unpaid interest thereon and then in reduction of the Class B-1-L
Principal Balance, and (g) seventh, (x) with respect to Realized Losses on
Subgroup 1 Loans, to the Class 1-A-1-L, Class 1-A-2-L, Class 1-A-3-L, Class
1-A-5-L, Class 1-A-6-L, Class 1-A-7-L, Class 1-A-8-L, Class 1-A-9-L, Class
1-A-10-L, Class 1-A-11-L and Class 1-A-12-L Regular Interests, pro rata,
according to accrued but unpaid interest on such Classes, in reduction thereof,
and then to such Classes, in reduction of the Class Principal Balances thereof
and (y) with respect to Realized Losses on Subgroup 2 Loans, to the Class
2-A-1-L Regular Interest, in reduction of accrued but unpaid interest on such
Class, and then to such Class, in reduction of the Class Principal Balance
thereof; provided, however, that until the Class 1-A-11-L Principal Balance has
been reduced to zero, all principal losses that would otherwise be allocated to
the Class 1-A-10-L Regular Interest pursuant to clause (i) of this paragraph
shall instead be allocated to the Class 1-A-11-L Regular Interest, in reduction
of the Class 1-A-11-L Principal Balance, and all interest losses that would
otherwise be allocated to the Class 1-A-10-L Regular Interest pursuant to clause
(ii) of this paragraph shall instead be allocated to the Class 1-A-11-L Regular
Interest, in reduction of accrued but unpaid interest thereon, and then in
reduction of the Class 1-A-11-L Principal Balance.

         For any Distribution Date, any amounts distributed to the Class P-L
Regular Interest pursuant to clauses (I)(c)(i) and (I)(c)(ii) of the definition
of "REMIC II Distribution Amount" shall be allocated as a loss to the most
junior Class (or Classes) of Class B-L Regular Interests, until the Class
Principal Balance thereof has been reduced to zero.

         Special Hazard Losses in excess of the Special Hazard Coverage, Fraud
Losses in excess of the Fraud Coverage and Bankruptcy Losses in excess of the
Bankruptcy Coverage shall be allocated among the REMIC II Regular Interests by
Pro Rata Allocation.

         Realized Losses allocated to any Class of REMIC II Regular Interests
pursuant to this definition of "Realized Loss" in reduction of the Class
Principal Balance thereof (including losses allocated to the Class B-L Regular
Interests pursuant to the second preceding paragraph of this definition of
"Realized Loss") shall also be allocated to the Corresponding Class of
Certificates in reduction of the Class Principal Balance thereof by the same
amount.



                                       40
<PAGE>

         On each Distribution Date, after giving effect to the principal
distributions and allocations of losses as provided in this Agreement (without
regard to this paragraph), if the aggregate Class Principal Balance of all
outstanding Classes of REMIC II Regular Interests and the Class R-1 Residual
Interest (plus any Cumulative Carry-Forward Subsequent Recoveries Amount for
such Distribution Date for any Subgroup) exceeds the aggregate principal balance
of the Mortgage Loans remaining to be paid at the close of business on the
Cut-Off Date, after deduction of (i) all principal payments due on or before the
Cut-Off Date in respect of each such Mortgage Loan whether or not paid, and (ii)
all amounts of principal in respect of each Mortgage Loan that have been
received or advanced and included in the REMIC II Available Distribution Amount
for the Subgroup 1-L and Subgroup 2-L Regular Interests and all losses in
respect of each Mortgage Loan that have been allocated to the REMIC II Regular
Interests on such Distribution Date or prior Distribution Dates, then such
excess will be deemed a principal loss and will be allocated to the most junior
Class of Class B-L Regular Interests, in reduction of the Class Principal
Balance thereof.

         Recognition Agreement: With respect to a Cooperative Loan, the
recognition agreement between the Cooperative and the originator of such
Cooperative Loan.

         Record Date: The last Business Day of the month immediately preceding
the month of the related Distribution Date.

         Reference Banks: Barclays Bank PLC, Deutsche Bank and JPMorgan Chase
Bank or, if any such bank shall cease to provide quotations for one-month United
States dollar deposits, any other leading bank with an established place of
business in London engaged in transactions in Eurodollar deposits in the
international Eurocurrency market not controlling, controlled by or under common
control with the Company, designated by the Company from time to time for the
purpose of providing quotations for one-month United States dollar-denominated
deposits.

         Regular Interest Group: The Subgroup 1-L, Subgroup 2-L or Class B-L
Regular Interests, as applicable.

         Regular Interests: (i) With respect to REMIC I, the REMIC I Regular
Interests, (ii) with respect to REMIC II, the REMIC II Regular Interests and
(iii) with respect to REMIC III, the REMIC III Regular Interests.

         Relief Act Shortfall: For any Distribution Date for any Mortgage Loan
with respect to which the Servicemembers Civil Relief Act, formerly known as the
Soldiers' and Sailors' Civil Relief Act of 1940, or any comparable state
legislation (collectively, the "Relief Act"), limits the amount of interest
payable by the related Mortgagor, an amount equal to one month's interest on
such Mortgage Loan at an annual interest rate equal to the excess, if any, of
(i) the annual interest rate otherwise payable by the Mortgagor on the related
Due Date under the terms of the related Mortgage Note over (ii) the annual
interest rate payable by the Mortgagor on the related Due Date by application of
the Relief Act.

         REMIC: A real estate mortgage investment conduit, as such term is
defined in the Code.

         REMIC Provisions: Sections 860A through 860G of the Code, related Code
provisions and regulations promulgated thereunder, as the foregoing may be in
effect from time to time.

                                       41
<PAGE>

         REMIC I: The segregated pool of assets of the Trust consisting of the
REMIC I Assets, which shall be a REMIC pursuant to the Code, with respect to
which a separate REMIC election is to be made and the beneficial interests in
which shall be the REMIC I Regular Interests and the Class R-1 Residual
Interest.

         REMIC I Assets: All of the Mortgage Pool Assets.

         REMIC I Available Distribution Amount: For each Subgroup for any
Distribution Date, the sum of the following amounts with respect to the Mortgage
Loans (or portions of Mortgage Loans) in such Subgroup:

         (1) the total amount of all cash received by or on behalf of the Master
Servicer with respect to such Mortgage Loans by the Determination Date for such
Distribution Date and not previously distributed, including Monthly P&I Advances
made by Servicers, Liquidation Proceeds and scheduled amounts of distributions
from Buydown Funds respecting Buydown Loans, if any, except:

         (a) all scheduled payments of principal and interest collected but due
subsequent to such Distribution Date;

         (b) all Curtailments received after the Prior Period;

         (c) all Payoffs received after the Payoff Period immediately preceding
such Distribution Date (together with any interest payment received with such
Payoffs to the extent that it represents the payment of interest accrued on the
Mortgage Loans for the period subsequent to the Prior Period), and interest
which was accrued and received on Payoffs received during the period from the
1st to the 14th day of the month of such Distribution Date, which interest shall
not be included in the calculation of the REMIC I Available Distribution Amount
for any Distribution Date;

         (d) Insurance Proceeds, Liquidation Proceeds and Subsequent Recoveries
received on such Mortgage Loans after the Prior Period;

         (e) all amounts in the Certificate Account which are due and
reimbursable to a Servicer or the Master Servicer pursuant to the terms of this
Agreement;

         (f) the sum of the Master Servicing Fee and the Servicing Fee for each
such Mortgage Loan, and any Special Primary Insurance Premium payable on such
Distribution Date with respect to such Mortgage Loan; and

         (g) Excess Liquidation Proceeds;

         (2) the sum, to the extent not previously distributed, of the following
amounts, to the extent advanced or received, as applicable, by the Master
Servicer:

         (a) any Monthly P&I Advance made by the Master Servicer to the Trustee
with respect to such Distribution Date relating to such Mortgage Loans; and



                                       42
<PAGE>

         (b) Compensating Interest; and

         (3) the total amount of any cash received during the Prior Period by
the Trustee or the Master Servicer in respect of a Purchase Obligation under
Section 2.07 and Section 2.08 or any permitted purchase of such a Mortgage Loan;

provided, however, that interest received or advanced (subject to the exceptions
stated above) on each Mortgage Loan, a portion of which Mortgage Loan is
included in such Subgroup and a portion of which is included in the other
Subgroup, shall be allocated to the REMIC I Available Distribution Amount for
such Subgroup in an amount equal to interest accrued on the portion of such
Mortgage Loan included in such Subgroup at a Pass-Through Rate equal to 5.500%
and 8.000% in the case of Subgroup 1 and Subgroup 2, respectively, rather than
at the actual Pass-Through Rate for such Mortgage Loan (or, in the event of a
shortfall in collections of interest on such Mortgage Loan, the interest
collected shall be allocated to the REMIC I Available Distribution Amount for
each Subgroup pro rata according to the amount for each Subgroup calculated as
described in this proviso); provided, further, that, with respect to each
Subgroup, in the event (a) the portion attributable to that Subgroup of
Uncompensated Interest Shortfall exceeds (b) the portion of Uncompensated
Interest Shortfall allocated, pursuant to the definition of "Uncompensated
Interest Shortfall," to the REMIC II Regular Interests related to that Subgroup
(or, in the case of the Class B-L Regular Interests, to the portions of the
Class B-L Regular Interests that derive their Interest Distribution Amounts from
such Subgroup), then the REMIC I Available Distribution Amount for such Subgroup
shall be increased by the amount of such excess; provided, further, that, with
respect to each Subgroup, in the event (a) the portion of Uncompensated Interest
Shortfall allocated, pursuant to the definition of "Uncompensated Interest
Shortfall," to the REMIC II Regular Interests related to that Subgroup (or, in
the case of the Class B-L Regular Interests, to the portions of the Class B-L
Regular Interests that derive their Interest Distribution Amounts from such
Subgroup) exceeds (b) the portion attributable to that Subgroup of Uncompensated
Interest Shortfall, then the REMIC I Available Distribution Amount for such
Subgroup shall be decreased by the amount of such excess.

         REMIC I Distribution Amount: For any Distribution Date, the REMIC I
Available Distribution Amount shall be distributed to the REMIC I Regular
Interests and the Class R-1 Residual Interest in the following amounts and
priority:

         (a) To the extent of the REMIC I Available Distribution Amount for
Subgroup 1:

         (i) first, to the Class P-M Regular Interest, the sum of (A) the
aggregate for all of the Class P Mortgage Loans of the product for each Class P
Mortgage Loan of the applicable Class P Fraction and the sum of (x) scheduled
payments of principal on such Class P Mortgage Loan due on or before the related
Due Date in respect of which no distribution has been made on any previous
Distribution Date and which were received by the Determination Date, or which
have been advanced as part of a Monthly P&I Advance with respect to such
Distribution Date, (y) the principal portion received in respect of such Class P
Mortgage Loan during the Prior Period of (1) Curtailments, (2) Insurance
Proceeds, (3) the amount, if any, of the principal portion of the Purchase Price
paid pursuant to a Purchase Obligation or any purchase of a Mortgage Loan
permitted hereunder and (4) Liquidation Proceeds and (z) the principal portion
of Payoffs received in respect of such Class P Mortgage Loan during the Payoff


                                       43
<PAGE>

Period and (B) the portion, if any, of the Subsequent Recoveries for Subgroup 1
for such Distribution Date not included in the Class C-Y-1 Principal
Distribution Amount or the Class C-Z-1 Principal Distribution Amount pursuant to
clause (B) of the respective definitions thereof;

         (ii) second, to the Class C-Y-1 and Class C-Z-1 Regular Interests and
the Class R-1 Residual Interest, concurrently, the Interest Distribution Amounts
for such Classes remaining unpaid from previous Distribution Dates, pro rata
according to their respective shares of such unpaid amounts;

         (iii) third, to the Class C-Y-1 and Class C-Z-1 Regular Interests and
the Class R-1 Residual Interest, concurrently, the Interest Distribution Amounts
for such Classes for the current Distribution Date, pro rata according to their
respective Interest Distribution Amounts;

         (iv) fourth, to the Class R-1 Residual Interest, until the Class
Principal Balance thereof has been reduced to zero; and

         (v) fifth, to the Class C-Y-1 and Class C-Z-1 Regular Interests, the
Class C-Y-1 Principal Distribution Amount and the Class C-Z-1 Principal
Distribution Amount, respectively.

         (b) To the extent of the REMIC I Available Distribution Amount for
Subgroup 2:

         (i) first, to the Class C-Y-2 and Class C-Z-2 Regular Interests,
concurrently, the Interest Distribution Amounts for such Classes remaining
unpaid from previous Distribution Dates, pro rata according to their respective
shares of such unpaid amounts;

         (ii) second, to the Class C-Y-2 and Class C-Z-2 Regular Interests,
concurrently, the Interest Distribution Amounts for such Classes for the current
Distribution Date, pro rata according to their respective Interest Distribution
Amounts; and

         (iii) third, to the Class C-Y-2 and Class C-Z-2 Regular Interests, the
Class C-Y-2 Principal Distribution Amount and the Class C-Z-2 Principal
Distribution Amount, respectively.

         (c) To the extent of the REMIC I Available Distribution Amounts for
Subgroup 1 and Subgroup 2 for such Distribution Date remaining after payment of
the amounts pursuant to paragraphs (a) and (b) of this definition of "REMIC I
Distribution Amount":

         (i) first, to the Class P-M Regular Interest, the aggregate amount of
any distributions to the Class P-L Regular Interest pursuant to paragraphs
(I)(c)(i) and (I)(c)(ii) of the definition of "REMIC II Distribution Amount" on


                                       44
<PAGE>

such Distribution Date; provided, however, that any amounts distributed pursuant
to this paragraph (c)(i) of this definition of "REMIC I Distribution Amount"
shall not cause a reduction in the Class Principal Balance of the Class P-M
Regular Interest;

         (ii) second, to each Class of Class C-Y and Class C-Z Regular
Interests, pro rata according to the amount of unreimbursed Realized Losses
allocable to principal previously allocated to each such Class, the aggregate
amount of any distributions to the Certificates pursuant to paragraph
(I)(c)(xxi) of the definition of "REMIC II Distribution Amount" on such
Distribution Date; provided, however, that any amounts distributed pursuant to
this paragraph (c)(ii) of this definition of "REMIC I Distribution Amount" shall
not cause a reduction in the Class Principal Balances of any of the Class C-Y
and Class C-Z Regular Interests; and

         (iii) third, to the Class R-1 Residual Interest, the Residual
Distribution Amount for the Class R-1 Residual Interest for such Distribution
Date.

         REMIC I Regular Interests: The Classes of undivided beneficial
interests in REMIC I designated as "regular interests" in the table titled
"REMIC I Interests" in the Preliminary Statement hereto. The REMIC I Regular
Interests, together with the Class R-1 Residual Interest, shall be deemed to be
a separate series of beneficial interests in the assets of the Trust consisting
of the REMIC I Assets pursuant to Section 3806(b)(2) of the Statutory Trust
Statute.

         REMIC II: The segregated pool of assets of the Trust consisting of the
REMIC II Assets, which shall be a REMIC pursuant to the Code, with respect to
which a separate REMIC election is to be made, and the beneficial interests in
which shall be the REMIC II Regular Interests and the Class R-2 Residual
Interest.

         REMIC II Assets: The REMIC I Regular Interests.

         REMIC II Available Distribution Amount: With respect to the Subgroup 1
and Class P Certificates, on any Distribution Date, the aggregate of all
distributions to the Class C-Y-1, Class C-Z-1 and Class P-M Regular Interests
(which amount shall be available for distributions to the Class P-L, Subgroup
1-L and Class B-L Regular Interests and the Class R-2 Residual Interest as
provided herein). With respect to the Subgroup 2 Certificates, on any
Distribution Date, the aggregate of all distributions to the Class C-Y-2 and
Class C-Z-2 Regular Interests (which amount shall be available for distributions
to the Subgroup 2-L and Class B-L Regular Interests and the Class R-2 Residual
Interest as provided herein).

         REMIC II Distribution Amount: (I) For any Distribution Date prior to
the Credit Support Depletion Date, the REMIC II Available Distribution Amount
for such Distribution Date shall be distributed to the REMIC II Regular
Interests and the Class R-2 Residual Interest in the following amounts and
priority:

         (a) With respect to the Class P-L and Subgroup 1-L Regular Interests,
on any Distribution Date prior to the Credit Support Depletion Date, to the


                                       45
<PAGE>

extent of the REMIC II Available Distribution Amount for the Subgroup 1-L
Regular Interests for such Distribution Date:

         (i) first, to the Class P-L Regular Interest, the aggregate for all
Class P Mortgage Loans of the product for each Class P Mortgage Loan of the
applicable Class P Fraction and the sum of (x) scheduled payments of principal
on such Class P Mortgage Loan due on or before the related Due Date in respect
of which no distribution has been made on any previous Distribution Date and
which were received by the Determination Date, or which have been advanced as
part of a Monthly P&I Advance with respect to such Distribution Date, (y) the
principal portion received in respect of such Class P Mortgage Loan during the
Prior Period of (1) Curtailments, (2) Insurance Proceeds, (3) the amount, if
any, of the principal portion of the Purchase Price paid pursuant to a Purchase
Obligation or any purchase of a Mortgage Loan permitted hereunder and (4)
Liquidation Proceeds and (z) the principal portion of Payoffs received in
respect of such Class P Mortgage Loan during the Payoff Period;

         (ii) second, to the Subgroup 1-L Regular Interests, concurrently, the
Interest Distribution Amounts for such Classes remaining unpaid from previous
Distribution Dates, pro rata according to their respective Interest Distribution
Amounts;

         (iii) third, to the Subgroup 1-L Regular Interests, concurrently, the
Interest Distribution Amounts for such Classes for the current Distribution
Date, pro rata according to their respective Interest Distribution Amounts; and

         (iv) fourth, to the Subgroup 1-L Regular Interests, as principal, the
Subgroup 1 Senior Principal Distribution Amount (reduced, on the first
Distribution Date, by $100), sequentially, as follows:

         (A) first, to the Class 1-A-10-L, Class 1-A-11-L and Class 1-A- 12-L
Regular Interests, pro rata according to Class Principal Balance, up to the
amount of the Lockout Priority Amount for that Distribution Date;

         (B) second, up to the amount necessary to reduce the aggregate Class
Principal Balance of the Class 1-A-1-L, Class 1-A-2-L and Class 1-A-3-L Regular
Interests to their aggregate Planned Principal Balance for that Distribution
Date, concurrently, as follows:

         (1) 63.29113974465%, sequentially, as follows:

         (a) first, to the Class 1-A-1-L Regular Interest, until the Class
1-A-1-L Principal Balance has been reduced to zero; and

         (b) second, to the Class 1-A-2-L Regular Interest, until the Class
1-A-2-L Principal Balance has been reduced to zero; and



                                       46
<PAGE>

         (2) 36.70886025535% to to the Class 1-A-3-L Regular Interest, until the
Class 1-A-3-L Principal Balance has been reduced to zero;

         (C) third, up to the amount necessary to reduce the aggregate Class
Principal Balance of the Class 1-A-5-L and Class 1-A-6-L Regular Interests to
their aggregate Targeted Principal Balance for that Distribution Date,
sequentially, as follows:

         (1) first, to to the Class 1-A-5-L Regular Interest, until the Class
1-A-5-L Principal Balance has been reduced to zero; and

         (2) second, to to the Class 1-A-6-L Regular Interest, until the Class
1-A-6-L Principal Balance has been reduced to zero;

         (D) fourth, to the Class 1-A-7-L and Class 1-A-8-L Regular Interests,
pro rata according to Class Principal Balance, until the Class 1-A-7-L and Class
1-A-8-L Principal Balances have each been reduced to zero;

         (E) fifth, to the Class 1-A-5-L Regular Interest (without regard to any
schedule), until the Class 1-A-5-L Principal Balance has been reduced to zero;

         (F) sixth, to the Class 1-A-6-L Regular Interest (without regard to any
schedule), until the Class 1-A-6-L Principal Balance has been reduced to zero;

         (G) seventh, to the Class 1-A-1-L, Class 1-A-2-L and Class 1-A-3-L
Regular Interests (without regard to their schedule), concurrently, as follows:

         (1) 63.29113974465%, sequentially, as follows:

         (a) first, to the Class 1-A-1-L Regular Interest, until the Class
1-A-1-L Principal Balance has been reduced to zero; and

         (b) second, to the Class 1-A-2-L Regular Interest, until the Class
1-A-2-L Principal Balance has been reduced to zero; and

         (2) 36.70886025535% to to the Class 1-A-3-L Regular Interest, until the
Class 1-A-3-L Principal Balance has been reduced to zero;



                                       47
<PAGE>

         (H) eighth, to the Class 1-A-9-L Regular Interest, until the Class
1-A-9-L Principal Balance has been reduced to zero; and

         (I) ninth, to the Class 1-A-10-L, Class 1-A-11-L and Class 1-A-12-L
Regular Interests, pro rata according to Class Principal Balance, until the
Class 1-A-10-L, Class 1-A-11-L and Class 1-A-12-L Principal Balances have each
been reduced to zero;

         (b) With respect to the Subgroup 2-L Regular Interests, on any
Distribution Date prior to the Credit Support Depletion Date, to the extent of
the REMIC II Available Distribution Amount for the Subgroup 2-L Regular
Interests for such Distribution Date:

         (i) first, to the Class 2-A-1-L Regular Interest, the Interest
Distribution Amount for such Class remaining unpaid from previous Distribution
Dates;

         (ii) second, to the Class 2-A-1-L Regular Interest, the Interest
Distribution Amount for such Class for the current Distribution Date; and

         (iii) third, to the Class 2-A-1-L Regular Interest, the Subgroup 2
Senior Principal Distribution Amount; and

         (c) With respect to the Subgroup 1-L, Subgroup 2-L, Class P-L and Class
B-L Regular Interests and the Class R-2 Residual Interest, on any Distribution
Date prior to the Credit Support Depletion Date, to the extent of the REMIC II
Available Distribution Amounts for the Subgroup 1-L and Subgroup 2-L Regular
Interests for such Distribution Date remaining after the payment of the amounts
pursuant to paragraphs (I)(a) and (I)(b) of this definition of "REMIC II
Distribution Amount":

         (i) first, to the Class P-L Regular Interest, to the extent of amounts
otherwise available to pay the Subordinate Principal Distribution Amount
(without regard to clause (B)(x) of the definition thereof) on such Distribution
Date and to the extent not paid to such Class of Regular Interests on previous
Distribution Dates pursuant to clause (I)(c)(ii) of this definition of "REMIC II
Distribution Amount," principal in an amount equal to the applicable Class P
Fraction of any Realized Loss on a Class P Mortgage Loan incurred prior to the
Prior Period (other than a Realized Loss which, pursuant to the definition of
"Realized Loss," is allocated by Pro Rata Allocation);

         (ii) second, to the Class P-L Regular Interest, to the extent of
amounts otherwise available to pay the Subordinate Principal Distribution Amount
(without regard to clause (B)(x) of the definition thereof) on such Distribution
Date, principal in an amount equal to the applicable Class P Fraction of any
Realized Loss on a Class P Mortgage Loan incurred in the Prior Period (other
than a Realized Loss which, pursuant to the definition of "Realized Loss," is
allocated by Pro Rata Allocation); provided, that any amounts distributed in
respect of losses pursuant to paragraph (I)(c)(i) or this paragraph (I)(c)(ii)
of this definition of "REMIC II Distribution Amount" shall not cause a reduction
in the Class P Principal Balance;
                                       48
<PAGE>

         (iii) third, to the Class B-1-L Regular Interest, the Interest
Distribution Amount for such Class of Regular Interests remaining unpaid from
previous Distribution Dates;

         (iv) fourth, to the Class B-1-L Regular Interest, the Interest
Distribution Amount for such Class of Regular Interests for the current
Distribution Date;

         (v) fifth, to the Class B-1-L Regular Interest, the portion of the
Subordinate Principal Distribution Amount allocable to such Class of Regular
Interests pursuant to the definition of "Subordinate Principal Distribution
Amount," until the Class B-1-L Principal Balance has been reduced to zero;

         (vi) sixth, to the Class B-2-L Regular Interest, the Interest
Distribution Amount for such Class of Regular Interests remaining unpaid from
previous Distribution Dates;

         (vii) seventh, to the Class B-2-L Regular Interest, the Interest
Distribution Amount for such Class of Regular Interests for the current
Distribution Date;

         (viii) eighth, to the Class B-2-L Regular Interest, the portion of the
Subordinate Principal Distribution Amount allocable to such Class of Regular
Interests pursuant to the definition of "Subordinate Principal Distribution
Amount," until the Class B-2-L Principal Balance has been reduced to zero;

         (ix) ninth, to the Class B-3-L Regular Interest, the Interest
Distribution Amount for such Class of Regular Interests remaining unpaid from
previous Distribution Dates;

         (x) tenth, to the Class B-3-L Regular Interest, the Interest
Distribution Amount for such Class of Regular Interests for the current
Distribution Date;

         (xi) eleventh, to the Class B-3-L Regular Interest, the portion of the
Subordinate Principal Distribution Amount allocable to such Class of Regular
Interests pursuant to the definition of "Subordinate Principal Distribution
Amount," until the Class B-3-L Principal Balance has been reduced to zero;

         (xii) twelfth, to the Class B-4-L Regular Interest, the Interest
Distribution Amount for such Class of Regular Interests remaining unpaid from
previous Distribution Dates;

         (xiii) thirteenth, to the Class B-4-L Regular Interest, the Interest
Distribution Amount for such Class of Regular Interests for the current
Distribution Date;

                                       49
<PAGE>

         (xiv) fourteenth, to the Class B-4-L Regular Interest, the portion of
the Subordinate Principal Distribution Amount allocable to such Class of Regular
Interests pursuant to the definition of "Subordinate Principal Distribution
Amount," until the Class B-4-L Principal Balance has been reduced to zero;

         (xv) fifteenth, to the Class B-5-L Regular Interest, the Interest
Distribution Amount for such Class of Regular Interests remaining unpaid from
previous Distribution Dates;

         (xvi) sixteenth, to the Class B-5-L Regular Interest, the Interest
Distribution Amount for such Class of Regular Interests for the current
Distribution Date;

         (xvii) seventeenth, to the Class B-5-L Regular Interest, the portion of
the Subordinate Principal Distribution Amount allocable to such Class of Regular
Interests pursuant to the definition of "Subordinate Principal Distribution
Amount," until the Class B-5-L Principal Balance has been reduced to zero;

         (xviii) eighteenth, to the Class B-6-L Regular Interest, the Interest
Distribution Amount for such Class of Regular Interests remaining unpaid from
previous Distribution Dates;

         (xix) nineteenth, to the Class B-6-L Regular Interest, the Interest
Distribution Amount for such Class of Regular Interests for the current
Distribution Date;

         (xx) twentieth, to the Class B-6-L Regular Interest, the portion of the
Subordinate Principal Distribution Amount allocable to such Class of Regular
Interests pursuant to the definition of "Subordinate Principal Distribution
Amount," until the Class B-6-L Principal Balance has been reduced to zero;

         (xxi) twenty-first, to each Class of REMIC II Regular Interests in
order of seniority (which, from highest to lowest, shall be as follows: the
Class P-L, Subgroup 1-L and Subgroup 2-L Regular Interests of equal seniority,
and then Class B-1-L, Class B-2-L, Class B-3-L, Class B-4-L, Class B-5-L and
Class B-6-L of decreasing seniority) the remaining portion, if any, of the REMIC
II Available Distribution Amounts for the Subgroup 1-L and Subgroup 2-L Regular
Interests, up to the amount of unreimbursed Realized Losses allocable to
principal previously allocated or to be allocated on such Distribution Date to
such Class, if any; provided, however, that in the case of Classes of REMIC II
Regular Interests of equal seniority, the amount distributable to such Classes
shall be allocated among such Classes according to the amount of losses
allocated thereto; provided, further, that any amounts distributed pursuant to
this paragraph (I)(c)(xxi) of this definition of "REMIC II Distribution Amount"
shall not cause a reduction in the Class Principal Balances of any of the
Regular Interests; and

                                       50
<PAGE>

         (xxii) twenty-second, to the Class R-2 Residual Interest, the Residual
Distribution Amounts for the Subgroup 1-L and Subgroup 2-L Regular Interests for
such Distribution Date.

         Notwithstanding the foregoing paragraph (I)(c) of this definition of
"REMIC II Distribution Amount,"

         (X) on any Distribution Date on which both of the following conditions
specified in clauses (1) and (2) are met:

         (1) the aggregate Class Principal Balance of either the Subgroup 1-L
Regular Interests or the Subgroup 2-L Regular Interests has been reduced to
zero, and

         (2) either (a) the Class B Percentage for such Distribution Date is
less than 200% of the Class B Percentage as of the Closing Date or (b) the
outstanding principal balance of the Mortgage Loans in either Subgroup 1 or
Subgroup 2 delinquent 60 days or more averaged over the last six months
(including Mortgage Loans in foreclosure and Mortgage Loans the Mortgaged
Property of which is held by REMIC I and acquired by foreclosure or deed in lieu
of foreclosure), as a percentage of the related Subordinate Component Balance,
is greater than or equal to 50%,

all principal received or advanced with respect to the Mortgage Loans in the
Subgroup related to the Class A-L Regular Interests that have been paid in full
(after distributions of principal to the Class P-L Regular Interest pursuant to
paragraph (I)(a)(i), (I)(c)(i) and (I)(c)(ii) above, if applicable shall be paid
as principal to the remaining Class A-L Regular Interests that have been not
been paid in full to the extent of and in reduction of the Class Principal
Balances thereof (and, in the case of the Subgroup 1-L Regular Interests, in the
order of priority of paragraph (I)(a)(iv)(a)-(i) above), prior to any
distributions of principal to the Class B-L Regular Interests pursuant to
paragraph (I)(c) above, and

         (Y) if on any Distribution Date either of Subgroup 1 or Subgroup 2 is
an Undercollateralized Subgroup and the other such Subgroup is an
Overcollateralized Subgroup, then the REMIC II Available Distribution Amount for
the Regular Interest Group related to the Overcollateralized Subgroup, to the
extent remaining following distributions of interest and principal to the
Subgroup 1-L, Subgroup 2-L and Class P-L Regular Interests pursuant to paragraph
(I)(a) or (I)(b) above, as applicable, shall be paid in the following priority:
(1) first, such remaining amount, up to the Total Transfer Amount for the
Undercollateralized Subgroup, shall be distributed (a) first, to the Class A-L
Regular Interests related to the Undercollateralized Subgroup, in payment of any
portion of the Interest Distribution Amounts for such Classes of Regular
Interests remaining unpaid from such Distribution Date or previous Distribution
Dates, and (b) second, to the Class A-L Regular Interests related to such
Undercollateralized Subgroup, as principal (and, in the case of the Subgroup 1-L
Regular Interests, in the order of priority of paragraph (I)(a)(iv)(a)-(i)
above) and, (2) second, any remaining amount shall be distributed pursuant to
paragraph (I)(c) above.

         (II) For any Distribution Date on or after the Credit Support Depletion
Date, the REMIC II Available Distribution Amount for such Distribution Date
shall be distributed to the outstanding Classes of REMIC II Regular Interests
and the Class R-2 Residual Interest in the following amounts and priority:



                                       51
<PAGE>

         (a) With respect to the Subgroup 1-L Regular Interests, on each
Distribution Date on or after the Credit Support Depletion Date, to the extent
of the REMIC II Available Distribution Amount for the Subgroup 1-L Regular
Interests for such Distribution Date:

         (i) first, to the Class P-L Regular Interest, principal in the amount
that would otherwise be distributed to such Class on such Distribution Date
pursuant to clause (I)(a)(i) of this definition of "REMIC II Distribution
Amount";

         (ii) second, to the Subgroup 1-L Regular Interests, the amount payable
to such Classes of Regular Interests on prior Distribution Dates pursuant to
clause (I)(a)(iii) or (II)(a)(iii) of this definition of "REMIC II Distribution
Amount," and remaining unpaid, pro rata according to such amount payable to the
extent of amounts available;

         (iii) third, to the Subgroup 1-L Regular Interests, concurrently, the
Interest Distribution Amounts for such Classes of Regular Interests for the
current Distribution Date, pro rata according to such amount payable to the
extent of amounts available;

         (iv) fourth, to the Subgroup 1-L Regular Interests, pro rata according
to Class Principal Balance, as principal, the Subgroup 1 Senior Principal
Distribution Amount; and

         (v) fifth, after any payments to the Subgroup 2-L Regular Interests
pursuant to the last paragraph of this definition of "REMIC II Distribution
Amount," to the Class R-2 Residual Interest, the Residual Distribution Amount
for the Subgroup 1-L Regular Interests for such Distribution Date.

         (b) With respect to the Subgroup 2-L Regular Interests, on each
Distribution Date on or after the Credit Support Depletion Date, to the extent
of the REMIC II Available Distribution Amount for the Subgroup 2-L Regular
Interests for such Distribution Date:

         (i) first, to the Class 2-A-1-L Regular Interest, the amount payable to
such Class of Regular Interests on prior Distribution Dates pursuant to clause
(I)(b)(ii) or (II)(b)(ii) of this definition of "REMIC II Distribution Amount,"
and remaining unpaid;

         (ii) second, to the Class 2-A-1-L Regular Interest, the Interest
Distribution Amount for such Class of Regular Interests for the current
Distribution Date;

         (iii) third, to the Class 2-A-1-L Regular Interest, as principal, the
Subgroup 2 Senior Principal Distribution Amount; and



                                       52
<PAGE>

         (iv) fourth, after any payments to the Subgroup 1-L Regular Interests
pursuant to the last paragraph of this definition of "REMIC II Distribution
Amount," to the Class R-2 Residual Interest, the Residual Distribution Amount
for the Subgroup 2-L Regular Interests for such Distribution Date.

         If on any Distribution Date either of Subgroup 1 or Subgroup 2 is an
Undercollateralized Subgroup and the other such Subgroup is an
Overcollateralized Subgroup, then the REMIC II Available Distribution Amount for
the Regular Interest Group related to the Overcollateralized Subgroup, to the
extent remaining following distributions of interest and principal to the
Subgroup 1-L and Subgroup 2-L Regular Interests pursuant to paragraph (II)(a)(i)
through (II)(a)(iv) or paragraph (II)(b)(i) through (II)(b)(iii), as applicable,
shall be paid in the following priority: (1) first, such remaining amount, up to
the Total Transfer Amount for the Undercollateralized Subgroup, shall be
distributed (a) first, to the Class A-L Regular Interests related to such
Undercollateralized Subgroup, in payment of any portion of the Interest
Distribution Amounts for such Classes of Regular Interests remaining unpaid from
such Distribution Date or previous Distribution Dates, pro rata according to
their respective shares of such unpaid amounts, and (b) second, to the Class A-L
Regular Interests related to such Undercollateralized Subgroup, as principal,
pro rata according to Class Principal Balance, and (2) second, any remaining
amount shall be distributed pursuant to paragraph (II)(a)(v) and (II)(b)(iv)
above, as applicable.

         REMIC II Regular Interests: The Classes of undivided beneficial
interests in REMIC II designated as "regular interests" in the table titled
"REMIC II Interests" in the Preliminary Statement hereto. The REMIC II Regular
Interests, together with the Class R-2 Residual Interest, shall be deemed to be
a separate series of beneficial interests in the assets of the Trust consisting
of the REMIC II Assets pursuant to Section 3806(b)(2) of the Statutory Trust
Statute.

         REMIC III: The segregated pool of assets of the Trust consisting of the
REMIC III Assets, which shall be a REMIC pursuant to the Code, with respect to
which a separate REMIC election is to be made, and the beneficial interests in
which shall be the REMIC III Regular Interests and the Class R-3 Residual
Interest.

         REMIC III Assets: The REMIC II Regular Interests.

         REMIC III Available Distribution Amount: For the Subgroup 1 and Class P
Certificates, on any Distribution Date, the aggregate of all distributions to
the Subgroup 1-L Regular Interests pursuant to clauses (I)(a), (I)(c) and
(II)(a) of the definition of "REMIC II Distribution Amount" (which amount shall
be available for distributions to the Subgroup 1 and Class P Certificates and
the Class R-3 Residual Interest as provided herein). For the Subgroup 2
Certificates, on any Distribution Date, the aggregate of all distributions to
the Subgroup 2-L Regular Interests pursuant to clauses (I)(b), (I)(c) and
(II)(b) of the definition of "REMIC II Distribution Amount" (which amount shall
be available for distributions to the Subgroup 2 Certificates and the Class R-3
Residual Interest as provided herein).

         REMIC III Distribution Amount: The REMIC III Available Distribution
Amount for any Distribution Date shall be distributed to the Certificates and
the Class R-3 Residual Interest in the following amounts and priority:



                                       53
<PAGE>

         (a) With respect to the Subgroup 1 and Class P Certificates, to the
extent of the REMIC III Available Distribution Amount for the Subgroup 1 and
Class P Certificates for such Distribution Date:

         (i) to the Class P Certificates and to each Class of Subgroup 1
Certificates (other than the Class 1-A-3 and Class 1-A-4 Certificates), the
amounts distributed to its Corresponding Class on such Distribution Date; and

         (ii) (A) to the Class 1-A-3 Certificates, the amount distributed as
principal to its Corresponding Class on such Distribution Date and (B) to each
Class of the Class 1-A-3 and Class 1-A-4 Certificates, the amount distributed as
interest to the Class 1-A-3-L Regular Interest on such Distribution Date, pro
rata according to, for each such Class, the product of 1/12 of the Certificate
Interest Rate for such Class and the Class Principal Balance or Class Notional
Amount, as applicable, for such Class before allocating principal losses and
giving effect to distributions of principal on such Distribution Date;

         (b) With respect to the Subgroup 2 Certificates, to the extent of the
REMIC III Available Distribution Amount for the Subgroup 2 Certificates for such
Distribution Date: (A) to the Class 2-A-1 Certificates, the amount distributed
as principal to its Corresponding Class on such Distribution Date and (B) to
each Class of the Class 2-A-1 and Class 2-A-2 Certificates, the amount
distributed as interest to the Class 2-A-1-L Regular Interest on such
Distribution Date, pro rata according to, for each such Class, the product of
1/12 of the Certificate Interest Rate for such Class and the Class Principal
Balance or Class Notional Amount, as applicable, for such Class before
allocating principal losses and giving effect to distributions of principal on
such Distribution Date;

         (c) With respect to the Class B Certificates, to the extent of the
REMIC III Available Distribution Amount for the Class B Certificates for such
Distribution Date, to each such Class of Certificates, the amounts distributed
to its Corresponding Class on such Distribution Date; and

         (d) To the Class R-3 Residual Interest, the Residual Distribution
Amount for the Class R-3 Residual Interest for such Distribution Date.

         In each case where a distribution is required to be made concurrently
to two or more Classes of Certificates pursuant to this definition of "REMIC III
Distribution Amount," if the portion of the REMIC III Available Distribution
Amount from which such distribution is required to be made is insufficient to
make such distribution in full to such Classes, such distribution shall be
allocated among such Classes pro rata according to the respective amounts to
which they are otherwise entitled from such distribution.

         REMIC III Regular Interests: The Classes of undivided beneficial
interests in REMIC III designated as "regular interests" in the table titled
"REMIC III Interests" in the Preliminary Statement hereto. The REMIC III Regular
Interests, together with the Class R-3 Residual Interest, shall be deemed to be
a separate series of beneficial interests in the assets of the Trust consisting
of the REMIC III Assets pursuant to Section 3806(b)(2) of the Statutory Trust
Statute.

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<PAGE>

         Residual Certificates: The Class R Certificates.

         Residual Distribution Amount: For any Distribution Date, with respect
to the Class R-1 Residual Interest, any portion of the REMIC I Available
Distribution Amounts for Subgroup 1 and Subgroup 2 remaining after all
distributions of such REMIC I Available Distribution Amounts pursuant to clauses
(a), (b) and (c) (other than the last subclause of clause (c)) of the definition
of "REMIC I Distribution Amount."

         For any Distribution Date, with respect to the Class R-2 Residual
Interest and for the Subgroup 1-L and Subgroup 2-L Regular Interests, any
portion of the REMIC II Available Distribution Amount for the Subgroup 1-L and
Subgroup 2-L Regular Interests, respectively, remaining after all distributions
of such REMIC II Available Distribution Amount pursuant to clauses (I)(a),
(I)(b), (I)(c), (II)(a) and (II)(b), as applicable, of the definition of "REMIC
II Distribution Amount" (other than the distributions pursuant to the last
subclause of clauses (I)(c), (II)(a) and (II)(b)).

         For any Distribution Date, with respect to the Class R-3 Residual
Interest, any portion of the REMIC III Available Distribution Amount for the
Subgroup 1 and Subgroup 2 and Class B Certificates remaining after all
distributions of the REMIC III Available Distribution Amount pursuant to clauses
(a), (b) and (c) of the definition of "REMIC III Distribution Amount."

         Upon termination of the obligations created by this Agreement and
liquidation of REMIC I, REMIC II and REMIC III, the amounts which remain on
deposit in the Certificate Account after payment to the Holders of the REMIC I
Regular Interests of the amounts set forth in Section 9.01 of this Agreement,
and subject to the conditions set forth therein, shall be distributed to the
Class R-1, Class R-2 and Class R-3 Residual Interests in accordance with the
preceding sentences of this definition as if the date of such distribution were
a Distribution Date.

         Responsible Officer: When used with respect to the Trustee or the
Delaware Trustee, any officer assigned to and working in the Corporate Trust
Office (in the case of the Trustee) or its corporate trust office (in the case
of the Delaware Trustee) or, in each case, in a similar group and also, with
respect to a particular matter, any other officer to whom such matter is
referred because of such officer's knowledge of and familiarity with the
particular subject.

         Secretary of State: The Secretary of State of the State of Delaware.

         Securities Act: The Securities Act of 1933, as amended.

         Security Agreement: With respect to a Cooperative Loan, the agreement
or mortgage creating a security interest in favor of the originator of the
Cooperative Loan in the related Cooperative Stock.

         Selling and Servicing Contract: (a) The contract (including the
Washington Mutual Mortgage Securities Corp. Selling Guide and Washington Mutual
Mortgage Securities Corp. Servicing Guide to the extent incorporated by
reference therein) between the Company and a Person relating to the sale of the
Mortgage Loans to the Company and the servicing of such Mortgage Loans for the
benefit of the Certificateholders, which contract is substantially in the form
of Exhibit E hereto, as such contract may be amended or modified from time to
time;

                                       55
<PAGE>

provided, however, that any such amendment or modification shall not materially
adversely affect the interests and rights of Certificateholders or (b) any other
similar contract, including any mortgage loan purchase and servicing agreement
or any assignment, assumption and recognition agreement related to a mortgage
loan purchase and sale agreement, providing substantially similar rights and
benefits as those provided by the forms of contract attached as Exhibit E
hereto.

         Senior Certificates: The Class P, Subgroup 1, Subgroup 2 and Residual
Certificates.

         Senior Subordinate Certificates: The Subordinate Certificates other
than the Junior Subordinate Certificates.

         Servicer: A mortgage loan servicing institution to which the Master
Servicer has assigned servicing duties with respect to any Mortgage Loan under a
Selling and Servicing Contract; provided, however, the Master Servicer may
designate itself or one or more other mortgage loan servicing institutions as
Servicer upon termination of an initial Servicer's servicing duties.

         Servicing Fee: For each Mortgage Loan, the fee paid to the Servicer
thereof to perform primary servicing functions for the Master Servicer with
respect to such Mortgage Loan, equal to the per annum rate set forth for each
Mortgage Loan in the Mortgage Loan Schedule on the outstanding Principal Balance
of such Mortgage Loan. In addition, any prepayment penalty received on a
Mortgage Loan will be paid as additional servicing compensation to the Master
Servicer or the related Servicer.

         Servicing Officer: Any officer of the Master Servicer involved in, or
responsible for, the administration and servicing of the Mortgage Loans or the
Certificates, as applicable, whose name and specimen signature appear on a list
of servicing officers furnished to the Trustee by the Master Servicer, as such
list may from time to time be amended.

         Special Hazard Coverage: The Special Hazard Coverage on the most recent
anniversary of the Cut-Off Date (calculated in accordance with the second
sentence of this paragraph) or, if prior to the first such anniversary,
$3,753,853, in each case reduced by Special Hazard Losses allocated to the
Certificates since the most recent anniversary of the Cut-Off Date (or, if prior
to the first such anniversary, since the Cut-Off Date). On each anniversary of
the Cut-Off Date, the Special Hazard Coverage shall be reduced, but not
increased, to an amount equal to the lesser of (1) the greatest of (a) the
aggregate principal balance of the Mortgage Loans located in the single
California zip code area containing the largest aggregate principal balance of
Mortgage Loans, (b) 1.0% of the aggregate unpaid principal balance of the
Mortgage Loans and (c) twice the unpaid principal balance of the largest single
Mortgage Loan, in each case calculated as of the Due Date in the immediately
preceding month, and (2) $3,753,853 as reduced by the Special Hazard Losses
allocated to the Certificates since the Cut-Off Date.

         The Special Hazard Coverage may be reduced upon written confirmation
from the Rating Agencies that such reduction will not adversely affect the then
current ratings assigned to the Certificates by the Rating Agencies.

         Special Hazard Loss: A Realized Loss (or portion thereof) with respect
to a Mortgage Loan arising from any direct physical loss or damage to a


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Mortgaged Property not covered by a standard hazard maintenance policy with
extended coverage which is caused by or results from any cause except: (i) fire,
lightning, windstorm, hail, explosion, riot, riot attending a strike, civil
commotion, vandalism, aircraft, vehicles, smoke, sprinkler leakage, except to
the extent of that portion of the loss which was uninsured because of the
application of a co-insurance clause of any insurance policy covering these
perils; (ii) normal wear and tear, gradual deterioration, inherent vice or
inadequate maintenance of all or part thereof; (iii) errors in design, faulty
workmanship or materials, unless the collapse of the property or a part thereof
ensues and then only for the ensuing loss; (iv) nuclear reaction or nuclear
radiation or radioactive contamination, all whether controlled or uncontrolled
and whether such loss be direct or indirect, proximate or remote or be in whole
or in part caused by, contributed to or aggravated by a peril covered by this
definition of Special Hazard Loss; (v) hostile or warlike action in time of
peace or war, including action in hindering, combating or defending against an
actual, impending or expected attack (a) by any government of sovereign power
(de jure or de facto), or by an authority maintaining or using military, naval
or air forces, (b) by military, naval or air forces, or (c) by an agent of any
such government, power, authority or forces; (vi) any weapon of war employing
atomic fission or radioactive force whether in time of peace or war; (vii)
insurrection, rebellion, revolution, civil war, usurped power or action taken by
governmental authority in hindering, combating or defending against such
occurrence; or (viii) seizure or destruction under quarantine or customs
regulations, or confiscation by order of any government or public authority.

         Special Primary Insurance Policy: Any Primary Insurance Policy covering
a Mortgage Loan the premium of which is payable by the Trustee pursuant to
Section 4.04(a), if so identified in the Mortgage Loan Schedule. There are no
Special Primary Insurance Policies with respect to any of the Mortgage Loans.

         Special Primary Insurance Premium: With respect to any Special Primary
Insurance Policy, the monthly premium payable thereunder.

         Statutory Trust Statute: Chapter 38 of Title 12 of the Delaware Code,
12 Del.C.ss.3801 et seq., as the same may be amended from time to time.

         Step Down Percentage: For any Distribution Date, the percentage
indicated below:

       Distribution Date Occurring In            Step Down Percentage
       --------------------------------          --------------------
       March 2004 through February 2009                   0%
       March 2009 through February 2010                   30%
       March 2010 through February 2011                   40%
       March 2011 through February 2012                   60%
       March 2012 through February 2013                   80%
       March 2013 and thereafter                         100%

         Subgroup: Subgroup 1 or Subgroup 2, as applicable.

         Subgroup 1: The group of Mortgage Loans (or portions of Mortgage Loans)
comprised of the Subgroup 1 Loans.

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<PAGE>

         Subgroup 1 Certificates: The Class 1-A-1, Class 1-A-2, Class 1-A-3,
Class 1-A-4, Class 1-A-5, Class 1-A-6, Class 1-A-7, Class 1-A-8, Class 1-A-9,
Class 1-A-10, Class 1-A-11 and Class 1-A-12 Certificates.

         Subgroup 1 Loans:  The following Mortgage Loans or portions thereof:

         (i) the Mortgage Loans with Pass-Through Rates less than or equal to
5.500%; and

         (ii) for any Mortgage Loan with a Pass-Through Rate greater than
5.500%, a fraction of the Principal Balance of that Mortgage Loan equal to (a)
8.000 minus the Pass-Through Rate of that Mortgage Loan, divided by (b) 2.5.

         Subgroup 1 Senior Principal Distribution Amount: For any Distribution
Date, an amount equal to the sum of (a) the Subgroup 1 Senior Percentage of the
Principal Payment Amount for Subgroup 1 (exclusive of the portion thereof
attributable to principal distributions to the Class P-L Regular Interest
pursuant to clause (I)(a)(i) and (II)(a)(i) of the definition of "REMIC II
Distribution Amount"), (b) the Subgroup 1 Senior Prepayment Percentage of the
Principal Prepayment Amount for Subgroup 1 (exclusive of the portion thereof
attributable to principal distributions to the Class P-L Regular Interest
pursuant to clauses (I)(a)(i) and (II)(a)(i) of the definition of "REMIC II
Distribution Amount") and (c) the Subgroup 1 Senior Liquidation Amount.

         Subgroup 1 Senior Liquidation Amount: For any Distribution Date, the
sum of (A) the aggregate, for each Subgroup 1 Loan which became a Liquidated
Mortgage Loan during the Prior Period, of the lesser of: (i) the Subgroup 1
Senior Percentage of the Principal Balance of such Mortgage Loan (or such
portion thereof) (exclusive of the Class P Fraction thereof, with respect to any
Class P Mortgage Loan) and (ii) the Subgroup 1 Senior Prepayment Percentage of
the Liquidation Principal with respect to such Mortgage Loan (or such portion
thereof) and (B) the Subgroup 1 Senior Prepayment Percentage of any Subsequent
Recoveries for Subgroup 1 for such Distribution Date.

         Subgroup 1 Senior Percentage: For any Distribution Date, the lesser of
(i) 100% and (ii) the aggregate Class Principal Balance of the Subgroup 1
Certificates and Class R Certificates divided by the aggregate Principal Balance
of the Subgroup 1 Loans (exclusive of the Class P Fraction thereof with respect
to any Class P Mortgage Loan), in each case immediately before such Distribution
Date.

         Subgroup 1 Senior Prepayment Percentage or Subgroup 2 Senior Prepayment
Percentage: For any Distribution Date, each of the Subgroup 1 Senior Prepayment
Percentage, and the Subgroup 2 Senior Prepayment Percentage shall equal 100%,
unless (i) the Subgroup 1 Senior Percentage for such Distribution Date is less
than or equal to the Subgroup 1 Senior Percentage as of the Closing Date and the
Subgroup 2 Senior Percentage for such Distribution Date is less than or equal to
the Subgroup 2 Senior Percentage as of the Closing Date, (ii) such Distribution
Date occurs on or after the fifth anniversary of the first Distribution Date and
(iii) the following tests specified in clauses (a) through (d) are met with
respect to each of Subgroup 1 and Subgroup 2:

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<PAGE>

         (a) the mean aggregate Principal Balance as of the Distribution Date in
each of the immediately preceding six calendar months of the Subgroup 1 Loans
which were 60 or more days delinquent as of such date (including Mortgage Loans
in bankruptcy or foreclosure and Mortgaged Properties held by REMIC I) is less
than or equal to 50% of the Subordinate Component Balance for Subgroup 1 as of
the current Distribution Date,

         (b) the mean aggregate Principal Balance as of the Distribution Date in
each of the immediately preceding six calendar months of the Subgroup 2 Loans
which were 60 or more days delinquent as of such date (including Mortgage Loans
in bankruptcy or foreclosure and Mortgaged Properties held by REMIC I) is less
than or equal to 50% of the Subordinate Component Balance for Subgroup 2 as of
the current Distribution Date,

         (c) cumulative Realized Losses on the Subgroup 1 Loans allocated to the
Class B-L Regular Interests, as a percentage of the Subordinate Component
Balance for Subgroup 1 as of the Closing Date, are less than or equal to, for
any Distribution Date (1) before the sixth anniversary of the first Distribution
Date, 30%, (2) on or after the sixth anniversary but before the seventh
anniversary of the first Distribution Date, 35%, (3) on or after the seventh
anniversary but before the eighth anniversary of the first Distribution Date,
40%, (4) on or after the eighth anniversary but before the ninth anniversary of
the first Distribution Date, 45%, and (5) on or after the ninth anniversary of
the first Distribution Date, 50%, and

         (d) cumulative Realized Losses on the Subgroup 2 Loans allocated to the
Class B-L Regular Interests, as a percentage of the Subordinate Component
Balance for Subgroup 2 as of the Closing Date, are less than or equal to, for
any Distribution Date (1) before the sixth anniversary of the first Distribution
Date, 30%, (2) on or after the sixth anniversary but before the seventh
anniversary of the first Distribution Date, 35%, (3) on or after the seventh
anniversary but before the eighth anniversary of the first Distribution Date,
40%, (4) on or after the eighth anniversary but before the ninth anniversary of
the first Distribution Date, 45%, and (5) on or after the ninth anniversary of
the first Distribution Date, 50%,

in which case the Subgroup 1 Senior Prepayment Percentage and the Subgroup 2
Senior Prepayment Percentage shall be calculated as follows: (1) for any such
Distribution Date on or after the fifth anniversary but before the sixth
anniversary of the first Distribution Date, the Subgroup 1 Senior Percentage or
Subgroup 2 Senior Percentage, as applicable, for such Distribution Date plus 70%
of the Subordinate Percentage for the related Subgroup for such Distribution
Date; (2) for any such Distribution Date on or after the sixth anniversary but
before the seventh anniversary of the first Distribution Date, the Subgroup 1
Senior Percentage, or Subgroup 2 Senior Percentage, as applicable, for such
Distribution Date plus 60% of the Subordinate Percentage for the related
Subgroup for such Distribution Date; (3) for any such Distribution Date on or
after the seventh anniversary but before the eighth anniversary of the first
Distribution Date, the Subgroup 1 Senior Percentage or Subgroup 2 Senior
Percentage, as applicable, for such Distribution Date plus 40% of the
Subordinate Percentage for the related Subgroup for such Distribution Date; (4)
for any such Distribution Date on or after the eighth anniversary but before the


                                       59
<PAGE>

ninth anniversary of the first Distribution Date, the Subgroup 1 Senior
Percentage or Subgroup 2 Senior Percentage, as applicable, for such Distribution
Date plus 20% of the Subordinate Percentage for the related Subgroup for such
Distribution Date; and (5) for any such Distribution Date thereafter, the
Subgroup 1 Senior Percentage or Subgroup 2 Senior Percentage, as applicable, for
such Distribution Date.

         If on any Distribution Date the allocation to the Subgroup 1-L or
Subgroup 2-L Regular Interests of Principal Prepayments in the percentage
required would reduce the Class Principal Balance of such Certificates below
zero, the Subgroup 1 Senior Prepayment Percentage or Subgroup 2 Senior
Prepayment Percentage, as applicable, for such Distribution Date shall be
limited to the percentage necessary to reduce such Class Principal Balance to
zero. Notwithstanding the foregoing, however, on each Distribution Date, the
Class P-L Regular Interest shall receive the applicable Class P Fraction of all
principal payments, including, without limitation, Principal Prepayments,
received in respect of Class P Mortgage Loans.

         Subgroup 1 Subordinate Balance: For any date of determination, an
amount equal to the then outstanding aggregate Principal Balance of the Subgroup
1 Loans reduced by the sum of (i) the aggregate Class Principal Balance of the
Subgroup 1 Certificates, Class P and Residual Certificates.

         Subgroup 1 Subordinate Percentage: For any Distribution Date, the
excess of 100% over the Subgroup 1 Senior Percentage for such date.

         Subgroup 1 Subordinate Prepayment Percentage: For any Distribution
Date, the excess of 100% over the Subgroup 1 Senior Prepayment Percentage for
such Distribution Date; provided, however, that if the aggregate Class Principal
Balance of the Subgroup 1 and Residual Certificates has been reduced to zero,
then the Subgroup 1 Subordinate Prepayment Percentage shall equal 100%.

         Subgroup 1-L Regular Interests: The Class 1-A-1-L, Class 1-A-2-L, Class
1-A-3-L, Class 1-A-5-L, Class 1-A-6-L, Class 1-A-7-L, Class 1-A-8-L, Class
1-A-9-L, Class 1-A-10-L, Class 1-A-11-L and Class 1-A-12-L Regular Interests.

         Subgroup 2: The group of Mortgage Loans (or portions of Mortgage Loans)
comprised of the Subgroup 2 Loans.

         Subgroup 2 Certificates:  The Class 2-A-1 and Class 2-A-2 Certificates.

         Subgroup 2 Loans: For any Mortgage Loan with a Pass-Through Rate
greater than 5.500%, a fraction of the Principal Balance of that Mortgage Loan
equal to (a) the Pass-Through Rate of that Mortgage Loan minus 5.500, divided by
(b) 2.5.

         Subgroup 2 Senior Principal Distribution Amount: For any Distribution
Date, an amount equal to the sum of (a) the Subgroup 2 Senior Percentage of the
Principal Payment Amount for Subgroup 2, (b) the Subgroup 2 Senior Prepayment
Percentage of the Principal Prepayment Amount for Subgroup 2 and (c) the
Subgroup 2 Senior Liquidation Amount.

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<PAGE>

         Subgroup 2 Senior Liquidation Amount: For any Distribution Date, the
sum of (A) the aggregate, for each Subgroup 2 Loan which became a Liquidated
Mortgage Loan during the Prior Period, of the lesser of: (i) the Subgroup 2
Senior Percentage of the Principal Balance of such Mortgage Loan (or such
portion thereof) and (ii) the Subgroup 2 Senior Prepayment Percentage of the
Liquidation Principal with respect to such Mortgage Loan (or such portion
thereof) and (B) the Subgroup 2 Senior Prepayment Percentage of any Subsequent
Recoveries for Subgroup 2 for such Distribution Date.

         Subgroup 2 Senior Percentage: For any Distribution Date, the lesser of
(i) 100% and (ii) the Class 2-A-1 Principal Balance divided by the aggregate
Principal Balance of the Subgroup 2 Loans, in each case immediately before such
Distribution Date.

         Subgroup 2 Senior Prepayment Percentage: See the definition of
"Subgroup 1 Senior Prepayment Percentage or Subgroup 2 Senior Prepayment
Percentage."

         Subgroup 2 Subordinate Balance: For any date of determination, an
amount equal to the then outstanding aggregate Principal Balance of the Subgroup
2 Loans reduced by the aggregate Class Principal Balance of the Subgroup 2
Certificates.

         Subgroup 2 Subordinate Percentage: For any Distribution Date, the
excess of 100% over the Subgroup 2 Senior Percentage for such date.

         Subgroup 2 Subordinate Prepayment Percentage: For any Distribution
Date, the excess of 100% over the Subgroup 2 Senior Prepayment Percentage for
such Distribution Date; provided, however, that if the aggregate Class Principal
Balance of the Subgroup 2 Certificates has been reduced to zero, then the
Subgroup 2 Subordinate Prepayment Percentage shall equal 100%.

         Subgroup 2-L Regular Interests:  The Class 2-A-1-L Regular Interest.

         Subordinate Certificates:  The Class B Certificates.

         Subordinate Component Balance: With respect to Subgroup 1 for any date
of determination, the then outstanding aggregate Principal Balance of the
Subgroup 1 Loans (less the applicable Class P Fraction thereof with respect to
any Class P Mortgage Loan) minus the then outstanding aggregate Class Principal
Balance of the Subgroup 1 and Residual Certificates. With respect to Subgroup 2
for any date of determination, the then outstanding aggregate Principal Balance
of the Subgroup 2 Loans minus the then outstanding aggregate Class Principal
Balance of the Subgroup 2 Certificates.

         Subordinate Liquidation Amount: For any Distribution Date, the excess,
if any, of the sum of (A) the aggregate of Liquidation Principal for all
Mortgage Loans which became Liquidated Mortgage Loans during the Prior Period
and (B) any Subsequent Recoveries for such Distribution Date for Subgroup 1 and
Subgroup 2, over the sum of the Subgroup 1 Senior Liquidation Amount and the
Subgroup 2 Senior Liquidation Amount for such Distribution Date.

         Subordinate Percentage: The Subgroup 1 Subordinate Percentage or the
Subgroup 2 Subordinate Percentage, as applicable.



                                       61
<PAGE>

         Subordinate Principal Distribution Amount: For any Distribution Date,
the excess of (A) the sum of (i) the Subgroup 1 Subordinate Percentage of the
Principal Payment Amount for Subgroup 1 (exclusive of the portion thereof
attributable to principal distributions to the Class P-L Regular Interest
pursuant to clause (I)(a)(i) of the definition of "REMIC II Distribution
Amount"), (ii) the Subgroup 2 Subordinate Percentage of the Principal Payment
Amount for Subgroup 2, (iii) the Subordinate Principal Prepayments Distribution
Amount (without regard to the proviso in the definition thereof) and (iv) the
Subordinate Liquidation Amount over (B) the sum of (x) the amounts required to
be distributed to the Class P-L Regular Interest pursuant to clauses (I)(c)(i)
and (I)(c)(ii) of the definition of "REMIC II Distribution Amount" on such
Distribution Date, (y) in the event that the aggregate Class Principal Balance
of either the Subgroup 1-L or Subgroup 2-L Regular Interests has been reduced to
zero, principal paid from the REMIC II Available Distribution Amount related to
such Class A-L Regular Interests to the remaining Class A-L Regular Interests,
as set forth in clause (X) of the sentence immediately following paragraph
(I)(c) of the definition of "REMIC II Distribution Amount," and (z) the amounts
paid from the REMIC II Available Distribution Amount for the Regular Interest
Subgroup related to an Overcollateralized Subgroup to the Class A-L Regular
Interests related to an Undercollateralized Subgroup pursuant to clause (Y) of
the sentence immediately following paragraph (I)(c) of the definition of "REMIC
II Distribution Amount."

         On any Distribution Date, the Subordinate Principal Distribution Amount
shall be allocated pro rata, by Class Principal Balance, among the Classes of
Class B-L Regular Interests and paid in the order of distribution to such
Classes pursuant to clause (I)(c) of the definition of "REMIC II Distribution
Amount" except as otherwise stated in such definition. Notwithstanding the
foregoing, on any Distribution Date prior to distributions on such date, if the
Subordination Level for any Class of Class B-L Regular Interests is less than
such Subordination Level as of the Closing Date, the pro rata portion of the
Subordinate Principal Prepayments Distribution Amount otherwise allocable to the
Class or Classes of Class B-L Regular Interests junior to such Class will be
distributed to the most senior Class of Class B-L Regular Interests for which
the Subordination Level is less than the Subordination Level as of the Closing
Date, and to the Class or Classes of Class B-L Regular Interests senior thereto,
pro rata according to the Class Principal Balances of such Classes. For purposes
of this definition and the definition of "Subordination Level," the relative
seniority, from highest to lowest, of the Class B-L Regular Interests shall be
as follows: Class B-1-L, Class B-2-L, Class B-3-L, Class B-4-L, Class B-5-L and
Class B-6-L.

         Subordinate Principal Prepayments Distribution Amount: For any
Distribution Date, the sum of (i) the Subgroup 1 Subordinate Prepayment
Percentage of the Principal Prepayment Amount for Subgroup 1 (exclusive of the
portion thereof attributable to principal distributions to the Class P-L Regular
Interest pursuant to clause (I)(a)(i) of the definition of "REMIC II
Distribution Amount") and (ii) the Subgroup 2 Subordinate Prepayment Percentage
of the Principal Prepayment Amount for Subgroup 2; provided, however, that if
the amount specified in clause (B) of the definition of "Subordinate Principal
Distribution Amount" is greater than the sum of the amounts specified in clauses
(A)(i), (A)(ii) and (A)(iv) of such definition, then the Subordinate Principal
Prepayments Distribution Amount shall be reduced by the amount of such excess.

         Subordination Level: On any specified date, with respect to any Class
of Class B-L Regular Interests, the percentage obtained by dividing the


                                       62
<PAGE>

aggregate Class Principal Balance of the Classes of Class B-L Regular Interests
which are subordinate in right of payment to such Class by the aggregate Class
Principal Balance of the Class P-L, Subgroup 1-L, Subgroup 2-L and Class B-L
Regular Interests and the Class R-1 Residual Interest as of such date prior to
giving effect to distributions of principal and interest and allocations of
Realized Losses on the Mortgage Loans on such date.

         Subsequent Recoveries: For any Distribution Date and any Subgroup,
amounts received by the Master Servicer during the Prior Period (after deduction
of amounts reimbursable under Section 3.05(a)(i) and (ii)) in connection with
the liquidation of defaulted Mortgage Loans (or portions of Mortgage Loans) in
such Subgroup after such Mortgage Loans (or portions thereof) became Liquidated
Mortgage Loans, for each such Mortgage Loan (or portion thereof) up to the
amount of Realized Losses, if any, previously allocated in respect of such
Mortgage Loan (or portion thereof) in reduction of the Class Principal Balance
of any Class of Certificates.

         Substitute Mortgage Loan: A Mortgage Loan which is substituted for
another Mortgage Loan pursuant to and in accordance with the provisions of
Section 2.07.

         Targeted Principal Balance: With respect to the Class 1-A-5 and Class
1-A-6 Certificates, the aggregate amount set forth in the table attached as
Appendix D to the Prospectus, for the applicable Distribution Date, under the
heading "Class 1-A-5 and Class 1-A-6 Aggregate Targeted Principal Balance".

         Tax Matters Person: With respect to each of REMIC I, REMIC II and REMIC
III, a Holder of a Class R Certificate with a Percentage Interest of at least
0.01% or any Permitted Transferee of such Class R Certificateholder designated
as succeeding to the position of Tax Matters Person in a notice to the Trustee
signed by authorized representatives of the transferor and transferee of such
Class R Certificate. The Company is hereby appointed to act as the Tax Matters
Person for REMIC I, REMIC II and REMIC III so long as it holds a Class R
Certificate with a Percentage Interest of at least 0.01%. The Company is hereby
appointed to act as agent for the Tax Matters Person for REMIC I, REMIC II and
REMIC III, to perform the functions of such Tax Matters Person as provided
herein, so long as the Company is the Master Servicer hereunder, in the event
that the Company ceases to hold a Class R Certificate with the required
Percentage Interest. In the event that the Company ceases to be the Master
Servicer hereunder, the successor Master Servicer is hereby appointed to act as
agent for the Tax Matters Person for REMIC I, REMIC II and REMIC III, to perform
the functions of such Tax Matters Person as provided herein. If the Tax Matters
Person for REMIC I, REMIC II and REMIC III becomes a Disqualified Organization,
the last preceding Holder, that is not a Disqualified Organization, of the Class
R Certificate held by the Disqualified Organization shall be Tax Matters Person
pursuant to and as permitted by Section 5.01(c). If any Person is appointed as
tax matters person by the Internal Revenue Service pursuant to the Code, such
Person shall be Tax Matters Person.

         Termination Date: The date upon which final payment of the Certificates
will be made pursuant to the procedures set forth in Section 9.01(b).

         Termination Payment: The final payment delivered to the
Certificateholders on the Termination Date pursuant to the procedures set forth
in Section 9.01(b).

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<PAGE>

         Total Transfer Amount: For any Distribution Date and for an
Undercollateralized Subgroup, an amount equal to the sum of the Interest
Transfer Amount and the Principal Transfer Amount for such Undercollateralized
Subgroup.

         Transfer: Any direct or indirect transfer or sale of any Ownership
Interest in a Residual Certificate.

         Transferee: Any Person who is acquiring by Transfer any Ownership
Interest in a Residual Certificate.

         Transferee Affidavit and Agreement: An affidavit and agreement in the
form attached hereto as Exhibit J.

         Trust: WaMu Mortgage Pass-Through Certificates Series 2004-S1 Trust, a
Delaware statutory trust, created pursuant to this Agreement.

         Trustee: Citibank, N.A., or its successor-in-interest as provided in
Section 8.09, or any successor trustee appointed as herein provided.

         Uncollected Interest: With respect to any Distribution Date for any
Mortgage Loan on which a Payoff was made by a Mortgagor during the related
Payoff Period, except for Payoffs received during the period from the first
through the 14th day of the month of such Distribution Date, an amount equal to
one month's interest at the applicable Pass-Through Rate on such Mortgage Loan
less the amount of interest actually paid by the Mortgagor with respect to such
Payoff.

         Uncompensated Interest Shortfall: For any Distribution Date, the sum of
(i) the aggregate Relief Act Shortfall for such Distribution Date, (ii)
aggregate Curtailment Shortfall for such Distribution Date and (iii) the excess,
if any, of (a) aggregate Uncollected Interest for such Distribution Date over
(b) Compensating Interest for such Distribution Date.

         Uncompensated Interest Shortfall shall be allocated to the REMIC II
Regular Interests pro rata to the amount of interest accrued on each such Class
during the immediately preceding accrual period, in reduction thereof.

         Uncompensated Interest Shortfall shall be allocated to the REMIC I
Regular Interests pro rata according to the amount of interest accrued but
unpaid on each such Class, in reduction thereof.

         Undercollateralized Subgroup: For any Distribution Date, Subgroup 1, if
immediately prior to such Distribution Date the aggregate Class Principal
Balance of the Subgroup 1 and Residual Certificates is greater than the
aggregate Principal Balance of the Subgroup 1 Loans (less the applicable Class P
Fraction thereof with respect to each Class P Mortgage Loan) and for any
Distribution Date, Subgroup 2, if immediately prior to such Distribution Date
the Class Principal Balance of the Subgroup 2 Certificates is greater than the
aggregate Principal Balance of the Subgroup 2 Loans.

         Underwriter: Bear, Stearns & Co.



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<PAGE>

         Underwriting Standards: The underwriting standards of the Company,
Washington Mutual Bank, FA or Washington Mutual Bank, a Washington state
chartered savings bank, as applicable.

         Uninsured Cause: Any cause of damage to a Mortgaged Property, the cost
of the complete restoration of which is not fully reimbursable under the hazard
insurance policies required to be maintained pursuant to Section 3.07.

         U.S. Person: A citizen or resident of the United States, a corporation,
partnership or other entity created or organized in or under the laws of the
United States, any state thereof or the District of Columbia, or an estate or
trust that is subject to U.S. federal income tax regardless of the source of its
income.

         VA: The Department of Veterans Affairs, formerly known as the Veterans
Administration, or any successor thereto.

         Withdrawal Date: Any day during the period commencing on the 18th day
of the month of the related Distribution Date (or if such day is not a Business
Day, the immediately preceding Business Day) and ending on the last Business Day
prior to the 21st day of the month of such Distribution Date. The "related Due
Date" for any Withdrawal Date is the Due Date immediately preceding the related
Distribution Date.

                                   ARTICLE II

     Creation of the Trust; Conveyance of the Mortgage Pool Assets, REMIC I
      Regular Interests and REMIC II Regular Interests; REMIC Election and
                Designations; Original Issuance of Certificates

         SECTION 2.01 Creation of the Trust. The Trust is hereby created and
shall be known as "WaMu Mortgage Pass-Through Certificates Series 2004-S1
Trust". The purpose of the Trust is, and the Trust shall have the power and
authority, to engage in the following activities, all as provided by and subject
to the terms of this Agreement:

         (i) to acquire, hold, lease, manage, administer, control, invest,
reinvest, operate and/or transfer the Mortgage Pool Assets, the REMIC II Assets
and the REMIC III Assets;

         (ii) to issue the REMIC I Regular Interests, the REMIC II Regular
Interests, the Class R-1, Class R-2 and Class R-3 Residual Interests and the
Certificates;

         (iii) to make distributions to the REMIC I Regular Interests, the REMIC
II Regular Interests and the Certificates; and

         (iv) to engage in such other activities, including entering into
agreements, as are described in or required by the terms of this Agreement or as
are necessary, suitable or convenient to accomplish the foregoing or incidental
thereto.



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<PAGE>

Citibank, N.A. is hereby appointed as a trustee of the Trust, to have all the
rights, duties and obligations of the Trustee with respect to the Trust
expressly set forth hereunder, and Citibank, N.A. hereby accepts such
appointment and the Trust created hereby. Christiana Bank & Trust Company is
hereby appointed as a Delaware trustee of the Trust, to have all the rights,
duties and obligations of the Delaware Trustee with respect to the Trust
hereunder, and Christiana Bank & Trust Company hereby accepts such appointment
and the Trust created hereby. It is the intention of the Company, the Trustee
and the Delaware Trustee that the Trust constitute a statutory trust under the
Statutory Trust Statute, that this Agreement constitute the governing instrument
of the Trust, and that this Agreement amend and restate the Original Trust
Agreement. The parties hereto acknowledge and agree that, prior to the execution
and delivery hereof, the Delaware Trustee has filed the Certificate of Trust.

         The assets of the Trust shall remain in the custody of the Trustee, on
behalf of the Trust, and shall be owned by the Trust except as otherwise
expressly set forth herein. Moneys to the credit of the Trust shall be held by
the Trustee and invested as provided herein. All assets received and held in the
Trust will not be subject to any right, charge, security interest, lien or claim
of any kind in favor of either of Citibank, N.A. or Christiana Bank & Trust
Company in its own right, or any Person claiming through it. Neither the Trustee
nor the Delaware Trustee, on behalf of the Trust, shall have the power or
authority to transfer, assign, hypothecate, pledge or otherwise dispose of any
of the assets of the Trust to any Person, except as permitted herein. No
creditor of a beneficiary of the Trust, of the Trustee, of the Delaware Trustee,
of the Master Servicer or of the Company shall have any right to obtain
possession of, or otherwise exercise legal or equitable remedies with respect
to, the property of the Trust, except in accordance with the terms of this
Agreement.

         SECTION 2.02 Restrictions on Activities of the Trust. Notwithstanding
any other provision of this Agreement and any provision of law that otherwise so
empowers the Trust, so long as any Certificates are outstanding, the Trust shall
not, and none of the Trustee, the Delaware Trustee, the Company or the Master
Servicer shall knowingly cause the Trust to, do any of the following:

         (i) engage in any business or activity other than those set forth in
Section 2.01;

         (ii) incur or assume any indebtedness except for such indebtedness that
may be incurred by the Trust in connection with the execution or performance of
this Agreement or any other agreement contemplated hereby;

         (iii) guarantee or otherwise assume liability for the debts of any
other party;

         (iv) do any act in contravention of this Agreement or any other
agreement contemplated hereby to which the Trust is a party;

         (v) do any act which would make it impossible to carry on the ordinary
business of the Trust;

         (vi) confess a judgment against the Trust;

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<PAGE>

         (vii) possess or assign the assets of the Trust for other than a Trust
purpose;

         (viii) cause the Trust to lend any funds to any entity, except as
contemplated by this Agreement; or

         (ix) change the purposes and powers of the Trust from those set forth
in this Agreement.

         SECTION 2.03 Separateness Requirements. Notwithstanding any other
provision of this Agreement and any provision of law that otherwise so empowers
the Trust, so long as any Certificates are outstanding, the Trust shall perform
the following:

         (i) except as expressly permitted by this Agreement, maintain its
books, records, bank accounts and files separate from those of any other Person;

         (ii) except as expressly permitted by this Agreement, maintain its
assets in its own separate name and in such a manner that it is not costly or
difficult to segregate, identify, or ascertain such assets;

         (iii) consider the interests of the Trust's creditors in connection
with its actions;

         (iv) hold itself out to creditors and the public as a legal entity
separate and distinct from any other Person and correct any known
misunderstanding regarding its separate identity and refrain from engaging in
any activity that compromises the separate legal identity of the Trust;

         (v) prepare and maintain separate records, accounts and financial
statements in accordance with generally accepted accounting principles,
consistently applied, and susceptible to audit. To the extent it is included in
consolidated financial statements or consolidated tax returns, such financial
statements and tax returns will reflect the separateness of the respective
entities and indicate that the assets of the Trust will not be available to
satisfy the debts of any other Person;

         (vi) allocate and charge fairly and reasonably any overhead shared with
any other Person;

         (vii) transact all business with affiliates on an arm's-length basis
and pursuant to written, enforceable agreements;

         (viii) conduct business solely in the name of the Trust. In that regard
all written and oral communications of the Trust, including, without limitation,
letters, invoices, purchase orders and contracts, shall be made solely in the
name of the Trust;

         (ix) maintain a separate office through which its business shall be
conducted, provided that such office may be an office of the Trustee, which
office shall not be shared with the Company or any affiliates of the Company;



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<PAGE>

         (x) in the event that services have been or are in the future performed
or paid by any Person on behalf of the Trust (other than the Trustee, the
Delaware Trustee, the Master Servicer or the Tax Matters Person as permitted
herein), reimburse such Person, as applicable, for the commercially reasonable
value of such services or expenses provided or incurred by such Person.
Accordingly, (i) the Trust shall reimburse such Person, as applicable, for the
commercially reasonable value of such services or expenses provided or incurred
by such Person; (ii) to the extent invoices for such services are not allocated
and separately billed to the Trust, the amount thereof that was or is to be
allocated and separately billed to the Trust was or will be reasonably related
to the services provided to the Trust; and (iii) any other allocation of direct,
indirect or overhead expenses for items shared between the Trust and any other
Person, was or will be, to the extent practicable, allocated on the basis of
actual use or value of services rendered or otherwise on a basis reasonably
related to actual use or the value of services rendered;

         (xi) except as expressly permitted by this Agreement, not commingle its
assets or funds with those of any other Person;

         (xii) except as expressly permitted by this Agreement, not assume,
guarantee, or pay the debts or obligations of any other Person;

         (xiii) except as expressly permitted by this Agreement, not pledge its
assets for the benefit of any other Person;

         (xiv) not hold out its credit or assets as being available to satisfy
the obligations of others;

         (xv) pay its liabilities only out of its funds;

         (xvi) pay the salaries of its own employees, if any; and

         (xvii) cause the agents and other representatives of the Trust, if any,
to act at all times with respect to the Trust consistently and in furtherance of
the foregoing.

         None of the Trustee, the Delaware Trustee, the Company or the Master
Servicer shall take any action that is inconsistent with the purposes of the
Trust or Section 2.02 or Section 2.03. Neither the Company nor the Master
Servicer shall direct the Trustee or the Delaware Trustee to take any action
that is inconsistent with the purposes of the Trust or Section 2.02 or Section
2.03.

         SECTION 2.04 Conveyance of Mortgage Pool Assets; Security Interest.

         Concurrently with the execution and delivery hereof, the Company does
hereby irrevocably sell, transfer, assign, set over and otherwise convey to the
Trust, without recourse, all the Company's right, title and interest in and to
the Mortgage Pool Assets, including but not limited to all scheduled payments of
principal and interest due after the Cut-Off Date and received by the Company
with respect to the Mortgage Loans at any time, and all Principal Prepayments
received by the Company after the Cut-Off Date with respect to the Mortgage


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<PAGE>

Loans (such transfer and assignment by the Company to be referred to herein as
the "Conveyance," and the assets so transferred and assigned to be referred to
herein as the "Conveyed Assets").

         It is the express intent of the parties hereto that the Conveyance of
the Conveyed Assets to the Trust by the Company as provided in this Section 2.04
be, and be construed as, an absolute sale of the Conveyed Assets. It is,
further, not the intention of the parties that such Conveyance be deemed the
grant of a security interest in the Conveyed Assets by the Company to the Trust
to secure a debt or other obligation of the Company. However, in the event that,
notwithstanding the intent of the parties, the Conveyed Assets are held to be
the property of the Company, or if for any other reason this Agreement is held
or deemed to create a security interest in the Conveyed Assets, then

         (a) this Agreement shall be deemed to be a security agreement;

         (b) the Conveyance provided for in this Section 2.04 shall be deemed to
be a grant by the Company to the Trust of, and the Company hereby grants to the
Trust, to secure all of the Company's obligations hereunder, a security interest
in all of the Company's right, title, and interest, whether now owned or
hereafter acquired, in and to:

         (I) (i) the Mortgage Loans identified on the Mortgage Loan Schedule,
including the related Mortgage Notes, Mortgages, Cooperative Stock Certificates,
Cooperative Leases, Security Agreements, Assignments of Proprietary Lease, and
Recognition Agreements, all Substitute Mortgage Loans and all distributions with
respect to the Mortgage Loans and Substitute Mortgage Loans payable on and after
the Cut-Off Date; (ii) the Certificate Account, the Investment Account and all
money or other property held therein, and the Custodial Accounts for P&I, the
Custodial Accounts for Reserves and any Buydown Fund Account (to the extent of
the amounts on deposit or other property therein attributable to the Mortgage
Loans); and (iii) amounts paid or payable by the insurer under any FHA insurance
policy or any Primary Insurance Policy and proceeds of any VA guaranty and any
other insurance policy related to any Mortgage Loan or the Mortgage Pool;

         (II) All rights arising from or by virtue of the disposition of, or
collections with respect to, or insurance proceeds payable with respect to, or
claims against other persons with respect to, all or any part of the collateral
described in (I) above (including any accrued discount realized on liquidation
of any investment purchased at a discount);

         (III) All accounts, general intangibles, chattel paper, instruments,
documents, money, deposit accounts, goods, letters of credit, letter-of-credit
rights, oil, gas, and other minerals, and investment property consisting of,
arising from or relating to any of the foregoing; and

         (IV) All proceeds of the foregoing;

         (c) the possession by the Trust of any of the foregoing property shall
be deemed to be possession by the secured party or possession by a purchaser for
purposes of perfecting the security interest pursuant to the Uniform Commercial
Code (including, without limitation, Sections 9-313 and 9-314 thereof) as in
force in the relevant jurisdiction; and



                                       69
<PAGE>

         (d) notifications to persons holding such property, and
acknowledgments, receipts or confirmations from persons holding such property,
shall be deemed to be notifications to, or acknowledgments, receipts or
confirmations from, securities intermediaries, bailees or agents of, or persons
holding for, the Trust, as applicable, for the purpose of perfecting such
security interest under applicable law.

         The Company shall file such financing statements, and the Company and
the Trustee acting on behalf of the Trust at the direction of the Company shall,
to the extent consistent with this Agreement, take such other actions as may be
necessary to ensure that, if this Agreement were deemed to create a security
interest in the Conveyed Assets, such security interest would be deemed to be a
perfected security interest of first priority under applicable law and will be
maintained as such throughout the term of the Agreement. In connection herewith,
the Trust shall have all of the rights and remedies of a secured party and
creditor under the Uniform Commercial Code as in force in the relevant
jurisdiction.

         SECTION 2.05 Delivery of Mortgage Files.

         In connection with the sale, transfer and assignment referred to in
Section 2.04, the Company, concurrently with the execution and delivery hereof,
does deliver to, and deposit with, or cause to be delivered to and deposited
with, the Trustee or Custodian the Mortgage Files, which shall at all times be
identified in the records of the Trustee or the Custodian, as applicable, as
being held by or on behalf of the Trust.

         Concurrently with the execution and delivery hereof, the Company shall
cause to be filed the UCC assignment or amendment referred to in clause (Y)(vii)
of the definition of "Mortgage File." In connection with its servicing of
Cooperative Loans, the Master Servicer will use its best efforts to file timely
continuation statements, if necessary, with regard to each financing statement
and assignment relating to Cooperative Loans.

         In instances where the original recorded Mortgage or any intervening
assignment thereof (recorded or in recordable form) required to be included in
the Mortgage File pursuant to the definition of "Mortgage File" relating to a
Mortgage Loan is not included in the Mortgage File delivered to the Trustee (or
the Custodian) prior to or concurrently with the execution and delivery hereof
(due to a delay on the part of the recording office), the Company shall deliver
to the Trustee (or the Custodian) a fully legible reproduction (which may be in
electronic form) of the original Mortgage or intervening assignment provided
that the originator, the related Lender or the escrow or title company which
provided closing services in connection with such Mortgage Loan certifies on the
face of such reproduction(s) or copy as follows: "Certified true and correct
copy of original which has been transmitted for recordation." For purposes
hereof, transmitted for recordation means having been mailed or otherwise
delivered for recordation to the appropriate authority. In all such instances,
the Company shall transmit the original recorded Mortgage and any intervening
assignments with evidence of recording thereon (or a copy of such original
Mortgage or intervening assignment certified by the applicable recording office)
(which may be in electronic form) (collectively, "Recording Documents") to the
Trustee (or the Custodian) within 270 days after the execution and delivery
hereof. In instances where, due to a delay on the part of the recording office
where any such Recording Documents have been delivered for recordation, the
Recording Documents cannot be delivered to the Trustee within 270 days after
execution and delivery hereof, the Company shall deliver to the Trustee within
such time period a certificate (a "Company Officer's Certificate") signed by the
Chairman of the Board, President, any Vice President or Treasurer of the Company


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stating the date by which the Company expects to receive such Recording
Documents from the applicable recording office. In the event that Recording
Documents have still not been received by the Company and delivered to the
Trustee (or the Custodian) by the date specified in its previous Company
Officer's Certificate delivered to the Trustee, the Company shall deliver to the
Trustee by such date an additional Company Officer's Certificate stating a
revised date by which the Company expects to receive the applicable Recording
Documents. This procedure shall be repeated until the Recording Documents have
been received by the Company and delivered to the Trustee (or the Custodian).

         For Mortgage Loans for which the Company has received a Payoff after
the Cut-Off Date and prior to the date of execution and delivery hereof, the
Company, in lieu of delivering the above documents, herewith delivers to the
Trustee a certification of a Servicing Officer of the nature set forth in
Section 3.10.

         The Trustee is authorized, with the Master Servicer's consent, to
appoint any bank or trust company approved by each of the Company and the Master
Servicer as Custodian of the documents or instruments referred to above in this
Section 2.05, and to enter into a Custodial Agreement for such purpose,
provided, however, that the Trustee shall be and remain liable for the acts of
any such Custodian only to the extent that it is responsible for its own acts
hereunder. Any documents delivered by the Company or the Master Servicer to the
Custodian, if any, shall be deemed to have been delivered to the Trustee for all
purposes hereunder; and any documents held by the Custodian, if any, shall be
deemed to be held by the Trustee for all purposes hereunder. Pursuant to the
Initial Custodial Agreement, the Initial Custodian shall perform
responsibilities of the Trustee with respect to the delivery, receipt,
examination and custody of the Mortgage Files on the Trustee's behalf, as
provided therein.

         On or promptly after the Closing Date, the Master Servicer shall cause
the MERS(R) System to indicate that each MERS Loan, if any, has been assigned to
"Citibank, N.A., as Custodian/Trustee, without recourse" or to "WaMu Mortgage
Pass-Through Certificates Series 2004-S1 Trust, without recourse" by including
in the MERS(R) System computer files (a) the code necessary to identify the
Trustee and (b) the code necessary to identify the series of the Certificates
issued in connection with such Mortgage Loans; provided, however, that in the
event the Company acquired such Mortgage Loans from an affiliate of the Company,
then the Master Servicer need not cause the MERS(R) System to indicate such
assignment. The Master Servicer shall not alter the codes referenced in this
paragraph with respect to any MERS Loan during the term of this Agreement except
in connection with an assignment of such MERS Loan or de-registration thereof
from the MERS(R) System in accordance with the terms of this Agreement.

         SECTION 2.06 REMIC Election for REMIC I.

         The Tax Matters Person, shall, on behalf of REMIC I, elect to treat
REMIC I as a REMIC within the meaning of Section 860D of the Code and, if
necessary, under applicable state laws. Such election shall be included in the
Form 1066 and any appropriate state return to be filed on behalf of REMIC I for
its first taxable year.

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<PAGE>

         The Closing Date is hereby designated as the "startup day" of REMIC I
within the meaning of Section 860G(a)(9) of the Code.

         The regular interests (as set forth in the table contained in the
Preliminary Statement hereto) relating to REMIC I are hereby designated as
"regular interests" in REMIC I for purposes of Section 860G(a)(1) of the Code.
The Class R-1 Residual Interest is hereby designated as the sole class of
"residual interest" in REMIC I for purposes of Section 860G(a)(2) of the Code.
The REMIC I Regular Interests and the Class R-1 Residual Interest shall together
be deemed to be a separate series of beneficial interests in the assets of the
Trust consisting of the REMIC I Assets pursuant to Section 3806(b)(2) of the
Statutory Trust Statute.

         The parties intend that the affairs of REMIC I shall constitute, and
that the affairs of REMIC I shall be conducted so as to qualify REMIC I as a
REMIC. In furtherance of such intention, the Tax Matters Person shall, on behalf
of REMIC I: (a) prepare and file, or cause to be prepared and filed, a federal
tax return using a calendar year as the taxable year and using an accrual method
of accounting for REMIC I when and as required by the REMIC Provisions and other
applicable federal income tax laws; (b) make an election, on behalf of the
trust, for REMIC I to be treated as a REMIC on the federal tax return of REMIC I
for its first taxable year, in accordance with the REMIC Provisions; (c) prepare
and forward, or cause to be prepared and forwarded, to the Holders of the REMIC
I Regular Interests and the Class R-1 Residual Interest and the Trustee, all
information reports as and when required to be provided to them in accordance
with the REMIC Provisions, and make available the information necessary for the
application of Section 860E(e) of the Code; (d) conduct the affairs of REMIC I
at all times that any REMIC I Regular Interests are outstanding so as to
maintain the status of REMIC I as a REMIC under the REMIC Provisions; (e) not
knowingly or intentionally take any action or omit to take any action that would
cause the termination of the REMIC status of REMIC I; and (f) pay the amount of
any federal prohibited transaction penalty taxes imposed on REMIC I when and as
the same shall be due and payable (but such obligation shall not prevent the
Company or any other appropriate person from contesting any such tax in
appropriate proceedings and shall not prevent the Company from withholding
payment of such tax, if permitted by law, pending the outcome of such
proceedings); provided, that the Company shall be entitled to be indemnified by
REMIC I for any such prohibited transaction penalty taxes if the Company's
failure to exercise reasonable care was not the primary cause of the imposition
of such prohibited transaction penalty taxes.

         The Trustee and the Master Servicer shall promptly provide the Company
with such information in the possession of the Trustee or the Master Servicer,
respectively, as the Company may from time to time request for the purpose of
enabling the Company to prepare tax returns.

         In the event that a Mortgage Loan is discovered to have a defect which,
had such defect been discovered before the startup day, would have prevented
such Mortgage Loan from being a "qualified mortgage" within the meaning of
Section 860G(a)(3) of the Code, and the Company does not repurchase such
Mortgage Loan within 90 days of such date, the Master Servicer, on behalf of the
Trustee, shall within 90 days of the date such defect is discovered sell such


                                       72
<PAGE>

Mortgage Loan at such price as the Master Servicer in its sole discretion,
determines to be the greatest price that will result in the purchase thereof
within 90 days of such date, unless the Master Servicer delivers to the Trustee
an Opinion of Counsel to the effect that continuing to hold such Mortgage Loan
will not adversely affect the status of the electing portion of REMIC I as a
REMIC for federal income tax purposes.

         In the event that any tax is imposed on "prohibited transactions" of
REMIC I as defined in Section 860F of the Code and not paid by the Company
pursuant to clause (f) of the third preceding paragraph, such tax shall be
charged against amounts otherwise distributable to the Class R-1 Residual
Interest. Notwithstanding anything to the contrary contained herein, the Trustee
is hereby authorized to retain from amounts otherwise distributable to the Class
R-1 Residual Interest on any Distribution Date sufficient funds to reimburse the
Tax Matters Person (or any agent therefor appointed in accordance with the
definition of "Tax Matters Person" herein, if applicable), for the payment of
such tax (upon the written request of the Tax Matters Person or its agent, to
the extent reimbursable, and to the extent that the Tax Matters Person or its
agent has not been previously reimbursed therefor).

         SECTION 2.07 Acceptance by Trustee. The Trustee acknowledges receipt
(or with respect to any Mortgage Loan subject to a Custodial Agreement, receipt
by the Custodian thereunder) on behalf of the Trust of the documents (or
certified copies thereof as specified in Section 2.05) referred to in Section
2.05 above, but without having made the review required to be made within 45
days pursuant to this Section 2.07. The Trustee agrees, for the benefit of the
Trust, to review (or cause the Initial Custodian to review) each Mortgage File
within 45 days after the Closing Date and deliver to the Company a certification
(or cause the Initial Custodian to deliver to the Company a certification, which
satisfies the applicable requirements of this Agreement) in the form attached as
Exhibit M hereto, to the effect that, except as noted, all documents required
(in the case of instruments described in clauses (X)(iv) and (Y)(ix) of the
definition of "Mortgage File," known by the Trustee to be required) pursuant to
the definition of "Mortgage File" and Section 2.05 have been executed and
received, and that such documents relate to the Mortgage Loans identified in the
Mortgage Loan Schedule. In performing such review, the Trustee may rely upon the
purported genuineness and due execution of any such document, and on the
purported genuineness of any signature thereon. The Trustee shall not be
required to make any independent examination of any documents contained in each
Mortgage File beyond the review specifically required herein. The Trustee makes
no representations as to: (i) the validity, legality, enforceability or
genuineness of any of the Mortgage Loans identified on the Mortgage Loan
Schedule, or (ii) the collectibility, insurability, effectiveness or suitability
of any Mortgage Loan. If the Trustee finds any document or documents
constituting a part of a Mortgage File not to have been executed or received, or
to be unrelated to the Mortgage Loans identified in the Mortgage Loan Schedule,
the Trustee shall promptly so notify the Company. The Company hereby covenants
and agrees that, if any such defect cannot be corrected or cured, the Company
shall, not later than 60 days after the Trustee's notice to it respecting such
defect, within the three-month period commencing on the Closing Date (or within
the two-year period commencing on the Closing Date if the related Mortgage Loan
is a "defective obligation" within the meaning of Section 860G(a)(4)(B)(ii) of
the Code and Treasury Regulation Section 1.860G-2(f)), either (i) repurchase the
related Mortgage Loan from the Trust at the Purchase Price, or (ii) substitute
for any Mortgage Loan to which such defect relates a different mortgage loan (a
"Substitute Mortgage Loan") which is a "qualified replacement mortgage" (as
defined in the Code) and, (iii) after such three-month or two-year period, as
applicable, the Company shall repurchase the Mortgage Loan from the Trust at the
Purchase Price but only if the Mortgage Loan is in default or default is, in the


                                       73
<PAGE>

judgment of the Company, reasonably imminent. If such defect would cause the
Mortgage Loan to be other than a "qualified mortgage" (as defined in the Code),
then notwithstanding the previous sentence or any provision in the definition of
"Purchase Price", the repurchase or substitution must occur within the sooner of
(i) 90 days from the date the defect was discovered or (ii) in the case of
substitution, two years from the Closing Date.

         Such Substitute Mortgage Loan shall mature no later than, and not more
than two years earlier than, have a principal balance and Loan-to-Value Ratio
equal to or less than, and have a Pass-Through Rate on the date of substitution
equal to or no more than 1 percentage point greater than the Mortgage Loan being
substituted for. If the aggregate of the principal balances of the Substitute
Mortgage Loans substituted for a Mortgage Loan is less than the Principal
Balance of such Mortgage Loan, the Company shall pay the difference in cash,
together with unpaid accrued interest, if any, on the difference between the
aggregate of the principal balances of the Substitute Mortgage Loans and the
Principal Balance of such Mortgage Loan during the calendar month in which the
substitution occurs to the last day of such month at a rate equal to the
applicable Pass-Through Rate, to the Trustee for deposit into the Certificate
Account, and such payment by the Company shall be treated in the same manner as
proceeds of the repurchase by the Company of a Mortgage Loan pursuant to this
Section 2.07. Furthermore, such Substitute Mortgage Loan shall otherwise have
such characteristics so that the representations and warranties of the Company
set forth in Section 2.08 hereof would not have been incorrect had such
Substitute Mortgage Loan originally been a Mortgage Loan, and the Company shall
be deemed to have made such representations and warranties as to such Substitute
Mortgage Loan. A Substitute Mortgage Loan may be substituted for a defective
Mortgage Loan whether or not such defective Mortgage Loan is itself a Substitute
Mortgage Loan. Notwithstanding anything herein to the contrary, each Substitute
Mortgage Loan shall be deemed to have the same Pass-Through Rate as the Mortgage
Loan for which it was substituted.

         The Purchase Price for each purchased or repurchased Mortgage Loan
shall be deposited by the Company in the Certificate Account and, upon receipt
by the Trustee of written notification of such deposit signed by a Servicing
Officer, the Trustee shall (or, if applicable, shall cause the Custodian to)
release to the Company the related Mortgage File and shall execute and deliver
(or, in the event that the Mortgage Files are held in the name of the Custodian,
shall cause the Custodian to execute and deliver) on behalf of the Trust such
instruments of transfer or assignment, in each case without recourse, as shall
be necessary to vest in the Company or its designee or assignee title to any
Mortgage Loan released pursuant hereto. In furtherance of the foregoing, if such
Mortgage Loan is a MERS Loan and as a result of the repurchase thereof such
Mortgage Loan shall cease to be serviced by a servicer that is a member of MERS
or if the Company or its assignee shall so request, the Master Servicer shall
cause MERS to execute and deliver an assignment of the Mortgage in recordable
form from MERS to the Company or its assignee and shall cause the Mortgage Loan
to be removed from registration on the MERS(R) System in accordance with MERS'
rules and procedures. The obligation of the Company to repurchase or substitute
any Mortgage Loan as to which such a defect in a constituent document exists
shall constitute the sole remedy respecting such defect available to the Trust
or the Holders of the REMIC I Regular Interests or the Class R-1 Residual
Interest.

         SECTION 2.08 Representations and Warranties of the Company Concerning
the Mortgage Loans. With respect to the conveyance of the Mortgage Loans
provided for in Section 2.04 herein, the Company hereby represents and warrants
to the Trust that as of the Cut-Off Date unless otherwise indicated:

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         (i) The information set forth in the Mortgage Loan Schedule was true
and correct in all material respects at the date or dates respecting which such
information is furnished;

         (ii) As of the Closing Date, each Mortgage relating to a Mortgage Loan
that is not a Cooperative Loan is a valid and enforceable (subject to Section
2.08(xvi)) first lien on an unencumbered estate in fee simple or (if the related
Mortgage Loan is secured by the interest of the Mortgagor as a lessee under a
ground lease) leasehold estate in the related Mortgaged Property subject only to
(a) liens for current real property taxes and special assessments; (b)
covenants, conditions and restrictions, rights of way, easements and other
matters of public record as of the date of recording such Mortgage, such
exceptions appearing of record being acceptable to mortgage lending institutions
generally or specifically reflected in the appraisal obtained in connection with
the origination of the Mortgage Loan; (c) exceptions set forth in the title
insurance policy relating to such Mortgage, such exceptions being acceptable to
mortgage lending institutions generally; and (d) other matters to which like
properties are commonly subject which do not materially interfere with the
benefits of the security intended to be provided by the Mortgage;

         (iii) Immediately upon the transfer and assignment contemplated herein,
the Trust shall have good title to, and will be the sole legal owner of, each
Mortgage Loan, free and clear of any encumbrance or lien (other than any lien
under this Agreement);

         (iv) As of the day prior to the Cut-Off Date, all payments due on each
Mortgage Loan had been made and no Mortgage Loan had been delinquent (i.e., was
more than 30 days past due) more than once in the preceding 12 months and any
such delinquency lasted for no more than 30 days;

         (v) As of the Closing Date, there is no late assessment for delinquent
taxes outstanding against any Mortgaged Property;

         (vi) As of the Closing Date, there is no offset, defense or
counterclaim to any Mortgage Note, including the obligation of the Mortgagor to
pay the unpaid principal or interest on such Mortgage Note except to the extent
that the Buydown Agreement for a Buydown Loan forgives certain indebtedness of a
Mortgagor;

         (vii) As of the Closing Date, each Mortgaged Property is free of damage
and in good repair, ordinary wear and tear excepted;

         (viii) Each Mortgage Loan at the time it was made complied with all
applicable local, state and federal laws, including, without limitation, usury,
equal credit opportunity, disclosure and recording laws, and predatory and
abusive lending laws applicable to the originating lender;

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         (ix) Each Mortgage Loan was originated by a savings association,
savings bank, credit union, insurance company, or similar institution which is
supervised and examined by a federal or state authority or by a mortgagee
approved by the FHA and will be serviced by an institution which meets the
servicer eligibility requirements established by the Company;

         (x) As of the Closing Date, each Mortgage Loan that is not a
Cooperative Loan is covered by an ALTA form or CLTA form of mortgagee title
insurance policy or other form of policy of insurance which has been issued by,
and is the valid and binding obligation of, a title insurer which, as of the
origination date of such Mortgage Loan, was qualified to do business in the
state in which the related Mortgaged Property is located. Such policy insures
the originator of the Mortgage Loan, its successors and assigns as to the first
priority lien of the Mortgage in the original principal amount of the Mortgage
Loan subject to the exceptions set forth in such policy. Such policy is in full
force and effect and inures to the benefit of the Trust upon the consummation of
the transactions contemplated by this Agreement and no claims have been made
under such policy, and no prior holder of the related Mortgage, including the
Company, has done, by act or omission, anything which would impair the coverage
of such policy;

         (xi) Each Mortgage Loan with a Loan-to-Value Ratio as of the Cut-Off
Date in excess of 80% was covered by a Primary Insurance Policy or an FHA
insurance policy or a VA guaranty, and such policy or guaranty is valid and
remains in full force and effect;

         (xii) As of the Closing Date, all policies of insurance required by
this Agreement or by a Selling and Servicing Contract have been validly issued
and remain in full force and effect, including such policies covering the
Company, the Master Servicer or any Servicer;

         (xiii) As of the Closing Date, each insurer issuing a Primary Insurance
Policy holds a rating acceptable to the Rating Agencies;

         (xiv) Each Mortgage (exclusive of any riders thereto) was documented by
appropriate Fannie Mae/Freddie Mac mortgage instruments in effect at the time of
origination, or other instruments approved by the Company;

         (xv) As of the Closing Date, the Mortgaged Property securing each
Mortgage relating to a Mortgage Loan that is not a Cooperative Loan is improved
with a one- to four-family dwelling unit, including units in a duplex, triplex,
fourplex, condominium project, townhouse, a planned unit development or a de
minimis planned unit development;

         (xvi) As of the Closing Date, each Mortgage and Mortgage Note is the
legal, valid and binding obligation of the maker thereof and is enforceable in
accordance with its terms, except only as such enforcement may be limited by
laws affecting the enforcement of creditors' rights generally and principles of
equity;

         (xvii) As of the date of origination, as to Mortgaged Properties which
are units in condominiums or planned unit developments, all of such units met
the applicable Underwriting Standards, are located in a condominium or planned
unit development projects which have received Fannie Mae or Freddie Mac
approval, or are approvable by Fannie Mae or Freddie Mac or have otherwise been
approved by the Company;

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         (xviii) Two of the Mortgage Loans are Buydown Loans;

         (xix) Based solely on representations of the Mortgagors obtained at the
origination of the related Mortgage Loans, approximately 96.75% (by Principal
Balance) of the Mortgage Loans will be secured by owner occupied Mortgaged
Properties which are the primary residences of the related Mortgagors,
approximately 2.97% (by Principal Balance) of the Mortgage Loans will be secured
by owner occupied Mortgaged Properties which were second or vacation homes of
the Mortgagors and approximately 0.28% (by Principal Balance) of the Mortgage
Loans will be secured by Mortgaged Properties which were investor properties of
the related Mortgagors;

         (xx) Prior to origination or refinancing, an appraisal of each
Mortgaged Property was made by an appraiser on a form satisfactory to Fannie Mae
or Freddie Mac;

         (xxi) The Mortgage Loans have been underwritten substantially in
accordance with the applicable Underwriting Standards;

         (xxii) All of the Mortgage Loans have due-on-sale clauses; however, the
due on sale provisions may not be exercised at the time of a transfer if
prohibited by law;

         (xxiii) The Company used no adverse selection procedures in selecting
the Mortgage Loans from among the outstanding fixed-rate conventional mortgage
loans purchased by it which were available for inclusion in the Mortgage Pool
and as to which the representations and warranties in this Section 2.08 could be
made;

         (xxiv) With respect to each Cooperative Loan, the Cooperative Stock
that is pledged as security for the Cooperative Loan is held by a person as a
tenant-stockholder (as defined in Section 216 of the Code) in a cooperative
housing corporation (as defined in Section 216 of the Code);

         (xxv) Each Cooperative Loan is secured by a valid, subsisting and
enforceable (except as such enforcement may be limited by laws affecting the
enforcement of creditors' rights generally and principles of equity) perfected
first lien and security interest in the related Cooperative Stock securing the
related Mortgage Note, subject only to (a) liens of the Cooperative for unpaid
assessments representing the Mortgagor's pro rata share of the Cooperative's
payments for its blanket mortgage, current and future real property taxes,
insurance premiums, maintenance fees and other assessments to which like
collateral is commonly subject, and (b) other matters to which like collateral
is commonly subject which do not materially interfere with the benefits of the
security intended to be provided by the Security Agreement;

         (xxvi) With respect to any Mortgage Loan as to which an affidavit has
been delivered to the Trustee certifying that the original Mortgage Note is a
Destroyed Mortgage Note, if such Mortgage Loan is subsequently in default, the
enforcement of such Mortgage Loan or of the related Mortgage by or on behalf of
the Trustee will not be materially adversely affected by the absence of the
original Mortgage Note (or portion thereof, as applicable);

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         (xxvii) Based upon an appraisal of the Mortgaged Property securing each
Mortgage Loan, approximately 95.49% (by Principal Balance) of the Mortgage Loans
had a current Loan-to-Value Ratio less than or equal to 80%, approximately 4.52%
(by Principal Balance) of the Mortgage Loans had a current Loan-to-Value Ratio
greater than 80% but less than or equal to 95% and no Mortgage Loan had a
current Loan-to-Value Ratio greater than 95%;

         (xxviii) Approximately 54.63% (by Principal Balance) of the Mortgage
Loans were originated for the purpose of refinancing existing mortgage debt,
including cash-out refinancings; and approximately 45.37% (by Principal Balance)
of the Mortgage Loans were originated for the purpose of purchasing the
Mortgaged Property;

         (xxix) Not less than approximately 82.75% (by Principal Balance) of the
Mortgage Loans were originated under full documentation programs;

         (xxx) No Mortgage Loan is subject to the Home Ownership and Equity
Protection Act of 1994 or Section 226.32 of Regulation Z, is a "high-cost" loan
or a "predatory" loan as defined under any state or local law or regulation
applicable to the originator of such Mortgage Loan or which would result in
liability to the purchaser or assignee of such Mortgage Loan under any predatory
or abusive lending law, or, without limiting the generality of the foregoing, is
a "covered" loan under the laws of the states of California, Colorado or Ohio;
and

         (xxxi) Each Mortgage Loan constitutes a qualified mortgage under
Section 860G(a)(3)(A) of the Code and Treasury Regulations Section
1.860G-2(a)(1).

         It is understood and agreed that the representations and warranties set
forth in this Section 2.08 shall survive delivery of the respective Mortgage
Files to the Trustee or the Custodian, as the case may be, and shall continue
throughout the term of this Agreement. Upon discovery by any of the Company, the
Master Servicer, the Trustee or the Custodian of a breach of any of the
foregoing representations and warranties which materially and adversely affects
the value of the related Mortgage Loans or the interests of the Trust in the
related Mortgage Loans, the Company, the Master Servicer, the Trustee or the
Custodian, as the case may be, discovering such breach shall give prompt written
notice to the others. Any breach of the representation set forth in clause (xxx)
of this Section 2.08 shall be deemed to materially and adversely affect the
value of the related Mortgage Loans or the interests of the Trust in the related


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Mortgage Loans. Within 90 days of its discovery or its receipt of notice of
breach, the Company shall repurchase, subject to the limitations set forth in
the definition of "Purchase Price," or substitute for the affected Mortgage Loan
or Mortgage Loans or any property acquired in respect thereof from the Trust,
unless it has cured such breach in all material respects. After the end of the
three-month period beginning on the "start-up day," any such substitution shall
be made only if the Company provides to the Trustee an Opinion of Counsel
addressed to the Trust and the Trustee reasonably satisfactory to the Trustee
that each Substitute Mortgage Loan will be a "qualified replacement mortgage"
within the meaning of Section 860G(a)(4) of the Code. Such substitution shall be
made in the manner and within the time limits set forth in Section 2.07. Any
such repurchase by the Company shall be accomplished in the manner and at the
Purchase Price, if applicable, but shall not be subject to the time limits, set
forth in Section 2.07. It is understood and agreed that the obligation of the
Company to provide such substitution or to make such repurchase of any affected
Mortgage Loan or Mortgage Loans or any property acquired in respect thereof as
to which a breach has occurred and is continuing shall constitute the sole
remedy respecting such breach available to the Holders of the REMIC I Regular
Interests and the Class R-1 Residual Interest or the Trustee on behalf of the
Holders of the REMIC I Regular Interests and the Class R-1 Residual Interest.

         SECTION 2.09 Acknowledgment of Transfer of Mortgage Pool Assets. The
Trustee hereby acknowledges and accepts on behalf of the Trust the transfer and
assignment to the Trust of the Mortgage Pool Assets, but without having made the
review required to be made within 45 days pursuant to Section 2.07, and declares
that as of the Closing Date it holds and shall hold any documents constituting a
part of the Mortgage Pool Assets, and the Mortgage Pool Assets, as Trustee in
trust, upon the trust herein set forth, for the use and benefit of all present
and future Holders of the REMIC I Regular Interests and the Class R-1 Residual
Interest. In connection therewith, as of the Closing Date, in exchange for the
Mortgage Pool Assets, the Trustee on behalf of the Trust does hereby issue to
the Company the REMIC I Regular Interests and the Class R-1 Residual Interest.

         SECTION 2.10 Conveyance of REMIC I Regular Interests; Security
Interest. Concurrently with the execution and delivery hereof, the Company does
hereby irrevocably sell, transfer, assign, set over, and otherwise convey to the
Trust, without recourse, all the Company's right, title and interest in and to
the REMIC II Assets, including all interest and principal received by the
Company on or with respect to the REMIC I Regular Interests after the Cut-Off
Date. Pursuant to Section 3818 of the Statutory Trust Statute, the REMIC I
Regular Interests shall not be cancelled and shall be held as treasury interests
owned by the Trust. It is the express intent of the parties hereto that the
conveyance of the REMIC II Assets to the Trust by the Company as provided in
this Section 2.10 be, and be construed as, an absolute sale of the REMIC II
Assets. It is, further, not the intention of the parties that such conveyance be
deemed the grant of a security interest in the REMIC II Assets by the Company to
the Trust to secure a debt or other obligation of the Company. However, in the
event that, notwithstanding the intent of the parties, the REMIC II Assets are
held to be the property of the Company, or if for any other reason this
Agreement is held or deemed to create a security interest in the REMIC II
Assets, then

         (a) this Agreement shall be deemed to be a security agreement;

         (b) the conveyance provided for in this Section 2.10 shall be deemed to
be a grant by the Company to the Trust of, and the Company hereby grants to the
Trust, to secure all of the Company's obligations hereunder, a security interest
in all of the Company's right, title, and interest, whether now owned or
hereafter acquired, in and to:

         (I) The REMIC I Regular Interests, including without limitation all
rights represented thereby in and to (i) the Mortgage Loans identified on the
Mortgage Loan Schedule, including the related Mortgage Notes, Mortgages,


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Cooperative Stock Certificates, Cooperative Leases, Security Agreements,
Assignments of Proprietary Lease, and Recognition Agreements, all Substitute
Mortgage Loans and all distributions with respect to such Mortgage Loans and
Substitute Mortgage Loans payable on and after the Cut-Off Date, (ii) the
Certificate Account, the Investment Account and all money or other property held
therein, and the Custodial Accounts for P&I, the Custodial Accounts for Reserves
and any Buydown Fund Account (to the extent of the amounts on deposit therein
attributable to the Mortgage Loans); (iii) amounts paid or payable by the
insurer under any FHA insurance policy or any Primary Insurance Policy and
proceeds of any VA guaranty and any other insurance policy related to any
Mortgage Loan or the Mortgage Pool; and (iv) all rights arising from or by
virtue of the disposition of, or collections with respect to, or insurance
proceeds payable with respect to, or claims against other persons with respect
to, all or any part of the collateral described in (i)-(iii) above (including
any accrued discount realized on liquidation of any investment purchased at a
discount);

         (II) All accounts, general intangibles, chattel paper, instruments,
documents, money, deposit accounts, goods, letters of credit, letter-of-credit
rights, oil, gas, and other minerals, and investment property consisting of,
arising from or relating to any of the foregoing; and

         (III) All proceeds of the foregoing;

         (c) the possession by the Trust of any of the foregoing property shall
be deemed to be possession by the secured party or possession by a purchaser for
purposes of perfecting the security interest pursuant to the Uniform Commercial
Code (including, without limitation, Sections 9-313 and 9-314 thereof) as in
force in the relevant jurisdiction; and

         (d) notifications to persons holding such property, and
acknowledgments, receipts or confirmations from persons holding such property,
shall be deemed notifications to, or acknowledgments, receipts or confirmations
from, securities intermediaries, bailees or agents of, or persons holding for,
the Trust, as applicable, for the purpose of perfecting such security interest
under applicable law.

         The Company shall file such financing statements, and the Company and
the Trustee acting on behalf of the Trust at the direction of the Company shall,
to the extent consistent with this Agreement, take such other actions as may be
necessary to ensure that, if this Agreement were deemed to create a security
interest in the REMIC II Assets, such security interest would be deemed to be a
perfected security interest of first priority under applicable law and will be
maintained as such throughout the term of this Agreement. In connection
herewith, the Trust shall have all of the rights and remedies of a secured party
and creditor under the Uniform Commercial Code as in force in the relevant
jurisdiction.

         The Trustee is authorized, with the Master Servicer's consent, to
appoint any bank or trust company approved by each of the Company and the Master
Servicer as Custodian of the documents or instruments referred to above in this
Section 2.10, and to enter into a Custodial Agreement for such purpose;
provided, however, that the Trustee shall be and remain liable for actions of


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any such Custodian only to the extent it would otherwise be responsible for such
acts hereunder. Any documents delivered by the Company or the Master Servicer to
the Custodian, if any, shall be deemed to have been delivered to the Trustee for
all purposes hereunder; and any documents held by the Custodian, if any, shall
be deemed to be held by the Trustee for all purposes hereunder. Pursuant to the
Initial Custodial Agreement, the Initial Custodian shall perform
responsibilities of the Trustee with respect to the delivery, receipt,
examination and custody of the Mortgage Files on the Trustee's behalf, as
provided therein.

         SECTION 2.11 REMIC Election for REMIC II.

         The Tax Matters Person shall, on behalf of REMIC II, elect to treat
REMIC II as a REMIC within the meaning of Section 860D of the Code and, if
necessary, under applicable state laws. Such election shall be included in the
Form 1066 and any appropriate state return to be filed on behalf of REMIC II for
its first taxable year.

         The Closing Date is hereby designated as the "startup day" of REMIC II
within the meaning of Section 860G(a)(9) of the Code.

         The regular interests (as set forth in the table contained in the
Preliminary Statement hereto) relating to REMIC II are hereby designated as
"regular interests" in REMIC II for purposes of Section 860G(a)(1) of the Code.
The Class R-2 Residual Interest is hereby designated as the sole class of
"residual interest" in REMIC II for purposes of Section 860G(a)(2) of the Code.
The REMIC II Regular Interests and the Class R-2 Residual Interest shall
together be deemed to be a separate series of beneficial interests in the assets
of the Trust consisting of the REMIC II Assets pursuant to Section 3806(b)(2) of
the Statutory Trust Statute.

         The parties intend that the affairs of REMIC II shall constitute, and
that the affairs of REMIC II shall be conducted so as to qualify it as, a REMIC.
In furtherance of such intention, the Tax Matters Person shall, on behalf of
REMIC II: (a) prepare and file, or cause to be prepared and filed, a federal tax
return using a calendar year as the taxable year for REMIC II when and as
required by the REMIC provisions and other applicable federal income tax laws;
(b) make an election, on behalf of REMIC II, to be treated as a REMIC on the
federal tax return of REMIC II for its first taxable year, in accordance with
the REMIC provisions; (c) prepare and forward, or cause to be prepared and
forwarded, to the Holders of the REMIC II Regular Interests and the Class R-2
Residual Interest all information reports as and when required to be provided to
them in accordance with the REMIC provisions; (d) conduct the affairs of REMIC
II at all times that any of the REMIC II Regular Interests and the Class R-2
Residual Interest are outstanding so as to maintain the status of REMIC II as a
REMIC under the REMIC provisions; (e) not knowingly or intentionally take any
action or omit to take any action that would cause the termination of the REMIC
status of REMIC II; and (f) pay the amount of any federal prohibited transaction
penalty taxes imposed on REMIC II when and as the same shall be due and payable
(but such obligation shall not prevent the Company or any other appropriate
person from contesting any such tax in appropriate proceedings and shall not
prevent the Company from withholding payment of such tax, if permitted by law,
pending the outcome of such proceedings); provided, that the Company shall be
entitled to be indemnified from REMIC II for any such prohibited transaction
penalty taxes if the Company's failure to exercise reasonable care was not the
primary cause of the imposition of such prohibited transaction penalty taxes.



                                       81
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         In the event that any tax is imposed on "prohibited transactions" of
REMIC II as defined in Section 860F of the Code and not paid by the Company
pursuant to clause (f) of the preceding paragraph, such tax shall be charged
against amounts otherwise distributable to the Holders of the Class R-2 Residual
Interest. Notwithstanding anything to the contrary contained herein, the Company
is hereby authorized to retain from amounts otherwise distributable to the
Holders of the Class R-2 Residual Interest on any Distribution Date sufficient
funds to reimburse the Company for the payment of such tax (to the extent that
the Company has not been previously reimbursed therefor).

         SECTION 2.12 Acknowledgement of Transfer of REMIC II Assets. The
Trustee hereby acknowledges and accepts on behalf of the Trust the assignment to
the Trust of the REMIC II Assets and declares that as of the Closing Date it
holds and shall hold any documents constituting a part of the REMIC II Assets,
and the REMIC II Assets, as Trustee in trust, upon the trust herein set forth,
for the use and benefit of all present and future Holders of the REMIC II
Regular Interests and the Class R-2 Residual Interest. In connection therewith,
as of the Closing Date, in exchange for the REMIC II Assets, the Trust does
hereby issue to the Company the REMIC II Regular Interests and the Class R-2
Residual Interest.

         SECTION 2.13 Conveyance of REMIC II Regular Interests; Security
Interest. Concurrently with the execution and delivery hereof, the Company does
hereby irrevocably sell, transfer, assign, set over, and otherwise convey to the
Trust, without recourse, all the Company's right, title and interest in and to
the REMIC III Assets, including all interest and principal received by the
Company on or with respect to the REMIC II Regular Interests after the Cut-Off
Date. Pursuant to Section 3818 of the Statutory Trust Statute, the REMIC II
Regular Interests shall not be cancelled and shall be held as treasury interests
owned by the Trust. It is the express intent of the parties hereto that the
conveyance of the REMIC III Assets to the Trust by the Company as provided in
this Section 2.13 be, and be construed as, an absolute sale of the REMIC III
Assets. It is, further, not the intention of the parties that such conveyance be
deemed the grant of a security interest in the REMIC III Assets by the Company
to the Trust to secure a debt or other obligation of the Company. However, in
the event that, notwithstanding the intent of the parties, the REMIC III Assets
are held to be the property of the Company, or if for any other reason this
Agreement is held or deemed to create a security interest in the REMIC III
Assets, then

         (a) this Agreement shall be deemed to be a security agreement;

         (b) the conveyance provided for in this Section 2.13 shall be deemed to
be a grant by the Company to the Trust of, and the Company hereby grants to the
Trust, to secure all of the Company's obligations hereunder, a security interest
in all of the Company's right, title, and interest, whether now owned or
hereafter acquired, in and to:

         (I) The REMIC II Regular Interests, including without limitation all
rights represented thereby in and to (i) the Mortgage Loans identified on the
Mortgage Loan Schedule, including the related Mortgage Notes, Mortgages,
Cooperative Stock Certificates, Cooperative Leases, Security Agreements,
Assignments of Proprietary Lease, and Recognition Agreements, all Substitute
Mortgage Loans and all distributions with respect to such Mortgage Loans and
Substitute Mortgage Loans payable on and after the Cut-Off Date, (ii) the


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Certificate Account, the Investment Account and all money or other property held
therein, and the Custodial Accounts for P&I, the Custodial Accounts for Reserves
and any Buydown Fund Account (to the extent of the amounts on deposit therein
attributable to the Mortgage Loans); (iii) amounts paid or payable by the
insurer under any FHA insurance policy or any Primary Insurance Policy and
proceeds of any VA guaranty and any other insurance policy related to any
Mortgage Loan or the Mortgage Pool; and (iv) all rights arising from or by
virtue of the disposition of, or collections with respect to, or insurance
proceeds payable with respect to, or claims against other persons with respect
to, all or any part of the collateral described in (i)-(iii) above (including
any accrued discount realized on liquidation of any investment purchased at a
discount);

         (II) All accounts, general intangibles, chattel paper, instruments,
documents, money, deposit accounts, goods, letters of credit, letter-of-credit
rights, oil, gas, and other minerals, and investment property consisting of,
arising from or relating to any of the foregoing; and

         (III) All proceeds of the foregoing;

         (c) the possession by the Trust of any of the foregoing property shall
be deemed to be possession by the secured party or possession by a purchaser for
purposes of perfecting the security interest pursuant to the Uniform Commercial
Code (including, without limitation, Sections 9-313 and 9-314 thereof) as in
force in the relevant jurisdiction; and

(d)      notifications to persons holding such property, and acknowledgments,
         receipts or confirmations from persons holding such property, shall be
         deemed notifications to, or acknowledgments, receipts or confirmations
         from, securities intermediaries, bailees or agents of, or persons
         holding for, the Trust, as applicable, for the purpose of perfecting
         such security interest under applicable law.

         The Company shall file such financing statements, and the Company and
the Trustee acting on behalf of the Trust at the direction of the Company shall,
to the extent consistent with this Agreement, take such other actions as may be
necessary to ensure that, if this Agreement were deemed to create a security
interest in the REMIC III Assets, such security interest would be deemed to be a
perfected security interest of first priority under applicable law and will be
maintained as such throughout the term of this Agreement. In connection
herewith, the Trust shall have all of the rights and remedies of a secured party
and creditor under the Uniform Commercial Code as in force in the relevant
jurisdiction.

         The Trustee is authorized, with the Master Servicer's consent, to
appoint any bank or trust company approved by each of the Company and the Master
Servicer as Custodian of the documents or instruments referred to above in this
Section 2.13, and to enter into a Custodial Agreement for such purpose;
provided, however, that the Trustee shall be and remain liable for actions of
any such Custodian only to the extent it would otherwise be responsible for such
acts hereunder. Any documents delivered by the Company or the Master Servicer to
the Custodian, if any, shall be deemed to have been delivered to the Trustee for


                                       83
<PAGE>

all purposes hereunder; and any documents held by the Custodian, if any, shall
be deemed to be held by the Trustee for all purposes hereunder.

         SECTION 2.14 REMIC Election for REMIC III. The Tax Matters Person
shall, on behalf of REMIC III, elect to treat REMIC III as a REMIC within the
meaning of Section 860D of the Code and, if necessary, under applicable state
laws. Such election shall be included in the Form 1066 and any appropriate state
return to be filed on behalf of REMIC III for its first taxable year.

         The Closing Date is hereby designated as the "startup day" of REMIC III
within the meaning of Section 860G(a)(9) of the Code.

         The regular interests (as set forth in the table contained in the
Preliminary Statement hereto) relating to REMIC III are hereby designated as
"regular interests" in REMIC III for purposes of Section 860G(a)(1) of the Code.
The Class R-3 Residual Interest is hereby designated as the sole class of
"residual interest" in REMIC III for purposes of Section 860G(a)(2) of the Code.
The REMIC III Regular Interests and the Class R-3 Residual Interest shall
together be deemed to be a separate series of beneficial interests in the assets
of the Trust consisting of the REMIC III Assets pursuant to Section 3806(b)(2)
of the Statutory Trust Statute.

         The parties intend that the affairs of REMIC III shall constitute, and
that the affairs of REMIC III shall be conducted so as to qualify it as, a
REMIC. In furtherance of such intention, the Tax Matters Person shall, on behalf
of REMIC III: (a) prepare and file, or cause to be prepared and filed, a federal
tax return using a calendar year as the taxable year for REMIC III when and as
required by the REMIC provisions and other applicable federal income tax laws;
(b) make an election, on behalf of REMIC III, to be treated as a REMIC on the
federal tax return of REMIC III for its first taxable year, in accordance with
the REMIC provisions; (c) prepare and forward, or cause to be prepared and
forwarded, to the Certificateholders and the Holders of the Class R-3 Residual
Interest all information reports as and when required to be provided to them in
accordance with the REMIC provisions; (d) conduct the affairs of REMIC III at
all times that any of the Certificates are outstanding so as to maintain the
status of REMIC III as a REMIC under the REMIC provisions; (e) not knowingly or
intentionally take any action or omit to take any action that would cause the
termination of the REMIC status of REMIC III; and (f) pay the amount of any
federal prohibited transaction penalty taxes imposed on REMIC III when and as
the same shall be due and payable (but such obligation shall not prevent the
Company or any other appropriate person from contesting any such tax in
appropriate proceedings and shall not prevent the Company from withholding
payment of such tax, if permitted by law, pending the outcome of such
proceedings); provided, that the Company shall be entitled to be indemnified
from REMIC III for any such prohibited transaction penalty taxes if the
Company's failure to exercise reasonable care was not the primary cause of the
imposition of such prohibited transaction penalty taxes.

         In the event that any tax is imposed on "prohibited transactions" of
REMIC III as defined in Section 860F of the Code and not paid by the Company
pursuant to clause (f) of the preceding paragraph, such tax shall be charged
against amounts otherwise distributable to the Holders of the Class R-3 Residual
Interest. Notwithstanding anything to the contrary contained herein, the Company
is hereby authorized to retain from amounts otherwise distributable to the


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Holders of the Class R-3 Residual Interest on any Distribution Date sufficient
funds to reimburse the Company for the payment of such tax (to the extent that
the Company has not been previously reimbursed therefor).

         SECTION 2.15 Acknowledgement of Transfer of REMIC III Assets;
Authentication of Certificates. The Trustee hereby acknowledges and accepts on
behalf of the Trust the assignment to the Trust of the REMIC III Assets and
declares that as of the Closing Date it holds and shall hold any documents
constituting a part of the REMIC III Assets, and the REMIC III Assets, as
Trustee in trust, upon the trust herein set forth, for the use and benefit of
all present and future Holders of the Certificates (other than the Class R
Certificates) and the Class R-3 Residual Interest. In connection therewith, as
of the Closing Date, in exchange for the REMIC III Assets, the Trustee on behalf
of the Trust shall cause to be authenticated and delivered, upon and pursuant to
the order of the Company, the Certificates in Authorized Denominations.

         SECTION 2.16 Legal Title. Legal title to all assets of the Trust shall
be vested at all times in the Trust as a separate legal entity.

         SECTION 2.17 Compliance with ERISA Requirements. For purposes of
ensuring compliance with the requirements of the "underwriter's exemption" (U.S.
Department of Labor Prohibited Transaction Exemption 2002-41, 67 Fed. Reg. 54487
(Aug. 22, 2002)), issued under ERISA, and for the avoidance of any doubt as to
the applicability of other provisions of this Agreement, to the fullest extent
permitted by applicable law and except as contemplated by this Agreement, (1)
the Trust shall not be a party to any merger, consolidation or reorganization,
or liquidate or sell its assets and (2) so long as any Certificates are
outstanding, none of the Company, the Trustee or the Delaware Trustee shall
institute against the Trust, or join in any institution against the Trust of,
any bankruptcy or insolvency proceedings under any federal or state bankruptcy,
insolvency or similar law.

         SECTION 2.18 Additional Representation of the Company Concerning the
Mortgage Loans. The Company hereby represents and warrants to the Trust that it
does not intend for the Mortgage Pool to include any Mortgage Loan that is a
"high-cost home loan" as defined under the New Jersey Home Ownership Security
Act of 2002 or the New Mexico Home Loan Protection Act. Based on the foregoing
representation and warranty and on the Company's obligation, pursuant to Section
2.08, to repurchase or substitute for the affected Mortgage Loan in the event of
a breach of the representation set forth in clause (xxx) of Section 2.08, the
other parties hereto agree and understand that it is not intended for the
Mortgage Pool to include any Mortgage Loan that is a "high-cost home loan" as
defined under the New Jersey Home Ownership Security Act of 2002 or the New
Mexico Home Loan Protection Act.

                                  ARTICLE III

                 Administration and Servicing of Mortgage Loans

         SECTION 3.01 The Company to Act as Master Servicer. The Company shall
act as Master Servicer to service and administer the Mortgage Loans on behalf of
the Trust and for the benefit of the Certificateholders in accordance with the


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terms hereof, consistent with prudent mortgage loan servicing practices and
(unless inconsistent with prudent mortgage loan servicing practices) in the same
manner in which, and with the same care, skill, prudence and diligence with
which, it services and administers similar mortgage loans for other portfolios,
and shall have full power and authority to do or cause to be done any and all
things in connection with such servicing and administration which a prudent
servicer of mortgage loans would do under similar circumstances, including,
without limitation, the power and authority to bring actions and defend the
Mortgage Pool Assets on behalf of the Trust in order to enforce the terms of the
Mortgage Notes. The Master Servicer may perform its master servicing
responsibilities through agents or independent contractors, but shall not
thereby be released from any of its responsibilities hereunder and the Master
Servicer shall diligently pursue all of its rights against such agents or
independent contractors.

         The Master Servicer shall make reasonable efforts to collect or cause
to be collected all payments called for under the terms and provisions of the
Mortgage Loans and shall, to the extent such procedures shall be consistent with
this Agreement and the terms and provisions of any Primary Insurance Policy, any
FHA insurance policy or VA guaranty, any hazard insurance policy, and federal
flood insurance, cause to be followed such collection procedures as are followed
with respect to mortgage loans comparable to the Mortgage Loans and held in
portfolios of responsible mortgage lenders in the local areas where each
Mortgaged Property is located. The Master Servicer shall enforce "due-on-sale"
clauses with respect to the related Mortgage Loans, to the extent permitted by
law, subject to the provisions set forth in Section 3.08.

         Consistent with the foregoing, the Master Servicer may, in accordance
with prudent mortgage loan servicing practices, (i) waive or cause to be waived
any assumption fee or late payment charge in connection with the prepayment of
any Mortgage Loan and (ii) only upon determining that the coverage of any
applicable insurance policy or guaranty related to a Mortgage Loan will not be
materially adversely affected, arrange a schedule, running for no more than 180
days after the first delinquent Due Date, for payment of any delinquent
installment on any Mortgage Note or for the liquidation of delinquent items.
Subject to the fourth sentence of this paragraph, the Master Servicer shall have
the right, but not the obligation, to purchase any Mortgage Loan delinquent 90
consecutive days or more for an amount equal to its Purchase Price; provided,
however, that the aggregate Purchase Price of Mortgage Loans so purchased
pursuant to this sentence shall not exceed one-half of one percent (0.50%) of
the aggregate Principal Balance, as of the Cut-Off Date, of all Mortgage Loans.
Subject to the fourth sentence of this paragraph, the Master Servicer shall also
have the right, but not the obligation, to purchase, for an amount equal to its
Purchase Price, any Mortgage Loan delinquent 90 consecutive days or more, for
the purpose of requiring the Person who sold such Mortgage Loan to the Company
to repurchase such Mortgage Loan based on a breach of a representation or
warranty made by such Person in connection with the Company's purchase or
acquisition of such Mortgage Loan. Notwithstanding the immediately preceding two
sentences, the Master Servicer's right to purchase any Mortgage Loan pursuant to
either of such preceding sentences shall be subject to the following additional
conditions: (x) if the date on which the Mortgage Loan first became 90-day
delinquent (the "Initial Delinquency Date") occurred during the first two
calendar months of a calendar quarter, the Master Servicer may exercise the
purchase right during the period commencing on the Initial Delinquency Date and
ending on the last Master Servicer Business Day of such calendar quarter, (y) if
the Initial Delinquency Date occurred during the third calendar month of a


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calendar quarter, the Master Servicer may exercise the purchase right during the
period commencing on the first day of the immediately succeeding calendar
quarter and ending on the last Master Servicer Business Day of such succeeding
calendar quarter and (z) if the Master Servicer does not exercise the purchase
right with respect to a Mortgage Loan during the period specified in clause (x)
or (y), as applicable, such Mortgage Loan shall thereafter again become eligible
for purchase pursuant to the preceding two sentences only after the Mortgage
Loan ceases to be 90-day delinquent and thereafter becomes 90-day delinquent
again. For purposes of this paragraph, a Mortgage Loan is considered delinquent
for 90 consecutive days if a Monthly Payment is not received by the first day of
the third month following the month during which such payment was due.

         Consistent with the terms of this Section 3.01, the Master Servicer may
waive, modify or vary any term of any Mortgage Loan or consent to the
postponement of strict compliance with any such term or in any manner grant
indulgence to any Mortgagor if it has determined, exercising its good faith
business judgment in the same manner as it would if it were the owner of the
related Mortgage Loan, that the security for, and the timely and full
collectibility of, such Mortgage Loan would not be adversely affected by such
waiver, modification, postponement or indulgence; provided, however, that
(unless the Mortgagor is in default with respect to the Mortgage Loan or in the
reasonable judgment of the Master Servicer such default is imminent) the Master
Servicer shall not permit any modification with respect to any Mortgage Loan
that would (i) change the applicable Mortgage Interest Rate, defer or forgive
the payment of any principal or interest, reduce the outstanding principal
balance (except for actual payments of principal) or extend the final maturity
date with respect to such Mortgage Loan, or (ii) be inconsistent with the terms
of any applicable Primary Insurance Policy, FHA insurance policy, VA guaranty,
hazard insurance policy or federal flood insurance policy. Notwithstanding the
foregoing, the Master Servicer shall not permit any modification with respect to
any Mortgage Loan that would both constitute a sale or exchange of such Mortgage
Loan within the meaning of Section 1001 of the Code (including any proposed,
temporary or final regulations promulgated thereunder) (other than in connection
with a proposed conveyance or assumption of such Mortgage Loan that is treated
as a Principal Prepayment or in a default situation) and cause any REMIC to fail
to qualify as such under the Code. The Master Servicer shall be entitled to
approve a request from a Mortgagor for a partial release of the related
Mortgaged Property, the granting of an easement thereon in favor of another
Person, any alteration or demolition of the related Mortgaged Property or other
similar matters if it has determined, exercising its good faith business
judgment in the same manner as it would if it were the owner of the related
Mortgage Loan, that the security for, and the timely and full collectibility of,
such Mortgage Loan would not be adversely affected thereby and that REMIC I,
REMIC II and REMIC III would not fail to continue to qualify as REMICs under the
Code as a result thereof and that no tax on "prohibited transactions" or
"contributions" after the startup day would be imposed on any REMIC as a result
thereof.

         The Master Servicer is hereby authorized and empowered by the Trust to
execute and deliver or cause to be executed and delivered on behalf of the
Holders of the REMIC I Regular Interests and the Class R-1 Residual Interest,
and the Trust or any of them, any and all instruments of satisfaction or
cancellation, or of partial or full release, discharge or modification,
assignments of Mortgages and endorsements of Mortgage Notes in connection with
refinancings (in jurisdictions where such assignments are the customary and


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usual standard of practice of mortgage lenders) and all other comparable
instruments, with respect to the Mortgage Loans and with respect to the
Mortgaged Properties. The Master Servicer is hereby further authorized and
empowered by the Trust to execute and deliver or cause to be executed and
delivered on behalf of the Holders of the REMIC I Regular Interests and the
Class R-1 Residual Interest and the Trust, or any of them, such instruments of
assignment or other comparable instruments as the Master Servicer shall, in its
sole judgment, deem appropriate in order to register any Mortgage Loan on the
MERS(R) System or to cause the removal of any Mortgage Loan from registration
thereon. Any expenses incurred in connection with the actions described in the
preceding sentence shall be borne by the Master Servicer with no right of
reimbursement; provided, however, that any such expenses incurred as a result of
any termination by MERS of the MERS(R) System shall be reimbursable to the
Master Servicer. The Trustee on behalf of the Trust shall execute and furnish to
the Master Servicer, at the Master Servicer's direction, any powers of attorney
and other documents prepared by the Master Servicer and determined by the Master
Servicer to be necessary or appropriate to enable the Master Servicer to carry
out its supervisory, servicing and administrative duties under this Agreement.

         The Master Servicer and each Servicer shall obtain (to the extent
generally commercially available) and maintain fidelity bond and errors and
omissions coverage acceptable to Fannie Mae or Freddie Mac with respect to their
obligations under this Agreement and the applicable Selling and Servicing
Contract, respectively. The Master Servicer or each Servicer, as applicable,
shall establish escrow accounts for, or pay when due (by means of an advance),
any tax liens in connection with the Mortgaged Properties that are not paid by
the Mortgagors when due to the extent that any such payment would not constitute
a Nonrecoverable Advance when made.

         In connection with the servicing and administering of each Mortgage
Loan, the Master Servicer and any affiliate of the Master Servicer (i) may
perform services such as appraisals, default management and (in the case of
affiliates only) brokerage services that are not customarily provided by
servicers of mortgage loans, and shall be entitled to reasonable compensation
therefor and (ii) may, at its own discretion and on behalf of the Trust, obtain
credit information in the form of a "credit score" from a credit repository.

         SECTION 3.02 Custodial Accounts and Buydown Fund Accounts. The Master
Servicer shall cause to be established and maintained by each Servicer under the
Master Servicer's supervision the Custodial Account for P&I, Buydown Fund
Accounts (if any) and special Custodial Account for Reserves and shall deposit
or cause to be deposited therein daily the amounts related to the Mortgage Loans
required by the Selling and Servicing Contracts to be so deposited. Proceeds
received with respect to individual Mortgage Loans from any title, hazard, or
FHA insurance policy, VA guaranty, Primary Insurance Policy or other insurance
policy (other than any Special Primary Insurance Policy) covering such Mortgage
Loans, if required for the restoration or repair of the related Mortgaged
Property, may be deposited either in the Custodial Account for Reserves or the
Custodial Account for P&I. Such proceeds (other than proceeds from any Special
Primary Insurance Policy), if not required for the restoration or repair of the
related Mortgaged Property, shall be deposited in the Custodial Account for P&I,
and shall be applied to the balances of the related Mortgage Loans as payments
of interest and principal.

         The Master Servicer is hereby authorized to make withdrawals from and
to issue drafts against the Custodial Accounts for P&I and the Custodial
Accounts for Reserves for the purposes required or permitted by this Agreement.


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<PAGE>

Each Custodial Account for P&I and each Custodial Account for Reserves shall
bear a designation clearly showing the respective interests of the applicable
Servicer, as trustee, and of the Master Servicer, in substantially one of the
following forms:

         (a) With respect to the Custodial Account for P&I: (i) [Servicer's
Name], as agent, trustee and/or bailee of principal and interest custodial
account for Washington Mutual Mortgage Securities Corp., its successors and
assigns, for various owners of interests in Washington Mutual Mortgage
Securities Corp. mortgage-backed pools or (ii) [Servicer's Name] in trust for
Washington Mutual Mortgage Securities Corp.;

         (b) With respect to the Custodial Account for Reserves: (i) [Servicer's
Name], as agent, trustee and/or bailee of taxes and insurance custodial account
for Washington Mutual Mortgage Securities Corp., its successors and assigns for
various mortgagors and/or various owners of interests in Washington Mutual
Mortgage Securities Corp. mortgage-backed pools or (ii) [Servicer's Name] in
trust for Washington Mutual Mortgage Securities Corp. and various Mortgagors.

         The Master Servicer hereby undertakes to assure remittance to the
Certificate Account of all amounts relating to the Mortgage Loans that have been
collected by any Servicer and are due to the Certificate Account pursuant to
Section 4.01 of this Agreement.

         Funds held in the Custodial Account for P&I and the Custodial Account
for Reserves may, at the Master Servicer's option, be invested in (i) one or
more Eligible Investments which shall in no event mature later than the Business
Day prior to the related Withdrawal Date (except if such Eligible Investments
are obligations of the Trustee, such Eligible Investments may mature on the
Withdrawal Date), or (ii) such other instruments as shall be required to
maintain the Ratings.

SECTION 3.03 The Investment Account; Eligible Investments. (a) Not later than
the Withdrawal Date, the Master Servicer shall withdraw or direct the withdrawal
of funds in the Custodial Accounts for P&I, for deposit in the Investment
Account, in an amount representing:

         (i) Scheduled installments of principal and interest on the Mortgage
Loans received or advanced by the applicable Servicers which were due on the
related Due Date, net of Servicing Fees due the applicable Servicers and less
any amounts to be withdrawn later by the applicable Servicers from the
applicable Buydown Fund Accounts;

         (ii) Payoffs and the proceeds of other types of liquidations of the
Mortgage Loans received by the applicable Servicer for such Mortgage Loans
during the applicable Payoff Period, with interest to the date of Payoff or
liquidation less any amounts to be withdrawn later by the applicable Servicers
from the applicable Buydown Fund Accounts; and

         (iii) Curtailments received by the applicable Servicers in the Prior
Period.



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         At its option, the Master Servicer may invest funds withdrawn from the
Custodial Accounts for P&I, as well as any Buydown Funds, Insurance Proceeds and
Liquidation Proceeds previously received by the Master Servicer (including
amounts paid by the Company in respect of any Purchase Obligation or its
substitution obligations set forth in Section 2.07 or Section 2.08 or in
connection with the exercise of the option to terminate this Agreement pursuant
to Section 9.01) for its own account and at its own risk, during any period
prior to their deposit in the Certificate Account. Such funds, as well as any
funds which were withdrawn from the Custodial Accounts for P&I on or before the
Withdrawal Date, but not yet deposited into the Certificate Account, shall
immediately be deposited by the Master Servicer with the Investment Depository
in an Investment Account in the name of the Master Servicer and the Trust for
investment only as set forth in this Section 3.03. The Master Servicer shall
bear any and all losses incurred on any investments made with such funds and
shall be entitled to retain all gains realized on such investments as additional
servicing compensation. Not later than the Business Day prior to the
Distribution Date, the Master Servicer shall deposit such funds, net of any
gains (except Payoff Earnings) earned thereon, in the Certificate Account.

         (b) Funds held in the Investment Account shall be invested in (i) one
or more Eligible Investments which shall in no event mature later than the
Business Day prior to the related Distribution Date (except if such Eligible
Investments are obligations of the Trustee, such Eligible Investments may mature
on the Distribution Date), or (ii) such other instruments as shall be required
to maintain the Ratings.

         SECTION 3.04 The Certificate Account.

         (a) On or prior to the Closing Date, the Trustee shall establish the
Certificate Account, which shall be entitled "Washington Mutual Mortgage
Securities Corp. Certificate Account under the Pooling and Servicing Agreement,
dated as of February 1, 2004, among Washington Mutual Mortgage Securities Corp.,
as Depositor and Master Servicer, and Citibank, N.A., as the Trustee, and
Christiana Bank & Trust Company, as the Delaware Trustee, for the benefit of the
WaMu Mortgage Pass-Through Certificates Series 2004-S1 Trust created pursuant
thereto". Promptly after the Closing Date, the Trustee shall communicate to the
Master Servicer the account number and wiring instructions for the Certificate
Account.

         Not later than the Business Day prior to the related Distribution Date,
the Master Servicer shall direct the Investment Depository to deposit into the
Certificate Account the amounts previously deposited into the Investment Account
(which may include a deposit of Eligible Investments) to which the Holders of
the REMIC I Regular Interests and the Class R-1 Residual Interest are entitled
or which are necessary for payment of any Special Primary Insurance Premiums. In
addition, not later than the Business Day prior to the Distribution Date, the
Master Servicer shall deposit into the Certificate Account any Monthly P&I
Advances or other payments required to be made by the Master Servicer pursuant
to Section 4.02 of this Agreement and any Insurance Proceeds or Liquidation
Proceeds (including amounts paid by the Company in respect of any Purchase
Obligation) not previously deposited in the Custodial Accounts for P&I or the
Investment Account, and any amounts paid by the Master Servicer in connection
with the exercise of its option to terminate this Agreement pursuant to Section
9.01 or any other purchase of Mortgage Loans permitted by this Agreement.



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         (b) Funds held in the Certificate Account shall be invested at the
written direction of the Master Servicer in (i) one or more Eligible Investments
which shall in no event mature later than the Business Day prior to the related
Distribution Date (except if such Eligible Investments are obligations of the
Trustee, such Eligible Investments may mature on the Distribution Date), or (ii)
such other instruments as shall be required to maintain the Ratings. The Master
Servicer shall be entitled to receive any gains earned on such Eligible
Investments and shall bear any losses suffered in connection therewith. If the
Trustee has not received such written investment directions from the Master
Servicer, the Trustee shall not invest funds held in the Certificate Account.
The Trustee shall have no liability for any losses on investments of funds held
in the Certificate Account.

         SECTION 3.05 Permitted Withdrawals from the Certificate Account, the
Investment Account and Custodial Accounts for P&I and of Buydown Funds from the
Buydown Fund Accounts.

         (a) The Master Servicer is authorized to make withdrawals (or, in the
case of the Certificate Account, to direct the Trustee to make withdrawals),
from time to time, from the Investment Account, the Certificate Account or the
Custodial Accounts for P&I established by the Servicers of amounts deposited
therein in respect of the Certificates (and, to the extent applicable, to make
deposits of the amounts withdrawn), as follows:

         (i) To reimburse itself or the applicable Servicer for Monthly P&I
Advances made pursuant to Section 4.02 or a Selling and Servicing Contract, such
right to reimbursement pursuant to this paragraph (i) being limited to amounts
received on particular Mortgage Loans (including, for this purpose, Insurance
Proceeds and Liquidation Proceeds) which represent late recoveries of principal
and/or interest respecting which any such Monthly P&I Advance was made;

         (ii) To reimburse itself or the applicable Servicer for amounts
expended by or for the account of the Master Servicer pursuant to Section 3.09
or amounts expended by such Servicer pursuant to the Selling and Servicing
Contracts in connection with the restoration of property damaged by an Uninsured
Cause or in connection with the liquidation of a Mortgage Loan;

         (iii) To pay to itself, with respect to the related Mortgage Loans, the
Master Servicing Fee (net of Compensating Interest reduced by Payoff Earnings
and Payoff Interest) as to which no prior withdrawals from funds deposited by
the Master Servicer have been made;

         (iv) To reimburse itself or the applicable Servicer for advances made
with respect to related Mortgage Loans (except for Mortgage Loans purchased
pursuant to a Purchase Obligation or pursuant to the second or third sentence of
the third paragraph of Section 3.01) which the Master Servicer has determined to
be Nonrecoverable Advances;

         (v) To pay to itself reinvestment earnings deposited or earned in the
Investment Account and the Certificate Account to which it is entitled and to
reimburse itself for expenses incurred by and reimbursable to it pursuant to
Section 6.03;



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<PAGE>

         (vi) To deposit to the Investment Account amounts in the Certificate
Account not required to be on deposit therein at the time of such withdrawal;

         (vii) To deposit in the Certificate Account, not later than the
Business Day prior to the related Distribution Date, the amounts in the
Investment Account specified in Section 3.04(a);

         (viii) To pay on behalf of the Trustee any Special Primary Insurance
Premium payable by the Trustee pursuant to Section 4.05(a); provided, the Master
Servicer shall give written notice thereof to the Trustee prior to noon New York
City time two Business Days prior to the applicable Distribution Date; and

         after making or providing for the above withdrawals

         (ix) To clear and terminate the Investment Account and the Certificate
Account following termination of this Agreement pursuant to Section 9.01.

         Since, in connection with withdrawals pursuant to paragraphs (i) and
(ii), the Master Servicer's entitlement thereto is limited to collections or
other recoveries on the related Mortgage Loan, the Master Servicer or the
applicable Servicer shall keep and maintain separate accounting for each
Mortgage Loan, for the purpose of justifying any such withdrawals.

         (b) The Master Servicer (or the applicable Servicer, if such Servicer
holds and maintains a Buydown Fund Account) is authorized to make withdrawals,
from time to time, of Buydown Funds from the Buydown Fund Account or Custodial
Account for P&I established by any Servicer under its supervision (and, to the
extent applicable, to make deposits of the amounts withdrawn), as follows:

         (i) To deposit each month in the Investment Account the amount
necessary to supplement payments received on Buydown Loans;

         (ii) In the event of a Payoff of any Mortgage Loan having a related
Buydown Fund, to apply amounts remaining in Buydown Fund Accounts to reduce the
required amount of such principal Payoff (or, if the Mortgagor has made a
Payoff, to refund such remaining Buydown Fund amounts to the Person entitled
thereto);

         (iii) In the event of foreclosure or liquidation of any Mortgage Loan
having a Buydown Fund, to deposit remaining Buydown Fund amounts in the
Investment Account as Liquidation Proceeds; and

         (iv) To clear and terminate the portion of any account representing
Buydown Funds following termination of this Agreement pursuant to Section 9.01;

         (c) The Trustee is authorized to make withdrawals from time to time
from the Certificate Account to reimburse itself for advances it has made
pursuant to Section 7.01(a) hereof that it has determined to be Nonrecoverable
Advances.



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<PAGE>

         (d) Each Servicer is authorized to make withdrawals, from time to time,
from the related Custodial Account for P&I, (i) to pay to itself, with respect
to the related Mortgage Loans, the Servicing Fee and (ii) to reimburse itself
for expenses to the same extent that the Master Servicer is authorized to make
withdrawals to reimburse the Servicer for expenses pursuant to clauses (i), (ii)
and (iv) of Section 3.05(a), in the case of each of clause (d)(i) and (d)(ii),
to the extent no prior withdrawals of such amounts have been made by the
Servicer or the Master Servicer.

         SECTION 3.06 Maintenance of Primary Insurance Policies; Collections
Thereunder. The Master Servicer shall use commercially reasonable efforts to
keep, and to cause the Servicers to keep, in full force and effect each Primary
Insurance Policy (except any Special Primary Insurance Policy) required with
respect to a Mortgage Loan, in the manner set forth in the applicable Selling
and Servicing Contract, until no longer required, and the Master Servicer shall
use commercially reasonable efforts to keep in full force and effect each
Special Primary Insurance Policy, if any. Notwithstanding the foregoing, the
Master Servicer shall have no obligation to maintain any Primary Insurance
Policy for a Mortgage Loan for which the outstanding Principal Balance thereof
at any time subsequent to origination was 80% or less of the Appraised Value of
the related Mortgaged Property, unless required by applicable law.

         Unless required by applicable law, the Master Servicer shall not cancel
or refuse to renew, or allow any Servicer under its supervision to cancel or
refuse to renew, any Primary Insurance Policy in effect at the date of the
initial issuance of the Certificates that is required to be kept in force
hereunder; provided, however, that neither the Master Servicer nor any Servicer
shall advance funds for the payment of any premium due under (i) any Primary
Insurance Policy (other than a Special Primary Insurance Policy) if it shall
determine that such an advance would be a Nonrecoverable Advance or (ii) any
Special Primary Insurance Policy.

         SECTION 3.07 Maintenance of Hazard Insurance. The Master Servicer shall
cause to be maintained for each Mortgage Loan (other than a Cooperative Loan)
fire insurance with extended coverage in an amount which is not less than the
original principal balance of such Mortgage Loan, except in cases approved by
the Master Servicer in which such amount exceeds the value of the improvements
to the Mortgaged Property. The Master Servicer shall also require fire insurance
with extended coverage in a comparable amount on property acquired upon
foreclosure, or deed in lieu of foreclosure, of any Mortgage Loan (other than a
Cooperative Loan). Any amounts collected under any such policies (other than
amounts to be applied to the restoration or repair of the related Mortgaged
Property) shall be deposited into the Custodial Account for P&I, subject to
withdrawal pursuant to the applicable Selling and Servicing Contract and
pursuant to Section 3.03 and Section 3.05. Any unreimbursed costs incurred in
maintaining any insurance described in this Section 3.07 shall be recoverable as
an advance by the Master Servicer from the Investment Account or the Certificate
Account. Such insurance shall be with insurers approved by the Master Servicer
and Fannie Mae or Freddie Mac. Other additional insurance may be required of a
Mortgagor, in addition to that required pursuant to such applicable laws and
regulations as shall at any time be in force and as shall require such
additional insurance. Where any part of any improvement to the Mortgaged
Property (other than a Mortgaged Property secured by a Cooperative Loan) is
located in a federally designated special flood hazard area and in a community
which participates in the National Flood Insurance Program at the time of
origination of the related Mortgage Loan, the Master Servicer shall cause flood
insurance to be provided. The hazard insurance coverage required by this Section
3.07 may be met with blanket policies providing protection equivalent to
individual policies otherwise required. The Master Servicer or the applicable


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Servicer shall be responsible for paying any deductible amount on any such
blanket policy. The Master Servicer agrees to present, or cause to be presented,
on behalf of and for the benefit of the Trust, claims under the hazard insurance
policy respecting any Mortgage Loan, and in this regard to take such reasonable
actions as shall be necessary to permit recovery under such policy.

         SECTION 3.08 Enforcement of Due-on-Sale Clauses; Assumption Agreements.
When any Mortgaged Property is about to be conveyed by the Mortgagor, the Master
Servicer shall, to the extent it has knowledge of such prospective conveyance
and prior to the time of the consummation of such conveyance, exercise on behalf
of the Trust the Trust's rights to accelerate the maturity of such Mortgage
Loan, to the extent that such acceleration is permitted by the terms of the
related Mortgage Note, under any "due-on-sale" clause applicable thereto;
provided, however, that the Master Servicer shall not exercise any such right if
the due-on-sale clause, in the reasonable belief of the Master Servicer, is not
enforceable under applicable law or if such exercise would result in
non-coverage of any resulting loss that would otherwise be covered under any
insurance policy. In the event the Master Servicer is prohibited from exercising
such right, the Master Servicer is authorized to take or enter into an
assumption and modification agreement from or with the Person to whom a
Mortgaged Property has been or is about to be conveyed, pursuant to which such
Person becomes liable under the Mortgage Note and, unless prohibited by
applicable state law or unless the Mortgage Note contains a provision allowing a
qualified borrower to assume the Mortgage Note, the Mortgagor remains liable
thereon; provided that the Mortgage Loan shall continue to be covered (if so
covered before the Master Servicer enters such agreement) by any related Primary
Insurance Policy. The Master Servicer is also authorized to enter into a
substitution of liability agreement with such Person, pursuant to which the
original Mortgagor is released from liability and such Person is substituted as
Mortgagor and becomes liable under the Mortgage Note. The Master Servicer shall
not enter into any substitution or assumption with respect to a Mortgage Loan if
such substitution or assumption shall (i) both constitute a "significant
modification" effecting an exchange or reissuance of such Mortgage Loan under
the Code (or Treasury regulations promulgated thereunder) and cause the REMICs
to fail to qualify as a REMIC under the REMIC Provisions or (ii) cause the
imposition of any tax on "prohibited transactions" or "contributions" after the
startup day under the REMIC Provisions. The Master Servicer shall notify the
Trustee that any such substitution or assumption agreement has been completed by
forwarding to the Trustee the original copy of such substitution or assumption
agreement and other documents and instruments constituting a part thereof. In
connection with any such assumption or substitution agreement, the terms of the
related Mortgage Note shall not be changed. Any fee collected by the applicable
Servicer for entering into an assumption or substitution of liability agreement
shall be retained by such Servicer as additional servicing compensation.

         Notwithstanding the foregoing paragraph or any other provision of this
Agreement, the Master Servicer shall not be deemed to be in default, breach or
any other violation of its obligations hereunder by reason of any assumption of
a Mortgage Loan by operation of law or any assumption which the Master Servicer
may be restricted by law from preventing, for any reason whatsoever.



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         SECTION 3.09 Realization Upon Defaulted Mortgage Loans. The Master
Servicer shall foreclose upon or otherwise comparably convert, or cause to be
foreclosed upon or comparably converted, the ownership of any Mortgaged Property
securing a Mortgage Loan which comes into and continues in default and as to
which no satisfactory arrangements can be made for collection of delinquent
payments pursuant to Section 3.01. In lieu of such foreclosure or other
conversion, and taking into consideration the desirability of maximizing net
Liquidation Proceeds after taking into account the effect of Insurance Proceeds
upon Liquidation Proceeds, the Master Servicer may, to the extent consistent
with prudent mortgage loan servicing practices, accept a payment of less than
the outstanding Principal Balance of a delinquent Mortgage Loan in full
satisfaction of the indebtedness evidenced by the related Mortgage Note and
release the lien of the related Mortgage upon receipt of such payment. The
Master Servicer shall not foreclose upon or otherwise comparably convert a
Mortgaged Property if the Master Servicer is aware of evidence of toxic waste,
other hazardous substances or other evidence of environmental contamination
thereon and the Master Servicer determines that it would be imprudent to do so.
In connection with such foreclosure or other conversion, the Master Servicer
shall cause to be followed such practices and procedures as it shall deem
necessary or advisable and as shall be normal and usual in general mortgage
servicing activities. The foregoing is subject to the provision that, in the
case of damage to a Mortgaged Property from an Uninsured Cause, the Master
Servicer shall not be required to advance its own funds towards the restoration
of the property unless it shall be determined in the sole judgment of the Master
Servicer, (i) that such restoration will increase the proceeds of liquidation of
the Mortgage Loan to Certificateholders after reimbursement to itself for such
expenses, and (ii) that such expenses will be recoverable to it through
Liquidation Proceeds. The Master Servicer shall be responsible for all other
costs and expenses incurred by it in any such proceedings; provided, however,
that it shall be entitled to reimbursement thereof (as well as its normal
servicing compensation) as an advance. The Master Servicer shall maintain
information required for tax reporting purposes regarding any Mortgaged Property
which is abandoned or which has been foreclosed or otherwise comparably
converted. The Master Servicer shall report such information to the Internal
Revenue Service and the Mortgagor in the manner required by applicable law.

         The Master Servicer may enter into one or more special servicing
agreements with a Lowest Class B Owner, subject to each Rating Agency's
acknowledgment that the Ratings of the Certificates in effect immediately prior
to the entering into of such agreement would not be qualified, downgraded or
withdrawn and the Certificates would not be placed on credit review status
(except for possible upgrading) as a result of such agreement. Any such
agreement may contain provisions whereby such Lowest Class B Owner may (a)
instruct the Master Servicer to instruct a Servicer to the extent provided in
the applicable Selling and Servicing Contract to commence or delay foreclosure
proceedings with respect to related delinquent Mortgage Loans, provided that the
Lowest Class B Owner deposits a specified amount of cash with the Master
Servicer that will be available for distribution to Certificateholders if
Liquidation Proceeds are less than they otherwise may have been had the Servicer
acted pursuant to its normal servicing procedures, (b) purchase such delinquent
Mortgage Loans from the Trust immediately prior to the commencement of
foreclosure proceedings at a price equal to the aggregate outstanding Principal
Balance of such Mortgage Loans plus accrued interest thereon at the applicable
Mortgage Interest Rate through the last day of the month in which such Mortgage
Loans are purchased and/or (c) assume all of the servicing rights and
obligations with respect to such delinquent Mortgage Loans so long as (i) the


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Master Servicer has the right to transfer the servicing rights and obligations
of such Mortgage Loans to another servicer and (ii) such Lowest Class B Owner
will service such Mortgage Loans in accordance with the applicable Selling and
Servicing Contract.

         REMIC I shall not acquire any real property (or personal property
incident to such real property) except in connection with a default or imminent
default of a Mortgage Loan. In the event that REMIC I acquires any real property
(or personal property incident to such real property) in connection with a
default or imminent default of a Mortgage Loan, such property shall be disposed
of by the Master Servicer as soon as practicable in a manner that, consistent
with prudent mortgage loan servicing practices, maximizes the net present value
of the recovery to the Trust, but in any event within three years after its
acquisition by the Master Servicer for REMIC I unless the Master Servicer
provides to the Trustee an Opinion of Counsel to the effect that the holding by
REMIC I of such Mortgaged Property subsequent to three years after its
acquisition will not result in the imposition of taxes on "prohibited
transactions" of REMIC I as defined in Section 860F of the Code or under the law
of any state in which real property securing a Mortgage Loan owned by REMIC I is
located or cause REMIC I to fail to qualify as a REMIC for federal income tax
purposes or for state tax purposes under the laws of any state in which real
property securing a Mortgage Loan owned by REMIC I is located at any time that
any Certificates are outstanding. The Master Servicer shall conserve, protect
and operate each such property for the Certificateholders solely for the purpose
of its prompt disposition and sale in a manner which does not cause such
property to fail to qualify as "foreclosure property" within the meaning of
Section 860G(a)(8) or result in the receipt by the REMIC of any "income from
non-permitted assets" within the meaning of Section 860F(a)(2)(B) of the Code or
any "net income from foreclosure property" which is subject to taxation under
the REMIC Provisions. Pursuant to its efforts to sell such property, the Master
Servicer shall either itself or through an agent selected by the Master Servicer
protect and conserve such property in the same manner and to such extent as is
customary in the locality where such property is located and may, incident to
its conservation and protection of the assets of the Trust, rent the same, or
any part thereof, as the Master Servicer deems to be in the best interest of the
Master Servicer and the Trust for the period prior to the sale of such property.
Additionally, the Master Servicer shall perform the tax withholding and shall
file information returns with respect to the receipt of mortgage interests
received in a trade or business, the reports of foreclosures and abandonments of
any Mortgaged Property and the information returns relating to cancellation of
indebtedness income with respect to any Mortgaged Property required by Sections
6050H, 6050J and 6050P, respectively, of the Code, and deliver to the Trustee an
Officers' Certificate on or before March 31 of each year stating that such
reports have been filed. Such reports shall be in form and substance sufficient
to meet the reporting requirements imposed by Sections 6050H, 6050J and 6050P of
the Code.

         Notwithstanding any other provision of this Agreement, the Master
Servicer and the Trustee, as applicable, shall comply with all federal
withholding requirements with respect to payments to Certificateholders of
interest or original issue discount that the Master Servicer or the Trustee
reasonably believes are applicable under the Code. The consent of
Certificateholders shall not be required for any such withholding. Without
limiting the foregoing, the Master Servicer agrees that it will not withhold
with respect to payments of interest or original issue discount in the case of a
Certificateholder that has furnished or caused to be furnished an effective Form
W-8 or an acceptable substitute form or a successor form and who is not a "10
percent shareholder" within the meaning of Code Section 871(h)(3)(B) or a


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"controlled foreign corporation" described in Code Section 881(c)(3)(C) with
respect to REMIC I, REMIC II, REMIC III or the depositor. In the event the
Trustee withholds any amount from interest or original issue discount payments
or advances thereof to any Certificateholder pursuant to federal withholding
requirements, the Trustee shall indicate the amount withheld to such
Certificateholder.

         SECTION 3.10 Trustee to Cooperate; Release of Mortgage Files. Upon the
Payoff or scheduled maturity of any Mortgage Loan, the Master Servicer shall
cause such final payment to be immediately deposited in the related Custodial
Account for P&I or the Investment Account. The Master Servicer shall promptly
notify the Trustee thereof by a certification (which certification shall include
a statement to the effect that all amounts received in connection with such
payment which are required to be deposited in either such account have been so
deposited) of a Servicing Officer and shall request delivery to it of the
Mortgage File; provided, however, that such certification shall not be required
if the Mortgage File is held by a Custodian which is also the Servicer of the
Mortgage Loan. Upon receipt of such certification and request, the Trustee
shall, not later than the fifth succeeding Business Day, release, or cause to be
released, the related Mortgage File to the Master Servicer or the applicable
Servicer indicated in such request. With any such Payoff or other final payment,
the Master Servicer is authorized (i) to prepare for and procure from the
trustee or mortgagee under the Mortgage which secured the Mortgage Note a deed
of full reconveyance or other form of satisfaction or assignment of Mortgage and
endorsement of Mortgage Note in connection with a refinancing covering the
Mortgaged Property, which satisfaction, endorsed Mortgage Note or assigning
document shall be delivered by the Master Servicer to the person or persons
entitled thereto, and (ii) with respect to any MERS Loan, to cause the removal
of such Mortgage Loan from registration on the MERS(R) System. No expenses
incurred in connection with such satisfaction or assignment shall be payable to
the Master Servicer by the Trustee or from the Certificate Account, the related
Investment Account or the related Custodial Account for P&I. From time to time
as appropriate for the servicing or foreclosure of any Mortgage Loan, including,
for this purpose, collection under any Primary Insurance Policy, the Trustee
shall, upon request of the Master Servicer and delivery to it of a trust receipt
signed by a Servicing Officer, release not later than the fifth Business Day
following the date of receipt of such request and trust receipt the related
Mortgage File to the Master Servicer or the related Servicer as indicated by the
Master Servicer and shall execute such documents as shall be necessary to the
prosecution of any such proceedings. Such trust receipt shall obligate the
Master Servicer to return the Mortgage File to the Trustee when the need
therefor by the Master Servicer no longer exists, unless the Mortgage Loan shall
be liquidated, in which case, upon receipt of a certificate of a Servicing
Officer similar to that herein above specified, the trust receipt shall be
released by the Trustee to the Master Servicer.

         SECTION 3.11 Compensation to the Master Servicer and the Servicers. As
compensation for its activities hereunder, the Master Servicer shall be entitled
to receive from the Investment Account or the Certificate Account the amounts
provided for by Section 3.05(a)(iii). The Master Servicer shall be required to
pay all expenses incurred by it in connection with its activities hereunder and
shall not be entitled to reimbursement therefor, except as specifically provided
herein.

         As compensation for its activities under the applicable Selling and
Servicing Contract, the applicable Servicer shall be entitled to withhold or
withdraw from the related Custodial Account for P&I the amounts provided for in


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such Selling and Servicing Contract to the extent not inconsistent with this
Agreement (including Section 3.05(d)). Each Servicer is required to pay all
expenses incurred by it in connection with its servicing activities under its
Selling and Servicing Contract (including payment of premiums for Primary
Insurance Policies, other than Special Primary Insurance Policies, if required)
and shall not be entitled to reimbursement therefor except as specifically
provided in such Selling and Servicing Contract and not inconsistent with this
Agreement.

         SECTION 3.12 Reports to the Trustee; Certificate Account Statement. Not
later than 15 days after each Distribution Date, the Master Servicer shall
forward a statement, certified by a Servicing Officer, to the Trustee setting
forth the status of the Certificate Account as of the close of business on such
Distribution Date and showing, for the period covered by such statement, the
aggregate of deposits into and withdrawals from the Certificate Account for each
category of deposit specified in Section 3.04 and each category of withdrawal
specified in Section 3.05, and stating that all distributions required by this
Agreement have been made (or if any required distribution has not been made,
specifying the nature and amount thereof). The Trustee shall make available such
statements to any Certificateholder upon request at the expense of the Master
Servicer. Such statement shall also, to the extent available, include
information regarding delinquencies on the Mortgage Loans, indicating the number
and aggregate Principal Balance of Mortgage Loans which are one, two, three or
more months delinquent, the number and aggregate Principal Balance of Mortgage
Loans with respect to which foreclosure proceedings have been initiated and the
book value of any Mortgaged Property acquired by the Trust through foreclosure,
deed in lieu of foreclosure or other exercise of the Trust's security interest
in the Mortgaged Property.

         SECTION 3.13 Annual Statement as to Compliance. The Master Servicer
shall deliver to the Trustee, on or before April 30 of each year, beginning with
the first April 30 succeeding the Cut-Off Date by at least six months, an
Officer's Certificate stating as to the signer thereof, that (i) a review of the
activities of the Master Servicer during the preceding calendar year and
performance under this Agreement has been made under such officer's supervision,
and (ii) to the best of such officer's knowledge, based on such review, the
Master Servicer has fulfilled all its obligations under this Agreement
throughout such year, or, if there has been a default in the fulfillment of any
such obligation, specifying each such default known to such officer and the
nature and status thereof. Copies of such statement shall be provided by the
Master Servicer to Certificateholders upon request or by the Trustee (solely to
the extent that such copies are available to the Trustee) at the expense of the
Master Servicer, should the Master Servicer fail to so provide such copies.

         SECTION 3.14 Access to Certain Documentation and Information Regarding
the Mortgage Loans. In the event that the Certificates are legal for investment
by federally-insured savings associations, the Master Servicer shall provide to
the OTS, the FDIC and the supervisory agents and examiners of the OTS and the
FDIC access to the documentation regarding the related Mortgage Loans required
by applicable regulations of the OTS or the FDIC, as applicable, and shall in
any event provide such access to the documentation regarding such Mortgage Loans
to the Trustee and its representatives, such access being afforded without
charge, but only upon reasonable request and during normal business hours at the
offices of the Master Servicer designated by it.



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         SECTION 3.15 Annual Independent Public Accountants' Servicing Report.
On or before April 30 of each year, beginning with the first April 30 succeeding
the Cut-Off Date by at least six months, the Master Servicer, at its expense,
shall furnish to the Trustee a copy of a report delivered to the Master Servicer
by a firm of independent public accountants (who may also render other services
to the Master Servicer or any affiliate thereof) to the effect that, on the
basis of an examination conducted by such firm in accordance with standards
established by the American Institute of Certified Public Accountants, the
Master Servicer has complied with certain minimum residential mortgage loan
servicing standards in its role as Master Servicer with respect to the servicing
of residential mortgage loans (including the Mortgage Loans) during the most
recently completed fiscal year. In rendering its report such firm may rely, (a)
as to matters relating to the Certificates, upon a statistical sampling of
series of mortgage-backed certificates which may include the Certificates and
(b) as to matters relating to the direct servicing of residential mortgage loans
by subservicers, upon comparable reports of firms of independent certified
public accountants rendered on the basis of examinations conducted in accordance
with the same standards (rendered within one year of such report) with respect
to those subservicers.

         SECTION 3.16 [Reserved.]

         SECTION 3.17 [Reserved.]

         SECTION 3.18 [Reserved.]

         SECTION 3.19 [Reserved.]

         SECTION 3.20 Assumption or Termination of Selling and Servicing
Contracts by Trustee. In the event the Master Servicer, or any successor Master
Servicer, shall for any reason no longer be the Master Servicer (including by
reason of an Event of Default), the Trustee as trustee hereunder or its designee
shall thereupon assume all of the rights and obligations of the Master Servicer
under the Selling and Servicing Contracts with respect to the related Mortgage
Loans unless the Trustee elects to terminate the Selling and Servicing Contracts
with respect to such Mortgage Loans in accordance with the terms thereof. The
Trustee, its designee or the successor servicer for the Trustee shall be deemed
to have assumed all of the Master Servicer's interest therein with respect to
the related Mortgage Loans and to have replaced the Master Servicer as a party
to the Selling and Servicing Contracts to the same extent as if the rights and
duties under the Selling and Servicing Contracts relating to such Mortgage Loans
had been assigned to the assuming party, except that the Master Servicer shall
not thereby be relieved of any liability or obligations under the Selling and
Servicing Contracts with respect to the Master Servicer's duties to be performed
prior to its termination hereunder.

         The Master Servicer at its expense shall, upon request of the Trustee,
deliver to the assuming party all documents and records relating to the Selling
and Servicing Contracts and the Mortgage Loans then being master serviced by the
Master Servicer and an accounting of amounts collected and held by the Master
Servicer and otherwise use its best efforts to effect the orderly and efficient
transfer of the rights and duties under the related Selling and Servicing
Contracts relating to such Mortgage Loans to the assuming party.



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                                   ARTICLE IV

               Payments to Certificateholders; Payment of Expenses

         SECTION 4.01 Distributions to Holders of REMIC I Regular Interests and
Class R-1 Residual Interest. On each Distribution Date, the Trustee (or any duly
appointed paying agent) (i) shall be deemed to have distributed from the
Certificate Account the REMIC I Distribution Amount to the Holders of the REMIC
I Regular Interests and to have deposited such amount for their benefit into the
Certificate Account and (ii) from the Certificate Account shall distribute to
the Class R Certificateholders, in accordance with the written statement
received from the Master Servicer pursuant to Section 4.02(b), the sum of (a)
the Excess Liquidation Proceeds and (b) the amounts to be distributed to the
Holders of the Class R-1 Residual Interest pursuant to the definition of "REMIC
I Distribution Amount" for such Distribution Date. Amounts distributed pursuant
to clause (ii) above shall be distributed by wire transfer in immediately
available funds for the account of each Class R Certificateholder, or by any
other means of payment acceptable to each Class R Certificateholder of record on
the immediately preceding Record Date (other than as provided in Section 9.01
respecting the final distribution), as specified by each such Certificateholder
and at the address of such Holder appearing in the Certificate Register.
Notwithstanding any other provision of this Agreement, no actual distributions
pursuant to clause (i) of this Section 4.01 shall be made on account of the
deemed distributions described in this paragraph except in the event of a
liquidation of REMIC III and REMIC II and not REMIC I.

         SECTION 4.02 Advances by the Master Servicer; Distribution Reports to
the Trustee.

         (a) To the extent described below, the Master Servicer is obligated to
advance its own funds to the Certificate Account to cover any shortfall between
(i) payments scheduled to be received in respect of Mortgage Loans, and (ii) the
amounts actually deposited in the Certificate Account on account of such
payments. The Master Servicer's obligation to make any advance or advances
described in this Section 4.02 is effective only to the extent that such advance
is, in the good faith judgment of the Master Servicer made on or before the
second Business Day prior to each Distribution Date, reimbursable from Insurance
Proceeds or Liquidation Proceeds of the related Mortgage Loans or recoverable as
late Monthly Payments with respect to the related Mortgage Loans or otherwise.

         Prior to the close of business on the second Business Day prior to each
Distribution Date, the Master Servicer shall determine whether or not it will
make a Monthly P&I Advance on the Business Day prior to such Distribution Date
(in the event that the applicable Servicer fails to make such advances) and
shall furnish a written statement to the Trustee, the Paying Agent, if any, and
to any Certificateholder requesting the same, setting forth the aggregate amount
to be advanced on account of principal and interest in respect of the Mortgage
Loans, stated separately.

         In the event that the Master Servicer shall be required to make a
Monthly P&I Advance, it shall on the Business Day prior to the related
Distribution Date either (i) deposit in the Certificate Account an amount equal


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to such Monthly P&I Advance, (ii) make an appropriate entry in the records of
the Certificate Account that funds in such account being held for future
distribution or withdrawal have been, as permitted by this Section 4.02, used by
the Master Servicer to make such Monthly P&I Advance, or (iii) make advances in
the form of any combination of (i) and (ii) aggregating the amount of such
Monthly P&I Advance. Any funds being held for future distribution to
Certificateholders and so used shall be replaced by the Master Servicer by
deposit in the Certificate Account on the Business Day immediately preceding any
future Distribution Date to the extent that funds in the Certificate Account on
such Distribution Date with respect to the Mortgage Loans shall be less than
payments to Certificateholders required to be made on such date with respect to
the Mortgage Loans. Under each Selling and Servicing Contract, the Master
Servicer is entitled to receive from the Custodial Accounts for P&I established
by the Servicers amounts received by the applicable Servicers on particular
Mortgage Loans as late payments of principal and interest or as Liquidation or
Insurance Proceeds and respecting which the Master Servicer has made an
unreimbursed advance of principal and interest. The Master Servicer is also
entitled to receive other amounts from the related Custodial Accounts for P&I
established by the Servicers to reimburse itself for prior Nonrecoverable
Advances respecting Mortgage Loans serviced by such Servicers. The Master
Servicer shall deposit these amounts in the Investment Account prior to
withdrawal pursuant to Section 3.05.

         In accordance with Section 3.05, Monthly P&I Advances are reimbursable
to the Master Servicer from cash in the Investment Account or the Certificate
Account to the extent that the Master Servicer shall determine that any such
advances previously made are Nonrecoverable Advances pursuant to Section 4.03.

         (b) Prior to noon New York City time two Business Days prior to each
Distribution Date, the Master Servicer shall provide (x) the Trustee and (y) the
Company (if the Company is no longer acting as Master Servicer) with a statement
in writing of (1) the amount, as applicable, of (i) interest, (ii) the interest
portion, if any, of Realized Losses, (iii) Uncompensated Interest Shortfall,
(iv) scheduled principal, (v) Principal Prepayments, (vi) Liquidation Principal,
(vii) Subsequent Recoveries, (viii) the principal portion of Realized Losses
(after giving effect to any reduction thereof by application of any Cumulative
Carry-Forward Subsequent Recoveries Amount), (ix) the Residual Distribution
Amount and (x) the Excess Liquidation Proceeds to be distributed or allocated,
as applicable, to each Class of Certificates on such Distribution Date (such
amounts to be determined in accordance with the definitions of "REMIC I
Distribution Amount," "REMIC II Distribution Amount" and "REMIC III Distribution
Amount," Section 4.01, Section 4.04 and Section 4.05 hereof and other related
definitions set forth in Article I hereof); (2) the applicable Class Principal
Balance after giving effect to such distributions and allocations; (3) the
Cumulative Carry-Forward Subsequent Recoveries Amount for such Distribution Date
and each Subgroup; and (4) the amount of any Special Primary Insurance Premium
payable on such Distribution Date.

         SECTION 4.03 Nonrecoverable Advances. Any advance previously made by a
Servicer pursuant to its Selling and Servicing Contract with respect to a
Mortgage Loan or by the Master Servicer that the Master Servicer shall determine
in its good faith judgment not to be ultimately recoverable from Insurance
Proceeds or Liquidation Proceeds or otherwise with respect to such Mortgage Loan
or recoverable as late Monthly Payments with respect to such Mortgage Loan shall
be a Nonrecoverable Advance. The determination by the Master Servicer that it or


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the applicable Servicer has made a Nonrecoverable Advance or that any advance
would constitute a Nonrecoverable Advance, shall be evidenced by an Officer's
Certificate of the Master Servicer delivered to the Trustee on the Determination
Date and detailing the reasons for such determination. Notwithstanding any other
provision of this Agreement, any insurance policy relating to the Mortgage
Loans, or any other agreement relating to the Mortgage Loans to which the
Company or the Master Servicer is a party, (a) the Master Servicer and each
Servicer shall not be obligated to, and shall not, make any advance that, after
reasonable inquiry and in its sole discretion, the Master Servicer or such
Servicer shall determine would be a Nonrecoverable Advance, and (b) the Master
Servicer and each Servicer shall be entitled to reimbursement for any advance as
provided in Section 3.05(a)(i), (ii) and (iv) of this Agreement.

         SECTION 4.04 Distributions to Holders of REMIC II Regular Interests and
Class R-2 Residual Interest. On each Distribution Date, the Trustee (or any duly
appointed paying agent) (i) shall be deemed to have distributed from the
Certificate Account the REMIC II Distribution Amount to the Holders of the REMIC
II Regular Interests, and to have deposited such amount for their benefit into
the Certificate Account and (ii) shall distribute from the Certificate Account
to the Class R Certificateholders, in accordance with the written statement
received from the Master Servicer pursuant to Section 4.02(b), the amounts to be
distributed to the Holders of the Class R-2 Residual Interest pursuant to the
definition of "REMIC II Distribution Amount" for such Distribution Date. Amounts
distributed to the Class R Certificateholders pursuant to clause (ii) above
shall be distributed by wire transfer in immediately available funds for the
account of each Class R Certificateholder, or by any other means of payment
acceptable to each Class R Certificateholder of record on the immediately
preceding Record Date (other than as provided in Section 9.01 respecting the
final distribution), as specified by each Class R Certificateholder and at the
address of such Holder appearing in the Certificate Register. Notwithstanding
any other provision of this Agreement, no actual distributions pursuant to
clause (i) of this Section 4.04 shall be made on account of the deemed
distributions described in this paragraph except in the event of a liquidation
of REMIC III and not REMIC II.

         SECTION 4.05 Distributions to Certificateholders; Payment of Special
Primary Insurance Premiums.

         (a) On each Distribution Date, the Trustee (or any duly appointed
paying agent) shall (i) subject to Section 3.05(a)(viii), withdraw from the
Certificate Account any Special Primary Insurance Premium payable on such
Distribution Date and pay such amount to the insurer under the applicable
Special Primary Insurance Policy and (ii) withdraw from the Certificate Account
the REMIC III Available Distribution Amount for such Distribution Date and
distribute, from the amount so withdrawn, to the extent of the REMIC III
Available Distribution Amount, the REMIC III Distribution Amount to the
Certificateholders (including the Class R Certificateholders with respect to any
distribution to the Holders of the Class R-3 Residual Interest), all in
accordance with the written statement received from the Master Servicer pursuant
to Section 4.02(b). Any Special Primary Insurance Premiums distributed pursuant
to clause (i) above shall be distributed by means of payment acceptable to the
insurer under the respective Special Primary Insurance Policy. Amounts
distributed to the Certificateholders pursuant to clause (ii) above shall be
distributed by wire transfer in immediately available funds for the account of,


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or by check mailed to, each such Certificateholder of record on the immediately
preceding Record Date (other than as provided in Section 9.01 respecting the
final distribution), as specified by each such Certificateholder and at the
address of such Holder appearing in the Certificate Register.

         (b) All reductions in the Certificate Principal Balance of a
Certificate effected by distributions of principal and all allocations of
Realized Losses made on any Distribution Date shall be binding upon all Holders
of such Certificate and of any Certificate issued upon the registration of
transfer or exchange therefor or in lieu thereof, whether or not such
distribution is noted on such Certificate. The final distribution of principal
of each Certificate (and the final distribution upon the Class R Certificates
upon (i) the termination of REMIC I, REMIC II and REMIC III and (ii) the
payment, or making provision for payment, of all liabilities of the Trust) shall
be payable in the manner provided above only upon presentation and surrender
thereof on or after the Distribution Date therefor at the office or agency of
the Certificate Registrar specified in the notice delivered pursuant to Section
4.05(c)(ii) and Section 9.01(b).

         (c) Whenever, on the basis of Curtailments, Payoffs and Monthly
Payments on the Mortgage Loans and Insurance Proceeds and Liquidation Proceeds
received and expected to be received during the Payoff Period, the Master
Servicer has notified the Trustee that it believes that the entire remaining
unpaid Class Principal Balance of any Class of Certificates will become
distributable on the next Distribution Date, the Trustee shall, no later than
the 18th day of the month of such Distribution Date, mail or cause to be mailed
to each Person in whose name a Certificate to be so retired is registered at the
close of business on the Record Date and to the Rating Agencies a notice to the
effect that:

         (i) it is expected that funds sufficient to make such final
distribution will be available in the Certificate Account on such Distribution
Date, and

         (ii) if such funds are available, (A) such final distribution will be
payable on such Distribution Date, but only upon presentation and surrender of
such Certificate at the office or agency of the Certificate Registrar maintained
for such purpose (the address of which shall be set forth in such notice), and
(B) no interest shall accrue on such Certificate after such Distribution Date.

         SECTION 4.06 Statements to Certificateholders. With each distribution
from the Certificate Account on a Distribution Date, the Trustee shall send to
each Rating Agency and shall make available to each Certificateholder the
statement required by Section 4.02(b). The Trustee may make available such
statement and certain other information, including, without limitation,
information required to be provided by the Trustee pursuant to Sections 3.12 and
3.13, to Certificateholders through the Trustee's Corporate Trust home page on
the world wide web. Such web page is currently located at
"www.sf.citidirect.com." The location of such web page and the procedures used
therein are subject to change from time to time at the Trustee's discretion.

         Upon request by any Certificateholder or Rating Agency or the Trustee,
the Master Servicer shall forward to such Certificateholder or Rating Agency and
the Trustee and the Company (if the Company is no longer acting as Master
Servicer) an additional report which sets forth with respect to the Mortgage
Loans:

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         (a) The number and aggregate Principal Balance of the Mortgage Loans
delinquent one, two and three months or more;

         (b) The (i) number and aggregate Principal Balance of Mortgage Loans
with respect to which foreclosure proceedings have been initiated, and (ii) the
number and aggregate book value of Mortgaged Properties acquired through
foreclosure, deed in lieu of foreclosure or other exercise of rights respecting
the Trust's security interest in the Mortgage Loans;

         (c) The amount of the Special Hazard Coverage available to the Senior
Certificates remaining as of the close of business on the applicable
Determination Date;

         (d) The amount of the Bankruptcy Coverage available to the Senior
Certificates remaining as of the close of business on the applicable
Determination Date;

         (e) The amount of the Fraud Coverage available to the Senior
Certificates remaining as of the close of business on the applicable
Determination Date; and

         (f) The cumulative amount of Realized Losses allocated to the related
Certificates since the Cut-Off Date.

         Upon request by any Certificateholder, the Master Servicer, as soon as
reasonably practicable, shall provide the requesting Certificateholder with such
information as is necessary and appropriate, in the Master Servicer's sole
discretion, for purposes of satisfying applicable reporting requirements under
Rule 144A of the Securities Act.

         The Company may make available any reports, statements or other
information to Certificateholders through the Company's home page on the world
wide web. As of the Closing Date, such web page is located at "www.wamumsc.com"
and information is available by clicking on "Investor Information."

                                   ARTICLE V

                                The Certificates

         SECTION 5.01 The Certificates.

         (a) The Certificates shall be substantially in the forms set forth in
Exhibit A and B with the additional insertion from Exhibit H attached hereto,
and shall be executed by the Trustee on behalf of the Trust, authenticated by
the Trustee (or any duly appointed Authenticating Agent) and delivered (i) upon
and pursuant to the order of the Company and (ii) upon receipt by the Trustee of
the documents specified in Section 2.01. The Certificates shall be issuable in
Authorized Denominations. Certificates shall be executed by manual or facsimile
signature on behalf of the Trust by authorized officers of the Trustee.
Certificates bearing the manual or facsimile signatures of individuals who were
at the time of execution the proper officers of the Trustee shall bind the
Trust, notwithstanding that such individuals or any of them have ceased to hold
such offices prior to the authentication and delivery of such Certificates or
did not hold such offices at the date of such Certificates. No Certificate shall
be entitled to any benefit under this Agreement, or be valid for any purpose,
unless there appears on such Certificate a certificate of authentication
substantially in the form provided for herein executed by the Trustee or any


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Authenticating Agent by manual signature, and such certificate upon any
Certificate shall be conclusive evidence, and the only evidence, that such
Certificate has been duly authenticated and delivered hereunder. All
Certificates shall be dated the date of their authentication.

         (b) The following definitions apply for purposes of this Section 5.01:
"Disqualified Organization" means any Person which is not a Permitted
Transferee, but does not include any "Pass-Through Entity" which owns or holds a
Residual Certificate and of which a Disqualified Organization, directly or
indirectly, may be a stockholder, partner or beneficiary; "Pass-Through Entity"
means any regulated investment company, real estate investment trust, common
trust fund, partnership, trust or estate, and any organization to which Section
1381 of the Code applies; "Ownership Interest" means, with respect to any
Residual Certificate, any ownership or security interest in such Residual
Certificate, including any interest in a Residual Certificate as the Holder
thereof and any other interest therein whether direct or indirect, legal or
beneficial, as owner or as pledgee; "Transfer" means any direct or indirect
transfer or sale of, or directly or indirectly transferring or selling any
Ownership Interest in a Residual Certificate; and "Transferee" means any Person
who is acquiring by Transfer any Ownership Interest in a Residual Certificate.

         (c) Restrictions on Transfers of the Residual Certificates to
Disqualified Organizations are set forth in this Section 5.01(c).

         (i) Each Person who has or who acquires any Ownership Interest in a
Residual Certificate shall be deemed by the acceptance or acquisition of such
Ownership Interest to have agreed to be bound by the following provisions and to
have irrevocably authorized the Trustee or its designee under clause (iii)(A)
below to deliver payments to a Person other than such Person and to negotiate
the terms of any mandatory sale under clause (iii)(B) below and to execute all
instruments of transfer and to do all other things necessary in connection with
any such sale. The rights of each Person acquiring any Ownership Interest in a
Residual Certificate are expressly subject to the following provisions:

         (A) Each Person holding or acquiring any Ownership Interest in a
Residual Certificate shall be a Permitted Transferee and shall promptly notify
the Trustee of any change or impending change in its status as a Permitted
Transferee.

         (B) In connection with any proposed Transfer of any Ownership Interest
in a Residual Certificate to a U.S. Person, the Trustee shall require delivery
to it, and shall not register the Transfer of any Residual Certificate until its
receipt of (1) an affidavit and agreement (a "Transferee Affidavit and
Agreement") attached hereto as Exhibit J from the proposed Transferee, in form
and substance satisfactory to the Company, representing and warranting, among
other things, that it is not a Non-U.S. Person, that such transferee is a
Permitted Transferee, that it is not acquiring its Ownership Interest in the
Residual Certificate that is the subject of the proposed Transfer as a nominee,
trustee or agent for any Person who is not a Permitted Transferee, that for so
long as it retains its Ownership Interest in a Residual Certificate, it will
endeavor to remain a Permitted Transferee, and that it has reviewed the
provisions of this Section 5.01(c) and agrees to be bound by them, and (2) a


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certificate, attached hereto as Exhibit I, from the Holder wishing to transfer
the Residual Certificate, in form and substance satisfactory to the Company,
representing and warranting, among other things, that no purpose of the proposed
Transfer is to allow such Holder to impede the assessment or collection of tax.

         (C) Notwithstanding the delivery of a Transferee Affidavit and
Agreement by a proposed Transferee under clause (B) above, if the Trustee has
actual knowledge that the proposed Transferee is not a Permitted Transferee, no
Transfer of an Ownership Interest in a Residual Certificate to such proposed
Transferee shall be effected.

         (D) Each Person holding or acquiring any Ownership Interest in a
Residual Certificate agrees by holding or acquiring such Ownership Interest (i)
to require a Transferee Affidavit and Agreement from any other Person to whom
such Person attempts to transfer its Ownership Interest and to provide a
certificate to the Trustee in the form attached hereto as Exhibit J; (ii) to
obtain the express written consent of the Company prior to any transfer of such
Ownership Interest, which consent may be withheld in the Company's sole
discretion; and (iii) to provide a certificate to the Trustee in the form
attached hereto as Exhibit I.

         (ii) The Trustee shall register the Transfer of any Residual
Certificate only if it shall have received the Transferee Affidavit and
Agreement, a certificate of the Holder requesting such transfer in the form
attached hereto as Exhibit J and all of such other documents as shall have been
reasonably required by the Trustee as a condition to such registration.

         (iii) (A) If any "disqualified organization" (as defined in Section
860E(e)(5) of the Code) shall become a holder of a Residual Certificate, then
the last preceding Permitted Transferee shall be restored, to the extent
permitted by law, to all rights and obligations as Holder thereof retroactive to
the date of registration of such Transfer of such Residual Certificate. If any
Non-U.S. Person shall become a holder of a Residual Certificate, then the last
preceding holder which is a U.S. Person shall be restored, to the extent
permitted by law, to all rights and obligations as Holder thereof retroactive to
the date of registration of the Transfer to such Non-U.S. Person of such
Residual Certificate. If a transfer of a Residual Certificate is disregarded
pursuant to the provisions of Treasury Regulations Section 1.860E-1 or Section
1.860G-3, then the last preceding Permitted Transferee shall be restored, to the
extent permitted by law, to all rights and obligations as Holder thereof
retroactive to the date of registration of such Transfer of such Residual
Certificate. Neither the Trust nor the Trustee shall be under any liability to
any Person for any registration of Transfer of a Residual Certificate that is in
fact not permitted by this Section 5.01(c) or for making any payments due on
such Certificate to the holder thereof or for taking any other action with
respect to such holder under the provisions of this Agreement.



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<PAGE>

         (B) If any purported Transferee shall become a Holder of a Residual
Certificate in violation of the restrictions in this Section 5.01(c) and to the
extent that the retroactive restoration of the rights of the Holder of such
Residual Certificate as described in clause (iii)(A) above shall be invalid,
illegal or unenforceable, then the Company shall have the right, without notice
to the Holder or any prior Holder of such Residual Certificate, to sell such
Residual Certificate to a purchaser selected by the Company on such terms as the
Company may choose. Such purported Transferee shall promptly endorse and deliver
each Residual Certificate in accordance with the instructions of the Company.
Such purchaser may be the Company itself or any affiliate of the Company. The
proceeds of such sale, net of the commissions (which may include commissions
payable to the Company or its affiliates), expenses and taxes due, if any, shall
be remitted by the Company to such purported Transferee. The terms and
conditions of any sale under this clause (iii)(B) shall be determined in the
sole discretion of the Company, and the Company shall not be liable to any
Person having an Ownership Interest in a Residual Certificate as a result of its
exercise of such discretion.

         (iv) The Company, on behalf of the Trustee, shall make available, upon
written request from the Trustee, all information necessary to compute any tax
imposed (A) as a result of the Transfer of an Ownership Interest in a Residual
Certificate to any Person who is not a Permitted Transferee, including the
information regarding "excess inclusions" of such Residual Certificates required
to be provided to the Internal Revenue Service and certain Persons as described
in Treasury Regulation Section 1.860D-1(b)(5), and (B) as a result of any
regulated investment company, real estate investment trust, common trust fund,
partnership, trust, estate or organizations described in Section 1381 of the
Code having as among its record holders at any time any Person who is not a
Permitted Transferee. Reasonable compensation for providing such information may
be required by the Company from such Person.

         (v) The provisions of this Section 5.01 set forth prior to this Section
(v) may be modified, added to or eliminated by the Company and the Trustee,
provided that there shall have been delivered to the Trustee the following:

         (A) written notification from each of the Rating Agencies to the effect
that the modification, addition to or elimination of such provisions will not
cause such Rating Agency to downgrade its then-current Ratings of the
Certificates; and

         (B) an Opinion of Counsel, in form and substance satisfactory to the
Company (as evidenced by a certificate of the Company), to the effect that such
modification, addition to or absence of such provisions will not cause REMIC I,
REMIC II and REMIC III to cease to qualify as a REMIC and will not create a risk
that (1) REMIC I, REMIC II and REMIC III may be subject to an entity-level tax
caused by the Transfer of any Residual Certificate to a Person which is not a
Permitted Transferee or (2) a Certificateholder or another Person will be
subject to a REMIC-related tax caused by the Transfer of a Residual Certificate
to a Person which is not a Permitted Transferee.



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         (vi) The following legend shall appear on all Residual Certificates:

         ANY RESALE, TRANSFER OR OTHER DISPOSITION OF THIS CERTIFICATE MAY BE
MADE ONLY IF THE PROPOSED TRANSFEREE PROVIDES A TRANSFER AFFIDAVIT TO THE
COMPANY AND THE TRUSTEE THAT (1) SUCH TRANSFEREE IS NOT EITHER (A) THE UNITED
STATES, ANY STATE OR POLITICAL SUBDIVISION THEREOF, ANY FOREIGN GOVERNMENT, ANY
INTERNATIONAL ORGANIZATION, OR ANY AGENCY OR INSTRUMENTALITY OF ANY OF THE
FOREGOING, (B) ANY ORGANIZATION (OTHER THAN A COOPERATIVE DESCRIBED IN SECTION
521 OF THE CODE) WHICH IS EXEMPT FROM THE TAX IMPOSED BY CHAPTER 1 OF THE CODE
UNLESS SUCH ORGANIZATION IS SUBJECT TO THE TAX IMPOSED BY SECTION 511 OF THE
CODE, (C) ANY ORGANIZATION DESCRIBED IN SECTION 1381(a)(2)(C) OF THE CODE (ANY
SUCH PERSON DESCRIBED IN THE FOREGOING CLAUSES (A), (B), OR (C) BEING
HEREINAFTER REFERRED TO AS A "DISQUALIFIED ORGANIZATION"), OR (D) AN AGENT OF A
DISQUALIFIED ORGANIZATION AND (2) NO PURPOSE OF SUCH TRANSFER IS TO ENABLE THE
TRANSFEROR TO IMPEDE THE ASSESSMENT OR COLLECTION OF TAX. SUCH AFFIDAVIT SHALL
INCLUDE CERTAIN REPRESENTATIONS AS TO THE FINANCIAL CONDITION OF THE PROPOSED
TRANSFEREE. NOTWITHSTANDING THE REGISTRATION IN THE CERTIFICATE REGISTER OF ANY
TRANSFER, SALE OR OTHER DISPOSITION OF THIS CLASS R CERTIFICATE TO A
DISQUALIFIED ORGANIZATION OR AN AGENT OF A DISQUALIFIED ORGANIZATION, SUCH
REGISTRATION SHALL BE DEEMED TO BE OF NO LEGAL FORCE OR EFFECT WHATSOEVER AND
SUCH PERSON SHALL NOT BE DEEMED TO BE A CERTIFICATEHOLDER FOR ANY PURPOSE
HEREUNDER, INCLUDING, BUT NOT LIMITED TO, THE RECEIPT OF DISTRIBUTIONS ON THIS
CERTIFICATE. EACH HOLDER OF THE CLASS R CERTIFICATE BY ACCEPTANCE OF THIS
CERTIFICATE SHALL BE DEEMED TO HAVE CONSENTED TO THE PROVISIONS OF THIS
PARAGRAPH.

         (xxxii) The Tax Matters Person for each of REMIC I, REMIC II and REMIC
III, while not a Disqualified Organization, shall be the tax matters person for
the related REMIC within the meaning of Section 6231(a)(7) of the Code and
Treasury Regulation Section 1.860F-4(d).

         (d) In the case of any Junior Subordinate Certificate presented for
registration in the name of any Person, the Trustee shall require (i) an
officer's certificate substantially in the form of Exhibit N attached hereto
acceptable to and in form and substance satisfactory to the Trustee and the
Company, which officer's certificate shall not be an expense of the Trust, the
Trustee, the Master Servicer or the Company, and (ii) only if such officer's
certificate indicates that a Benefit Plan Opinion is delivered in connection
therewith, a Benefit Plan Opinion.

         In the case of any Residual Certificate presented for registration in
the name of any Person, the Trustee shall require (i) a Transferee Affidavit and
Agreement which includes the representation set forth in paragraph 19 of the
form attached hereto as Exhibit J and (ii) only if the representation set forth


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in such paragraph 19 indicates that a Benefit Plan Opinion is delivered in
connection therewith, a Benefit Plan Opinion.

         (e) No transfer, sale, pledge or other disposition of a Junior
Subordinate Certificate shall be made unless such transfer, sale, pledge or
other disposition is made in accordance with this Section 5.01(e) or Section
5.01(f). Each Person who, at any time, acquires any ownership interest in any
Junior Subordinate Certificate shall be deemed by the acceptance or acquisition
of such ownership interest to have agreed to be bound by the following
provisions of this Section 5.01(e) and Section 5.01(f), as applicable. No
transfer of a Junior Subordinate Certificate shall be deemed to be made in
accordance with this Section 5.01(e) unless such transfer is made pursuant to an
effective registration statement under the Securities Act or unless the Trustee
is provided with the certificates and an Opinion of Counsel, if required, on
which the Trustee may conclusively rely, to the effect that such transfer is
exempt from the registration requirements under the Securities Act, as follows:
In the event that a transfer is to be made in reliance upon an exemption from
the Securities Act, the Trustee shall require, in order to assure compliance
with the Securities Act, that the Certificateholder desiring to effect such
transfer certify to the Trustee in writing, in substantially the form attached
hereto as Exhibit F, the facts surrounding the transfer, with such modifications
to such Exhibit F as may be appropriate to reflect the actual facts of the
proposed transfer, and that the Certificateholder's proposed transferee certify
to the Trustee in writing, in substantially the form attached hereto as Exhibit
G, the facts surrounding the transfer, with such modifications to such Exhibit G
as may be appropriate to reflect the actual facts of the proposed transfer. If
such certificate of the proposed transferee does not contain substantially the
substance of Exhibit G, the Trustee shall require an Opinion of Counsel that
such transfer may be made without registration, which Opinion of Counsel shall
not be obtained at the expense of the Trustee, the Trust or the Company. Such
Opinion of Counsel shall allow for the forwarding, and the Trustee shall
forward, a copy thereof to the Rating Agencies. Notwithstanding the foregoing,
any Junior Subordinate Certificate may be transferred, sold, pledged or
otherwise disposed of in accordance with the requirements set forth in Section
5.01(f).

         (f) To effectuate a Certificate transfer of a Junior Subordinate
Certificate in accordance with this Section 5.01(f), the proposed transferee of
such Certificate must provide the Trustee and the Company with an investment
letter substantially in the form of Exhibit L attached hereto, which investment
letter shall not be an expense of the Trust, the Trustee or the Company, and
which investment letter states that, among other things, such transferee (i) is
a "qualified institutional buyer" as defined under Rule 144A, acting for its own
account or the accounts of other "qualified institutional buyers" as defined
under Rule 144A, and (ii) is aware that the proposed transferor intends to rely
on the exemption from registration requirements under the Securities Act
provided by Rule 144A. Notwithstanding the foregoing, the proposed transferee of
such Certificate shall not be required to provide the Trustee or the Company
with Annex 1 or Annex 2 to the form of Exhibit L attached hereto if the Company
so consents prior to each such transfer. Such transfers shall be deemed to have
complied with the requirements of this Section 5.01(f). The Holder of a
Certificate desiring to effect such transfer does hereby agree to indemnify the
Trust, the Trustee, the Company, and the Certificate Registrar against any
liability that may result if transfer is not made in accordance with this
Agreement.

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         (g) (1) In the case of any ERISA Restricted Certificate presented for
registration in the name of any Person, the prospective transferee shall be
required to provide the Trustee and the Company (A) an officer's certificate
substantially in the form of Exhibit O attached hereto acceptable to and in form
and substance satisfactory to the Trustee and the Company, which officer's
certificate shall not be an expense of the Trust, the Trustee, the Master
Servicer or the Company, and (B) only if such officer's certificate indicates
that a Benefit Plan Opinion is delivered in connection therewith, a Benefit Plan
Opinion.

         (2) Notwithstanding the foregoing, a certification (and, if applicable,
a Benefit Plan Opinion) as described in Section 5.01(g)(1) above will not be
required with respect to the transfer of any ERISA Restricted Certificate to a
Clearing Agency, or for any subsequent transfer of any interest in a ERISA
Restricted Certificate for so long as such Certificate is a Book-Entry
Certificate (each such ERISA Restricted Certificate, a "Book-Entry ERISA
Restricted Certificate"). Any transferee of a Book-Entry ERISA Restricted
Certificate will be deemed to have represented, by virtue of its acquisition or
holding of such Certificate (or interest therein), that either (i) such
transferee is not an employee benefit or other plan subject to the prohibited
transaction provisions of ERISA or Section 4975 of the Code, or any person
(including an investment manager, a named fiduciary or a trustee of any such
plan) acting, directly or indirectly, on behalf of or purchasing such
Certificate with "plan assets" of any such plan (a "Plan Investor"), (ii) such
transferee is an insurance company, the source of funds to be used by it to
acquire or hold such Certificate is an "insurance company general account"
(within the meaning of Department of Labor Prohibited Transaction Class
Exemption ("PTCE") 95-60), and the conditions in Section I and III of PTCE 95-60
have been satisfied (each entity that satisfies this clause (ii), a "Complying
Insurance Company") or (iii) such Certificate was rated "BBB-" or better (or its
equivalent) by at least one of the Rating Agencies at the time of such
transferee's acquisition of such Certificate (or interest therein).

         (3) If any Book-Entry ERISA Restricted Certificate (or any interest
therein) is acquired or held in violation of the provisions of Section
5.01(g)(2) above, then the last preceding transferee that either (i) is not a
Plan Investor, (ii) is a Complying Insurance Company or (iii) acquired such
Certificate at a time when such Certificate was rated "BBB-" or better (or its
equivalent) by at least one of the Rating Agencies shall be restored, to the
extent permitted by law, to all rights and obligations as Beneficial Holder
thereof retroactive to the date of transfer of such Certificate by such
preceding transferee. Neither the Trust nor the Trustee shall be under any
liability to any Person for making any payments due on such Certificate to such
preceding transferee.

         (4) Any purported Beneficial Holder whose acquisition or holding of any
Book-Entry ERISA Restricted Certificate (or interest therein) was effected in
violation of the restrictions in this Section 5.01(g) shall indemnify and hold
harmless the Company, the Trustee, the Master Servicer, the Trust and the
Underwriter from and against any and all liabilities, claims, costs or expenses
incurred by such parties as a result of such acquisition or holding.

         SECTION 5.02 Certificates Issuable in Classes; Distributions of
Principal and Interest; Authorized Denominations. The aggregate principal amount


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of the Certificates that may be authenticated and delivered under this Agreement
is limited to the aggregate Principal Balance of the Mortgage Loans as of the
Cut-Off Date, as specified in the Preliminary Statement to this Agreement,
except for Certificates authenticated and delivered upon registration of
transfer of, or in exchange for, or in lieu of, other Certificates pursuant to
Section 5.03. Such aggregate principal amount shall be allocated among one or
more Classes having designations, types of interests, initial per annum
Certificate Interest Rates, initial Class Principal Balances and Final Maturity
Dates as specified in the Preliminary Statement to this Agreement. The aggregate
Percentage Interest of each Class of Certificates of which the Class Principal
Balance equals zero as of the Cut-Off Date that may be authenticated and
delivered under this Agreement is limited to 100%. Certificates shall be issued
in Authorized Denominations.

         SECTION 5.03 Registration of Transfer and Exchange of Certificates. The
Trustee shall cause to be maintained at one of its offices or at its designated
agent, a Certificate Register in which there shall be recorded the name and
address of each Certificateholder. Subject to such reasonable rules and
regulations as the Trustee may prescribe, the Certificate Register shall be
amended from time to time by the Trustee or its agent to reflect notice of any
changes received by the Trustee or its agent pursuant to Section 10.06. The
Trustee hereby appoints itself as the initial Certificate Registrar.

         Upon surrender for registration of transfer of any Certificate to the
Trustee at the Corporate Trust Office of the Trustee, or such other address or
agency as may hereafter be provided to the Master Servicer in writing by the
Trustee, the Trustee shall execute, and the Trustee or any Authenticating Agent
shall authenticate and deliver, in the name of the designated transferee or
transferees, one or more new Certificates of Authorized Denominations. At the
option of the Certificateholders, Certificates may be exchanged for other
Certificates in Authorized Denominations of like Certificate Principal Balance
or Percentage Interest, as applicable, upon surrender of the Certificates to be
exchanged at any such office or agency. Whenever any Certificates are so
surrendered for exchange, the Trustee on behalf of the Trust shall execute, and
the Trustee, or any Authenticating Agent, shall authenticate and deliver, the
Certificates which the Certificateholder making the exchange is entitled to
receive. Every Certificate presented or surrendered for transfer shall (if so
required by the Trustee or any Authenticating Agent) be duly endorsed by, or be
accompanied by a written instrument of transfer in form satisfactory to the
Trustee or any Authenticating Agent and duly executed by, the Holder thereof or
such Holder's attorney duly authorized in writing.

         A reasonable service charge may be made for any such exchange or
transfer of Certificates, and the Trustee may require payment of a sum
sufficient to cover any tax or governmental charge that may be imposed in
connection with any exchange or transfer of Certificates.

         All Certificates surrendered for exchange or transfer shall be
cancelled by the Trustee or any Authenticating Agent.

         SECTION 5.04 Mutilated, Destroyed, Lost or Stolen Certificates. If (i)
any mutilated Certificate is surrendered to the Trustee or any Authenticating
Agent, or (ii) the Trustee or any Authenticating Agent receives evidence to
their satisfaction of the destruction, loss or theft of any Certificate, and


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there is delivered to the Trustee or any Authenticating Agent such security or
indemnity as may be required by them to save each of them and the Trust
harmless, then, in the absence of notice to the Trustee or any Authenticating
Agent that such Certificate has been acquired by a protected purchaser, the
Trustee shall execute and the Trustee or any Authenticating Agent shall
authenticate and deliver, in exchange for or in lieu of any such mutilated,
destroyed, lost or stolen Certificate, a new Certificate of like Certificate
Principal Balance or Percentage Interest as applicable. Upon the issuance of any
new Certificate under this Section 5.04, the Trustee or any Authenticating Agent
may require the payment of a sum sufficient to cover any tax or other
governmental charge that may be imposed in relation thereto and any other
expenses (including the fees and expenses of the Trustee or any Authenticating
Agent) connected therewith. Any replacement Certificate issued pursuant to this
Section 5.04 shall constitute complete and indefeasible evidence of ownership in
REMIC III (or with respect to the Class R Certificates, the residual ownership
interests in REMIC I, REMIC II and REMIC III) as if originally issued, whether
or not the lost or stolen Certificate shall be found at any time.

         SECTION 5.05 Persons Deemed Owners. The Company, the Master Servicer,
the Trust, the Trustee, the Delaware Trustee and any agent of any of them may
treat the Person in whose name any Certificate is registered as the owner of
such Certificate for the purpose of receiving distributions pursuant to Section
4.01 and Section 4.04 and for all other purposes whatsoever, and neither the
Company, the Master Servicer, the Trust, the Trustee, the Delaware Trustee, the
Certificate Registrar nor any agent of the Company, the Master Servicer, the
Trust, the Trustee or the Delaware Trustee shall be affected by notice to the
contrary.

         SECTION 5.06 Temporary Certificates. Upon the initial issuance of the
Certificates, the Trustee on behalf of the Trust may execute, and the Trustee or
any Authenticating Agent shall authenticate and deliver, temporary Certificates
which are printed, lithographed, typewritten or otherwise produced, in any
Authorized Denomination, of the tenor of the definitive Certificates in lieu of
which they are issued and with such variations in form from the forms of the
Certificates set forth as Exhibits A, B and H hereto as the Trustee's officers
executing such Certificates may determine, as evidenced by their execution of
the Certificates. Notwithstanding the foregoing, the Certificates may remain in
the form of temporary Certificates.

         If temporary Certificates are issued, the Trustee shall cause
definitive Certificates to be prepared within ten Business Days after the
Closing Date or as soon as practicable thereafter. After preparation of
definitive Certificates, the temporary Certificates shall be exchangeable for
definitive Certificates upon surrender of the temporary Certificates at the
office or agency of the Trustee to be maintained as provided in Section 5.10
hereof, without charge to the holder. Any tax or governmental charge that may be
imposed in connection with any such exchange shall be borne by the Master
Servicer. Upon surrender for cancellation of any one or more temporary
Certificates, the Trustee on behalf of the Trust shall execute and the Trustee
or any Authenticating Agent shall authenticate and deliver in exchange therefor
a like principal amount of definitive Certificates of Authorized Denominations.
Until so exchanged, the temporary Certificates shall in all respects be entitled
to the same benefits under this Agreement as definitive Certificates.

         SECTION 5.07 Book-Entry for Book-Entry Certificates. Notwithstanding
the foregoing, the Book-Entry Certificates, upon original issuance, shall be
issued in the form of one or more typewritten Certificates of Authorized


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Denomination representing the Book-Entry Certificates, to be delivered to DTC,
the initial Clearing Agency, by, or on behalf of, the Company. The Book-Entry
Certificates shall initially be registered on the Certificate Register in the
name of Cede & Co., the nominee of DTC, as the initial Clearing Agency, and no
Beneficial Holder shall receive a definitive certificate representing such
Beneficial Holder's interest in any Class of Book-Entry Certificate, except as
provided above and in Section 5.09. Each Book-Entry Certificate shall bear the
following legend:

         Unless this Certificate is presented by an authorized representative of
The Depository Trust Company, a New York corporation ("DTC"), to the Company or
its agent for registration of transfer, exchange, or payment, and any
Certificate issued is registered in the name of Cede & Co. or such other name as
is requested by an authorized representative of DTC (and any payment is made to
Cede & Co. or to such other entity as is requested by an authorized
representative of DTC), ANY TRANSFER, PLEDGE OR OTHER USE HEREOF FOR VALUE OR
OTHERWISE BY OR TO ANY PERSON IS WRONGFUL inasmuch as the registered owner
hereof, Cede & Co., has an interest herein.

         Unless and until definitive, fully registered Book-Entry Certificates
(the "Definitive Certificates") have been issued to the Beneficial Holders
pursuant to Section 5.09:

         (a) the provisions of this Section 5.07 shall be in full force and
effect with respect to the Book-Entry Certificates;

         (b) the Master Servicer and the Trustee may deal with the Clearing
Agency for all purposes with respect to the Book-Entry Certificates (including
the making of distributions on the Book-Entry Certificates) as the sole
Certificateholder;

         (c) to the extent that the provisions of this Section 5.07 conflict
with any other provisions of this Agreement, the provisions of this Section 5.07
shall control; and

         (d) the rights of the Beneficial Holders shall be exercised only
through the Clearing Agency and the DTC Participants and shall be limited to
those established by law and agreements between such Beneficial Holders and the
Clearing Agency and/or the DTC Participants. Pursuant to the Depositary
Agreement, unless and until Definitive Certificates are issued pursuant to
Section 5.09, the initial Clearing Agency will make book-entry transfers among
the DTC Participants and receive and transmit distributions of principal and
interest on the related Class of Book-Entry Certificates to such DTC
Participants.

         For purposes of any provision of this Agreement requiring or permitting
actions with the consent of, or at the direction of, Holders of Book-Entry
Certificates evidencing a specified Percentage Interest, such direction or
consent may be given by the Clearing Agency at the direction of Beneficial
Holders owning Book-Entry Certificates evidencing the requisite Percentage
Interest represented by the Book-Entry Certificates. The Clearing Agency may
take conflicting actions with respect to the Book-Entry Certificates to the
extent that such actions are taken on behalf of the Beneficial Holders.



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         SECTION 5.08 Notices to Clearing Agency. Whenever notice or other
communication to the Certificateholders is required under this Agreement, unless
and until Definitive Certificates shall have been issued to the related
Certificateholders pursuant to Section 5.09, the Trustee shall give all such
notices and communications specified herein to be given to Holders of the
Book-Entry Certificates to the Clearing Agency which shall give such notices and
communications to the related DTC Participants in accordance with its applicable
rules, regulations and procedures.

         SECTION 5.09 Definitive Certificates. If (a) the Master Servicer
notifies the Trustee in writing that the Clearing Agency is no longer willing or
able to discharge properly its responsibilities under the Depositary Agreement
with respect to the Book-Entry Certificates and the Trustee or the Master
Servicer is unable to locate a qualified successor, (b) the Master Servicer, at
its option, advises the Trustee in writing that it elects to terminate the
book-entry system with respect to the Book-Entry Certificates through the
Clearing Agency or (c) after the occurrence of an Event of Default,
Certificateholders holding Book-Entry Certificates evidencing Percentage
Interests aggregating not less than 66% of the aggregate Class Principal Balance
of such Certificates advise the Trustee and the Clearing Agency through DTC
Participants in writing that the continuation of a book-entry system with
respect to the Book-Entry Certificates through the Clearing Agency is no longer
in the best interests of the Certificateholders with respect to such
Certificates, the Trustee shall notify all Certificateholders of Book-Entry
Certificates of the occurrence of any such event and of the availability of
Definitive Certificates. Upon surrender to the Trustee of the Book-Entry
Certificates by the Clearing Agency, accompanied by registration instructions
from the Clearing Agency for registration, the Trustee on behalf of the Trust
shall execute and the Trustee or any Authenticating Agent shall authenticate and
deliver the Definitive Certificates. Neither the Company, the Master Servicer,
the Trust nor the Trustee shall be liable for any delay in delivery of such
instructions and may conclusively rely on, and shall be protected in relying on,
such instructions. Upon the issuance of Definitive Certificates for all of the
Certificates all references herein to obligations imposed upon or to be
performed by the Clearing Agency shall be deemed to be imposed upon and
performed by the Trustee, to the extent applicable with respect to such
Definitive Certificates, and the Trustee shall recognize the Holders of
Definitive Certificates as Certificateholders hereunder.

         SECTION 5.10 Office for Transfer of Certificates. The Trustee shall
maintain in New York, New York, an office or agency where Certificates may be
surrendered for registration of transfer or exchange. The Corporate Trust Office
is initially designated for said purpose.

         SECTION 5.11 Nature of Certificates. The Certificates shall be personal
property giving only the rights specifically set forth therein and in this
Agreement. The Certificates shall have no preemptive or similar rights and when
issued and delivered to the Holders against payment of the purchase price
therefor will be fully paid and nonassessable by the Trust. The Holders of the
Certificates, in their capacities as such, shall be entitled to the same
limitation of personal liability extended to stockholders of private
corporations for profit organized under the General Corporation Law of the State
of Delaware. THE RECEIPT AND ACCEPTANCE OF A CERTIFICATE OR ANY INTEREST THEREIN
BY OR ON BEHALF OF A HOLDER OR ANY BENEFICIAL OWNER, WITHOUT ANY SIGNATURE OR
FURTHER MANIFESTATION OF ASSENT, SHALL CONSTITUTE THE UNCONDITIONAL ACCEPTANCE


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BY THE HOLDER AND ALL OTHERS HAVING A BENEFICIAL INTEREST IN SUCH CERTIFICATE OF
ALL THE TERMS AND PROVISIONS OF THIS AGREEMENT, AND SHALL CONSTITUTE THE
AGREEMENT OF THE TRUST, SUCH HOLDER AND SUCH OTHERS THAT THE TERMS AND
PROVISIONS OF THIS AGREEMENT SHALL BE BINDING, OPERATIVE AND EFFECTIVE AS
BETWEEN THE TRUST AND SUCH HOLDER AND SUCH OTHERS.

                                   ARTICLE VI

                       The Company and the Master Servicer

         SECTION 6.01 Liability of the Company and the Master Servicer. The
Company and the Master Servicer shall be liable in accordance herewith only to
the extent of the obligations specifically imposed upon and undertaken by the
Company or the Master Servicer, as applicable, herein.

         SECTION 6.02 Merger or Consolidation of the Company, or the Master
Servicer. Any Corporation into which the Company or the Master Servicer may be
merged or consolidated, or any Corporation resulting from any merger, conversion
or consolidation to which the Company or the Master Servicer shall be a party,
or any Corporation succeeding to the business of the Company or the Master
Servicer, shall be the successor of the Company or the Master Servicer
hereunder, without the execution or filing of any paper or any further act on
the part of any of the parties hereto, anything herein to the contrary
notwithstanding.

         SECTION 6.03 Limitation on Liability of the Company, the Master
Servicer and Others. Neither the Company nor the Master Servicer nor any of the
directors, officers, employees or agents of the Company or the Master Servicer
shall be under any liability to the Trust, the Holders of the REMIC I or REMIC
II Regular Interests or the Certificateholders for any action taken by such
Person or by a Servicer or for such Person's or Servicer's refraining from the
taking of any action in good faith pursuant to this Agreement, or for errors in
judgment; provided, however, that this provision shall not protect the Company,
the Master Servicer or any such Person against any liability which would
otherwise be imposed by reason of willful misfeasance, bad faith or gross
negligence in the performance of duties or by reason of reckless disregard of
duties and obligations hereunder. The Company, the Master Servicer and any
director, officer, employee or agent of the Company or the Master Servicer may
rely in good faith on any document of any kind properly executed and submitted
by any Person respecting any matters arising hereunder. The Company, the Master
Servicer and any director, officer, employee or agent of the Company or the
Master Servicer shall be indemnified by the Trust and held harmless against any
loss, liability or expense incurred in connection with any legal action relating
to this Agreement or the Certificates, other than any loss, liability or expense
relating to any Mortgage Loan (other than as otherwise permitted in this
Agreement) or incurred by reason of willful misfeasance, bad faith or gross
negligence in the performance of duties hereunder or by reason of reckless
disregard of obligations and duties hereunder. The Company and the Master
Servicer shall not be under any obligation to appear in, prosecute or defend any
legal action which is not incidental to its duties to service the Mortgage Loans
in accordance with this Agreement and which in its opinion may involve it in any
expense or liability; provided, however, that the Company or the Master Servicer
may in its discretion undertake any such action which it may deem necessary or
desirable with respect to the Mortgage Loans, this Agreement, the Certificates


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or the rights and duties of the parties hereto and the interests of the
Certificateholders hereunder. In such event, the legal expenses and costs of
such action and any liability resulting therefrom shall be expenses, costs and
liabilities of the Trust and the Company and the Master Servicer shall be
entitled to be reimbursed therefor out of the Certificate Account, as provided
by Section 3.05.

         SECTION 6.04 The Company and the Master Servicer not to Resign. The
Company shall not resign from the obligations and duties (including, without
limitation, its obligations and duties as initial Master Servicer) hereby
imposed on it except upon determination that its duties hereunder are no longer
permissible under applicable law. Any successor Master Servicer shall not resign
from the obligations and duties hereby imposed on it except upon determination
that its duties hereunder are no longer permissible under applicable law. Any
such determination permitting the resignation of the Company or any successor
Master Servicer shall be evidenced by an Opinion of Counsel to such effect
delivered to the Trustee. No such resignation shall become effective until the
Trustee or a successor Master Servicer shall have assumed the Master Servicer's
responsibilities and obligations in accordance with Section 7.02 hereof.

         If the Company is no longer acting as Master Servicer, then the
successor Master Servicer shall give prompt written notice to the Company of any
information received by such successor Master Servicer which affects or relates
to an ongoing obligation or right of the Company under this Agreement.

         SECTION 6.05 Trustee Access. The Master Servicer shall afford the
Company and the Trustee, upon reasonable notice, during normal business hours
access to all records maintained by the Master Servicer, in respect of the
Mortgage Loans and in respect of its rights and obligations hereunder and access
to such of its officers as are responsible for such obligations. Upon reasonable
request, the Master Servicer, shall furnish the Company and the Trustee with its
most recent financial statements (or, for so long as the Company is the Master
Servicer, the most recent consolidated financial statements for the Company
appearing in the audited financial statements of Washington Mutual, Inc., or the
entity with whose financial statements the financial statements of the Company
are consolidated) and such other information as it possesses, and which it is
not prohibited by law or, to the extent applicable, binding obligations to third
parties with respect to confidentiality from disclosing, regarding its business,
affairs, property and condition, financial or otherwise.

                                  ARTICLE VII

                                     Default

         SECTION 7.01 Events of Default. (a) In case one or more of the
following Events of Default by the Master Servicer or by a successor Master
Servicer shall occur and be continuing, that is to say:

         (i) Any failure by the Master Servicer to deposit into the Certificate
Account any payment required to be deposited therein by the Master Servicer
under the terms of this Agreement which continues unremedied for a period of


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five Business Days after the date upon which written notice of such failure,
requiring the same to be remedied, shall have been given to the Master Servicer
by the Trustee or to the Master Servicer and the Trustee by the Holders of
Certificates evidencing Percentage Interests aggregating not less than 25% of
REMIC III; or

         (ii) Failure on the part of the Master Servicer duly to observe or
perform in any material respect any other of the covenants or agreements on the
part of the Master Servicer contained in the Certificates or in this Agreement
which continues unremedied for a period of 60 days after the date on which
written notice of such failure, requiring the same to be remedied, shall have
been given to the Master Servicer by the Trustee, or to the Master Servicer and
the Trustee by the Holders of Certificates evidencing Percentage Interests
aggregating not less than 25% of REMIC III; or

         (iii) A decree or order of a court or agency or supervisory authority
having jurisdiction in the premises for the appointment of a trustee in
bankruptcy, conservator or receiver or liquidator in any bankruptcy, insolvency,
readjustment of debt, marshalling of assets and liabilities or similar
proceedings, or for the winding-up or liquidation of its affairs, shall have
been entered against the Master Servicer and such decree or order shall have
remained in force undischarged or unstayed for a period of 60 days; or

         (iv) The Master Servicer shall consent to the appointment of a trustee
in bankruptcy, conservator or receiver or liquidator in any bankruptcy,
insolvency, readjustment of debt, marshalling of assets and liabilities or
similar proceedings of or relating to the Master Servicer or of or relating to
all or substantially all of its property; or

         (v) The Master Servicer shall admit in writing its inability to pay its
debts generally as they become due, file a petition to take advantage of any
applicable bankruptcy, insolvency or reorganization statute, make an assignment
for the benefit of its creditors, or voluntarily suspend payment of its
obligations; or

         (vi) Any failure of the Master Servicer to make any Monthly P&I Advance
(other than a Nonrecoverable Advance) which continues unremedied at the opening
of business on the Distribution Date in respect of which such Monthly P&I
Advance was to have been made;

then, and in each and every such case, so long as an Event of Default shall not
have been remedied, either the Trustee or the Holders of Certificates evidencing
Percentage Interests aggregating not less than 25% of REMIC III, by notice in
writing to the Company and the Master Servicer (and to the Trustee if given by
the Certificateholders, in which case such notice shall set forth evidence
reasonably satisfactory to the Trustee that such Event of Default has occurred
and shall not have been remedied) may terminate all of the rights (other than
its right to reimbursement for advances) and obligations of the Master Servicer,
including its right to the Master Servicing Fee, under this Agreement and in and
to the Mortgage Loans and the proceeds thereof, if any. Such determination shall
be final and binding. On or after the receipt by the Master Servicer of such
written notice, all authority and power of the Master Servicer under this
Agreement, whether with respect to the Certificates or the Mortgage Loans or
otherwise, shall pass to and be vested in the Trustee pursuant to and under this
Section 7.01; and, without limitation, the Trustee is hereby authorized and
empowered to execute and deliver, on behalf of the Master Servicer, as


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attorney-in-fact or otherwise, any and all documents and other instruments, and
to do or accomplish all other acts or things necessary or appropriate to effect
the purposes of such notice of termination, whether to complete the transfer and
endorsement or assignment of the Mortgage Loans and related documents, or
otherwise. The Master Servicer agrees to cooperate with the Trustee in effecting
the termination of the Master Servicer's responsibilities and rights hereunder,
including, without limitation, the transfer to the Trustee for administration by
it of all cash amounts which shall at the time be credited by the Master
Servicer to the Certificate Account or thereafter be received with respect to
the Mortgage Loans.

         Notwithstanding the foregoing, if an Event of Default described in
clause (vi) of this Section 7.01(a) shall occur, the Trustee shall, by notice in
writing to the Master Servicer, which may be delivered by telecopy, immediately
suspend all of the rights and obligations of the Master Servicer thereafter
arising under this Agreement, but without prejudice to any rights it may have as
a Certificateholder or to reimbursement of Monthly P&I Advances and other
advances of its own funds, and the Trustee shall act as provided in Section 7.02
to carry out the duties of the Master Servicer, including the obligation to make
any Monthly P&I Advance the nonpayment of which was an Event of Default
described in clause (vi) of this Section 7.01(a). Any such action taken by the
Trustee must be prior to the distribution on the relevant Distribution Date. If
the Master Servicer shall within two Business Days following such suspension
remit to the Trustee the amount of any Monthly P&I Advance the nonpayment of
which by the Master Servicer was an Event of Default described in clause (vi) of
this Section 7.01(a), the Trustee, subject to the last sentence of this
paragraph, shall permit the Master Servicer to resume its rights and obligations
as Master Servicer hereunder. The Master Servicer agrees that it will reimburse
the Trustee for actual, necessary and reasonable costs incurred by the Trustee
because of action taken pursuant to clause (vi) of this Section 7.01(a). The
Master Servicer agrees that if an Event of Default as described in clause (vi)
of this Section 7.01(a) shall occur more than two times in any twelve month
period, the Trustee shall be under no obligation to permit the Master Servicer
to resume its rights and obligations as Master Servicer hereunder.

         (b) In case one or more of the following Events of Default by the
Company shall occur and be continuing, that is to say:

         (i) Failure on the part of the Company duly to observe or perform in
any material respect any of the covenants or agreements on the part of the
Company contained in the Certificates or in this Agreement which continues
unremedied for a period of 60 days after the date on which written notice of
such failure, requiring the same to be remedied, shall have been given to the
Company by the Trustee, or to the Company and the Trustee by the Holders of
Certificates evidencing Percentage Interests aggregating not less than 25% of
REMIC III; or

         (ii) A decree or order of a court or agency or supervisory authority
having jurisdiction in the premises for the appointment of a trustee in
bankruptcy, conservator or receiver or liquidator in any bankruptcy, insolvency,
readjustment of debt, marshalling of assets and liabilities or similar
proceedings, or for the winding-up or liquidation of its affairs, shall have


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been entered against the Company and such decree or order shall have remained in
force undischarged or unstayed for a period of 60 days; or

         (iii) The Company shall consent to the appointment of a trustee in
bankruptcy, conservator or receiver or liquidator in any bankruptcy, insolvency,
readjustment of debt, marshalling of assets and liabilities or similar
proceedings of or relating to the Company or of or relating to all or
substantially all of its property; or

         (iv) The Company shall admit in writing its inability to pay its debts
generally as they become due, file a petition to take advantage of any
applicable bankruptcy, insolvency or reorganization statute, make an assignment
for the benefit of creditors, or voluntarily suspend payment of its obligations;

         then, and in each and every such case, so long as such Event of Default
shall not have been remedied, the Holders of Certificates evidencing Percentage
Interests aggregating not less than 25% of REMIC III, by notice in writing to
the Company and the Trustee, may direct the Trustee in accordance with Section
10.03 to institute an action, suit or proceeding in its own name as Trustee
hereunder to enforce the Company's obligations hereunder.

         (c) In any circumstances in which this Agreement states that
Certificateholders owning Certificates evidencing a certain percentage
Percentage Interest in REMIC III may take certain action, such action shall be
taken by the Trustee, but only if the requisite percentage of Certificateholders
required under this Agreement for taking like action or giving like instruction
to the Trustee under this Agreement shall have so directed the Trustee in
writing.

         SECTION 7.02 Trustee to Act; Appointment of Successor.

         (a) On and after the date on which the Master Servicer receives a
notice of termination pursuant to Section 7.01 or the Master Servicer resigns
pursuant to Section 6.04, the Trustee shall be the successor in all respects to
the Master Servicer under this Agreement and under the Selling and Servicing
Contracts with respect to the Mortgage Loans in the Mortgage Pool and with
respect to the transactions set forth or provided for herein and shall have all
the rights and powers and be subject to all the responsibilities, duties and
liabilities relating thereto arising on or after such date of termination or
resignation placed on the Master Servicer by the terms and provisions hereof and
thereof, and shall have the same limitations on liability herein granted to the
Master Servicer; provided, that the Trustee shall not under any circumstances be
responsible for any representations and warranties or any Purchase Obligation of
the Company or any liability incurred by the Master Servicer prior to such date
of termination or resignation and the Trustee shall not be obligated to make a
Monthly P&I Advance if it is prohibited by law from so doing. As compensation
therefor, the Trustee shall be entitled to all funds relating to the Mortgage
Loans which the Master Servicer would have been entitled to retain or to
withdraw from the Certificate Account if the Master Servicer had continued to
act hereunder, except for those amounts due to the Master Servicer as
reimbursement for advances previously made or amounts previously expended and
are otherwise reimbursable hereunder. Notwithstanding the above, the Trustee
may, if it shall be unwilling to so act, or shall if it is unable to so act,
appoint, or petition a court of competent jurisdiction to appoint, any
established housing and home finance institution having a net worth of not less
than $10,000,000 as the successor to the Master Servicer hereunder in the
assumption of all or any part of the responsibilities, duties or liabilities of
the Master Servicer hereunder. Pending any such appointment, the Trustee is
obligated to act in such capacity. In connection with such appointment and
assumption, the Trustee may make such arrangements for the compensation of such


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successor out of payments on Mortgage Loans as it and such successor shall
agree; provided, however, that no such compensation shall, together with the
compensation to the Trustee, be in excess of that permitted the Master Servicer
hereunder. The Trustee and such successor shall take such actions, consistent
with this Agreement, as shall be necessary to effectuate any such succession.

         (b) In connection with any termination or resignation of the Master
Servicer hereunder, in the event that any of the Mortgage Loans are MERS Loans,
either (i) the successor Master Servicer (including the Trustee if the Trustee
is acting as successor Master Servicer) shall represent and warrant that it is a
member of MERS in good standing and shall agree to comply in all material
respects with the rules and procedures of MERS in connection with the servicing
of the MERS Loans, in which case the predecessor Master Servicer shall cooperate
with the successor Master Servicer in registering the transfer of servicing of
the MERS Loans to the successor Master Servicer on the MERS(R) System in
accordance with MERS' rules and procedures, or (ii) if the successor Master
Servicer is not a member of MERS, the predecessor Master Servicer shall
cooperate with the successor Master Servicer in (A) de-registering the MERS
Loans from the MERS(R) System and (B) causing MERS to execute and deliver an
assignment from MERS to the Trust of the Mortgage securing each MERS Loan in
recordable form and in the form otherwise provided under clause (X)(iii) of the
definition of "Mortgage File" herein and to execute and deliver such other
notices, documents and other instruments as may be necessary or desirable to
effect such de-registration and assignment. The predecessor Master Servicer
shall bear any and all fees of MERS and all fees and costs of preparing and
recording any assignments of Mortgages as required under this Section 7.02(b).

         SECTION 7.03 Notification to Certificateholders. Upon any such
termination or appointment of a successor to the Master Servicer, the Trustee
shall give prompt written notice thereof to the Certificateholders at their
respective addresses appearing in the Certificate Register.

                                  ARTICLE VIII

                             Concerning the Trustees

         SECTION 8.01 Duties of Trustees.

         (a) The Trustee, prior to the occurrence of an Event of Default and
after the curing of all Events of Default which may have occurred, undertakes to
perform such duties and only such duties as are specifically set forth in this
Agreement. In case an Event of Default has occurred (which has not been cured or
waived) the Trustee shall exercise such of the rights and powers vested in it by
this Agreement, and use the same degree of care and skill in its exercise as a
prudent person would exercise or use under the circumstances in the conduct of
such person's own affairs.

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         (b) The Trustee, upon receipt of all resolutions, certificates,
statements, opinions, reports, documents, orders or other instruments furnished
to it which are specifically required to be furnished to it pursuant to any
provision of this Agreement, shall examine them to determine whether they are in
the form required by this Agreement; provided, however, that the Trustee shall
not be responsible for the accuracy or content of any such certificate,
statement, opinion, report, or other order or instrument furnished by the
Company or Master Servicer to the Trustee pursuant to this Agreement.

         (c) No provision of this Agreement shall be construed to relieve the
Trustee or the Delaware Trustee from liability for its own negligent action, its
own negligent failure to act or its own willful misconduct; provided, however,
that:

         (i) Prior to the occurrence of an Event of Default and after the curing
of all such Events of Default which may have occurred, the duties and
obligations of the Trustee shall be determined solely by the express provisions
of this Agreement,

         (ii) Neither the Trustee nor the Delaware Trustee shall be liable
except for the performance of such duties and obligations as are specifically
set forth in this Agreement, no implied covenants or obligations shall be read
into this Agreement against the Trustee or the Delaware Trustee, and, in the
absence of bad faith on the part of the Trustee or the Delaware Trustee, such
trustee may conclusively rely, as to the truth of the statements and the
correctness of the opinions expressed therein, upon any certificates or opinions
furnished to such trustee and conforming to the requirements of this Agreement;
and

         (iii) Neither the Trustee nor the Delaware Trustee shall be personally
liable with respect to any action taken or omitted to be taken by it in good
faith in accordance with the direction of the Certificateholders holding
Certificates which evidence Percentage Interests aggregating not less than 25%
of REMIC III relating to the time, method and place of conducting any proceeding
for any remedy available to such trustee, or relating to the exercise of any
trust or power conferred upon such trustee under this Agreement.

         (d) Within ten Business Days after the occurrence of any Event of
Default known to the Trustee, the Trustee shall transmit by mail to the Rating
Agencies notice of each Event of Default. Within 90 days after the occurrence of
any Event of Default known to the Trustee, the Trustee shall transmit by mail to
all Certificateholders (with a copy to the Rating Agencies) notice of each Event
of Default, unless such Event of Default shall have been cured or waived;
provided, however, the Trustee shall be protected in withholding such notice if
and so long as a Responsible Officer of the Trustee in good faith determines
that the withholding of such notice is in the best interests of the
Certificateholders; and provided, further, that in the case of any Event of
Default of the character specified in Section 7.01(i) and Section 7.01(ii) no
such notice to Certificateholders or to the Rating Agencies shall be given until
at least 30 days after the occurrence thereof.

         SECTION 8.02 Certain Matters Affecting the Trustees. Except as
otherwise provided in Section 8.01:



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         (i) Each of the Trustee and the Delaware Trustee may request and rely
upon and shall be protected in acting or refraining from acting upon any
resolution, Officer's Certificate, certificate of auditors or any other
certificate, statement, instrument, opinion, report, notice, request, consent,
order, approval, bond or other paper or document believed by it to be genuine
and to have been signed or presented by the proper party or parties;

         (ii) Each of the Trustee and the Delaware Trustee may consult with
counsel and any Opinion of Counsel shall be full and complete authorization and
protection in respect of any action taken or suffered or omitted by it hereunder
in good faith and in accordance with such Opinion of Counsel;

         (iii) Neither the Trustee nor the Delaware Trustee shall be personally
liable for any action taken or omitted by it in good faith and reasonably
believed by it to be authorized or within the discretion or rights or powers
conferred upon it by this Agreement;

         (iv) Prior to the occurrence of an Event of Default hereunder and after
the curing of all Events of Default which may have occurred, neither the Trustee
nor the Delaware Trustee shall be bound to make any investigation into the facts
or matters stated in any resolution, certificate, statement, instrument,
opinion, report, notice, request, consent, order, approval, bond or other paper
or document, unless requested in writing to do so by the Holders of Certificates
evidencing Percentage Interests aggregating not less than 25% of REMIC III;
provided, however, that if the payment within a reasonable time to the Trustee
or the Delaware Trustee of the costs, expenses or liabilities likely to be
incurred by it in the making of such investigation is, in the opinion of such
trustee, not reasonably assured to such trustee by the security, if any,
afforded to it by the terms of this Agreement, such trustee may require
reasonable indemnity against such expense or liability as a condition to
proceeding;

         (v) Each of the Trustee and the Delaware Trustee may execute the trust
or any of the powers hereunder or perform any duties hereunder either directly
or by or through agents or attorneys selected by it with reasonable care (as in
the case of the Initial Custodian) or designated by the Company;

         (vi) Neither the Trustee nor the Delaware Trustee shall be deemed to
have knowledge or notice of any matter, including without limitation an Event of
Default, unless actually known by a Responsible Officer, or unless written
notice thereof referencing this Agreement or the Certificates is received at the
Notice Address of such trustee;

         (vii) In no event shall the Trustee or the Delaware Trustee be held
liable for acts or omissions of the Master Servicer or the other trustee
(excepting the Trustee's own actions as Master Servicer). No provision of this
Agreement shall require the Trustee or the Delaware Trustee to expend or risk
its own funds or otherwise incur any financial liability in the performance of
any of its duties hereunder (except for the giving of required notices), or in


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the exercise of any of its rights or powers, if it shall have reasonable grounds
for believing the repayment of such funds or adequate indemnity against such
risk or liability is not reasonably assured to it;

         (viii) When the Trustee is acting as Master Servicer pursuant to
Section 7.02, and to the extent permitted under applicable law, the Trustee is
hereby authorized, in making or disposing of any investment permitted hereunder,
to deal with itself (in its individual capacity) or with any one or more of its
affiliates, whether it or its affiliate is acting as an agent of the Trustee or
of any third person or dealing as principal for its own account;

         (ix) Except as expressly provided in this Agreement, in no event shall
the Trustee be under any duty or obligation to monitor, determine, investigate
or compel compliance by the Trust with the requirements of the Statutory Trust
Statute; and

         (x) In no event shall the Trustee be obligated or responsible for
preparing, executing, filing or delivering in respect of the Trust or another
party either (A) any report or filing required by the Securities and Exchange
Commission to be prepared, executed, filed or delivered in respect of the Trust
or another party or (B) any certification in respect of a report or filing
required by the Securities and Exchange Commission.

         SECTION 8.03 Trustees Not Liable for Certificates or Mortgage Loans.
The recitals contained herein (other than those relating to the due
organization, power and authority of the Trustee and the Delaware Trustee) and
in the Certificates (other than the execution of, and certificate of
authentication on, the Certificates) shall be taken as the statements of the
Company or the Trust, as applicable, and neither the Trustee nor the Delaware
Trustee assumes any responsibility for their correctness. Neither the Trustee
nor the Delaware Trustee makes any representations as to the validity or
sufficiency of this Agreement or of the Certificates or any Mortgage Loan.
Neither the Trustee nor the Delaware Trustee shall be accountable for the use or
application by the Company or the Trust, as applicable, of any of the
Certificates or of the proceeds of such Certificates, or for the use or
application of any funds paid to the Master Servicer, the Servicers or the
Company in respect of the Mortgage Loans or deposited into the Custodial
Accounts for P&I, any Buydown Fund Account, or the Custodial Accounts for P&I by
any Servicer or into the Investment Account, or the Certificate Account by the
Master Servicer or the Company.

         SECTION 8.04 Trustees May Own Certificates. The Trustee, the Delaware
Trustee or any agent or affiliate of such trustee, in its individual or any
other capacity, may become the owner or pledgee of Certificates with the same
rights it would have if it were not trustee.

         SECTION 8.05 The Master Servicer to Pay Trustees' Fees and Expenses.
Subject to separate written agreements with the Trustee and the Delaware
Trustee, the Master Servicer covenants and agrees to, and the Master Servicer
shall, pay each of the Trustee and the Delaware Trustee from time to time, and
such trustee shall be entitled to payment, for all services rendered by it in
the execution of the trust hereby created and in the exercise and performance of


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any of the powers and duties hereunder of such trustee. Except as otherwise
expressly provided herein, the Master Servicer shall pay or reimburse each of
the Trustee and the Delaware Trustee upon such trustee's request for all
reasonable expenses and disbursements incurred or made by such trustee in
accordance with any of the provisions of this Agreement and indemnify such
trustee from any loss, liability or expense incurred by it hereunder (including
the reasonable compensation and the expenses and disbursements of its counsel
and of all persons not regularly in its employ and any expenses which arise out
of or are imposed upon the Trustee or the Delaware Trustee in connection with
the creation, operation or termination of the Trust) except any such expense or
disbursement as may arise from its own negligence or bad faith. Such obligation
shall survive the termination of this Agreement or resignation or removal of the
Trustee or the Delaware Trustee. The Tax Matters Person shall, at its expense,
prepare or cause to be prepared all federal and state income tax and franchise
tax and information returns relating to REMIC I, REMIC II or REMIC III required
to be prepared or filed by the Trustee or the Delaware Trustee and shall
indemnify the Trustee and the Delaware Trustee for any liability of such
trustees arising from any error in such returns.

         SECTION 8.06 Eligibility Requirements for Trustees. The Trustee
hereunder shall at all times be (i) an institution insured by the FDIC, (ii) a
Corporation organized and doing business under the laws of the United States of
America or of any state, authorized under such laws to exercise corporate trust
powers, having a combined capital and surplus of not less than $50,000,000 and
subject to supervision or examination by federal or state authority and (iii)
acceptable to the Rating Agencies. If such Corporation publishes reports of
condition at least annually, pursuant to law or to the requirements of any
aforementioned supervising or examining authority, then for the purposes of this
Section 8.06, the combined capital and surplus of such Corporation shall be
deemed to be its combined capital and surplus as set forth in its most recent
report of condition so published. The Delaware Trustee hereunder shall at all
times have its principal place of business in the State of Delaware and shall
satisfy the applicable requirements under the laws of the State of Delaware
authorizing it to act as the Delaware trustee of the Trust. In case at any time
the Trustee or the Delaware Trustee shall cease to be eligible in accordance
with the provisions of this Section 8.06, such trustee shall resign immediately
in the manner and with the effect specified in Section 8.07.

         SECTION 8.07 Resignation and Removal of Trustees. Each of the Trustee
and the Delaware Trustee may at any time resign and be discharged from the trust
hereby created by giving written notice thereof to the Master Servicer. Upon
receiving such notice of resignation, the Master Servicer shall promptly appoint
a successor trustee by written instrument, in duplicate, one copy of which
instrument shall be delivered to the resigning trustee and one copy to the
successor trustee. If no successor trustee shall have been so appointed and
shall have accepted appointment within 30 days after the giving of such notice
of resignation, the resigning trustee may petition any court of competent
jurisdiction for the appointment of a successor trustee.

         If at any time the Trustee or the Delaware Trustee shall cease to be
eligible in accordance with the provisions of Section 8.06 and shall fail to
resign after written request therefor by the Master Servicer, or if at any time
the Trustee or the Delaware Trustee shall become incapable of acting, or shall
be adjudged bankrupt or insolvent, or a receiver of such trustee or of its
property shall be appointed, or any public officer shall take charge or control
of such trustee or of its property or affairs for the purpose of rehabilitation,
conservation or liquidation, then the Master Servicer may remove such trustee


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and appoint a successor trustee by written instrument, in duplicate, copies of
which instrument shall be delivered to the trustee so removed, the trustee
continuing in its capacity and the successor trustee.

         The Holders of Certificates evidencing Percentage Interests aggregating
more than 50% of REMIC III may at any time remove the Trustee or the Delaware
Trustee and appoint a successor trustee by written instrument or instruments, in
triplicate, signed by such Holders or their attorneys in-fact duly authorized,
one complete set of which instruments shall be delivered to the Master Servicer,
one complete set to the Trustee so removed and one complete set to the successor
so appointed.

         Any resignation or removal of the Trustee or the Delaware Trustee and
appointment of a successor trustee pursuant to any of the provisions of this
Section 8.07 shall become effective upon acceptance of appointment by the
successor trustee as provided in Section 8.08. Any expenses associated with the
resignation of the Trustee or the Delaware Trustee shall be borne by such
trustee, and any expenses associated with the removal of the Trustee or the
Delaware Trustee shall be borne by the Master Servicer.

         SECTION 8.08 Successor Trustee. Any successor trustee appointed as
provided in Section 8.07 shall execute, acknowledge and deliver to the Master
Servicer and to its predecessor trustee an instrument accepting such appointment
hereunder, and thereupon the resignation or removal of the predecessor trustee
shall become effective and such successor trustee, without any further act, deed
or conveyance, shall become fully vested with all the rights, powers, duties and
obligations of its predecessor hereunder, with like effect as if originally
named as Trustee or Delaware Trustee herein. The predecessor shall deliver to
the successor trustee all Mortgage Files, related documents, statements and all
other property held by it hereunder, and the Master Servicer and the predecessor
trustee shall execute and deliver such instruments and do such other things as
may reasonably be required for more fully and certainly vesting and confirming
in the successor trustee all such rights, powers, duties and obligations.

         No successor trustee shall accept appointment as provided in this
Section 8.08 unless at the time of such appointment such successor trustee shall
be eligible under the provisions of Section 8.06.

         Upon acceptance of appointment by a successor trustee as provided in
this Section 8.08, the Master Servicer shall mail notice of the succession of
such trustee hereunder to (i) all Certificateholders at their addresses as shown
in the Certificate Register and (ii) the Rating Agencies. If the Master Servicer
fails to mail such notice within ten days after acceptance of appointment by the
successor trustee, the successor trustee shall cause such notice to be mailed.

         SECTION 8.09 Merger or Consolidation of Trustee. Any Corporation into
which the Trustee or the Delaware Trustee may be merged or converted or with
which it may be consolidated, or any Corporation resulting from any merger,
conversion or consolidation to which the Trustee or the Delaware Trustee shall
be a party, or any Corporation succeeding to the corporate trust business of
such trustee, shall be the successor of such trustee hereunder, provided such
resulting or successor Corporation shall be eligible under the provisions of
Section 8.06, without the execution or filing of any paper or any further act on
the part of any of the parties hereto, anything herein to the contrary
notwithstanding.



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         SECTION 8.10 Appointment of Co-Trustee or Separate Trustee.
Notwithstanding any other provisions hereof, at any time, for the purpose of
meeting any legal requirements of any jurisdiction in which any part of the
assets of the Trust may at the time be located, the Master Servicer and the
Trustee or the Delaware Trustee, as applicable, acting jointly shall have the
power and shall execute and deliver all instruments to appoint one or more
Persons approved by such trustee to act as co-trustee or co-trustees, jointly
with such trustee, or separate trustee or separate trustees, of all or any part
of the assets of the Trust and to vest in such Person or Persons, in such
capacity, such title to the assets of the Trust, or any part thereof, and,
subject to the other provisions of this Section 8.10, such powers, duties,
obligations, rights and trusts as the Master Servicer and the Trustee or the
Delaware Trustee, as applicable, may consider necessary or desirable; provided,
that the Trustee or the Delaware Trustee, as applicable, shall remain liable for
all of its obligations and duties under this Agreement. If the Master Servicer
shall not have joined in such appointment within 15 days after the receipt by it
of a request so to do, or in case an Event of Default shall have occurred and be
continuing, the Trustee or the Delaware Trustee, as applicable, alone shall have
the power to make such appointment; provided, that such trustee shall remain
liable for all of its obligations and duties under this Agreement. No co-trustee
or separate trustee hereunder shall be required to meet the terms of eligibility
as a successor trustee under Section 8.06 hereunder and no notice to
Certificateholders of the appointment of co-trustee(s) or separate trustee(s)
shall be required under Section 8.08 hereof.

         In the case of any appointment of a co-trustee or separate trustee
pursuant to this Section 8.10, all rights, powers, duties and obligations
conferred or imposed upon the Trustee or the Delaware Trustee, as applicable,
shall be conferred or imposed upon and exercised or performed by the Trustee or
the Delaware Trustee, as applicable, and such separate trustee or co-trustee
jointly and severally, except to the extent that under any law of any
jurisdiction in which any particular act or acts are to be performed by the
Trustee or the Delaware Trustee, as applicable (whether as Trustee or Delaware
Trustee hereunder or as successor to the Master Servicer hereunder), such
trustee shall be incompetent or unqualified to perform such act or acts, in
which event such rights, powers, duties and obligations (including the holding
of title to the assets of the Trust or any portion thereof in any such
jurisdiction) shall be exercised and performed by such separate trustee or
co-trustee at the direction of the Trustee or the Delaware Trustee, as
applicable.

         Any notice, request or other writing given to the Trustee or the
Delaware Trustee shall be deemed to have been given to each of the then related
separate trustee(s) and co-trustee(s), as effectively as if given to each of
them. Every instrument appointing any separate trustee(s) or co-trustee(s) shall
refer to this Agreement and the conditions of this Article VIII. Each separate
trustee and co-trustee, upon its acceptance of the trusts conferred, shall be
vested with the estates or property specified in its instrument of appointment,
either jointly with the Trustee or the Delaware Trustee, as applicable, or
separately, as may be provided therein, subject to all the provisions of this
Agreement, specifically including every provision of this Agreement relating to
the conduct of, affecting the liability of, or affording protection to, the
Trustee or the Delaware Trustee, as applicable. Every such instrument shall be
filed with the Trustee or the Delaware Trustee, as applicable.

         Any separate trustee or co-trustee may, at any time, constitute the
Trustee or the Delaware Trustee, as applicable, its agent or attorney-in-fact,


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with full power and authority, to the extent not prohibited by law, to do any
lawful act under or in respect of this Agreement on its behalf and in its name.
If any separate trustee or co-trustee shall die, become incapable of acting,
resign or be removed, all of its estates, properties, rights, remedies and the
trust shall vest in and be exercised by the Trustee or the Delaware Trustee, as
applicable, to the extent permitted by law, without the appointment of a new or
successor trustee.

         SECTION 8.11 Authenticating Agents. The Trustee may appoint one or more
Authenticating Agents which shall be authorized to act on behalf of the Trustee
in authenticating Certificates. Wherever reference is made in this Agreement to
the authentication of Certificates by the Trustee or the Trustee's certificate
of authentication, such reference shall be deemed to include authentication on
behalf of the Trustee by an Authenticating Agent and a certificate of
authentication executed on behalf of the Trustee by an Authenticating Agent.
Each Authenticating Agent must be acceptable to the Master Servicer and must be
a corporation, trust company or banking association organized and doing business
under the laws of the United States of America or of any state, having an office
and place of business in New York, New York, having a combined capital and
surplus of at least $15,000,000, authorized under such laws to do a trust
business and subject to supervision or examination by federal or state
authorities.

         Any corporation into which any Authenticating Agent may be merged or
converted or with which it may be consolidated, or any corporation resulting
from any merger, conversion or consolidation to which any Authenticating Agent
shall be a party, or any corporation succeeding to the corporate agency business
of any Authenticating Agent, shall continue to be the Authenticating Agent so
long as it shall be eligible in accordance with the provisions of the first
paragraph of this Section 8.11 without the execution or filing of any paper or
any further act on the part of the Trustee or the Authenticating Agent.

         Any Authenticating Agent may at any time resign by giving written
notice of resignation to the Trustee and the Master Servicer. The Trustee may,
upon prior written approval of the Master Servicer, at any time terminate the
agency of any Authenticating Agent by giving written notice of termination to
such Authenticating Agent and to the Master Servicer. Upon receiving a notice of
resignation or upon such a termination, or in case at any time any
Authenticating Agent shall cease to be eligible in accordance with the
provisions of the first paragraph of this Section 8.11, the Trustee may appoint,
upon prior written approval of the Master Servicer, a successor Authenticating
Agent, shall give written notice of such appointment to the Master Servicer and
shall mail notice of such appointment to all Certificateholders. Any successor
Authenticating Agent upon acceptance of its appointment hereunder shall become
vested with all the rights, powers, duties and responsibilities of its
predecessor hereunder, with like effect as if originally named as Authenticating
Agent. Any reasonable compensation paid to an Authenticating Agent shall be a
reimbursable expense pursuant to Section 8.05 if paid by the Trustee.

         SECTION 8.12 Paying Agents. The Trustee may appoint one or more Paying
Agents which shall be authorized to act on behalf of the Trustee in making
withdrawals from the Certificate Account, and distributions to
Certificateholders as provided in Section 4.01, Section 4.04, Section 4.05(a)
and Section 9.01(b) to the extent directed to do so by the Master Servicer.
Wherever reference is made in this Agreement to the withdrawal from the
Certificate Account by the Trustee, such reference shall be deemed to include
such a withdrawal on behalf of the Trustee by a Paying Agent. Whenever reference
is made in this Agreement to a distribution by the Trustee or the furnishing of


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a statement to Certificateholders by the Trustee, such reference shall be deemed
to include such a distribution or furnishing on behalf of the Trustee by a
Paying Agent. Each Paying Agent shall provide to the Trustee such information
concerning the Certificate Account as the Trustee shall request from time to
time. Each Paying Agent must be reasonably acceptable to the Master Servicer and
must be a corporation, trust company or banking association organized and doing
business under the laws of the United States of America or of any state, having
an office and place of business in New York, New York, having a combined capital
and surplus of at least $15,000,000, authorized under such laws to do a trust
business and subject to supervision or examination by federal or state
authorities.

         Any corporation into which any Paying Agent may be merged or converted
or with which it may be consolidated, or any corporation resulting from any
merger, conversion or consolidation to which any Paying Agent shall be a party,
or any corporation succeeding to the corporate agency business of any Paying
Agent, shall continue to be the Paying Agent provided that such corporation
after the consummation of such merger, conversion, consolidation or succession
meets the eligibility requirements of this Section 8.12.

         Any Paying Agent may at any time resign by giving written notice of
resignation to the Trustee and to the Master Servicer; provided, that the Paying
Agent has returned to the Certificate Account or otherwise accounted, to the
reasonable satisfaction of the Master Servicer, for all amounts it has withdrawn
from the Certificate Account. The Trustee may, upon prior written approval of
the Master Servicer, at any time terminate the agency of any Paying Agent by
giving written notice of termination to such Paying Agent and to the Master
Servicer. Upon receiving a notice of resignation or upon such a termination, or
in case at any time any Paying Agent shall cease to be eligible in accordance
with the provisions of the first paragraph of this Section 8.12, the Trustee may
appoint, upon prior written approval of the Master Servicer, a successor Paying
Agent, shall give written notice of such appointment to the Master Servicer and
shall mail notice of such appointment to all Certificateholders. Any successor
Paying Agent upon acceptance of its appointment hereunder shall become vested
with all the rights, powers, duties and responsibilities of its predecessor
hereunder, with like effect as if originally named as Paying Agent. Any
reasonable compensation paid to any Paying Agent shall be a reimbursable expense
pursuant to Section 8.05 if paid by the Trustee.

         SECTION 8.13 Duties of Delaware Trustee.

         (a) The Delaware Trustee is appointed to serve as the trustee of the
Trust in the State of Delaware for the sole purpose of satisfying the
requirement of Section 3807(a) of the Statutory Trust Statute that the Trust
have at least one trustee with a principal place of business in Delaware. It is
understood and agreed by the parties hereto that the Delaware Trustee shall have
none of the duties or liabilities of the Trustee.

         (b) The duties of the Delaware Trustee shall be limited to (i)
accepting legal process served on the Trust in the State of Delaware, (ii) the
execution of any certificates with respect to the Trust required to be filed
with the Secretary of State which the Delaware Trustee is required to execute
under Section 3811 of the Statutory Trust Statute and (iii) such other duties as
are set forth in this Article VIII. To the extent that, at law or in equity, the
Delaware Trustee has duties (including fiduciary duties) and liabilities
relating thereto to the Trust or the Holders of the REMIC I Regular Interests,


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the REMIC II Regular Interests or the Certificates, it is hereby understood and
agreed by the parties hereto that such duties and liabilities are replaced by
the duties and liabilities of the Delaware Trustee expressly set forth in this
Agreement.

         SECTION 8.14 Amendment to Certificate of Trust. If at any time required
by Section 3810 of the Statutory Trust Statute, the Trustee, the Delaware
Trustee and any other trustee of the Trust shall cause an amendment to the
Certificate of Trust to be filed with the Secretary of State in accordance with
the provisions of such Section 3810.

         SECTION 8.15 Limitation of Liability. It is expressly understood and
agreed by the parties hereto that (a) each of the representations, undertakings
and agreements herein made on the part of the Trust is made and intended not as
personal representations, undertakings and agreements by the Trustee but is made
and intended for the purpose of binding only the Trust and (b) under no
circumstances shall the Trustee be personally liable for the payment of any
indebtedness or expenses of the Trust or be liable for the breach or failure of
any obligation, representation, warranty or covenant made or undertaken by the
Trust under this Agreement.

                                   ARTICLE IX

                                   Termination

         SECTION 9.01 Termination Upon Purchase by the Master Servicer or
Liquidation of All Mortgage Loans.

         (a) Except as otherwise set forth in this Article IX, including,
without limitation, the obligation of the Master Servicer to make payments to
Certificateholders as hereafter set forth, the Trust and the respective
obligations and responsibilities of the Company, the Master Servicer, the
Trustee and the Delaware Trustee created hereby shall terminate in accordance
with Section 3808 of the Statutory Trust Statute upon (i) the purchase by the
Master Servicer pursuant to the following paragraph of this Section 9.01(a) of
all Mortgage Loans (other than Liquidated Mortgage Loans), all property acquired
in respect of any Mortgage Loan remaining in the Trust and all other property
included in any REMIC formed under this Agreement at a price equal, after the
deduction of related advances, to the sum of (x) the excess of (A) 100% of the
aggregate outstanding Principal Balance of such Mortgage Loans (other than
Liquidated Mortgage Loans) plus accrued interest at the applicable Pass-Through
Rate with respect to such Mortgage Loan (other than a Liquidated Mortgage Loan)
through the last day of the month of such purchase, over (B) with respect to any
Mortgage Loan which is not a Liquidated Mortgage Loan, the amount of the
Bankruptcy Loss incurred with respect to such Mortgage Loan as of the date of
such purchase by the Master Servicer to the extent that the Principal Balance of
such Mortgage Loan has not been previously reduced by such Bankruptcy Loss, and
(y) the appraised fair market value as of the effective date of the termination
of the Trust of (A) all property in the Trust which secured a Mortgage Loan and
which was acquired by foreclosure or deed in lieu of foreclosure after the
Cut-Off Date, including related Insurance Proceeds, and (B) all other property
included in any REMIC formed under this Agreement, any such appraisal to be
conducted by an appraiser mutually agreed upon by the Master Servicer and the
Trustee, or (ii) the later of the final payment or other liquidation (or any
advance with respect thereto) of the last Mortgage Loan remaining in the Trust
or the disposition of all property acquired upon foreclosure in respect of any


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Mortgage Loan, and the payment to the Certificateholders of all amounts required
to be paid to them hereunder; provided, however, that in no event shall the
Trust continue beyond the expiration of 21 years from the death of the survivor
of the issue of Joseph P. Kennedy, the late ambassador of the United States to
the Court of St. James, living on the date hereof.

         On any Distribution Date after the first date on which the aggregate
Principal Balance of the Mortgage Loans is less than the Clean-Up Call
Percentage of the aggregate Principal Balance of the Mortgage Loans as of the
Cut-Off Date, the Master Servicer may purchase the outstanding Mortgage Loans
(other than Liquidated Mortgage Loans), all property acquired in respect of any
Mortgage Loan remaining in the Trust and all other property included in any
REMIC formed under this Agreement at the price stated in clause (i) of the
preceding paragraph; provided, that the Master Servicer may not so purchase the
outstanding Mortgage Loans (other than Liquidated Mortgage Loans), all property
acquired in respect of any Mortgage Loan remaining in the Trust and all other
property included in any REMIC formed under this Agreement if the price stated
in clause (i) of the preceding paragraph exceeds the fair market value,
determined in accordance with prudent industry practices, of all outstanding
Mortgage Loans (other than Liquidated Mortgage Loans), all property acquired in
respect of any Mortgage Loan remaining in the Trust and all other property
included in any REMIC formed under this Agreement. If such right is exercised,
the Master Servicer shall provide to the Trustee (and to the Company, if the
Company is no longer acting as Master Servicer) the written certification of an
officer of the Master Servicer (which certification shall include a statement to
the effect that all amounts required to be paid in order to purchase the
Mortgage Loans have been deposited in the Certificate Account) and the Trustee
on behalf of the Trust shall promptly execute all instruments as may be
necessary to release and assign to the Master Servicer the Mortgage Files and
any foreclosed Mortgaged Property pertaining to the Trust.

         In no event shall the Master Servicer be required to expend any amounts
other than those described in the first paragraph of this Section 9.01(a) in
order to terminate the Trust or purchase the Mortgage Loans under this Section
9.01, and in no event shall the Company be required to expend any amounts in
connection with such termination or purchase.

         (b) Notice of any termination, specifying the date upon which the
Certificateholders may surrender their Certificates to the Trustee for payment
and cancellation, shall be given promptly by letter from the Trustee to
Certificateholders mailed not less than 30 days prior to such final
distribution, specifying (i) the date upon which final payment of the
Certificates will be made upon presentation and surrender of Certificates at the
office of the Certificate Registrar therein designated (the "Termination Date"),
(ii) the amount of such final payment (the "Termination Payment") and (iii) that
the Record Date otherwise applicable to the Distribution Date upon which the
Termination Date occurs is not applicable, payments being made only upon
presentation and surrender of the Certificates at the office of the Certificate
Registrar therein specified. Upon any such notice, the Certificate Account shall
terminate subject to the Master Servicer's obligation to hold all amounts
payable to Certificateholders in trust without interest pending such payment.

         In the event that all of the Certificateholders shall not surrender
their Certificates for cancellation within six months after the Termination


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Date, the Master Servicer shall give a second written notice to the remaining
Certificateholders to surrender their Certificates for cancellation and receive
the Termination Payment with respect thereto. If within one year after the
second notice all the Certificates shall not have been surrendered for
cancellation, the Master Servicer may take appropriate steps to contact the
remaining Certificateholders concerning surrender of their Certificates, and the
cost thereof shall be paid out of the funds and other assets which remain in
trust hereunder.

         Upon the completion of winding up of the Trust, including the payment
or the making reasonable provision for payment of all obligations of the Trust
in accordance with Section 3808(e) of the Statutory Trust Statute, the Delaware
Trustee shall prepare, the Trustee, the Delaware Trustee and any other trustee
hereunder shall sign, and the Delaware Trustee (upon the Trustee's consent
acting at the direction of the Master Servicer) shall file, a certificate of
cancellation with the Secretary of State in accordance with Section 3810 of the
Statutory Trust Statute, at which time the Trust and this Agreement shall
terminate. The Master Servicer shall act as the liquidator of the Trust and
shall be responsible for taking all actions in connection with winding up the
Trust, in accordance with the requirements of this Agreement (including this
Section 9.01 and Section 9.02) and applicable law.

         SECTION 9.02 Additional Termination Requirements.

         (a) In the event the Master Servicer exercises its purchase option as
provided in Section 9.01, REMIC I, REMIC II and REMIC III shall be terminated in
accordance with the following additional requirements, unless the Master
Servicer, at its own expense, obtains for the Trustee an Opinion of Counsel to
the effect that the failure of REMIC I, REMIC II and REMIC III to comply with
the requirements of this Section 9.02 will not (i) result in the imposition of
taxes on "prohibited transactions" of REMIC I, REMIC II and REMIC III as
described in Section 860F of the Code, or (ii) cause REMIC I, REMIC II or REMIC
III to fail to qualify as a REMIC at any time that any Certificates are
outstanding:

         (i) Within 90 days prior to the final Distribution Date set forth in
the notice given by the Trustee under Section 9.01, the Tax Matters Person shall
prepare the documentation required and the Tax Matters Person and the Trustee
shall adopt a plan of complete liquidation on behalf of REMIC I, REMIC II and
REMIC III meeting the requirements of a qualified liquidation under Section 860F
of the Code and any regulations thereunder, as evidenced by an Opinion of
Counsel obtained at the expense of the Master Servicer, on behalf of REMIC I,
REMIC II and REMIC III; and

         (ii) At or after the time of adoption of such a plan of complete
liquidation and at or prior to the final Distribution Date, the Master Servicer
as agent of the Trust shall sell all of the assets of REMIC I, REMIC II and
REMIC III to the Master Servicer for cash in the amount specified in Section
9.01.

         (b) By its acceptance of any Residual Certificate, the Holder thereof
hereby agrees to authorize the Tax Matters Person and the Trustee to adopt such
a plan of complete liquidation upon the written request of the Tax Matters
Person and the Trustee and to take such other action in connection therewith as
may be reasonably requested by the Tax Matters Person or the Trustee.



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         SECTION 9.03 Trust Irrevocable. Except as expressly provided herein,
the trust created hereby is irrevocable.

                                   ARTICLE X

                            Miscellaneous Provisions

         SECTION 10.01 Amendment.

         (a) This Agreement may be amended from time to time by the Master
Servicer, the Company and the Trustee, without the consent of any of the
Certificateholders:

         (i) to cure any ambiguity;

         (ii) to correct or supplement any provision herein which may be
defective or inconsistent with any other provisions herein;

         (iii) to comply with any requirements imposed by the Code or any
regulations thereunder;

         (iv) to correct the description of any property at any time included in
REMIC I, REMIC II or REMIC III, or to assure the conveyance to the Trust of any
property included in REMIC I, REMIC II or REMIC III;

         (v) pursuant to Section 5.01(c)(v); and

         (vi) to add any provision to, or amend any provision in, this
Agreement, provided that such amendment or addition does not adversely affect in
any material respect the interests of any Certificateholder;

provided, however, that any such amendment which modifies the rights or
obligations of the Delaware Trustee hereunder shall require the consent of the
Delaware Trustee. No such amendment (other than one entered into pursuant to
clause (iii) of the preceding sentence) shall change the powers of the Master
Servicer. Prior to entering into any amendment (other than one entered into
pursuant to clause (iii) of the second preceding sentence) without the consent
of Certificateholders pursuant to this paragraph, the Trustee shall require an
Opinion of Counsel addressed to the Trust and the Trustee to the effect that
such amendment is permitted under this Agreement and has no material adverse
effect on the interests of the Certificateholders; provided, however, that no
such Opinion of Counsel shall be required if the Company obtains a letter from
each Rating Agency stating that the amendment would not result in the
downgrading or withdrawal of the respective ratings then assigned to the
Certificates. Prior to entering into any amendment pursuant to clause (iii) of
the third preceding sentence without the consent of Certificateholders pursuant
to this paragraph, the Trustee shall require an Opinion of Counsel to the effect
that such action is necessary or helpful to comply with the requirements imposed
by the Code or any regulations thereunder and shall not cause any REMIC formed
under this Agreement to fail to qualify as such under the Code.

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         (b) This Agreement may also be amended from time to time by the Master
Servicer, the Company and the Trustee with the consent of the Holders of
Certificates evidencing Percentage Interests aggregating not less than 66% of
REMIC III for the purpose of adding any provisions to, or changing in any manner
or eliminating any of the provisions of, this Agreement or of modifying in any
manner the rights of the Certificateholders; provided, however, that no such
amendment shall, without the consent of the Holder of each Certificate affected
thereby (i) reduce in any manner the amount of, or delay the timing of,
distributions of principal or interest required to be made hereunder or reduce
the Certificateholder's Percentage Interest, the Certificate Interest Rate or
the Termination Payment with respect to any of the Certificates, (ii) reduce the
percentage of Percentage Interests specified in this Section 10.01 which are
required to amend this Agreement, (iii) create or permit the creation of any
lien against any part of REMIC I, REMIC II or REMIC III, or (iv) modify any
provision in any way which would permit an earlier retirement of the
Certificates; provided, further, that any such amendment which modifies the
rights or obligations of the Delaware Trustee hereunder shall require the
consent of the Delaware Trustee.

         Promptly after the execution of any such amendment, the Trustee shall
furnish written notification of the substance of such amendment to the Delaware
Trustee and each Certificateholder. Any failure to provide such notice, or any
defect therein, shall not, however, in any way impair or affect the validity of
any such amendment.

         It shall not be necessary for the consent of Certificateholders under
this Section 10.01 to approve the particular form of any proposed amendment, but
it shall be sufficient if such consent shall approve the substance thereof. The
manner of obtaining such consents and of evidencing the authorization of the
execution thereof by Certificateholders shall be subject to such reasonable
regulations as the Trustee may prescribe.

         SECTION 10.02 Recordation of Agreement. To the extent permitted by
applicable law, this Agreement is subject to recordation in all appropriate
public offices for real property records in all the counties or the comparable
jurisdictions in which any Mortgaged Property is situated, and in any other
appropriate public recording office or elsewhere, such recordation to be
effected by the Company and at its expense on direction by the Trustee, but only
upon direction accompanied by an Opinion of Counsel to the effect that such
recordation materially and beneficially affects the interests of the
Certificateholders.

         SECTION 10.03 Limitation on Rights of Certificateholders. The death or
incapacity of any Certificateholder shall not operate to terminate this
Agreement or the Trust, nor entitle such Certificateholder's legal
representatives or heirs to claim an accounting or to take any action or
proceeding in any court for a partition or winding-up of the Trust, nor
otherwise affect the rights, obligations and liabilities of the parties hereto
or any of them.

         No Certificateholder shall have any right to vote or in any manner
otherwise to control the operation and management of the Trust or the
obligations of the parties hereto (except as provided in Section 5.09, Section
7.01, Section 8.01, Section 8.02, Section 8.07, Section 10.01 and this Section
10.03), nor shall anything herein set forth, or contained in the terms of the
Certificates, be construed so as to constitute the Certificateholders from time
to time as partners or members of an association; nor shall any


                                      133
<PAGE>

Certificateholder be under any liability to any third person by reason of any
action taken by the parties to this Agreement pursuant to any provision hereof.

         No Certificateholder shall have any right by virtue or by availing of
any provision of this Agreement to institute any suit, action or proceeding in
equity or at law upon or under or with respect to this Agreement, unless such
Holder previously shall have given to the Trustee a written notice of default
and of the continuance thereof, as hereinbefore provided, and unless also the
Holders of Certificates evidencing Percentage Interests aggregating not less
than 25% of REMIC III shall have made written request upon the Trustee to
institute such action, suit or proceeding in its own name as Trustee hereunder
and shall have offered to the Trustee such reasonable indemnity as it may
require against the costs, expenses and liabilities to be incurred therein or
thereby, and the Trustee, for 60 days after its receipt of such notice, request
and offer of indemnity, shall have neglected or refused to institute any such
action, suit or proceeding. However, the Trustee is under no obligation to
exercise any of the extraordinary trusts or powers vested in it by this
Agreement or to make any investigation of matters arising hereunder or to
institute, conduct or defend any litigation hereunder or in relation hereto at
the request, order or direction of any of the Certificateholders unless such
Certificateholders have offered to the Trustee reasonable security or indemnity
against the costs, expenses and liabilities which may be incurred therein or
thereby. It is understood and intended, and expressly covenanted by each
Certificateholder with every other Certificateholder and the Trustee, that no
one or more Holders of Certificates shall have any right in any manner whatever
by virtue or by availing of any provision of this Agreement to affect, disturb
or prejudice the rights of the Holders of any other of such Certificates, or to
obtain or seek to obtain priority over or preference to any other such Holder,
or to enforce any right under this Agreement, except in the manner herein
provided and for the equal, ratable and common benefit of all
Certificateholders. For the protection and enforcement of the provisions of this
Section 10.03, each and every Certificateholder and the Trustee shall be
entitled to such relief as can be given either at law or in equity.

         SECTION 10.04 Access to List of Certificateholders. The Certificate
Registrar shall furnish or cause to be furnished to the Trustee, within 30 days
after receipt of a request by the Trustee in writing, a list, in such form as
the Trustee may reasonably require, of the names and addresses of the
Certificateholders as of the most recent Record Date for payment of
distributions to such Certificateholders.

         If three or more Certificateholders (hereinafter referred to as
"applicants") apply in writing to the Trustee, and such application states that
the applicants desire to communicate with other Certificateholders with respect
to their rights under this Agreement or under the Certificates and is
accompanied by a copy of the communication which such applicants propose to
transmit, then the Trustee shall, within five Business Days after the receipt of
such list from the Certificate Registrar, afford such applicants access during
normal business hours to the most recent list of Certificateholders held by the
Trustee. If such a list is as of a date more than 90 days prior to the date of
receipt of such applicants' request, the Trustee shall promptly request from the
Certificate Registrar a current list as provided above, and shall afford such
applicants access to such list promptly upon receipt.

         Every Certificateholder, by receiving and holding the same, agrees with
the Master Servicer, the Trust, the Trustee and the Delaware Trustee that none
of the Master Servicer, the Trust, the Trustee or the Delaware Trustee shall be


                                      134
<PAGE>

held accountable by reason of the disclosure of any such information as to the
names and addresses of the Certificateholders hereunder, regardless of the
source from which such information was derived.

         SECTION 10.05 Governing Law. This Agreement shall be construed in
accordance with the laws of the State of Delaware without giving effect to its
conflict of laws provisions and the obligations, rights and remedies of the
parties hereunder shall be determined in accordance with such laws without
giving effect to conflict of laws provisions.

         SECTION 10.06 Notices. All demands, notices and communications
hereunder shall be in writing and shall be deemed to have been duly given if
personally delivered at or mailed by registered or certified mail to the
applicable Notice Address. Notices to the Rating Agencies shall also be deemed
to have been duly given if mailed by first class mail, postage prepaid, to the
above listed addresses of the Rating Agencies. Any notice required or permitted
to be mailed to a Certificateholder shall be given by first class mail, postage
prepaid, at the address of such Holder as shown in the Certificate Register. Any
notice so mailed within the time prescribed in this Agreement shall be
conclusively presumed to have been duly given, whether or not the
Certificateholder receives such notice.

         SECTION 10.07 Severability of Provisions. If any one or more of the
covenants, agreements, provisions or terms of this Agreement shall be for any
reason whatsoever held invalid, then such covenants, agreements, provisions or
terms shall be deemed severable from the remaining covenants, agreements,
provisions or terms of this Agreement and shall in no way affect the validity or
enforceability of the other provisions of this Agreement or of the Certificates
or the rights of the Holders thereof.

         SECTION 10.08 Counterpart Signatures. For the purpose of facilitating
the recordation of this Agreement as herein provided and for other purposes,
this Agreement may be executed simultaneously in any number of counterparts,
each of which counterparts shall be deemed to be an original, and such
counterparts shall constitute but one and the same instrument.

         SECTION 10.09 Benefits of Agreement. Nothing in this Agreement or in
any Certificate, expressed or implied, shall give to any Person, other than the
parties hereto and their respective successors hereunder, any separate trustee
or co-trustee appointed under Section 8.10 and the Certificateholders, any
benefit or any legal or equitable right, remedy or claim under this Agreement.

         SECTION 10.10 Notices and Copies to Rating Agencies.

         (a) The Trustee shall notify the Rating Agencies of the occurrence of
any of the following events, in the manner provided in Section 10.06:

         (i) the occurrence of an Event of Default pursuant to Section 7.01,
subject to the provisions of Section 8.01(d); and

         (ii) the appointment of a successor Master Servicer pursuant to Section
7.02;

                                      135
<PAGE>

         (b) The Master Servicer shall notify the Rating Agencies of the
occurrence of any of the following events, or in the case of clauses (iii),
(iv), (vii) and (viii) promptly upon receiving notice thereof, in the manner
provided in Section 10.06:

         (i) any amendment of this Agreement pursuant to Section 10.01;

         (ii) the appointment of a successor Trustee or successor Delaware
Trustee pursuant to Section 8.08;

         (iii) the filing of any claim under or the cancellation or modification
of any fidelity bond and errors and omissions coverage pursuant to Section 3.01
and Section 3.06 with respect to the Master Servicer or any Servicer;

         (iv) any change in the location of the Certificate Account, any
Custodial Account for P&I or any Custodial Account for Reserves;

         (v) the purchase of any Mortgage Loan pursuant to a Purchase Obligation
or as permitted by this Agreement or the purchase of the outstanding Mortgage
Loans pursuant to Section 9.01;

         (vi) the occurrence of the final Distribution Date or the termination
of the trust pursuant to Section 9.01(a)(ii);

         (vii) the failure of the Master Servicer to make a Monthly P&I Advance
following a determination on the Determination Date that the Master Servicer
would make such advance pursuant to Section 4.02; and

         (viii) the failure of the Master Servicer to make a determination on
the Determination Date regarding whether it would make a Monthly P&I Advance
when a shortfall exists between (x) payments scheduled to be received in respect
of the Mortgage Loans and (y) the amounts actually deposited in the Certificate
Account on account of such payments, pursuant to Section 4.02.

         The Master Servicer shall provide copies of the statements pursuant to
Section 4.02, Section 4.06, Section 3.12, Section 3.13 or Section 3.15 or any
other statements or reports to the Rating Agencies in such time and manner that
such statements or determinations are required to be provided to
Certificateholders. With respect to the reports described in the second
paragraph of Section 4.06, the Master Servicer shall provide such reports to the
Rating Agencies in respect of each Distribution Date, without regard to whether
any Certificateholder or the Trustee or the Delaware Trustee has requested such
report for such Distribution Date.




                                      136
<PAGE>

        IN WITNESS WHEREOF, the Company, the Trustee and the Delaware Trustee
have caused their names to be signed hereto by their respective officers,
thereunto duly authorized, all as of the day and year first above written.

                                 WASHINGTON MUTUAL MORTGAGE SECURITIES CORP.

                                 By:/s/ Thomas G. Lehman
                                    Name: Thomas G. Lehmann
                                    Title: First Vice President

                                 CITIBANK, N.A.,
                                 as Trustee

                                 By: /s/ Karen Schluter
                                    Name: Karen Schluter
                                    Title: Vice President

                                CHRISTIANA BANK & TRUST COMPANY,
                                 as Delaware Trustee

                                 By: /s/ James M. Young
                                    Name: James M. Young
                                    Title: Assistant Vice President

   [Signature page to Pooling and Servicing Agreement for WaMu Series 2004-S1]

<PAGE>

                         ACKNOWLEDGEMENT OF CORPORATION

STATE OF WASHINGTON                                  )
                                                     ) SS.
COUNTY OF KING                                       )


         I certify that I know or have satisfactory evidence that
Thomas G. Lehmann is the person who appeared before me, and said person
acknowledged that he signed this instrument, on oath stated that. he was
authorized to execute the instrument and acknowledged it as the
First Vice President of WASHINGTON MUTUAL MORTGAGE SECURITIES CORP., to be
the free and voluntary act of such party for the uses and purposes mentioned
therein.

Dated this 26th day of February, 2004.

                            Chrisdelda Landon
                            Notary Public in and for the State of Washington,
                            residing at Seattle
                            My commission expires:  2-26-2007


<PAGE>



                                 ACKNOWLEDGEMENT

STATE OF NEW YORK                     )
                                      ) SS.
COUNTY OF NEW YORK                    )

         On this 18th day of February 2004 before me, a Notary Public in and for
said State, personally appeared Karen Schluter, personally known to me
(or proved to me on the basis of satisfactory evidence) to be the person(s)
whose name(s) is/are subscribed to the within instrument and acknowledged to me
that he/she/they executed the same in his/her/their authorized capacit(ies), and
that by his/her/their signature(s) on the instrument the person(s), or the
entity upon behalf of which the person(s) acted, executed the instrument.

         WITNESS my hand and official seal.

         Signature Nanette Murphy

         (SEAL)Notary Public, State of New York No. 01MU6086415
               Qualifed in Kings County
               Commission Expires 1/21/07



<PAGE>


                                 ACKNOWLEDGEMENT

STATE OF DELAWARE                     )
                                      ) SS.
COUNTY OF NEWCASTLE                   )

         On this 19th day of February 2004 before me, a Notary Public in and for
said State, personally appeared James M. Young, personally known to me
(or proved to me on the basis of satisfactory evidence) to be the person(s)
whose name(s) is/are subscribed to the within instrument and acknowledged to me
that he/she/they executed the same in his/her/their authorized capacit(ies), and
that by his/her/their signature(s) on the instrument the person(s), or the
entity upon behalf of which the person(s) acted, executed the instrument.

         WITNESS my hand and official seal.

         Signature Patricia A. Smith

         (SEAL)Patricia M. Smith
               Notary Public, State of Delaware
               Commission Expires May 29, 2005



<PAGE>


        Appendix 1: Definition of Class C-Y Principal Reduction Amounts

         Copies of Appendix 1 (which has been intentionally omitted from this
filing) may be obtained from Washington Mutual Mortgage Securities Corp. or
Citibank, N.A., by contacting,

          in the case of Washington Mutual Mortgage Securities Corp.,

               Laura Kelsey
               Master Servicing Department
               Washington Mutual Mortgage Securities Corp.
               75 N. Fairway Drive, VHF2A01
               Vernon Hills, IL 60061
               Telephone: (847) 393-5198
               Facsimile: (847) 549-2997

          in the case of Citibank, N.A.,

               Karen Schluter
               Citibank, N.A.
               111 Wall Street
               14th Floor, Zone 3
               New York, New York  10005
               Telephone: (212) 657-7781
               Facsimile: (212) 657-4009


<PAGE>


                                                               Exhibit A
                                                               CUSIP 92922F LR 7


                     WaMu MORTGAGE PASS-THROUGH CERTIFICATE

                                   Class 1-A-1

Evidencing a beneficial  interest in a pool of assets  consisting  of beneficial
interests  in another  pool of assets  consisting  of  beneficial  interests  in
another pool of assets  consisting of, among other things,  conventional one- to
four-family mortgage loans formed and administered by

                   WASHINGTON MUTUAL MORTGAGE SECURITIES CORP.

This  Certificate is issued by WaMu Mortgage  Pass-Through  Certificates  Series
2004-S1 Trust. This Certificate  represents ownership of a "regular interest" in
a "real  estate  mortgage  investment  conduit,"  as those  terms are defined in
Sections 860G and 860D,  respectively,  of the Internal Revenue Code of 1986, as
amended. The issue date of this Certificate is February 24, 2004.

Unless this  Certificate  is presented by an  authorized  representative  of The
Depository Trust Company, a New York corporation  ("DTC"), to the Company or its
agent for registration of transfer,  exchange,  or payment,  and any Certificate
issued  is  registered  in the  name of  Cede & Co.  or  such  other  name as is
requested  by an  authorized  representative  of DTC (and any payment is made to
Cede  &  Co.  or  to  such  other  entity  as  is  requested  by  an  authorized
representative  of DTC),  ANY TRANSFER,  PLEDGE OR OTHER USE HEREOF FOR VALUE OR
OTHERWISE  BY OR TO ANY PERSON IS  WRONGFUL  inasmuch  as the  registered  owner
hereof, Cede & Co., has an interest herein.

  Series 2004-S1            Portion of the Class 1-A-1 Principal Balance as of
                            the Cut-Off Date Evidenced by this Certificate:
                            $99,827,849.00


Class 1-A-1 Certificate Interest Rate: 4.050%

Cut-Off Date: February 1, 2004

First Distribution Date: March 25, 2004

Last Scheduled Distribution Date: March 25, 2034

Class 1-A-1 Principal Balance
as of the Cut-Off Date: $99,827,849.00

                                   Cede & Co.
                                Registered Owner


                                      A-1

<PAGE>



                                                    Exhibit A
                                                    CUSIP 92922F LS 5


                     WaMu MORTGAGE PASS-THROUGH CERTIFICATE

                                   Class 1-A-2

Evidencing a beneficial  interest in a pool of assets  consisting  of beneficial
interests  in another  pool of assets  consisting  of  beneficial  interests  in
another pool of assets  consisting of, among other things,  conventional one- to
four-family mortgage loans formed and administered by

                   WASHINGTON MUTUAL MORTGAGE SECURITIES CORP.

This  Certificate is issued by WaMu Mortgage  Pass-Through  Certificates  Series
2004-S1 Trust. This Certificate  represents ownership of a "regular interest" in
a "real  estate  mortgage  investment  conduit,"  as those  terms are defined in
Sections 860G and 860D,  respectively,  of the Internal Revenue Code of 1986, as
amended. The issue date of this Certificate is February 24, 2004.

     Unless this Certificate is presented by an authorized representative of The
Depository Trust Company, a New York corporation  ("DTC"), to the Company or its
agent for registration of transfer,  exchange,  or payment,  and any Certificate
issued  is  registered  in the  name of  Cede & Co.  or  such  other  name as is
requested  by an  authorized  representative  of DTC (and any payment is made to
Cede  &  Co.  or  to  such  other  entity  as  is  requested  by  an  authorized
representative  of DTC),  ANY TRANSFER,  PLEDGE OR OTHER USE HEREOF FOR VALUE OR
OTHERWISE  BY OR TO ANY PERSON IS  WRONGFUL  inasmuch  as the  registered  owner
hereof, Cede & Co., has an interest herein.

        Series 2004-S1     Portion of the Class  1-A-2  Principal  Balance as of
                           the Cut-Off Date Evidenced by this Certificate:
                           $13,000,000.00


Class 1-A-2 Certificate Interest Rate: 4.050%

Cut-Off Date: February 1, 2004

First Distribution Date: March 25, 2004

Last Scheduled Distribution Date: March 25, 2034

Class 1-A-2 Principal Balance
as of the Cut-Off Date: $13,000,000.00

                                   Cede & Co.
                                Registered Owner


                                      A-2
<PAGE>



                                                      Exhibit A
                                                      CUSIP 92922F LT 3


                     WaMu MORTGAGE PASS-THROUGH CERTIFICATE

                                   Class 1-A-3

Evidencing a beneficial  interest in a pool of assets  consisting  of beneficial
interests  in another  pool of assets  consisting  of  beneficial  interests  in
another pool of assets  consisting of, among other things,  conventional one- to
four-family mortgage loans formed and administered by

                   WASHINGTON MUTUAL MORTGAGE SECURITIES CORP.

This  Certificate is issued by WaMu Mortgage  Pass-Through  Certificates  Series
2004-S1 Trust. This Certificate  represents ownership of a "regular interest" in
a "real  estate  mortgage  investment  conduit,"  as those  terms are defined in
Sections 860G and 860D,  respectively,  of the Internal Revenue Code of 1986, as
amended. The issue date of this Certificate is February 24, 2004.

Unless this  Certificate  is presented by an  authorized  representative  of The
Depository Trust Company, a New York corporation  ("DTC"), to the Company or its
agent for registration of transfer,  exchange,  or payment,  and any Certificate
issued  is  registered  in the  name of  Cede & Co.  or  such  other  name as is
requested  by an  authorized  representative  of DTC (and any payment is made to
Cede  &  Co.  or  to  such  other  entity  as  is  requested  by  an  authorized
representative  of DTC),  ANY TRANSFER,  PLEDGE OR OTHER USE HEREOF FOR VALUE OR
OTHERWISE  BY OR TO ANY PERSON IS  WRONGFUL  inasmuch  as the  registered  owner
hereof, Cede & Co., has an interest herein.



    Series 2004-S1      Portion of the Class  1-A-3  Principal  Balance as of
                        the Cut-Off Date Evidenced by this Certificate:
                        $65,440,151.00




Class 1-A-3 Certificate Interest Rate: Variable

Cut-Off Date: February 1, 2004

First Distribution Date: March 25, 2004

Last Scheduled Distribution Date: March 25, 2034

Class 1-A-3 Principal Balance
as of the Cut-Off Date: $65,440,151.00

                                   Cede & Co.
                                Registered Owner


                                      A-3

<PAGE>


                                                        Exhibit A
                                                        CUSIP 92922F LU 0


                     WaMu MORTGAGE PASS-THROUGH CERTIFICATE

                                   Class 1-A-4

Evidencing a beneficial  interest in a pool of assets  consisting  of beneficial
interests  in another  pool of assets  consisting  of  beneficial  interests  in
another pool of assets  consisting of, among other things,  conventional one- to
four-family mortgage loans formed and administered by

                   WASHINGTON MUTUAL MORTGAGE SECURITIES CORP.

This  Certificate is issued by WaMu Mortgage  Pass-Through  Certificates  Series
2004-S1 Trust. This Certificate  represents ownership of a "regular interest" in
a "real  estate  mortgage  investment  conduit,"  as those  terms are defined in
Sections 860G and 860D,  respectively,  of the Internal Revenue Code of 1986, as
amended. The issue date of this Certificate is February 24, 2004.

Unless this  Certificate  is presented by an  authorized  representative  of The
Depository Trust Company, a New York corporation  ("DTC"), to the Company or its
agent for registration of transfer,  exchange,  or payment,  and any Certificate
issued  is  registered  in the  name of  Cede & Co.  or  such  other  name as is
requested  by an  authorized  representative  of DTC (and any payment is made to
Cede  &  Co.  or  to  such  other  entity  as  is  requested  by  an  authorized
representative  of DTC),  ANY TRANSFER,  PLEDGE OR OTHER USE HEREOF FOR VALUE OR
OTHERWISE  BY OR TO ANY PERSON IS  WRONGFUL  inasmuch  as the  registered  owner
hereof, Cede & Co., has an interest herein.



Series 2004-S1         Portion of the Class  1-A-4 P  Notional  Amount as of
                       the Cut-Off Date Evidenced by this Certificate:
                       $65,440,151.00


Class 1-A-4 Certificate Interest Rate: Variable, applied to the
Class 1-A-4 Notional Amount

Cut-Off Date: February 1, 2004

First Distribution Date: March 25, 2004

Last Scheduled Distribution Date: March 25, 2034

Class 1-A-4 Principal Balance
as of the Cut-Off Date: $0.00

Class 1-A-4 Notional Amount
as of the Cut-Off Date: $65,440,151.00

                                   Cede & Co.
                                Registered Owner


                                      A-4

<PAGE>



                                                                    Exhibit A
                                                              CUSIP 92922F LV 8


                     WaMu MORTGAGE PASS-THROUGH CERTIFICATE

                                   Class 1-A-5

Evidencing a beneficial  interest in a pool of assets  consisting  of beneficial
interests  in another  pool of assets  consisting  of  beneficial  interests  in
another pool of assets  consisting of, among other things,  conventional one- to
four-family mortgage loans formed and administered by

                   WASHINGTON MUTUAL MORTGAGE SECURITIES CORP.

This  Certificate is issued by WaMu Mortgage  Pass-Through  Certificates  Series
2004-S1 Trust. This Certificate  represents ownership of a "regular interest" in
a "real  estate  mortgage  investment  conduit,"  as those  terms are defined in
Sections 860G and 860D,  respectively,  of the Internal Revenue Code of 1986, as
amended. The issue date of this Certificate is February 24, 2004.

Unless this  Certificate  is presented by an  authorized  representative  of The
Depository Trust Company, a New York corporation  ("DTC"), to the Company or its
agent for registration of transfer,  exchange,  or payment,  and any Certificate
issued  is  registered  in the  name of  Cede & Co.  or  such  other  name as is
requested  by an  authorized  representative  of DTC (and any payment is made to
Cede  &  Co.  or  to  such  other  entity  as  is  requested  by  an  authorized
representative  of DTC),  ANY TRANSFER,  PLEDGE OR OTHER USE HEREOF FOR VALUE OR
OTHERWISE  BY OR TO ANY PERSON IS  WRONGFUL  inasmuch  as the  registered  owner
hereof, Cede & Co., has an interest herein.

Series 2004-S1         Portion of the Class  1-A-5  Principal  Balance as of
                       the Cut-Off Date Evidenced by this Certificate:
                       $56.668,000.00




Class 1-A-5 Certificate Interest Rate: 5.500%

Cut-Off Date: February 1, 2004

First Distribution Date: March 25, 2004

Last Scheduled Distribution Date: March 25, 2034

Class 1-A-5 Principal Balance
as of the Cut-Off Date: $56,668,000.00

                                   Cede & Co.
                                Registered Owner





                                      A-5
<PAGE>


                                                           Exhibit A
                                                           CUSIP 92922F LW 6


                     WaMu MORTGAGE PASS-THROUGH CERTIFICATE

                                   Class 1-A-6

Evidencing a beneficial  interest in a pool of assets  consisting  of beneficial
interests  in another  pool of assets  consisting  of  beneficial  interests  in
another pool of assets  consisting of, among other things,  conventional one- to
four-family mortgage loans formed and administered by

                   WASHINGTON MUTUAL MORTGAGE SECURITIES CORP.

This  Certificate is issued by WaMu Mortgage  Pass-Through  Certificates  Series
2004-S1 Trust. This Certificate  represents ownership of a "regular interest" in
a "real  estate  mortgage  investment  conduit,"  as those  terms are defined in
Sections 860G and 860D,  respectively,  of the Internal Revenue Code of 1986, as
amended. The issue date of this Certificate is February 24, 2004.

Unless this  Certificate  is presented by an  authorized  representative  of The
Depository Trust Company, a New York corporation  ("DTC"), to the Company or its
agent for registration of transfer,  exchange,  or payment,  and any Certificate
issued  is  registered  in the  name of  Cede & Co.  or  such  other  name as is
requested  by an  authorized  representative  of DTC (and any payment is made to
Cede  &  Co.  or  to  such  other  entity  as  is  requested  by  an  authorized
representative  of DTC),  ANY TRANSFER,  PLEDGE OR OTHER USE HEREOF FOR VALUE OR
OTHERWISE  BY OR TO ANY PERSON IS  WRONGFUL  inasmuch  as the  registered  owner
hereof, Cede & Co., has an interest herein.



 Series 2004-S1        Portion of the Class  1-A-6  Principal  Balance as of
                       the Cut-Off Date Evidenced by this Certificate:
                       $7,747,663.00


Class 1-A-6 Certificate Interest Rate: 5.500%

Cut-Off Date: February 1, 2004

First Distribution Date: March 25, 2004

Last Scheduled Distribution Date: March 25, 2034

Class 1-A-6 Principal Balance
as of the Cut-Off Date: $7,747,663.00


                                   Cede & Co.
                                Registered Owner




                                      A-6
<PAGE>

                                                          Exhibit A
                                                          CUSIP 92922F LX 4


                     WaMu MORTGAGE PASS-THROUGH CERTIFICATE

                                   Class 1-A-7

Evidencing a beneficial  interest in a pool of assets  consisting  of beneficial
interests  in another  pool of assets  consisting  of  beneficial  interests  in
another pool of assets  consisting of, among other things,  conventional one- to
four-family mortgage loans formed and administered by

                   WASHINGTON MUTUAL MORTGAGE SECURITIES CORP.

This  Certificate is issued by WaMu Mortgage  Pass-Through  Certificates  Series
2004-S1 Trust. This Certificate  represents ownership of a "regular interest" in
a "real  estate  mortgage  investment  conduit,"  as those  terms are defined in
Sections 860G and 860D,  respectively,  of the Internal Revenue Code of 1986, as
amended. The issue date of this Certificate is February 24, 2004.

Unless this  Certificate  is presented by an  authorized  representative  of The
Depository Trust Company, a New York corporation  ("DTC"), to the Company or its
agent for registration of transfer,  exchange,  or payment,  and any Certificate
issued  is  registered  in the  name of  Cede & Co.  or  such  other  name as is
requested  by an  authorized  representative  of DTC (and any payment is made to
Cede  &  Co.  or  to  such  other  entity  as  is  requested  by  an  authorized
representative  of DTC),  ANY TRANSFER,  PLEDGE OR OTHER USE HEREOF FOR VALUE OR
OTHERWISE  BY OR TO ANY PERSON IS  WRONGFUL  inasmuch  as the  registered  owner
hereof, Cede & Co., has an interest herein.



Series 2004-S1          Portion of the Class  1-A-7  Principal  Balance as of
                        the Cut-Off Date Evidenced by this Certificate:
                        $19,800,000.00


Class 1-A-7 Certificate Interest Rate: Variable

Cut-Off Date: February 1, 2004

First Distribution Date: March 25, 2004

Last Scheduled Distribution Date: March 25, 2034

Class 1-A-7 Principal Balance
as of the Cut-Off Date: $19,800,000.00

                                   Cede & Co.
                                Registered Owner


                                      A-7
<PAGE>


                                                         Exhibit A
                                                         CUSIP 92922F LY 2


                     WaMu MORTGAGE PASS-THROUGH CERTIFICATE

                                   Class 1-A-8

Evidencing a beneficial  interest in a pool of assets  consisting  of beneficial
interests  in another  pool of assets  consisting  of  beneficial  interests  in
another pool of assets  consisting of, among other things,  conventional one- to
four-family mortgage loans formed and administered by

                   WASHINGTON MUTUAL MORTGAGE SECURITIES CORP.

This  Certificate is issued by WaMu Mortgage  Pass-Through  Certificates  Series
2004-S1 Trust. This Certificate  represents ownership of a "regular interest" in
a "real  estate  mortgage  investment  conduit,"  as those  terms are defined in
Sections 860G and 860D,  respectively,  of the Internal Revenue Code of 1986, as
amended. The issue date of this Certificate is February 24, 2004.

Unless this  Certificate  is presented by an  authorized  representative  of The
Depository Trust Company, a New York corporation  ("DTC"), to the Company or its
agent for registration of transfer,  exchange,  or payment,  and any Certificate
issued  is  registered  in the  name of  Cede & Co.  or  such  other  name as is
requested  by an  authorized  representative  of DTC (and any payment is made to
Cede  &  Co.  or  to  such  other  entity  as  is  requested  by  an  authorized
representative  of DTC),  ANY TRANSFER,  PLEDGE OR OTHER USE HEREOF FOR VALUE OR
OTHERWISE  BY OR TO ANY PERSON IS  WRONGFUL  inasmuch  as the  registered  owner
hereof, Cede & Co., has an interest herein.



Series 2004-S1           Portion of the Class  1-A-8  Principal  Balance as of
                         the Cut-Off Date Evidenced by this Certificate:
                         $7,200,000.00


Class 1-A-8 Certificate Interest Rate: Variable

Cut-Off Date: February 1, 2004

First Distribution Date: March 25, 2004

Last Scheduled Distribution Date: March 25, 2034

Class 1-A-8 Principal Balance
as of the Cut-Off Date: $7,200,000.00

                                   Cede & Co.
                                Registered Owner


                                      A-8
<PAGE>



                                                    Exhibit A
                                                    CUSIP 92922F LZ 9


                                      WaMu MORTGAGE PASS-THROUGH CERTIFICATE

                                                    Class 1-A-9

Evidencing a beneficial  interest in a pool of assets  consisting  of beneficial
interests  in another  pool of assets  consisting  of  beneficial  interests  in
another pool of assets  consisting of, among other things,  conventional one- to
four-family mortgage loans formed and administered by

                   WASHINGTON MUTUAL MORTGAGE SECURITIES CORP.

This  Certificate is issued by WaMu Mortgage  Pass-Through  Certificates  Series
2004-S1 Trust. This Certificate  represents ownership of a "regular interest" in
a "real  estate  mortgage  investment  conduit,"  as those  terms are defined in
Sections 860G and 860D,  respectively,  of the Internal Revenue Code of 1986, as
amended. The issue date of this Certificate is February 24, 2004.

Unless this  Certificate  is presented by an  authorized  representative  of The
Depository Trust Company, a New York corporation  ("DTC"), to the Company or its
agent for registration of transfer,  exchange,  or payment,  and any Certificate
issued  is  registered  in the  name of  Cede & Co.  or  such  other  name as is
requested  by an  authorized  representative  of DTC (and any payment is made to
Cede  &  Co.  or  to  such  other  entity  as  is  requested  by  an  authorized
representative  of DTC),  ANY TRANSFER,  PLEDGE OR OTHER USE HEREOF FOR VALUE OR
OTHERWISE  BY OR TO ANY PERSON IS  WRONGFUL  inasmuch  as the  registered  owner
hereof, Cede & Co., has an interest herein.

Series 2004-S1             Portion of the Class  1-A-9  Principal  Balance as of
                           the Cut-Off Date Evidenced by this Certificate:
                           $15,000,000.00




Class 1-A-9 Certificate Interest Rate: 5.500%

Cut-Off Date: February 1, 2004

First Distribution Date: March 25, 2004

Last Scheduled Distribution Date: March 25, 2034

Class 1-A-9 Principal Balance
as of the Cut-Off Date: $15,000,000.00

                                   Cede & Co.
                                Registered Owner




                                      A-9
<PAGE>


                                                          Exhibit A
                                                          CUSIP 92922F MA 3


                     WaMu MORTGAGE PASS-THROUGH CERTIFICATE

                                  Class 1-A-10

Evidencing a beneficial  interest in a pool of assets  consisting  of beneficial
interests  in another  pool of assets  consisting  of  beneficial  interests  in
another pool of assets  consisting of, among other things,  conventional one- to
four-family mortgage loans formed and administered by

                   WASHINGTON MUTUAL MORTGAGE SECURITIES CORP.

This  Certificate is issued by WaMu Mortgage  Pass-Through  Certificates  Series
2004-S1 Trust. This Certificate  represents ownership of a "regular interest" in
a "real  estate  mortgage  investment  conduit,"  as those  terms are defined in
Sections 860G and 860D,  respectively,  of the Internal Revenue Code of 1986, as
amended. The issue date of this Certificate is February 24, 2004.

Unless this  Certificate  is presented by an  authorized  representative  of The
Depository Trust Company, a New York corporation  ("DTC"), to the Company or its
agent for registration of transfer,  exchange,  or payment,  and any Certificate
issued  is  registered  in the  name of  Cede & Co.  or  such  other  name as is
requested  by an  authorized  representative  of DTC (and any payment is made to
Cede  &  Co.  or  to  such  other  entity  as  is  requested  by  an  authorized
representative  of DTC),  ANY TRANSFER,  PLEDGE OR OTHER USE HEREOF FOR VALUE OR
OTHERWISE  BY OR TO ANY PERSON IS  WRONGFUL  inasmuch  as the  registered  owner
hereof, Cede & Co., has an interest herein.



 Series 2004-S1      Portion of the Class 1-A-10  Principal  Balance as of
                     the Cut-Off Date Evidenced by this Certificate:
                     $20,000,000.00

Class 1-A-10 Certificate Interest Rate: 5.500%

Cut-Off Date: February 1, 2004

First Distribution Date: March 25, 2004

Last Scheduled Distribution Date: March 25, 2034

Class 1-A-10 Principal Balance
as of the Cut-Off Date: $20,000,000.00

                                   Cede & Co.
                                Registered Owner


                                      A-10
<PAGE>


                                                           Exhibit A
                                                           CUSIP 92922F MB 1


                     WaMu MORTGAGE PASS-THROUGH CERTIFICATE

                                  Class 1-A-11

Evidencing a beneficial  interest in a pool of assets  consisting  of beneficial
interests  in another  pool of assets  consisting  of  beneficial  interests  in
another pool of assets  consisting of, among other things,  conventional one- to
four-family mortgage loans formed and administered by

                   WASHINGTON MUTUAL MORTGAGE SECURITIES CORP.

This  Certificate is issued by WaMu Mortgage  Pass-Through  Certificates  Series
2004-S1 Trust. This Certificate  represents ownership of a "regular interest" in
a "real  estate  mortgage  investment  conduit,"  as those  terms are defined in
Sections 860G and 860D,  respectively,  of the Internal Revenue Code of 1986, as
amended. The issue date of this Certificate is February 24, 2004.

Unless this  Certificate  is presented by an  authorized  representative  of The
Depository Trust Company, a New York corporation  ("DTC"), to the Company or its
agent for registration of transfer,  exchange,  or payment,  and any Certificate
issued  is  registered  in the  name of  Cede & Co.  or  such  other  name as is
requested  by an  authorized  representative  of DTC (and any payment is made to
Cede  &  Co.  or  to  such  other  entity  as  is  requested  by  an  authorized
representative  of DTC),  ANY TRANSFER,  PLEDGE OR OTHER USE HEREOF FOR VALUE OR
OTHERWISE  BY OR TO ANY PERSON IS  WRONGFUL  inasmuch  as the  registered  owner
hereof, Cede & Co., has an interest herein.

The Class 1-A-11  Certificates  will provide  credit support to another Class of
Certificates, as described in the Pooling Agreement.



Series 2004-S1        Portion of the Class 1-A-11  Principal  Balance as of
                      the Cut-Off Date Evidenced by this Certificate:
                      $600,000.00


Class 1-A-11 Certificate Interest Rate: 5.500%

Cut-Off Date: February 1, 2004

First Distribution Date: March 25, 2004

Last Scheduled Distribution Date: March 25, 2034

Class 1-A-11 Principal Balance
as of the Cut-Off Date: $600,000.00

                                   Cede & Co.
                                Registered Owner




                                      A-11
<PAGE>


                                                    Exhibit A
                                                    CUSIP 92922F MC 9


                     WaMu MORTGAGE PASS-THROUGH CERTIFICATE

                                  Class 1-A-12

Evidencing a beneficial  interest in a pool of assets  consisting  of beneficial
interests  in another  pool of assets  consisting  of  beneficial  interests  in
another pool of assets  consisting of, among other things,  conventional one- to
four-family mortgage loans formed and administered by

                   WASHINGTON MUTUAL MORTGAGE SECURITIES CORP.

This  Certificate is issued by WaMu Mortgage  Pass-Through  Certificates  Series
2004-S1 Trust. This Certificate  represents ownership of a "regular interest" in
a "real  estate  mortgage  investment  conduit,"  as those  terms are defined in
Sections 860G and 860D,  respectively,  of the Internal Revenue Code of 1986, as
amended. The issue date of this Certificate is February 24, 2004.

Unless this  Certificate  is presented by an  authorized  representative  of The
Depository Trust Company, a New York corporation  ("DTC"), to the Company or its
agent for registration of transfer,  exchange,  or payment,  and any Certificate
issued  is  registered  in the  name of  Cede & Co.  or  such  other  name as is
requested  by an  authorized  representative  of DTC (and any payment is made to
Cede  &  Co.  or  to  such  other  entity  as  is  requested  by  an  authorized
representative  of DTC),  ANY TRANSFER,  PLEDGE OR OTHER USE HEREOF FOR VALUE OR
OTHERWISE  BY OR TO ANY PERSON IS  WRONGFUL  inasmuch  as the  registered  owner
hereof, Cede & Co., has an interest herein.

 Series 2004-S1      Portion of the Class 1-A-12  Principal  Balance as of
                     the Cut-Off Date Evidenced by this Certificate:
                     $11,031,529.00




Class 1-A-12 Certificate Interest Rate: 5.500%

Cut-Off Date: February 1, 2004

First Distribution Date: March 25, 2004

Last Scheduled Distribution Date: March 25, 2034

Class 1-A-12 Principal Balance
as of the Cut-Off Date: $11,031,529.00

                                   Cede & Co.

                                Registered Owner



                                      A-12
<PAGE>


                                                          Exhibit A
                                                          CUSIP 92922F MD 7


                     WaMu MORTGAGE PASS-THROUGH CERTIFICATE

                                   Class 2-A-1

Evidencing a beneficial  interest in a pool of assets  consisting  of beneficial
interests  in another  pool of assets  consisting  of  beneficial  interests  in
another pool of assets  consisting of, among other things,  conventional one- to
four-family mortgage loans formed and administered by

                   WASHINGTON MUTUAL MORTGAGE SECURITIES CORP.

This  Certificate is issued by WaMu Mortgage  Pass-Through  Certificates  Series
2004-S1 Trust. This Certificate  represents ownership of a "regular interest" in
a "real  estate  mortgage  investment  conduit,"  as those  terms are defined in
Sections 860G and 860D,  respectively,  of the Internal Revenue Code of 1986, as
amended. The issue date of this Certificate is February 24, 2004.

Unless this  Certificate  is presented by an  authorized  representative  of The
Depository Trust Company, a New York corporation  ("DTC"), to the Company or its
agent for registration of transfer,  exchange,  or payment,  and any Certificate
issued  is  registered  in the  name of  Cede & Co.  or  such  other  name as is
requested  by an  authorized  representative  of DTC (and any payment is made to
Cede  &  Co.  or  to  such  other  entity  as  is  requested  by  an  authorized
representative  of DTC),  ANY TRANSFER,  PLEDGE OR OTHER USE HEREOF FOR VALUE OR
OTHERWISE  BY OR TO ANY PERSON IS  WRONGFUL  inasmuch  as the  registered  owner
hereof, Cede & Co., has an interest herein.



Series 2004-S1       Portion of the Class  2-A-1  Principal  Balance as of
                     the Cut-Off Date Evidenced by this Certificate:
                     $45,369,689.00


Class 2-A-1 Certificate Interest Rate: Variable

Cut-Off Date: February 1, 2004

First Distribution Date: March 25, 2004

Last Scheduled Distribution Date: March 25, 2034

Class 2-A-1 Principal Balance
as of the Cut-Off Date: $45,369,689.00

                                   Cede & Co.
                                Registered Owner


                                      A-13
<PAGE>


                                                     Exhibit A
                                                     CUSIP 92922F ME 5


                     WaMu MORTGAGE PASS-THROUGH CERTIFICATE

                                   Class 2-A-2

Evidencing a beneficial  interest in a pool of assets  consisting  of beneficial
interests  in another  pool of assets  consisting  of  beneficial  interests  in
another pool of assets  consisting of, among other things,  conventional one- to
four-family mortgage loans formed and administered by

                   WASHINGTON MUTUAL MORTGAGE SECURITIES CORP.

This  Certificate is issued by WaMu Mortgage  Pass-Through  Certificates  Series
2004-S1 Trust. This Certificate  represents ownership of a "regular interest" in
a "real  estate  mortgage  investment  conduit,"  as those  terms are defined in
Sections 860G and 860D,  respectively,  of the Internal Revenue Code of 1986, as
amended. The issue date of this Certificate is February 24, 2004.

Unless this  Certificate  is presented by an  authorized  representative  of The
Depository Trust Company, a New York corporation  ("DTC"), to the Company or its
agent for registration of transfer,  exchange,  or payment,  and any Certificate
issued  is  registered  in the  name of  Cede & Co.  or  such  other  name as is
requested  by an  authorized  representative  of DTC (and any payment is made to
Cede  &  Co.  or  to  such  other  entity  as  is  requested  by  an  authorized
representative  of DTC),  ANY TRANSFER,  PLEDGE OR OTHER USE HEREOF FOR VALUE OR
OTHERWISE  BY OR TO ANY PERSON IS  WRONGFUL  inasmuch  as the  registered  owner
hereof, Cede & Co., has an interest herein.

        Series 2004-S1  Portion of the Class 2-A-2 Notional Amount as of
                        the Cut-Off Date Evidenced by this Certificate:
                        $45,369,689.00


Class 2-A-2 Certificate Interest Rate: Variable, applied to the

Class 2-A-2 Notional Amount

Cut-Off Date: February 1, 2004

First Distribution Date: March 25, 2004

Last Scheduled Distribution Date: March 25, 2034

Class 2-A-2 Principal Balance
as of the Cut-Off Date: $0.00

Class 2-A-2 Notional Amount
as of the Cut-Off Date: $45,369,689.00

                                   Cede & Co.
                                Registered Owner




                                      A-14
<PAGE>



                                                  Exhibit A
                                                  CUSIP 92922F MF 2


                     WaMu MORTGAGE PASS-THROUGH CERTIFICATE

                                     Class P

Evidencing a beneficial  interest in a pool of assets  consisting  of beneficial
interests  in another  pool of assets  consisting  of  beneficial  interests  in
another pool of assets  consisting of, among other things,  conventional one- to
four-family mortgage loans formed and administered by

                   WASHINGTON MUTUAL MORTGAGE SECURITIES CORP.

This  Certificate is issued by WaMu Mortgage  Pass-Through  Certificates  Series
2004-S1 Trust. This Certificate  represents ownership of a "regular interest" in
a "real  estate  mortgage  investment  conduit,"  as those  terms are defined in
Sections 860G and 860D,  respectively,  of the Internal Revenue Code of 1986, as
amended.  The issue date of this  Certificate is February 24, 2004.  Interest is
not payable with respect to this Certificate.

Unless this  Certificate  is presented by an  authorized  representative  of The
Depository Trust Company, a New York corporation  ("DTC"), to the Company or its
agent for registration of transfer,  exchange,  or payment,  and any Certificate
issued  is  registered  in the  name of  Cede & Co.  or  such  other  name as is
requested  by an  authorized  representative  of DTC (and any payment is made to
Cede  &  Co.  or  to  such  other  entity  as  is  requested  by  an  authorized
representative  of DTC),  ANY TRANSFER,  PLEDGE OR OTHER USE HEREOF FOR VALUE OR
OTHERWISE  BY OR TO ANY PERSON IS  WRONGFUL  inasmuch  as the  registered  owner
hereof, Cede & Co., has an interest herein.

        Series 2004-S1      Portion of the Class P Principal Balance as of
                            the Cut-Off Date Evidenced by this Certificate:
                            $2,438,018.00


Class P Certificate Interest Rate: 0.00%

Cut-Off Date: February 1, 2004

First Distribution Date: March 25, 2004

Last Scheduled Distribution Date: March 25, 2034

Class P Principal Balance
as of the Cut-Off Date: $2,438,018.00

                                   Cede & Co.
                                Registered Owner




                                      A-15
<PAGE>


                                                         Exhibit A
                                                         CUSIP 92922F MG 0


                                      WaMu MORTGAGE PASS-THROUGH CERTIFICATE

                                    Class B-1

     Evidencing  a  beneficial  interest  in a  pool  of  assets  consisting  of
beneficial  interests  in  another  pool  of  assets  consisting  of  beneficial
interests  in  another  pool  of  assets  consisting  of,  among  other  things,
conventional one- to four-family mortgage loans formed and administered by

                   WASHINGTON MUTUAL MORTGAGE SECURITIES CORP.

     This  Certificate  is issued  by WaMu  Mortgage  Pass-Through  Certificates
Series  2004-S1  Trust.  This  Certificate  represents  ownership  of a "regular
interest" in a "real  estate  mortgage  investment  conduit," as those terms are
defined in Sections 860G and 860D, respectively, of the Internal Revenue Code of
1986, as amended. The issue date of this Certificate is February 24, 2004.

     Unless this Certificate is presented by an authorized representative of The
Depository Trust Company, a New York corporation  ("DTC"), to the Company or its
agent for registration of transfer,  exchange,  or payment,  and any Certificate
issued  is  registered  in the  name of  Cede & Co.  or  such  other  name as is
requested  by an  authorized  representative  of DTC (and any payment is made to
Cede  &  Co.  or  to  such  other  entity  as  is  requested  by  an  authorized
representative  of DTC),  ANY TRANSFER,  PLEDGE OR OTHER USE HEREOF FOR VALUE OR
OTHERWISE  BY OR TO ANY PERSON IS  WRONGFUL  inasmuch  as the  registered  owner
hereof, Cede & Co., has an interest herein.

     NO TRANSFER OF THIS CLASS B-1  CERTIFICATE  WILL BE MADE UNLESS THE TRUSTEE
HAS  RECEIVED  (I) AN  OFFICER'S  CERTIFICATE  IN THE FORM  DESCRIBED IN SECTION
5.01(g) OF THE POOLING  AGREEMENT  AND (II) IF SO  INDICATED  IN SUCH  OFFICER'S
CERTIFICATE,  AN  OPINION  OF COUNSEL  ACCEPTABLE  TO AND IN FORM AND  SUBSTANCE
SATISFACTORY  TO THE TRUSTEE AND THE COMPANY TO THE EFFECT THAT THE PURCHASE AND
HOLDING OF THIS  CERTIFICATE  ARE  PERMISSIBLE  UNDER  APPLICABLE  LAW, WILL NOT
CONSTITUTE OR RESULT IN A NON-EXEMPT PROHIBITED TRANSACTION UNDER SECTION 406 OF
ERISA OR SECTION 4975 OF THE CODE, AND WILL NOT SUBJECT THE TRUST,  THE TRUSTEE,
THE MASTER  SERVICER OR THE COMPANY TO ANY  OBLIGATION  OR LIABILITY  (INCLUDING
OBLIGATIONS  OR  LIABILITIES  UNDER  SECTION 406 OF ERISA OR SECTION 4975 OF THE
CODE) IN ADDITION TO THOSE UNDERTAKEN IN THE POOLING AGREEMENT, WHICH OPINION OF
COUNSEL SHALL NOT BE AN EXPENSE OF THE TRUST,  THE TRUSTEE,  THE MASTER SERVICER
OR THE COMPANY.

     NOTWITHSTANDING  THE FOREGOING  PARAGRAPH,  WITH RESPECT TO THE TRANSFER OF
THIS CLASS B-1 CERTIFICATE TO DTC OR ANY OTHER CLEARING AGENCY OR ANY SUBSEQUENT
TRANSFER OF ANY INTEREST IN THIS  CERTIFICATE FOR SO LONG AS THIS CERTIFICATE IS
HELD BY DTC OR ANY OTHER CLEARING AGENCY, (I) AN OFFICER'S  CERTIFICATE (AND, IF
APPLICABLE,  A BENEFIT PLAN OPINION),  AS DESCRIBED IN THE FOREGOING  PARAGRAPH,
SHALL NOT BE REQUIRED, AND (II) THE FOLLOWING CONDITIONS SHALL APPLY:

     1. ANY TRANSFEREE OF THIS CERTIFICATE  WILL BE DEEMED TO HAVE  REPRESENTED,
BY VIRTUE  OF ITS  ACQUISITION  OR  HOLDING  OF THIS  CERTIFICATE  (OR  INTEREST
HEREIN),  THAT EITHER (A) SUCH  TRANSFEREE  IS NOT AN EMPLOYEE  BENEFIT OR OTHER
PLAN SUBJECT TO THE PROHIBITED  TRANSACTION  PROVISIONS OF ERISA OR SECTION 4975
OF THE CODE, OR ANY PERSON (INCLUDING AN INVESTMENT  MANAGER,  A NAMED FIDUCIARY
OR A TRUSTEE OF ANY SUCH PLAN) ACTING,  DIRECTLY OR INDIRECTLY,  ON BEHALF OF OR
PURCHASING  THIS  CERTIFICATE  WITH  "PLAN  ASSETS"  OF ANY  SUCH  PLAN (A "PLAN
INVESTOR"),  (B) SUCH TRANSFEREE IS AN INSURANCE COMPANY, THE SOURCE OF FUNDS TO
BE USED BY IT TO  ACQUIRE  OR HOLD THIS  CERTIFICATE  IS AN  "INSURANCE  COMPANY
GENERAL   ACCOUNT"  (WITHIN  THE  MEANING  OF  DEPARTMENT  OF  LABOR  PROHIBITED
TRANSACTION CLASS EXEMPTION ("PTCE") 95-60), AND THE CONDITIONS IN SECTION I AND
III OF PTCE 95-60 HAVE BEEN  SATISFIED  (EACH ENTITY THAT  SATISFIES THIS CLAUSE
(B), A "COMPLYING  INSURANCE  COMPANY") OR (C) THIS CERTIFICATE WAS RATED "BBB-"
OR BETTER (OR ITS EQUIVALENT) BY AT LEAST ONE OF THE RATING AGENCIES AT THE TIME
OF SUCH TRANSFEREE'S ACQUISITION OF THIS CERTIFICATE (OR INTEREST HEREIN); AND

     2. IF THIS  CERTIFICATE  (OR ANY  INTEREST  HEREIN) IS  ACQUIRED OR HELD IN
VIOLATION OF THE PROVISIONS OF THE PRECEDING PARAGRAPH,  THEN THE LAST PRECEDING
TRANSFEREE THAT EITHER (I) IS NOT A PLAN INVESTOR, (II) IS A COMPLYING INSURANCE
COMPANY OR (III) ACQUIRED THIS  CERTIFICATE AT A TIME WHEN THIS  CERTIFICATE WAS


                                      A-16
<PAGE>

RATED  "BBB-"  OR  BETTER  (OR ITS  EQUIVALENT)  BY AT LEAST  ONE OF THE  RATING
AGENCIES  SHALL BE RESTORED,  TO THE EXTENT  PERMITTED BY LAW, TO ALL RIGHTS AND
OBLIGATIONS AS BENEFICIAL HOLDER THEREOF  RETROACTIVE TO THE DATE OF TRANSFER OF
THIS CERTIFICATE BY SUCH PRECEDING TRANSFEREE. NEITHER THE TRUST NOR THE TRUSTEE
SHALL BE UNDER ANY  LIABILITY  TO ANY PERSON FOR MAKING ANY PAYMENTS DUE ON THIS
CERTIFICATE TO SUCH PRECEDING TRANSFEREE.

     ANY  PURPORTED  BENEFICIAL  HOLDER  WHOSE  ACQUISITION  OR  HOLDING OF THIS
CERTIFICATE (OR INTEREST  HEREIN) WAS EFFECTED IN VIOLATION OF THE  RESTRICTIONS
IN SECTION  5.01(g) OF THE POOLING  AGREEMENT  SHALL INDEMNIFY AND HOLD HARMLESS
THE COMPANY,  THE TRUSTEE,  THE MASTER  SERVICER,  THE TRUST AND THE UNDERWRITER
FROM AND AGAINST ANY AND ALL LIABILITIES,  CLAIMS, COSTS OR EXPENSES INCURRED BY
SUCH PARTIES AS A RESULT OF SUCH ACQUISITION OR HOLDING.

     The Class B-1  Certificates  will be subordinate in right of payment to and
provide credit support to certain Classes of  Certificates,  as described in the
Pooling Agreement.



        Series 2004-S1        Portion of the Class B-1 Principal Balance as of
                              the Cut-Off Date Evidenced by this Certificate:
                              $5,256,000.00


Class B-1 Certificate Interest Rate: Variable

Cut-Off Date: February 1, 2004

First Distribution Date: March 25, 2004

Last Scheduled Distribution Date: March 25, 2034

Class B-1 Principal Balance
as of the Cut-Off Date: $5,256,000.00

                                                    Cede & Co.
                                                 Registered Owner



                                      A-17
<PAGE>


                                                       Exhibit A
                                                       CUSIP 92922F MH 8

                     WaMu MORTGAGE PASS-THROUGH CERTIFICATE

                                    Class B-2

     Evidencing  a  beneficial  interest  in a  pool  of  assets  consisting  of
beneficial  interests  in  another  pool  of  assets  consisting  of  beneficial
interests  in  another  pool  of  assets  consisting  of,  among  other  things,
conventional one- to four-family mortgage loans formed and administered by

                   WASHINGTON MUTUAL MORTGAGE SECURITIES CORP.

     This  Certificate  is issued  by WaMu  Mortgage  Pass-Through  Certificates
Series  2004-S1  Trust.  This  Certificate  represents  ownership  of a "regular
interest" in a "real  estate  mortgage  investment  conduit," as those terms are
defined in Sections 860G and 860D, respectively, of the Internal Revenue Code of
1986, as amended. The issue date of this Certificate is February 24, 2004.

     Unless this Certificate is presented by an authorized representative of The
Depository Trust Company, a New York corporation  ("DTC"), to the Company or its
agent for registration of transfer,  exchange,  or payment,  and any Certificate
issued  is  registered  in the  name of  Cede & Co.  or  such  other  name as is
requested  by an  authorized  representative  of DTC (and any payment is made to
Cede  &  Co.  or  to  such  other  entity  as  is  requested  by  an  authorized
representative  of DTC),  ANY TRANSFER,  PLEDGE OR OTHER USE HEREOF FOR VALUE OR
OTHERWISE  BY OR TO ANY PERSON IS  WRONGFUL  inasmuch  as the  registered  owner
hereof, Cede & Co., has an interest herein.

     NO TRANSFER OF THIS CLASS B-2  CERTIFICATE  WILL BE MADE UNLESS THE TRUSTEE
HAS  RECEIVED  (I) AN  OFFICER'S  CERTIFICATE  IN THE FORM  DESCRIBED IN SECTION
5.01(g) OF THE POOLING  AGREEMENT  AND (II) IF SO  INDICATED  IN SUCH  OFFICER'S
CERTIFICATE,  AN  OPINION  OF COUNSEL  ACCEPTABLE  TO AND IN FORM AND  SUBSTANCE
SATISFACTORY  TO THE TRUSTEE AND THE COMPANY TO THE EFFECT THAT THE PURCHASE AND
HOLDING OF THIS  CERTIFICATE  ARE  PERMISSIBLE  UNDER  APPLICABLE  LAW, WILL NOT
CONSTITUTE OR RESULT IN A NON-EXEMPT PROHIBITED TRANSACTION UNDER SECTION 406 OF
ERISA OR SECTION 4975 OF THE CODE, AND WILL NOT SUBJECT THE TRUST,  THE TRUSTEE,
THE MASTER  SERVICER OR THE COMPANY TO ANY  OBLIGATION  OR LIABILITY  (INCLUDING
OBLIGATIONS  OR  LIABILITIES  UNDER  SECTION 406 OF ERISA OR SECTION 4975 OF THE
CODE) IN ADDITION TO THOSE UNDERTAKEN IN THE POOLING AGREEMENT, WHICH OPINION OF
COUNSEL SHALL NOT BE AN EXPENSE OF THE TRUST,  THE TRUSTEE,  THE MASTER SERVICER
OR THE COMPANY.

     NOTWITHSTANDING  THE FOREGOING  PARAGRAPH,  WITH RESPECT TO THE TRANSFER OF
THIS CLASS B-2 CERTIFICATE TO DTC OR ANY OTHER CLEARING AGENCY OR ANY SUBSEQUENT
TRANSFER OF ANY INTEREST IN THIS  CERTIFICATE FOR SO LONG AS THIS CERTIFICATE IS
HELD BY DTC OR ANY OTHER CLEARING AGENCY, (I) AN OFFICER'S  CERTIFICATE (AND, IF
APPLICABLE,  A BENEFIT PLAN OPINION),  AS DESCRIBED IN THE FOREGOING  PARAGRAPH,
SHALL NOT BE REQUIRED, AND (II) THE FOLLOWING CONDITIONS SHALL APPLY:

     1. ANY TRANSFEREE OF THIS CERTIFICATE  WILL BE DEEMED TO HAVE  REPRESENTED,
BY VIRTUE  OF ITS  ACQUISITION  OR  HOLDING  OF THIS  CERTIFICATE  (OR  INTEREST
HEREIN),  THAT EITHER (A) SUCH  TRANSFEREE  IS NOT AN EMPLOYEE  BENEFIT OR OTHER
PLAN SUBJECT TO THE PROHIBITED  TRANSACTION  PROVISIONS OF ERISA OR SECTION 4975
OF THE CODE, OR ANY PERSON (INCLUDING AN INVESTMENT  MANAGER,  A NAMED FIDUCIARY
OR A TRUSTEE OF ANY SUCH PLAN) ACTING,  DIRECTLY OR INDIRECTLY,  ON BEHALF OF OR
PURCHASING  THIS  CERTIFICATE  WITH  "PLAN  ASSETS"  OF ANY  SUCH  PLAN (A "PLAN
INVESTOR"),  (B) SUCH TRANSFEREE IS AN INSURANCE COMPANY, THE SOURCE OF FUNDS TO
BE USED BY IT TO  ACQUIRE  OR HOLD THIS  CERTIFICATE  IS AN  "INSURANCE  COMPANY
GENERAL   ACCOUNT"  (WITHIN  THE  MEANING  OF  DEPARTMENT  OF  LABOR  PROHIBITED
TRANSACTION CLASS EXEMPTION ("PTCE") 95-60), AND THE CONDITIONS IN SECTION I AND
III OF PTCE 95-60 HAVE BEEN  SATISFIED  (EACH ENTITY THAT  SATISFIES THIS CLAUSE
(B), A "COMPLYING  INSURANCE  COMPANY") OR (C) THIS CERTIFICATE WAS RATED "BBB-"
OR BETTER (OR ITS EQUIVALENT) BY AT LEAST ONE OF THE RATING AGENCIES AT THE TIME
OF SUCH TRANSFEREE'S ACQUISITION OF THIS CERTIFICATE (OR INTEREST HEREIN); AND

     2. IF THIS  CERTIFICATE  (OR ANY  INTEREST  HEREIN) IS  ACQUIRED OR HELD IN
VIOLATION OF THE PROVISIONS OF THE PRECEDING PARAGRAPH,  THEN THE LAST PRECEDING
TRANSFEREE THAT EITHER (I) IS NOT A PLAN INVESTOR, (II) IS A COMPLYING INSURANCE
COMPANY OR (III) ACQUIRED THIS  CERTIFICATE AT A TIME WHEN THIS  CERTIFICATE WAS
RATED  "BBB-"  OR  BETTER  (OR ITS  EQUIVALENT)  BY AT LEAST  ONE OF THE  RATING
AGENCIES  SHALL BE RESTORED,  TO THE EXTENT  PERMITTED BY LAW, TO ALL RIGHTS AND
OBLIGATIONS AS BENEFICIAL HOLDER THEREOF  RETROACTIVE TO THE DATE OF TRANSFER OF


                                      A-18
<PAGE>

     THIS  CERTIFICATE BY SUCH PRECEDING  TRANSFEREE.  NEITHER THE TRUST NOR THE
TRUSTEE  SHALL BE UNDER ANY  LIABILITY TO ANY PERSON FOR MAKING ANY PAYMENTS DUE
ON THIS CERTIFICATE TO SUCH PRECEDING TRANSFEREE.

     ANY  PURPORTED  BENEFICIAL  HOLDER  WHOSE  ACQUISITION  OR  HOLDING OF THIS
CERTIFICATE (OR INTEREST  HEREIN) WAS EFFECTED IN VIOLATION OF THE  RESTRICTIONS
IN SECTION  5.01(g) OF THE POOLING  AGREEMENT  SHALL INDEMNIFY AND HOLD HARMLESS
THE COMPANY,  THE TRUSTEE,  THE MASTER  SERVICER,  THE TRUST AND THE UNDERWRITER
FROM AND AGAINST ANY AND ALL LIABILITIES,  CLAIMS, COSTS OR EXPENSES INCURRED BY
SUCH PARTIES AS A RESULT OF SUCH ACQUISITION OR HOLDING.

     The Class B-2  Certificates  will be subordinate in right of payment to and
provide credit support to certain Classes of  Certificates,  as described in the
Pooling Agreement.

        Series 2004-S1        Portion of the Class B-2 Principal Balance as of
                              the Cut-Off Date Evidenced by this Certificate:
                              $2,252,000.00




Class B-2 Certificate Interest Rate: Variable

Cut-Off Date: February 1, 2004

First Distribution Date: March 25, 2004

Last Scheduled Distribution Date: March 25, 2034

Class B-2 Principal Balance
as of the Cut-Off Date: $2,252,000.00


                                   Cede & Co.
                                Registered Owner





                                      A-19
<PAGE>



                                                           Exhibit A
                                                           CUSIP 92922F MJ 4


                     WaMu MORTGAGE PASS-THROUGH CERTIFICATE

                                    Class B-3

     Evidencing  a  beneficial  interest  in a  pool  of  assets  consisting  of
beneficial  interests  in  another  pool  of  assets  consisting  of  beneficial
interests  in  another  pool  of  assets  consisting  of,  among  other  things,
conventional one- to four-family mortgage loans formed and administered by

                   WASHINGTON MUTUAL MORTGAGE SECURITIES CORP.

     This  Certificate  is issued  by WaMu  Mortgage  Pass-Through  Certificates
Series  2004-S1  Trust.  This  Certificate  represents  ownership  of a "regular
interest" in a "real  estate  mortgage  investment  conduit," as those terms are
defined in Sections 860G and 860D, respectively, of the Internal Revenue Code of
1986, as amended. The issue date of this Certificate is February 24, 2004.

     Unless this Certificate is presented by an authorized representative of The
Depository Trust Company, a New York corporation  ("DTC"), to the Company or its
agent for registration of transfer,  exchange,  or payment,  and any Certificate
issued  is  registered  in the  name of  Cede & Co.  or  such  other  name as is
requested  by an  authorized  representative  of DTC (and any payment is made to
Cede  &  Co.  or  to  such  other  entity  as  is  requested  by  an  authorized
representative  of DTC),  ANY TRANSFER,  PLEDGE OR OTHER USE HEREOF FOR VALUE OR
OTHERWISE  BY OR TO ANY PERSON IS  WRONGFUL  inasmuch  as the  registered  owner
hereof, Cede & Co., has an interest herein.

     NO TRANSFER OF THIS CLASS B-3  CERTIFICATE  WILL BE MADE UNLESS THE TRUSTEE
HAS  RECEIVED  (I) AN  OFFICER'S  CERTIFICATE  IN THE FORM  DESCRIBED IN SECTION
5.01(g) OF THE POOLING  AGREEMENT  AND (II) IF SO  INDICATED  IN SUCH  OFFICER'S
CERTIFICATE,  AN  OPINION  OF COUNSEL  ACCEPTABLE  TO AND IN FORM AND  SUBSTANCE
SATISFACTORY  TO THE TRUSTEE AND THE COMPANY TO THE EFFECT THAT THE PURCHASE AND
HOLDING OF THIS  CERTIFICATE  ARE  PERMISSIBLE  UNDER  APPLICABLE  LAW, WILL NOT
CONSTITUTE OR RESULT IN A NON-EXEMPT PROHIBITED TRANSACTION UNDER SECTION 406 OF
ERISA OR SECTION 4975 OF THE CODE, AND WILL NOT SUBJECT THE TRUST,  THE TRUSTEE,
THE MASTER  SERVICER OR THE COMPANY TO ANY  OBLIGATION  OR LIABILITY  (INCLUDING
OBLIGATIONS  OR  LIABILITIES  UNDER  SECTION 406 OF ERISA OR SECTION 4975 OF THE
CODE) IN ADDITION TO THOSE UNDERTAKEN IN THE POOLING AGREEMENT, WHICH OPINION OF
COUNSEL SHALL NOT BE AN EXPENSE OF THE TRUST,  THE TRUSTEE,  THE MASTER SERVICER
OR THE COMPANY.

     NOTWITHSTANDING  THE FOREGOING  PARAGRAPH,  WITH RESPECT TO THE TRANSFER OF
THIS CLASS B-3 CERTIFICATE TO DTC OR ANY OTHER CLEARING AGENCY OR ANY SUBSEQUENT
TRANSFER OF ANY INTEREST IN THIS  CERTIFICATE FOR SO LONG AS THIS CERTIFICATE IS
HELD BY DTC OR ANY OTHER CLEARING AGENCY, (I) AN OFFICER'S  CERTIFICATE (AND, IF
APPLICABLE,  A BENEFIT PLAN OPINION),  AS DESCRIBED IN THE FOREGOING  PARAGRAPH,
SHALL NOT BE REQUIRED, AND (II) THE FOLLOWING CONDITIONS SHALL APPLY:

     1. ANY TRANSFEREE OF THIS CERTIFICATE  WILL BE DEEMED TO HAVE  REPRESENTED,
BY VIRTUE  OF ITS  ACQUISITION  OR  HOLDING  OF THIS  CERTIFICATE  (OR  INTEREST
HEREIN),  THAT EITHER (A) SUCH  TRANSFEREE  IS NOT AN EMPLOYEE  BENEFIT OR OTHER
PLAN SUBJECT TO THE PROHIBITED  TRANSACTION  PROVISIONS OF ERISA OR SECTION 4975
OF THE CODE, OR ANY PERSON (INCLUDING AN INVESTMENT  MANAGER,  A NAMED FIDUCIARY
OR A TRUSTEE OF ANY SUCH PLAN) ACTING,  DIRECTLY OR INDIRECTLY,  ON BEHALF OF OR
PURCHASING  THIS  CERTIFICATE  WITH  "PLAN  ASSETS"  OF ANY  SUCH  PLAN (A "PLAN
INVESTOR"),  (B) SUCH TRANSFEREE IS AN INSURANCE COMPANY, THE SOURCE OF FUNDS TO
BE USED BY IT TO  ACQUIRE  OR HOLD THIS  CERTIFICATE  IS AN  "INSURANCE  COMPANY
GENERAL   ACCOUNT"  (WITHIN  THE  MEANING  OF  DEPARTMENT  OF  LABOR  PROHIBITED
TRANSACTION CLASS EXEMPTION ("PTCE") 95-60), AND THE CONDITIONS IN SECTION I AND
III OF PTCE 95-60 HAVE BEEN  SATISFIED  (EACH ENTITY THAT  SATISFIES THIS CLAUSE
(B), A "COMPLYING  INSURANCE  COMPANY") OR (C) THIS CERTIFICATE WAS RATED "BBB-"
OR BETTER (OR ITS EQUIVALENT) BY AT LEAST ONE OF THE RATING AGENCIES AT THE TIME
OF SUCH TRANSFEREE'S ACQUISITION OF THIS CERTIFICATE (OR INTEREST HEREIN); AND

     2. IF THIS  CERTIFICATE  (OR ANY  INTEREST  HEREIN) IS  ACQUIRED OR HELD IN
VIOLATION OF THE PROVISIONS OF THE PRECEDING PARAGRAPH,  THEN THE LAST PRECEDING
TRANSFEREE THAT EITHER (I) IS NOT A PLAN INVESTOR, (II) IS A COMPLYING INSURANCE
COMPANY OR (III) ACQUIRED THIS  CERTIFICATE AT A TIME WHEN THIS  CERTIFICATE WAS
RATED  "BBB-"  OR  BETTER  (OR ITS  EQUIVALENT)  BY AT LEAST  ONE OF THE  RATING
AGENCIES  SHALL BE RESTORED,  TO THE EXTENT  PERMITTED BY LAW, TO ALL RIGHTS AND


                                      A-20
<PAGE>

OBLIGATIONS AS BENEFICIAL HOLDER THEREOF  RETROACTIVE TO THE DATE OF TRANSFER OF
THIS CERTIFICATE BY SUCH PRECEDING TRANSFEREE. NEITHER THE TRUST NOR THE TRUSTEE
SHALL BE UNDER ANY  LIABILITY  TO ANY PERSON FOR MAKING ANY PAYMENTS DUE ON THIS
CERTIFICATE TO SUCH PRECEDING TRANSFEREE.

     ANY  PURPORTED  BENEFICIAL  HOLDER  WHOSE  ACQUISITION  OR  HOLDING OF THIS
CERTIFICATE (OR INTEREST  HEREIN) WAS EFFECTED IN VIOLATION OF THE  RESTRICTIONS
IN SECTION  5.01(g) OF THE POOLING  AGREEMENT  SHALL INDEMNIFY AND HOLD HARMLESS
THE COMPANY,  THE TRUSTEE,  THE MASTER  SERVICER,  THE TRUST AND THE UNDERWRITER
FROM AND AGAINST ANY AND ALL LIABILITIES,  CLAIMS, COSTS OR EXPENSES INCURRED BY
SUCH PARTIES AS A RESULT OF SUCH ACQUISITION OR HOLDING.

     The Class B-3  Certificates  will be subordinate in right of payment to and
provide credit support to certain Classes of  Certificates,  as described in the
Pooling Agreement.



        Series 2004-S1      Portion of the Class B-3 Principal Balance as of
                            the Cut-Off Date Evidenced by this Certificate:
                            $1,502,000.00


Class B-3 Certificate Interest Rate: Variable

Cut-Off Date: February 1, 2004

First Distribution Date: March 25, 2004

Last Scheduled Distribution Date: March 25, 2034

Class B-3 Principal Balance
as of the Cut-Off Date: $1,502,000.00

                                   Cede & Co.
                                Registered Owner



                                      A-21
<PAGE>


                                                        Exhibit A
                                                        CUSIP 92922F LN 6

                     WaMu MORTGAGE PASS-THROUGH CERTIFICATE

                                    Class B-4

     Evidencing  a  beneficial  interest  in a  pool  of  assets  consisting  of
beneficial  interests  in  another  pool  of  assets  consisting  of  beneficial
interests  in  another  pool  of  assets  consisting  of,  among  other  things,
conventional one- to four-family mortgage loans formed and administered by

                   WASHINGTON MUTUAL MORTGAGE SECURITIES CORP.

     This  Certificate  is issued  by WaMu  Mortgage  Pass-Through  Certificates
Series  2004-S1  Trust.  This  Certificate  represents  ownership  of a "regular
interest" in a "real  estate  mortgage  investment  conduit," as those terms are
defined in Sections 860G and 860D, respectively, of the Internal Revenue Code of
1986, as amended. The issue date of this Certificate is February 24, 2004.

     NO TRANSFER OF THIS CLASS B-4  CERTIFICATE  WILL BE MADE UNLESS THE TRUSTEE
HAS  RECEIVED  (I) AN  OFFICER'S  CERTIFICATE  IN THE FORM  DESCRIBED IN SECTION
5.01(d) OF THE POOLING  AGREEMENT  AND (II) IF SO  INDICATED  IN SUCH  OFFICER'S
CERTIFICATE,  AN  OPINION  OF COUNSEL  ACCEPTABLE  TO AND IN FORM AND  SUBSTANCE
SATISFACTORY  TO THE TRUSTEE AND THE COMPANY TO THE EFFECT THAT THE PURCHASE AND
HOLDING OF THIS  CERTIFICATE  ARE  PERMISSIBLE  UNDER  APPLICABLE  LAW, WILL NOT
CONSTITUTE OR RESULT IN A NON-EXEMPT PROHIBITED TRANSACTION UNDER SECTION 406 OF
ERISA OR SECTION 4975 OF THE CODE, AND WILL NOT SUBJECT THE TRUST,  THE TRUSTEE,
THE DELAWARE  TRUSTEE,  THE MASTER  SERVICER OR THE COMPANY TO ANY OBLIGATION OR
LIABILITY  (INCLUDING  OBLIGATIONS OR LIABILITIES  UNDER SECTION 406 OF ERISA OR
SECTION  4975 OF THE  CODE) IN  ADDITION  TO  THOSE  UNDERTAKEN  IN THE  POOLING
AGREEMENT,  WHICH OPINION OF COUNSEL  SHALL NOT BE AN EXPENSE OF THE TRUST,  THE
TRUSTEE, THE MASTER SERVICER OR THE COMPANY.

     THE SECURITIES  REPRESENTED BY THIS  CERTIFICATE  HAVE NOT BEEN  REGISTERED
UNDER THE SECURITIES  ACT OF 1933.  THESE  SECURITIES MAY NOT BE OFFERED,  SOLD,
TRANSFERRED,  PLEDGED OR  HYPOTHECATED  IN THE  ABSENCE OF  REGISTRATION  OR THE
AVAILABILITY OF AN EXEMPTION FROM REGISTRATION  UNDER THE SECURITIES ACT OF 1933
AND EXCEPT IN ACCORDANCE WITH SECTION 5.01(e) OF THE POOLING AGREEMENT.

     The Class B-4  Certificates  will be subordinate in right of payment to and
provide credit support to certain Classes of  Certificates,  as described in the
Pooling Agreement.


        Series 2004-S1   Portion of the Class B-4 Principal Balance as of
                         the Cut-Off Date Evidenced by this Certificate:
                         $750,000.00




Class B-4 Certificate Interest Rate: Variable

Cut-Off Date: February 1, 2004

First Distribution Date: March 25, 2004

Last Scheduled Distribution Date: March 25, 2034

Class B-4 Principal Balance
as of the Cut-Off Date: $750,000.00

                                ________________
                                Registered Owner



                                      A-22
<PAGE>


                                                             Exhibit A
                                                             CUSIP 92922F LP 1

                     WaMu MORTGAGE PASS-THROUGH CERTIFICATE

                                    Class B-5

     Evidencing  a  beneficial  interest  in a  pool  of  assets  consisting  of
beneficial  interests  in  another  pool  of  assets  consisting  of  beneficial
interests  in  another  pool  of  assets  consisting  of,  among  other  things,
conventional one- to four-family mortgage loans formed and administered by

                   WASHINGTON MUTUAL MORTGAGE SECURITIES CORP.

     This  Certificate  is issued  by WaMu  Mortgage  Pass-Through  Certificates
Series  2004-S1  Trust.  This  Certificate  represents  ownership  of a "regular
interest" in a "real  estate  mortgage  investment  conduit," as those terms are
defined in Sections 860G and 860D, respectively, of the Internal Revenue Code of
1986, as amended. The issue date of this Certificate is February 24, 2004.

     NO TRANSFER OF THIS CLASS B-5  CERTIFICATE  WILL BE MADE UNLESS THE TRUSTEE
HAS  RECEIVED  (I) AN  OFFICER'S  CERTIFICATE  IN THE FORM  DESCRIBED IN SECTION
5.01(d) OF THE POOLING  AGREEMENT  AND (II) IF SO  INDICATED  IN SUCH  OFFICER'S
CERTIFICATE,  AN  OPINION  OF COUNSEL  ACCEPTABLE  TO AND IN FORM AND  SUBSTANCE
SATISFACTORY  TO THE TRUSTEE AND THE COMPANY TO THE EFFECT THAT THE PURCHASE AND
HOLDING OF THIS  CERTIFICATE  ARE  PERMISSIBLE  UNDER  APPLICABLE  LAW, WILL NOT
CONSTITUTE OR RESULT IN A NON-EXEMPT PROHIBITED TRANSACTION UNDER SECTION 406 OF
ERISA OR SECTION 4975 OF THE CODE, AND WILL NOT SUBJECT THE TRUST,  THE TRUSTEE,
THE DELAWARE  TRUSTEE,  THE MASTER  SERVICER OR THE COMPANY TO ANY OBLIGATION OR
LIABILITY  (INCLUDING  OBLIGATIONS OR LIABILITIES  UNDER SECTION 406 OF ERISA OR
SECTION  4975 OF THE  CODE) IN  ADDITION  TO  THOSE  UNDERTAKEN  IN THE  POOLING
AGREEMENT,  WHICH OPINION OF COUNSEL  SHALL NOT BE AN EXPENSE OF THE TRUST,  THE
TRUSTEE, THE MASTER SERVICER OR THE COMPANY.

     THE SECURITIES  REPRESENTED BY THIS  CERTIFICATE  HAVE NOT BEEN  REGISTERED
UNDER THE SECURITIES  ACT OF 1933.  THESE  SECURITIES MAY NOT BE OFFERED,  SOLD,
TRANSFERRED,  PLEDGED OR  HYPOTHECATED  IN THE  ABSENCE OF  REGISTRATION  OR THE
AVAILABILITY OF AN EXEMPTION FROM REGISTRATION  UNDER THE SECURITIES ACT OF 1933
AND EXCEPT IN ACCORDANCE WITH SECTION 5.01(e) OF THE POOLING AGREEMENT.

     The Class B-5  Certificates  will be subordinate in right of payment to and
provide credit support to certain Classes of  Certificates,  as described in the
Pooling Agreement.



        Series 2004-S1       Portion of the Class B-5 Principal Balance as of
                             the Cut-Off Date Evidenced by this Certificate:
                             $751,000.00


Class B-5 Certificate Interest Rate: Variable

Cut-Off Date: February 1, 2004

First Distribution Date: March 25, 2004

Last Scheduled Distribution Date: March 25, 2034

Class B-5 Principal Balance
as of the Cut-Off Date: $751,000.00
                                ________________
                                Registered Owner





                                      A-23
<PAGE>


                                                     Exhibit A
                                                     CUSIP 92922F LQ 9


                     WaMu MORTGAGE PASS-THROUGH CERTIFICATE

                                    Class B-6

     Evidencing  a  beneficial  interest  in a  pool  of  assets  consisting  of
beneficial  interests  in  another  pool  of  assets  consisting  of  beneficial
interests  in  another  pool  of  assets  consisting  of,  among  other  things,
conventional one- to four-family mortgage loans formed and administered by

                   WASHINGTON MUTUAL MORTGAGE SECURITIES CORP.

     This  Certificate  is issued  by WaMu  Mortgage  Pass-Through  Certificates
Series  2004-S1  Trust.  This  Certificate  represents  ownership  of a "regular
interest" in a "real  estate  mortgage  investment  conduit," as those terms are
defined in Sections 860G and 860D, respectively, of the Internal Revenue Code of
1986, as amended. The issue date of this Certificate is February 24, 2004.

     NO TRANSFER OF THIS CLASS B-6  CERTIFICATE  WILL BE MADE UNLESS THE TRUSTEE
HAS  RECEIVED  (I) AN  OFFICER'S  CERTIFICATE  IN THE FORM  DESCRIBED IN SECTION
5.01(d) OF THE POOLING  AGREEMENT  AND (II) IF SO  INDICATED  IN SUCH  OFFICER'S
CERTIFICATE,  AN  OPINION  OF COUNSEL  ACCEPTABLE  TO AND IN FORM AND  SUBSTANCE
SATISFACTORY  TO THE TRUSTEE AND THE COMPANY TO THE EFFECT THAT THE PURCHASE AND
HOLDING OF THIS  CERTIFICATE  ARE  PERMISSIBLE  UNDER  APPLICABLE  LAW, WILL NOT
CONSTITUTE OR RESULT IN A NON-EXEMPT PROHIBITED TRANSACTION UNDER SECTION 406 OF
ERISA OR SECTION 4975 OF THE CODE, AND WILL NOT SUBJECT THE TRUST,  THE TRUSTEE,
THE DELAWARE  TRUSTEE,  THE MASTER  SERVICER OR THE COMPANY TO ANY OBLIGATION OR
LIABILITY  (INCLUDING  OBLIGATIONS OR LIABILITIES  UNDER SECTION 406 OF ERISA OR
SECTION  4975 OF THE  CODE) IN  ADDITION  TO  THOSE  UNDERTAKEN  IN THE  POOLING
AGREEMENT,  WHICH OPINION OF COUNSEL  SHALL NOT BE AN EXPENSE OF THE TRUST,  THE
TRUSTEE, THE MASTER SERVICER OR THE COMPANY.

     THE SECURITIES  REPRESENTED BY THIS  CERTIFICATE  HAVE NOT BEEN  REGISTERED
UNDER THE SECURITIES  ACT OF 1933.  THESE  SECURITIES MAY NOT BE OFFERED,  SOLD,
TRANSFERRED,  PLEDGED OR  HYPOTHECATED  IN THE  ABSENCE OF  REGISTRATION  OR THE
AVAILABILITY OF AN EXEMPTION FROM REGISTRATION  UNDER THE SECURITIES ACT OF 1933
AND EXCEPT IN ACCORDANCE WITH SECTION 5.01(e) OF THE POOLING AGREEMENT.

     The Class B-6  Certificates  will be subordinate in right of payment to and
provide credit support to certain Classes of  Certificates,  as described in the
Pooling Agreement.



        Series 2004-S1       Portion of the Class B-6 Principal Balance as of
                             the Cut-Off Date Evidenced by this Certificate:
                             $751,346.35


Class B-6 Certificate Interest Rate: Variable

Cut-Off Date: February 1, 2004

First Distribution Date: March 25, 2004

Last Scheduled Distribution Date: March 25, 2034

Class B-6 Principal Balance
as of the Cut-Off Date: $751,346.35

                                                 ________________
                                                 Registered Owner




                                      A-24
<PAGE>

                                                      Exhibit B
                                                      CUSIP 92922F MK 1


                     WaMu MORTGAGE PASS-THROUGH CERTIFICATE

                                     Class R

     Evidencing a Percentage Interest in certain distributions with respect to a
pool of conventional one- to four-family  mortgage loans formed and administered
by

                   WASHINGTON MUTUAL MORTGAGE SECURITIES CORP.

     ANY RESALE,  TRANSFER OR OTHER  DISPOSITION OF THIS CERTIFICATE MAY BE MADE
ONLY IF THE PROPOSED TRANSFEREE PROVIDES A TRANSFER AFFIDAVIT TO THE COMPANY AND
THE TRUSTEE THAT (1) SUCH  TRANSFEREE IS NOT EITHER (A) THE UNITED  STATES,  ANY
STATE  OR  POLITICAL   SUBDIVISION   THEREOF,   ANY  FOREIGN   GOVERNMENT,   ANY
INTERNATIONAL  ORGANIZATION,  OR ANY  AGENCY  OR  INSTRUMENTALITY  OF ANY OF THE
FOREGOING,  (B) ANY ORGANIZATION (OTHER THAN A COOPERATIVE  DESCRIBED IN SECTION
521 OF THE CODE)  WHICH IS EXEMPT  FROM THE TAX IMPOSED BY CHAPTER 1 OF THE CODE
UNLESS  SUCH  ORGANIZATION  IS SUBJECT TO THE TAX  IMPOSED BY SECTION 511 OF THE
CODE, (C) ANY ORGANIZATION  DESCRIBED IN SECTION  1381(a)(2)(C) OF THE CODE (ANY
SUCH  PERSON  DESCRIBED  IN  THE  FOREGOING  CLAUSES  (A),  (B),  OR  (C)  BEING
HEREINAFTER REFERRED TO AS A "DISQUALIFIED ORGANIZATION"),  OR (D) AN AGENT OF A
DISQUALIFIED  ORGANIZATION  AND (2) NO PURPOSE OF SUCH TRANSFER IS TO ENABLE THE
TRANSFER TO IMPEDE THE  ASSESSMENT OR COLLECTION  OF TAX. SUCH  AFFIDAVIT  SHALL
INCLUDE CERTAIN  REPRESENTATIONS  AS TO THE FINANCIAL  CONDITION OF THE PROPOSED
TRANSFEREE.  NOTWITHSTANDING THE REGISTRATION IN THE CERTIFICATE REGISTER OF ANY
TRANSFER,   SALE  OR  OTHER  DISPOSITION  OF  THIS  CLASS  R  CERTIFICATE  TO  A
DISQUALIFIED  ORGANIZATION  OR AN AGENT  OF A  DISQUALIFIED  ORGANIZATION,  SUCH
REGISTRATION  SHALL BE DEEMED TO BE OF NO LEGAL FORCE OR EFFECT  WHATSOEVER  AND
SUCH  PERSON  SHALL  NOT BE  DEEMED TO BE A  CERTIFICATEHOLDER  FOR ANY  PURPOSE
HEREUNDER,  INCLUDING,  BUT NOT LIMITED TO, THE RECEIPT OF DISTRIBUTIONS ON THIS
CERTIFICATE.  EACH  HOLDER  OF A  CLASS  R  CERTIFICATE  BY  ACCEPTANCE  OF THIS
CERTIFICATE  SHALL  BE  DEEMED  TO  HAVE  CONSENTED  TO THE  PROVISIONS  OF THIS
PARAGRAPH.


     IN THE CASE OF ANY CLASS R CERTIFICATE  PRESENTED FOR  REGISTRATION  IN THE
NAME OF ANY PERSON,  THE TRUSTEE SHALL REQUIRE (I) AN OFFICER'S  CERTIFICATE  IN
THE FORM  DESCRIBED IN SECTION  5.01(d) OF THE POOLING  AGREEMENT AND (II) IF SO
INDICATED IN SUCH OFFICER'S CERTIFICATE, AN OPINION OF COUNSEL ACCEPTABLE TO AND
IN FORM AND SUBSTANCE  SATISFACTORY TO THE TRUSTEE AND THE COMPANY TO THE EFFECT
THAT THE PURCHASE AND HOLDING OF A CLASS R  CERTIFICATE  ARE  PERMISSIBLE  UNDER
APPLICABLE  LAW,  WILL NOT  CONSTITUTE  OR  RESULT  IN A  NON-EXEMPT  PROHIBITED
TRANSACTION UNDER SECTION 406 OF THE EMPLOYEE  RETIREMENT INCOME SECURITY ACT OF
1974, AS AMENDED ("ERISA"), OR SECTION 4975 OF THE CODE AND WILL NOT SUBJECT THE
TRUST,  THE TRUSTEE,  THE MASTER  SERVICER OR THE COMPANY TO ANY  OBLIGATION  OR
LIABILITY  (INCLUDING  OBLIGATIONS OR LIABILITIES  UNDER SECTION 406 OF ERISA OR
SECTION  4975 OF THE  CODE) IN  ADDITION  TO  THOSE  UNDERTAKEN  IN THE  POOLING
AGREEMENT,  WHICH OPINION OF COUNSEL  SHALL NOT BE AN EXPENSE OF THE TRUST,  THE
TRUSTEE, THE MASTER SERVICER OR THE COMPANY.


     This  Certificate  is issued  by WaMu  Mortgage  Pass-Through  Certificates
Series  2004-S1  Trust.  Solely  for U.S.  federal  income  tax  purposes,  this
Certificate  represents "residual interests" in "real estate mortgage investment
conduits," as those terms are defined in Sections  860G and 860D,  respectively,
of the Internal Revenue Code of 1986, as amended.



        Series 2004-S1     Percentage  Interest  evidenced  by  this  Class R
                           Certificate in the  distributions  to be made with
                           respect to the Class R Certificates:
                           _______%


Class R Certificate Interest Rate: 5.500%.
Additionally the Class R Certificates are entitled
to Excess Liquidation Proceeds and the Residual
Distribution Amount as defined in the Pooling
Agreement.
Cut-Off Date: February 1, 2004
First Distribution Date: March 25, 2004
Last Scheduled Distribution Date: March 25, 2034
Class R Principal Balance as of the Cut-Off Date:
$100.00
                                  _____________
                                Registered Owner

                            Certificate No. _________



                                      B-1
<PAGE>


     This  Certificate  does not  represent  an  obligation  of or  interest  in
Washington  Mutual Mortgage  Securities Corp. or any of its affiliates.  Neither
this Certificate nor the underlying  Mortgage Loans are guaranteed by any agency
or instrumentality of the United States.

     This  certifies  that the  above-named  Registered  Owner is the registered
owner of certain  interests in (i) a pool of assets  ("REMIC I")  consisting of,
among  other  things,  conventional  one- to  four-family  mortgage  loans  (the
"Mortgage  Loans"),  formed  and  administered  by  Washington  Mutual  Mortgage
Securities Corp. (the "Company"), which term includes any successor entity under
the Pooling  Agreement  referred to below,  (ii) a pool of assets  ("REMIC  II")
consisting  of  interests  in REMIC I and (iii) a pool of assets  ("REMIC  III")
consisting  of  interests  in REMIC  II.  REMIC I,  REMIC II and  REMIC III were
created pursuant to a Pooling and Servicing  Agreement,  dated as of the Cut-Off
Date stated above (the "Pooling Agreement"),  among the Company, Citibank, N.A.,
as Trustee (the  "Trustee"),  and Christiana  Bank & Trust Company,  as Delaware
Trustee, a summary of certain of the pertinent  provisions of which is set forth
hereafter.  To the extent not defined herein,  the capitalized terms used herein
have the meanings  assigned in the Pooling  Agreement.  Nothing  herein shall be
deemed inconsistent with such meanings, and in the event of any conflict between
the Pooling Agreement and the terms of this  Certificate,  the Pooling Agreement
shall  control.  This  Certificate  is issued under and is subject to the terms,
provisions and conditions of the Pooling  Agreement,  to which Pooling Agreement
the Holder of this Certificate,  by virtue of the acceptance hereof, assents and
by which such Holder is bound.

     Distributions will be made, pursuant to the Pooling Agreement,  on the 25th
day of each month or, if such 25th day is not a Business  Day,  the Business Day
immediately  following  (the  "Distribution  Date"),  commencing  on  the  first
Distribution  Date specified above, to the Person in whose name this Certificate
is  registered  at the close of business on the last day (or if such last day is
not a Business Day, the Business Day immediately preceding such last day) of the
month immediately  preceding the month of such distribution (the "Record Date"),
to the extent of such  Certificateholder's  Percentage  Interest  represented by
this Certificate in the portions (if any) then distributable on the Certificates
of this  Class  of (i) the  REMIC  I  Available  Distribution  Amount  for  such
Distribution Date, as specified in Section 4.01 of the Pooling  Agreement,  (ii)
the REMIC II  Available  Distribution  Amount  for such  Distribution  Date,  as
specified  in  Section  4.04 of the  Pooling  Agreement  and (iii) the REMIC III
Available  Distribution  Amount for such  Distribution  Date,  as  specified  in
Section 4.05 of the Pooling Agreement.

     Distributions  on this  Certificate  will be  made by the  Trustee  by wire
transfer or check mailed to the address of the Person entitled thereto,  as such
name and address shall appear on the Certificate  Register.  Notwithstanding the
above, the final  distribution on this Certificate will be made after due notice
by the Trustee of the pendency of such  distribution and only upon  presentation
and surrender of this Certificate to the Certificate Registrar.

     Reference is hereby made to the further  provisions of this Certificate set
forth below,  which  further  provisions  shall for all  purposes  have the same
effect as if set forth at this place.

     Unless the certificate of authentication  hereon has been executed by or on
behalf  of the  Trustee,  by manual  signature,  this  Certificate  shall not be
entitled to any benefit under the Pooling Agreement or be valid for any purpose.


                                      B-2
<PAGE>
     IN  WITNESS  WHEREOF,  the Trust has  caused  this  Certificate  to be duly
executed.

                        WaMu MORTGAGE PASS-THROUGH CERTIFICATES
                        SERIES 2004-S1 TRUST



                        By:   CITIBANK, N.A., as Trustee



                              By:





                    (TRUSTEE'S CERTIFICATE OF AUTHENTICATION)

     This is one of the Certificates referred to in the within-mentioned Pooling
Agreement.

CITIBANK, N.A.,
as Trustee



By:

Dated:


                                      B-3
<PAGE>

                   WASHINGTON MUTUAL MORTGAGE SECURITIES CORP.
                     WaMu MORTGAGE PASS-THROUGH CERTIFICATE

     This  Certificate  is  one  of a  duly  authorized  issue  of  Certificates
designated as WaMu Mortgage  Pass-Through  Certificates  of the Series and Class
specified hereon (herein called the  "Certificates")  and  representing  certain
interests in REMIC I, REMIC II and REMIC III.

     The  Certificates do not represent an obligation of, or an interest in, the
Company  or any of its  affiliates  and are not  insured  or  guaranteed  by any
governmental agency. The Certificates are limited in right of payment to certain
collections  and  recoveries   respecting  the  Mortgage  Loans,   all  as  more
specifically set forth herein and in the Pooling  Agreement.  In the event funds
are advanced with respect to any Mortgage Loan,  such advance is reimbursable to
the Master  Servicer  from the related  recoveries on such Mortgage Loan or from
other cash deposited in the Certificate  Account to the extent that such advance
is not otherwise recoverable.

     As provided  in the Pooling  Agreement,  withdrawals  from the  Certificate
Account may be made from time to time for purposes other than  distributions  to
Certificateholders, such purposes including reimbursement to the Master Servicer
of advances made, or certain expenses incurred, by it.

     The Pooling Agreement  permits,  with certain  exceptions therein provided,
the amendment  thereof and the modification of the rights and obligations of the
Company and the rights of the Certificateholders  under the Pooling Agreement at
any time by the Company, the Master Servicer and the Trustee with the consent of
the Holders of the Certificates  evidencing Percentage Interests aggregating not
less than 66% of REMIC III. The Pooling  Agreement  also  permits the  amendment
thereof, in certain limited circumstances, without the consent of the Holders of
any of the Certificates.

     As  provided in the Pooling  Agreement  and subject to certain  limitations
therein  set forth,  the  transfer of this  Certificate  is  registrable  in the
Certificate  Register upon surrender of this  Certificate  for  registration  of
transfer at the offices of the Certificate Registrar or the office maintained by
the Trustee in the City and State of New York,  duly endorsed by, or accompanied
by an assignment  in the form below or other  written  instrument of transfer in
form satisfactory to the Trustee or any  Authenticating  Agent duly executed by,
the Holder hereof or such  Holder's  attorney  duly  authorized in writing,  and
thereupon one or more new  Certificates of Authorized  Denominations  evidencing
the same  Percentage  Interest  set  forth  hereinabove  will be  issued  to the
designated transferee or transferees.

     The  Certificates  are issuable  only as  registered  Certificates  without
coupons in  Authorized  Denominations  specified  in the Pooling  Agreement.  As
provided in the Pooling Agreement and subject to certain limitations therein set
forth,   Certificates  are  exchangeable  for  new  Certificates  of  Authorized
Denominations of like Certificate  Principal Balance or Percentage Interest,  as
applicable, as requested by the Holder surrendering the same.

     A  reasonable  service  charge  may be made  for any such  registration  of
transfer or exchange, and the Trustee may require payment of a sum sufficient to
cover any tax or other governmental charge payable in connection therewith.

     The Company, the Trustee and the Certificate Registrar and any agent of the
Company, the Trustee or the Certificate  Registrar may treat the Person in whose
name this  Certificate  is registered as the owner hereof for all purposes,  and
neither the Company, the Trustee,  the Certificate  Registrar nor any such agent
shall be affected by notice to the contrary.



                                      B-4
<PAGE>

     The  obligations  created by the Pooling  Agreement  and the Trust  created
thereby shall terminate upon (i) the later of the maturity or other  liquidation
(including  purchase by the Master Servicer) of the last Mortgage Loan remaining
in the Trust or the  disposition  of all property  acquired upon  foreclosure or
deed in lieu of  foreclosure  of any  Mortgage  Loan,  and (ii) the  payment  to
Certificateholders of all amounts held by the Trustee and required to be paid to
them  pursuant  to the Pooling  Agreement.  In the event that the Company or the
Master Servicer  purchases any Mortgage Loan pursuant to the Pooling  Agreement,
the Pooling  Agreement  generally  requires  that the Trustee  distribute to the
Certificateholders  in the  aggregate  an  amount  equal  to 100% of the  unpaid
Principal Balance of such Mortgage Loan, plus unpaid accrued interest thereon at
the  applicable  Pass-Through  Rate to the last day of the  month in which  such
purchase occurs. The Pooling Agreement permits, but does not require, the Master
Servicer  to  purchase  from the Trust all  Mortgage  Loans at the time  subject
thereto and all property  acquired in respect of any Mortgage  Loan upon payment
to the Certificateholders of the amounts specified in the Pooling Agreement. The
exercise of such right will effect early  retirement  of the  Certificates,  the
Master  Servicer's  right to purchase  being subject to the aggregate  Principal
Balance  of the  Mortgage  Loans at the time of  purchase  being  less  than the
Clean-Up  Call  Percentage of the  aggregate  Principal  Balance of the Mortgage
Loans as of the Cut-Off Date.




                                      B-5
<PAGE>

                                   ASSIGNMENT



     FOR VALUE  RECEIVED  the  undersigned  hereby  sell(s)  and  assign(s)  and
transfer(s)  unto ____________________________________________________________
(Please print or typewrite name and address,  including postal
zip code of assignee.  Please insert social security or other identifying number
of assignee.) the within WaMu Mortgage  Pass-Through  Certificate and hereby
irrevocably constitutes and appoints _________________________________________
Attorney to transfer said  Certificate on the  Certificate  Register,  with
full power of substitution in the premises.

Dated: ______________________ ________________________________________
                              Signature Guaranteed

    __________________________________________________________________________
    NOTICE: The signature to this  assignment  must  correspond  with the name
            as  written  upon  the  face of the  within  instrument  in  every
            particular,  without  alteration  or  enlargement  or  any  change
            whatever.  This  Certificate  does not  represent an obligation of
            or an interest in Washington  Mutual Mortgage  Securities Corp. or
            any  of  its   affiliates.   Neither  this   Certificate  nor  the
            underlying   Mortgage  Loans  are  guaranteed  by  any  agency  or
            instrumentality of the United States.





                                      B-6
<PAGE>

                                    Exhibit C

                                   [Reserved]


                                      C-1
<PAGE>

                                    Exhibit D


                             Mortgage Loan Schedule

     Copies of the Mortgage Loan Schedule (which has been intentionally omitted
from this filing) may be obtained from Washington Mutual Mortgage Securities
Corp. or Citibank, N.A. by contacting:


         in the case of Washington Mutual Mortgage Securities Corp.,

               Laura Kelsey
               Master Servicing Department
               Washington Mutual Mortgage Securities Corp.
               75 N. Fairway Drive, VHF2A01
               Vernon Hills, IL 60061
               Telephone: (847) 393-5198
               Facsimile: (847) 549-2997

          in the case of Citibank, N.A.,

               Karen Schluter
               Citibank, N.A.
               111 Wall Street
               14th Floor, Zone 3
               New York, New York  10005
               Telephone: (212) 657-7781
               Facsimile: (212) 657-4009



                                      D-1
<PAGE>

                                    Exhibit E



     This Selling and Servicing  Contract (this "Agreement") is made and entered
into by Washington  Mutual  Mortgage  Securities  Corp.  and its  successors and
assigns  ("Washington  Mutual Mortgage") and the entity identified below and its
successors and assigns (the "Company").


                                   WITNESSETH:

     WHEREAS,  this Company wishes to sell first lien residential mortgage loans
to, and service first lien residential  mortgage loans on behalf of,  Washington
Mutual Mortgage; and

     WHEREAS,  the Company  has  submitted a Seller  Application  to  Washington
Mutual  Mortgage  and has  been  approved  by  Washington  Mutual  Mortgage  for
participation in the Washington Mutual Mortgage Purchase Programs; and

     WHEREAS,  the Company has  received  and  reviewed  the  Washington  Mutual
Mortgage  Purchase  Programs Seller Guide (the "Seller  Guide"),  as well as the
Washington Mutual Mortgage  Servicing Guide (the "Servicing Guide" and, together
with the Seller Guide,  the "Guides"),  and understands each and every provision
thereof;

     NOW,  THEREFORE,  in  consideration  of the  premises  and  of  the  mutual
agreements herein  contained,  Washington Mutual Mortgage and the Company hereby
agree as follows:

     1. Guides. The Guides, which set forth the terms and conditions under which
Washington  Mutual  Mortgage  may  elect to  purchase  mortgage  loans  from the
Company,  and the Company shall service  mortgage  loans on behalf of Washington
Mutual Mortgage,  are a supplement to this Agreement and such Guides,  as may be
amended or supplemented  from time to time by Washington  Mutual  Mortgage,  are
incorporated  into this Agreement in full by reference and made a part hereof as
fully as if set forth at  length  herein.  All  capitalized  terms  used and not
defined herein have the meanings ascribed to them in the Guides.

     2.  Company's  Duties.  The  Company  shall  diligently  perform all duties
incident to the origination, sale and servicing of the mortgage loans subject to
this Agreement.  In the performance of its servicing  duties,  the Company shall
exercise the same degree of care it exercises when servicing  mortgage loans for
its own  account,  but in no event shall the Company  exercise  less care than a
reasonable  prudent  servicer  would exercise  under similar  circumstances.  In
addition,  the Company shall comply with all of the provisions of the Guides and
with all other requirements and instructions of Washington Mutual Mortgage.  The
Company  shall  perform  such duties at its sole  expense,  except as  otherwise
expressly provided in the Guides.

     3.  Representations,  Warranties and Covenants of the Company;  Remedies of
Washington  Mutual  Mortgage.  With  respect to each  mortgage  loan sold by the
Company to Washington  Mutual Mortgage  pursuant to the terms of this Agreement,
the Company shall make all of the representations,  warranties and covenants set
forth  in  the  Guide  and,   in  the  event  of  the  breach  of  any  of  such
representations, warranties and covenants, Washington Mutual Mortgage shall have
all of  the  remedies  available  at law or in  equity,  as  well  as all of the
remedies set forth in the Guide,  including,  but not limited to, repurchase and
indemnification.  The  representations  and warranties  made by the Company with


                                      E-1
<PAGE>

respect to any mortgage loan subject to this Agreement,  as well as the remedies
available to Washington Mutual Mortgage upon the breach thereof,  shall survive:
(a) any investigation regarding the mortgage loan conducted by Washington Mutual
Mortgage, its assignees or designees,  (b) the liquidation of the mortgage loan,
(c) the  purchase  of the  mortgage  loan by  Washington  Mutual  Mortgage,  its
assignee or designee, (d) the repurchase of the mortgage loan by the Company and
(e) the termination of this Agreement.

     4.  Compensation.  The  Company  shall  be  compensated  for  its  services
hereunder as specified in the Guides.

     5. No Assignment. This Agreement may not be assigned by the Company without
the prior written  consent of Washington  Mutual  Mortgage.  The Company  hereby
consents to the assignment by Washington  Mutual  Mortgage of all or any part of
its rights and obligations  under this Agreement to any affiliate  designated by
Washington  Mutual  Mortgage.  Any other transfer by Washington  Mutual Mortgage
will be allowed  and be  effective  upon  written  notice by  Washington  Mutual
Mortgage to the Company.

     6. Prior  Agreements.  This Agreement  supersedes any prior  agreements and
understandings  between Washington Mutual Mortgage and the Company governing the
subject matter hereof; provided, however, the Company shall not be released from
any  responsibility  or liability that may have arisen under such agreements and
understanding.

     7. Effective Date of Agreement. This Agreement is not effective until it is
executed  and  accepted  by  Washington  Mutual  Mortgage  at its home office in
Illinois.

     8. Notices. All notices, requests, demands or other communications that are
to be  given  under  this  Agreement  shall  be in  writing,  addressed  to  the
appropriate  parties,  and  shall  be sent by  certified  mail,  return  receipt
requested,  postage prepaid,  if to the Company, at the address below and, if to
Washington  Mutual  Mortgage,  to the  appropriate  address or facsimile  number
specified in the Guides. Any such notice, request, demand or other communication
shall be deemed effective upon receipt.

     9. Independent  Contractor.  At no time shall the Company represent that it
is acting as an agent,  partner or joint venturer of Washington Mutual Mortgage.
The Company shall at all times act as an independent contracting party.

     10. Amendment. This Agreement may not be amended or modified orally, and no
provision of this  Agreement may be waived or amended,  except in writing signed
by the party  against  whom  enforcement  is  sought.  Such a written  waiver or
amendment must expressly  reference this Agreement.  However, by their terms the
Guides may be amended or supplemented by Washington Mutual Mortgage from time to
time.  Any such  amendment(s)  to the Guides  shall be in writing and be binding
upon the parties hereto on and after the effective date specified therein.

     11. Miscellaneous.  This Agreement, including all documents incorporated by
reference  herein,  constitutes  the entire  understanding  between  the parties
hereto  and  supersedes  all  other  agreements,   covenants,   representations,
warranties,  understandings  and  communications  between the  parties,  whether
written  or  oral,  with  respect  to  the  transactions  contemplated  by  this
Agreement.  All section  headings  contained herein are for convenience only and
shall  not be  construed  as part  of  this  Agreement.  Any  provision  of this


                                      E-2
<PAGE>

Agreement that is prohibited or unenforceable  in any  jurisdiction  shall as to
such   jurisdiction  be  ineffective  to  the  extent  of  such  prohibition  or
unenforceability without invalidating the remaining portions hereof or affecting
the validity or enforceability of such provision in any other jurisdiction,  and
to this end,  the  provisions  hereof are  severable.  This  Agreement  shall be
governed by, and construed and enforced in accordance with,  applicable  federal
laws and laws of the State of  Illinois,  without  reference to conflict of laws
principles. This Agreement may be executed in one or more counterparts,  each of
which shall  constitute an original and all of which shall  constitute  the same
Agreement.

     IN WITNESS  WHEREOF,  the parties have  executed  this  Agreement by proper
officials duly  authorized on the dates  hereinafter  set forth.  This Agreement
shall take  effect as of the date of its  execution  in  original  or  facsimile
signature by a duly authorized officer of Washington Mutual Mortgage.


_______________________                 _______________________________
Name of the  Company                    Company  I.D.  Number
_______________________                 _______________________________
Type of organization                    Organized under laws of
____________________________            _____________________________________
Principal place of business:            street address, city, state, zip code
________________________________________________________
Typed name and title of the Company's authorized officer
_______________________________________________________  _______________________
Signature of the Company's authorized officer            Date

Agreed to and accepted by Washington Mutual Mortgage Securities Corp.
________________________________________________________________________________
Typed name and title of authorized representative
_______________________________________________________   ______________________
Signature of authorized representative                    Date



                                      E-3
<PAGE>

                                                                     Exhibit F


                       FORM OF TRANSFEROR CERTIFICATE FOR
                         JUNIOR SUBORDINATE CERTIFICATES


                                     [Date]

Citibank, N.A., as Trustee
111 Wall Street, 14th Floor, Zone 3
New York, New York 10005
Attn:  Structured Finance Group, Washington Mutual 2004-S1


Re:  Purchase of  Washington  Mutual  Mortgage  Securities  Corp.  WaMu Mortgage
     Pass-Through Certificates Series 2004-S1, Class [ ] (the "Certificates")

Ladies and Gentlemen:

     In connection  with our  disposition of the above  Certificates  we certify
that (a) we  understand  the  Certificates  have not been  registered  under the
Securities Act of 1933, as amended (the "Act") and are being disposed by us in a
transaction  that is exempt from the  registration  requirements of the Act, and
(b) we have not offered or sold any  certificates to, or solicited offers to buy
any Certificates  from, any person,  or otherwise  approached or negotiated with
any person with respect thereto, or taken any other action which would result in
a violation of Section 5 of the Act.



                                                      Very truly yours,

                                                      [Name of Transferor]



                                                      By:
                                                         Authorized Officer


                                      F-1
<PAGE>


                                    Exhibit G


                       FORM OF TRANSFEREE'S AGREEMENT FOR
                         JUNIOR SUBORDINATE CERTIFICATES

                                     [Date]

Citibank, N.A., as Trustee
111 Wall Street, 14th Floor, Zone 3
New York, New York 10005
Attn:  Structured Finance Group, Washington Mutual 2004-S1

Washington Mutual Mortgage Securities Corp.
75 N. Fairway Drive
Vernon Hills, Illinois  60061


     The undersigned (the  "Purchaser")  proposes to purchase  Washington Mutual
Mortgage  Securities  Corp.  WaMu  Mortgage  Pass-Through  Certificates,  Series
2004-S1,  Class [ ] (the "Purchased  Certificates")  in the principal  amount of
$______________.  In doing so, the Purchaser  hereby  acknowledges and agrees as
follows:

     Section 1. Definitions. Each capitalized term used herein and not otherwise
defined  herein  shall  have  the  meaning  ascribed  to it in the  Pooling  and
Servicing Agreement, dated as of February 1, 2004 (the "Pooling Agreement"),  by
and among Washington  Mutual Mortgage  Securities Corp.  ("Washington  Mutual"),
Citibank, N.A., as trustee (the "Trustee"), and Christiana Bank & Trust Company,
as Delaware  trustee,  of the Washington  Mutual Mortgage  Securities Corp. WaMu
Mortgage Pass-Through Certificates, Series 2004-S1.

     Section 2.  Representations and Warranties of the Purchaser.  In connection
with the proposed transfer,  the Purchaser represents and warrants to Washington
Mutual, the Trustee and the Trust that:

     (a) The Purchaser is duly organized,  validly existing and in good standing
under the laws of the  jurisdiction  in which the  Purchaser  is  organized,  is
authorized  to  invest in the  Purchased  Certificates,  and to enter  into this
Agreement, and duly executed and delivered this Agreement;

     (b) The  Purchaser  is acquiring  the  Purchased  Certificates  for its own
account as principal and not with a view to the distribution  thereof,  in whole
or in part;

     (c) The  Purchaser is an  "accredited  investor" as such term is defined in
paragraph (a)(1),  (a)(2), (a)(3), (a)(7) or (a)(8) of Section 501 of Regulation
D under the  Securities  Act of 1933,  as amended (the "Act"),  has knowledge of
financial and business matters and is capable of evaluating the merits and risks
of an investment in the  Purchased  Certificates;  the Purchaser has sought such
accounting,  legal and tax  advice  as it has  considered  necessary  to make an
informed  investment  decision;  and the  Purchaser is able to bear the economic
risk of an investment in the  Purchased  Certificates  and can afford a complete
loss of such investment;

     (d) The Purchaser is not affiliated with the Trustee;


<PAGE>

     (e) The Purchaser confirms that Washington Mutual has made available to the
Purchaser  the  opportunity  to ask  questions  of,  and  receive  answers  from
Washington Mutual concerning the trust created pursuant to the Pooling Agreement
(the "Trust"),  the purchase by the Purchaser of the Purchased  Certificates and
all matters  relating  thereto that Washington  Mutual  possesses or can acquire
without unreasonable effort or expense; and

     (f) If applicable, the Purchaser has complied, and will continue to comply,
with the guidelines established by Thrift Bulletin 13a issued April 23, 1998, by
the Office of Regulatory Activities of the Federal Home Loan Bank System.

     Section 3. Transfer of Purchased Certificates.

     (a) The Purchaser understands that the Purchased Certificates have not been
registered  under the Act, or any state securities laws and that no transfer may
be made unless the Purchased Certificates are registered under the Act and under
applicable state law or unless an exemption from registration is available.  The
Purchaser  further  understands that neither  Washington Mutual nor the Trust is
under any obligation to register the Purchased Certificates or make an exemption
available. In the event that such a transfer is to be made within two years from
the  Closing  Date  without  registration  under  the  Act or  applicable  state
securities  laws, (i) the Trustee shall require,  in order to assure  compliance
with such laws, that the Certificateholder's prospective transferee each certify
to Washington  Mutual, the Trustee and the Trust as to the factual basis for the
registration  or  qualification  exemption  relied upon, and (ii) the Trustee or
Washington  Mutual may require an Opinion of Counsel  that such  transfer may be
made  pursuant to an exemption  from the Act and state  securities  laws,  which
Opinion  of  Counsel  shall not be an  expense  of the  Trust,  the  Trustee  or
Washington Mutual. Any such  Certificateholder  desiring to effect such transfer
shall, and does hereby agree to, indemnify the Trust, the Trustee and Washington
Mutual against any liability that may result if the transfer is not so exempt or
is not made in accordance with such federal and state laws.

     (b) No  transfer  of a  Purchased  Certificate  shall  be made  unless  the
transferee  provides  Washington  Mutual and the Trustee with (i) a Transferee's
Agreement,  substantially  in the  form of  this  Agreement,  (ii) an  affidavit
substantially in the form of Exhibit N to the Pooling  Agreement and (iii) if so
indicated in such affidavit,  a Benefit Plan Opinion (as defined in Section 1.01
of the Pooling Agreement).

     (c) The  Purchaser  acknowledges  that its  Purchased  Certificates  bear a
legend setting forth the applicable restrictions on transfer.


<PAGE>

     IN WITNESS WHEREOF, the undersigned has caused this Agreement to be validly
executed by its duly authorized  representative as of the day and the year first
above written.

                                [Purchaser]



                                By:___________________
                                   Its:_______________


<PAGE>


                                                                    Exhibit H


                   FORM OF ADDITIONAL MATTER INCORPORATED INTO
       THE FORM OF THE CERTIFICATES (OTHER THAN THE CLASS R CERTIFICATES)

     This  Certificate  does not  represent  an  obligation  of or  interest  in
Washington  Mutual Mortgage  Securities Corp. or any of its affiliates.  Neither
this Certificate nor the underlying  Mortgage Loans are guaranteed by any agency
or instrumentality of the United States.

     This  certifies  that the  above-named  Registered  Owner is the registered
owner of certain  interests  in a pool of assets  ("REMIC  III")  consisting  of
interests in another  pool of assets  ("REMIC  II")  consisting  of interests in
another  pool  of  assets   ("REMIC  I")  consisting  of,  among  other  things,
conventional one- to four-family  mortgage loans (the "Mortgage Loans"),  formed
and administered by Washington Mutual Mortgage Securities Corp. (the "Company"),
which term includes any successor entity under the Pooling Agreement referred to
below.  REMIC I, REMIC II and REMIC III were  created  pursuant to a Pooling and
Servicing  Agreement,  dated as of the Cut-Off Date stated  above (the  "Pooling
Agreement"),  among the Company, Citibank, N.A., as Trustee (the "Trustee"), and
Christiana Bank & Trust Company,  as Delaware  Trustee,  a summary of certain of
the  pertinent  provisions  of which is set forth  hereafter.  To the extent not
defined herein,  the capitalized terms used herein have the meanings assigned in
the Pooling  Agreement.  Nothing herein shall be deemed  inconsistent  with such
meanings, and in the event of any conflict between the Pooling Agreement and the
terms of this Certificate, the Pooling Agreement shall control. This Certificate
is issued under and is subject to the terms,  provisions  and  conditions of the
Pooling Agreement, to which Pooling Agreement the Holder of this Certificate, by
virtue of the acceptance hereof, assents and by which such Holder is bound.

     Distributions will be made, pursuant to the Pooling Agreement,  on the 25th
day of each month or, if such 25th day is not a Business  Day,  the Business Day
immediately  following  (the  "Distribution  Date"),  commencing  on  the  first
Distribution  Date specified above, to the Person in whose name this Certificate
is  registered  at the close of business on the last day (or if such last day is
not a Business Day, the Business Day immediately preceding such last day) of the
month immediately  preceding the month of such distribution (the "Record Date"),
to the extent of such  Certificateholder's  Percentage  Interest  represented by
this Certificate in the portion of the REMIC III Available  Distribution  Amount
for such Distribution Date then distributable on the Certificates of this Class,
as specified in Section 4.05 of the Pooling Agreement.

     Distributions  on this  Certificate  will be  made by the  Trustee  by wire
transfer or check mailed to the address of the Person entitled thereto,  as such
name and address shall appear on the Certificate  Register.  Notwithstanding the
above, the final  distribution on this Certificate will be made after due notice
by the Trustee of the pendency of such  distribution and only upon  presentation
and surrender of this Certificate to the Certificate Registrar.

     Reference is hereby made to the further  provisions of this Certificate set
forth below,  which  further  provisions  shall for all  purposes  have the same
effect as if set forth at this place.

     Unless the certificate of authentication  hereon has been executed by or on
behalf  of the  Trustee,  by manual  signature,  this  Certificate  shall not be
entitled to any benefit under the Pooling Agreement or be valid for any purpose.

<PAGE>

     IN  WITNESS  WHEREOF,  the Trust has  caused  this  Certificate  to be duly
executed.

                WaMu MORTGAGE PASS-THROUGH CERTIFICATES SERIES 2004-S1 TRUST



                By:   CITIBANK, N.A., as Trustee



                      By:_____________________________________________





                    (TRUSTEE'S CERTIFICATE OF AUTHENTICATION)

     This is one of the Certificates referred to in the within-mentioned Pooling
Agreement.

CITIBANK, N.A.,
as Trustee



By:_____________________________

Dated:__________________________


<PAGE>

                   WASHINGTON MUTUAL MORTGAGE SECURITIES CORP.
                     WaMu MORTGAGE PASS-THROUGH CERTIFICATE

     This  Certificate  is  one  of a  duly  authorized  issue  of  Certificates
designated as WaMu Mortgage  Pass-Through  Certificates  of the Series and Class
specified hereon (herein called the  "Certificates")  and  representing  certain
interests in REMIC III.

     The  Certificates do not represent an obligation of, or an interest in, the
Company  or any of its  affiliates  and are not  insured  or  guaranteed  by any
governmental agency. The Certificates are limited in right of payment to certain
collections  and  recoveries   respecting  the  Mortgage  Loans,   all  as  more
specifically set forth herein and in the Pooling  Agreement.  In the event funds
are advanced with respect to any Mortgage Loan,  such advance is reimbursable to
the Master  Servicer  from the related  recoveries on such Mortgage Loan or from
other cash deposited in the Certificate  Account to the extent that such advance
is not otherwise recoverable.

     As provided  in the Pooling  Agreement,  withdrawals  from the  Certificate
Account may be made from time to time for purposes other than  distributions  to
Certificateholders, such purposes including reimbursement to the Master Servicer
of advances made, or certain expenses incurred, by it.

     The Pooling Agreement  permits,  with certain  exceptions therein provided,
the amendment  thereof and the modification of the rights and obligations of the
Company and the rights of the Certificateholders  under the Pooling Agreement at
any time by the Company, the Master Servicer and the Trustee with the consent of
the Holders of the Certificates  evidencing Percentage Interests aggregating not
less than 66% of REMIC III. Any such  consent by the Holder of this  Certificate
shall be  conclusive  and binding on such Holder and upon all future  Holders of
this  Certificate and of any  Certificate  issued upon the transfer hereof or in
exchange  herefor or in lieu hereof  whether or not  notation of such consent is
made upon this  Certificate.  The Pooling  Agreement  also permits the amendment
thereof, in certain limited circumstances, without the consent of the Holders of
any of the Certificates.

     As  provided in the Pooling  Agreement  and subject to certain  limitations
therein  set forth,  the  transfer of this  Certificate  is  registrable  in the
Certificate  Register upon surrender of this  Certificate  for  registration  of
transfer at the offices of the Certificate Registrar or the office maintained by
the Trustee in the City and State of New York,  duly endorsed by, or accompanied
by an assignment  in the form below or other  written  instrument of transfer in
form satisfactory to the Trustee or any  Authenticating  Agent duly executed by,
the Holder hereof or such  Holder's  attorney  duly  authorized in writing,  and
thereupon one or more new  Certificates of Authorized  Denominations  evidencing
the same  Percentage  Interest  set  forth  hereinabove  will be  issued  to the
designated transferee or transferees.

     [to be used only in the case of the Junior  Subordinate  Certificates:] [No
transfer of a Certificate will be made unless such transfer is exempt from or is
made in accordance with the  registration  requirements of the Securities Act of
1933, as amended (the  "Securities  Act") and any  applicable  state  securities
laws.  In the  event  that a  transfer  is to be made  without  registration  or
qualification  under  applicable  laws,  (i) in the event such  transfer is made
pursuant  to Rule 144A under the  Securities  Act,  the  Company and the Trustee
shall require the  transferee to execute an investment  letter in  substantially
the form attached as Exhibit L to the Pooling Agreement, which investment letter
shall not be an expense of the Company,  the Master  Servicer,  the Trust or the
Trustee and (ii) in the event that such a transfer is not made  pursuant to Rule

<PAGE>

144A under the  Securities  Act,  the  Trustee may require an Opinion of Counsel
satisfactory  to the  Trustee  that  such  transfer  may be  made  without  such
registration or qualification,  which Opinion of Counsel shall not be an expense
of the  Company,  the Master  Servicer,  the Trust or the  Trustee.  Neither the
Company nor the Trust will register the  Certificate  under the Securities  Act,
qualify the Certificate  under any state securities law or provide  registration
rights to any purchaser.  Any Holder desiring to effect such transfer shall, and
does hereby agree to,  indemnify  the Trust,  the  Trustee,  the Company and the
Master Servicer  against any liability that may result if the transfer is not so
exempt or is not made in accordance with such federal and state laws.]

     The  Certificates  are issuable  only as  registered  Certificates  without
coupons in  Authorized  Denominations  specified  in the Pooling  Agreement.  As
provided in the Pooling Agreement and subject to certain limitations therein set
forth,   Certificates  are  exchangeable  for  new  Certificates  of  Authorized
Denominations of like Certificate  Principal Balance or Percentage Interest,  as
applicable, as requested by the Holder surrendering the same.

     A  reasonable  service  charge  may be made  for any such  registration  of
transfer or exchange, and the Trustee may require payment of a sum sufficient to
cover any tax or other governmental charge payable in connection therewith.

     The Company, the Trustee and the Certificate Registrar and any agent of the
Company, the Trustee or the Certificate  Registrar may treat the Person in whose
name this  Certificate  is registered as the owner hereof for all purposes,  and
neither the Company, the Trustee,  the Certificate  Registrar nor any such agent
shall be affected by notice to the contrary.

     The  obligations  created by the Pooling  Agreement  and the Trust  created
thereby shall terminate upon (i) the later of the maturity or other  liquidation
(including  purchase by the Master Servicer) of the last Mortgage Loan remaining
in the Trust or the  disposition  of all property  acquired upon  foreclosure or
deed in lieu of  foreclosure  of any  Mortgage  Loan,  and (ii) the  payment  to
Certificateholders of all amounts held by the Trustee and required to be paid to
them  pursuant  to the Pooling  Agreement.  In the event that the Company or the
Master Servicer  purchases any Mortgage Loan pursuant to the Pooling  Agreement,
the Pooling  Agreement  generally  requires  that the Trustee  distribute to the
Certificateholders  in the  aggregate  an  amount  equal  to 100% of the  unpaid
Principal Balance of such Mortgage Loan, plus unpaid accrued interest thereon at
the  applicable  Pass-Through  Rate to the last day of the  month in which  such
purchase occurs. The Pooling Agreement permits, but does not require, the Master
Servicer  to  purchase  from the Trust all  Mortgage  Loans at the time  subject
thereto and all property  acquired in respect of any Mortgage  Loan upon payment
to the Certificateholders of the amounts specified in the Pooling Agreement. The
exercise of such right will effect early  retirement  of the  Certificates,  the
Master  Servicer's  right to purchase  being subject to the aggregate  Principal
Balance  of the  Mortgage  Loans at the time of  purchase  being  less  than the
Clean-Up  Call  Percentage of the  aggregate  Principal  Balance of the Mortgage
Loans as of the Cut-Off Date.


<PAGE>

                                   ASSIGNMENT



     FOR VALUE  RECEIVED  the  undersigned  hereby  sell(s)  and  assign(s)  and
transfer(s)  unto ____________________________________________________________
(Please print or typewrite name and address,  including postal
zip code of assignee.  Please insert social security or other identifying number
of assignee.) the within WaMu Mortgage  Pass-Through  Certificate and hereby
irrevocably constitutes and appoints _________________________________________
Attorney to transfer said  Certificate on the  Certificate  Register,  with
full power of substitution in the premises.

Dated: ______________________ ________________________________________
                              Signature Guaranteed

    __________________________________________________________________________
    NOTICE: The signature to this  assignment  must  correspond  with the name
            as  written  upon  the  face of the  within  instrument  in  every
            particular,  without  alteration  or  enlargement  or  any  change
            whatever.  This  Certificate  does not  represent an obligation of
            or an interest in Washington  Mutual Mortgage  Securities Corp. or
            any  of  its   affiliates.   Neither  this   Certificate  nor  the
            underlying   Mortgage  Loans  are  guaranteed  by  any  agency  or
            instrumentality of the United States.


<PAGE>





                                                                  Exhibit I


                             TRANSFEROR CERTIFICATE

                                                      [Date]

Citibank, N.A., as Trustee
111 Wall Street, 14th Floor, Zone 3
New York, New York 10005
Attn:  Structured Finance Group, Washington Mutual 2004-S1

Re:  Washington  Mutual Mortgage  Securities  Corp.  WaMu Mortgage  Pass-Through
     Certificates, Series 2004-S1, Class R

Ladies and Gentlemen:

     This  letter  is  delivered  to you in  connection  with the sale from (the
"Seller") to (the  "Purchaser")  of  $____________________  initial  Certificate
Principal Balance of WaMu Mortgage  Pass-Through  Certificates,  Series 2004-S1,
Class  R (the  "Certificate"),  pursuant  to  Section  5.01 of the  Pooling  and
Servicing  Agreement  (the  "Pooling  Agreement"),  dated as of February 1, 2004
among  Washington  Mutual  Mortgage  Securities  Corp.,  as depositor and master
servicer  (the  "Company"),  Citibank,  N.A.,  as trustee (the  "Trustee"),  and
Christiana Bank & Trust Company, as Delaware trustee.  All terms used herein and
not  otherwise  defined  shall  have  the  meanings  set  forth  in the  Pooling
Agreement.  The  Seller  hereby  certifies,  represents  and  warrants  to,  and
covenants with, the Company, the Trustee and the Trust that:

     1. No purpose of the Seller  relating to the sale of the Certificate by the
Seller to the  Purchaser  is or will be to  enable  the  Seller  to  impede  the
assessment or collection of tax.

     2. The Seller  understands  that the Purchaser has delivered to the Trustee
and the Company a transferee affidavit and agreement in the form attached to the
Pooling  Agreement  as Exhibit J. The Seller  does not know or believe  that any
representation contained therein is false.

     3. The Seller has no actual knowledge that the proposed Transferee is not a
Permitted Transferee.

     4. The Seller has no actual knowledge that the Purchaser would be unwilling
or unable to pay taxes due on its share of the taxable  income  attributable  to
the Certificates.

     5. The Seller has  conducted a reasonable  investigation  of the  financial
condition of the Purchaser and, as a result of the investigation, found that the
Purchaser  has  historically  paid its  debts as they  came  due,  and  found no
significant evidence to indicate that the Purchaser will not continue to pay its
debts as they come due in the future.


<PAGE>

     6. The Purchaser has  represented  to the Seller that, if the  Certificates
constitute a noneconomic residual interest, it (i) understands that as holder of
a noneconomic  residual  interest it may incur tax  liabilities in excess of any
cash flows generated by the interest,  and (ii) intends to pay taxes  associated
with its holding of the Certificates as they become due.

                                          Very truly yours,

                                          [Seller]

                                          By:
                                               Name:
                                               Title:

<PAGE>


                                                                      Exhibit J


                       TRANSFEREE AFFIDAVIT AND AGREEMENT



STATE OF                   )
                           )   ss:
COUNTY OF                  )



     [NAME OF OFFICER], being first duly sworn, deposes and says:

     1. That he is [Title of Officer] of [Name of Owner]  (record or  beneficial
owner  of the  Class R  Certificate  (the  "Owner")),  a  [savings  institution]
[corporation] duly organized and existing under the laws of [the State of ] [the
United States], on behalf of which he makes this affidavit and agreement.

     2. That the Owner (i) is not and will not be a "disqualified  organization"
as of [date of  transfer]  within  the  meaning  of  Section  860E(e)(5)  of the
Internal  Revenue Code of 1986,  as amended  (the  "Code") and will  endeavor to
remain  other than a  disqualified  organization  for so long as it retains  its
ownership interest in the Class R Certificates,  and (ii) is acquiring the Class
R  Certificates  for its own  account or for the  account of another  Owner from
which it has received an affidavit and agreement in substantially  the same form
as this affidavit and agreement. (For this purpose, a disqualified organization"
means the United  States,  any state or political  subdivision  thereof,  or any
agency or instrumentality of any of the foregoing (other than an instrumentality
all of the  activities  of which are subject to tax and,  except for the Federal
Home Loan  Mortgage  Corporation,  a majority of whose board of directors is not
selected  by any  such  governmental  entity),  or  any  foreign  government  or
international  organization,  or any agency or  instrumentality  of such foreign
government or organization,  any rural electric or telephone cooperative, or any
organization (other than certain farmers' cooperatives) that is generally exempt
from  federal  income  tax  unless  such  organization  is subject to the tax on
unrelated business taxable income).

     3.  That the  Owner  is aware  (i) of the tax  that  would  be  imposed  on
transfers of the Class R Certificates  after March 31, 1988;  (ii) that such tax
would be on the  transferor,  or, if such  transfer  is through an agent  (which
person   includes  a  broker,   nominee  or   middle-man)   for  a  disqualified
organization,  on the agent;  (iii) that the person otherwise liable for the tax
shall be relieved of liability for the tax if the  transferee  furnishes to such
person an affidavit that the transferee is not a disqualified  organization and,
at the time of  transfer,  such person does not have actual  knowledge  that the
affidavit is false; and (iv) that the Class R Certificates may be a "noneconomic
residual  interest"  within the  meaning  of  Treasury  regulations  promulgated
pursuant to the Code and that the transferor of a noneconomic  residual interest
will remain liable for any taxes due with respect to the income on such residual
interest,  if a significant purpose of the transfer was to enable the transferor
to impede the assessment or collection of tax.

     4. That the Owner is aware of the tax  imposed on a  "pass-through  entity"
holding the Class R  Certificates  if at any time during the taxable year of the
pass-through  entity a  disqualified  organization  is the  record  holder of an
interest in such entity.  (For this purpose,  a "pass through entity" includes a
regulated  investment  company,  a real estate  investment trust or common trust
fund, a partnership, trust or estate, and certain cooperatives.)

<PAGE>

     5. That the Owner is aware that the Trustee  will not register the Transfer
of the Class R-1 Certificates unless the transferee,  or the transferees' agent,
delivers to it an affidavit and agreement,  among other things, in substantially
the same form as this affidavit and agreement.  The Owner expressly  agrees that
it will not consummate any such transfer if it knows or believes that any of the
representations contained in such affidavit and agreement are false.

     6. That the Owner has  reviewed the  restrictions  set forth on the face of
the Class R  Certificates  and the  provisions  of Section  5.01 of the  Pooling
Agreement  under  which the Class R  Certificates  were  issued (in  particular,
clauses  (iii)(A) and (iii)(B) of Section 5.01(c) which authorize the Trustee to
deliver payments to a person other than the Owner and negotiate a mandatory sale
by the Trustee in the event the Owner holds such  Certificates  in  violation of
Section 5.01). The Owner expressly agrees to be bound by and to comply with such
restrictions and provisions.

     7. That the Owner consents to any additional  restrictions  or arrangements
that shall be deemed necessary upon advice of counsel to constitute a reasonable
arrangement to ensure that the Class R Certificates will only be owned, directly
or indirectly, by an Owner that is not a disqualified organization.

     8. The Owner's Taxpayer Identification Number is .

     9. That no purpose of the Owner  relating  to the  purchase  of the Class R
Certificates  by the Owner is or will be to enable the  transferor to impede the
assessment  or collection  of tax, and that in making this  representation,  the
Owner warrants that the Owner is familiar with Treasury  Regulation  1.860E-1(c)
and with the preamble to the adoption of  amendments  to that  regulation  as of
July 19, 2002, attached hereto as Exhibit 1.

     10. That the Owner  anticipates that it will, so long as it holds the Class
R Certificates,  have  sufficient  assets to pay any taxes owed by the holder of
such  Certificates,  and hereby  represents to and for the benefit of the person
from whom it acquired  the Class R  Certificates  that the Owner  intends to pay
taxes  associated  with  holding  such  Certificates  as they become due,  fully
understanding  that it may incur  tax  liabilities  in excess of any cash  flows
generated by the Class R  Certificates.  That the Owner has  provided  financial
statements  or  other  financial  information  requested  by the  transferor  in
connection  with  the  transfer  of the  Class  R  Certificates  to  permit  the
transferor to assess the financial capability of the Owner to pay such taxes.

     11. That the Owner has no present  knowledge or expectation that it will be
unable to pay any United  States  taxes owed by it so long as any of the Class R
Certificates remain outstanding.

     12. That the Owner has no present  knowledge  or  expectation  that it will
become insolvent or subject to a bankruptcy proceeding for so long as any of the
Class R Certificates remain outstanding.

     13. That the Owner is familiar with  Treasury  Regulation  1.860E-1(c)  and
with the preamble to the adoption of  amendments  to that  regulation as of July
19,  2002,  attached  hereto  as  Exhibit  1, and that no  purpose  of the Owner
relating to any sale of the Class R Certificates  by the Owner will be to impede
the assessment or collection of tax.

     14. The Owner is a citizen or resident of the United States, a corporation,
partnership or other entity  treated as a partnership  or  corporation  for U.S.
federal  income tax purposes  created or organized in, or under the laws of, the
United States or any state thereof or the District of Columbia,  or an estate or
trust whose income from sources without the United States is includible in gross
income  for  United  States  federal  income  tax  purposes  regardless  of  its
connection with the conduct of a trade or business within the United States.

<PAGE>

     15. The Owner hereby  agrees that it will not cause income from the Class R
Certificates to be attributable to a foreign  permanent  establishment  or fixed
base  (within  the meaning of an  applicable  income tax treaty) of the Owner or
another United States taxpayer.

     16. The Owner hereby  agrees to cooperate  with the Company and to take any
action required of it by the Code or Treasury  regulations  thereunder  (whether
now or hereafter promulgated) in order to create or maintain the REMIC status of
REMIC I, REMIC II and REMIC III (the "REMICs").

     17. The Owner  hereby  agrees  that it will not take any action  that could
endanger  the REMIC status of the REMICs or result in the  imposition  of tax on
the REMICs  unless  counsel for, or  acceptable  to, the Company has provided an
opinion that such action will not result in the loss of such REMIC status or the
imposition of such tax, as applicable.

     18. The Owner as transferee of the Class R Certificates  has represented to
the  transferor  that,  if the Class R  Certificates  constitute  a  noneconomic
residual  interest,  the Owner (i)  understands  that as holder of a noneconomic
residual  interest  it may incur  tax  liabilities  in excess of any cash  flows
generated by the  interest,  and (ii) intends to pay taxes  associated  with its
holding of the Class R Certificates as they become due.

     19. That the Owner  satisfies the  condition in the paragraph  marked below
[mark one paragraph only]:

     ___ The Owner is not an  employee  benefit  or other  plan  subject  to the
prohibited transaction provisions of the Employee Retirement Income Security Act
of 1974,  as amended,  or Section 4975 of the Internal  Revenue Code of 1986, as
amended (a "Plan"),  or any other person  (including  an investment  manager,  a
named  fiduciary or a trustee of any Plan) acting,  directly or  indirectly,  on
behalf of, or  purchasing  the Class R  Certificates  with "plan assets" of, any
Plan within the meaning of the  Department  of Labor  ("DOL")  regulation  at 29
C.F.R. Section 2510.3-101.

     ___ The Owner has  delivered a Benefit  Plan Opinion (as defined in Section
1.01 of the Pooling Agreement under which the Class R Certificates were issued).

     IN WITNESS WHEREOF,  the Owner has caused this instrument to be executed on
its behalf,  pursuant to the authority of its Board of Directors,  by its [Title
of Officer]  and its  corporate  seal to be hereunto  attached,  attested by its
[Assistant] Secretary, this day of , 20 __ .

                                 [Name of Owner]

                                 By:
                                                [Name of Officer]
                                               [Title of Officer]

[Corporate Seal]

ATTEST:

<PAGE>





[Assistant] Secretary

     Personally  appeared before me the above-named [Name of Officer],  known or
proved to me to be the same person who executed the foregoing  instrument and to
be the [Title of Officer] of the Owner,  and Acknowledged to me that he executed
the same as his free act and deed and the free act and deed of the Owner.

     Subscribed and sworn before me this ___ day of __________________, 20__.





                                        NOTARY PUBLIC

                                        COUNTY OF
                                        STATE OF
                                        My Commission expires the     day
                                        of                , 20

<PAGE>

                                       Exhibit 1 to Transferee Affidavit


         DEPARTMENT OF THE TREASURY
         Internal Revenue Service
         26 CFR Parts 1 and 602
         [TD 9004]
         RIN 1545-AW98

         Real Estate Mortgage Investment Conduits

         AGENCY: Internal Revenue Service (IRS), Treasury.

         ACTION: Final regulations.

         -----------------------------------------------------------------------

     SUMMARY:  This document contains final regulations  relating to safe harbor
transfers of noneconomic  residual interests in real estate mortgage  investment
conduits (REMICs).  The final regulations provide additional  limitations on the
circumstances under which transferors may claim safe harbor treatment.

DATES:  Effective  Date:   These   regulations  are  effective  July  19,  2002.
        Applicability   Date:  For  dates  of   applicability,   see  Sec.
        1.860E-(1)(c)(10).

     FOR FURTHER INFORMATION CONTACT: Courtney Shepardson at (202) 622-3940 (not
a toll-free number).

     SUPPLEMENTARY INFORMATION:

     Paperwork Reduction Act

     The  collection  of  information  in this final rule has been reviewed and,
pending  receipt and  evaluation of public  comments,  approved by the Office of
Management  and Budget (OMB) under 44 U.S.C.  3507 and assigned  control  number
1545-1675.  The  collection  of  information  in  this  regulation  is  in  Sec.
1.860E-1(c)(5)(ii).  This  information  is  required to enable the IRS to verify
that a  taxpayer  is  complying  with the  conditions  of this  regulation.  The
collection of information is mandatory and is required.  Otherwise, the taxpayer
will not  receive  the  benefit of safe  harbor  treatment  as  provided  in the
regulation.   The  likely   respondents  are  businesses  and  other  for-profit
institutions.

     Comments on the collection of  information  should be sent to the Office of
Management  and Budget,  Attn:  Desk Officer for the Department of the Treasury,
Office of Information and Regulatory Affairs, Washington, DC, 20503, with copies
to  the  Internal  Revenue  Service,   Attn:  IRS  Reports  Clearance   Officer,
W:CAR:MP:FP:S,  Washington,  DC 20224. Comments on the collection of information


<PAGE>

should be received by September 17, 2002.  Comments are  specifically  requested
concerning:

     Whether  the   collection  of  information  is  necessary  for  the  proper
performance of the functions of the Internal Revenue Service,  including whether
the information will have practical utility;

     The accuracy of the  estimated  burden  associated  with the  collection of
information (see below);

     How the quality,  utility,  and clarity of the  information to be collected
may be enhanced;

     How the burden of  complying  with the  collection  of  information  may be
minimized,  including through the application of automated collection techniques
or other forms of information technology; and

     Estimates of capital or start-up costs and costs of operation, maintenance,
and purchase of service to provide information.

     An agency  may not  conduct or  sponsor,  and a person is not  required  to
respond to, a  collection  of  information  unless it  displays a valid  control
number assigned by the Office of Management and Budget.

     The  estimated  total  annual  reporting  burden is 470 hours,  based on an
estimated  number of respondents  of 470 and an estimated  average annual burden
hours per respondent of one hour.

     Books or records  relating to a collection of information  must be retained
as long as their  contents  may become  material  in the  administration  of any
internal  revenue law.  Generally,  tax returns and tax return  information  are
confidential, as required by 26 U.S.C. 6103.

     Background

     This document contains final regulations  regarding the proposed amendments
to 26 CFR part 1 under  section  860E of the Internal  Revenue Code (Code).  The
regulations  provide the circumstances under which a transferor of a noneconomic
REMIC  residual   interest   meeting  the   investigation   and   representation
requirements  may avail  itself  of the safe  harbor by  satisfying  either  the
formula test or the asset test.

     Final regulations governing REMICs, issued in 1992, contain rules governing
the transfer of noneconomic REMIC residual interests.  In general, a transfer of
a  noneconomic  residual  interest  is  disregarded  for all tax  purposes  if a
significant  purpose of the transfer is to enable the  transferor  to impede the
assessment  or  collection  of tax.  A  purpose  to  impede  the  assessment  or
collection of tax (a wrongful purpose) exists if the transferor,  at the time of
the  transfer,  either  knew or should have known that the  transferee  would be
unwilling or unable to pay taxes due on its share of the REMIC's taxable income.

<PAGE>

     Under  a safe  harbor,  the  transferor  of a  REMIC  noneconomic  residual
interest  is presumed  not to have a wrongful  purpose if two  requirements  are
satisfied:  (1)  the  transferor  conducts  a  reasonable  investigation  of the
transferee's  financial condition (the investigation  requirement);  and (2) the
transferor  secures a representation  from the transferee to the effect that the
transferee  understands the tax  obligations  associated with holding a residual
interest and intends to pay those taxes (the representation requirement).

     The  IRS  and  Treasury  have  been  concerned  that  some  transferors  of
noneconomic  residual  interests  claim they  satisfy  the safe  harbor  even in
situations  where the economics of the transfer  clearly indicate the transferee
is unwilling or unable to pay the tax associated with holding the interest.  For
this reason,  on February 7, 2000, the IRS published in the Federal Register (65
FR 5807) a notice of proposed rulemaking (REG-100276-97; REG-122450-98) designed
to clarify the safe harbor by adding the ``formula test,'' an economic test. The
proposed  regulation  provides  that the safe harbor is  unavailable  unless the
present value of the  anticipated  tax  liabilities  associated with holding the
residual  interest  does not  exceed the sum of:  (1) The  present  value of any
consideration  given to the transferee to acquire the interest;  (2) the present
value of the expected future distributions on the interest;  and (3) the present
value of the anticipated tax savings associated with holding the interest as the
REMIC generates losses.

     The notice of proposed rulemaking also contained rules for FASITs.  Section
1.860H-6(g) of the proposed regulations  provides  requirements for transfers of
FASIT  ownership  interests  and adopts a safe harbor by  reference  to the safe
harbor provisions of the REMIC regulations.

     In January 2001, the IRS published Rev. Proc.  2001-12 (2001-3 I.R.B.  335)
to set forth an alternative  safe harbor that taxpayers  could use while the IRS
and the  Treasury  considered  comments on the proposed  regulations.  Under the
alternative safe harbor, if a transferor meets the investigation requirement and
the representation  requirement but the transfer fails to meet the formula test,
the transferor  may invoke the safe harbor if the  transferee  meets a two-prong
test (the asset test). A transferee generally meets the first prong of this test
if, at the time of the transfer, and in each of the two years preceding the year
of  transfer,  the  transferee's  gross  assets  exceed $100 million and its net
assets exceed $10 million. A transferee generally meets the second prong of this
test if it is a  domestic,  taxable  corporation  and agrees in  writing  not to
transfer  the  interest  to any person  other  than  another  domestic,  taxable
corporation that also satisfies the requirements of the asset test. A transferor
cannot rely on the asset test if the  transferor  knows,  or has reason to know,
that the  transferee  will not comply  with its written  agreement  to limit the
restrictions on subsequent transfers of the residual interest.

     Rev.  Proc.  2001-12  provides that the asset test fails to be satisfied in
the case of a transfer or  assignment of a  noneconomic  residual  interest to a
foreign  branch of an  otherwise  eligible  transferee.  If such a  transfer  or
assignment  were  permitted,  a corporate  taxpayer might seek to claim that the
provisions of an applicable  income tax treaty would resource  excess  inclusion
income as foreign  source  income,  and that,  as a  consequence,  any U.S.  tax
liability attributable to the excess inclusion income could be offset by foreign
tax credits.  Such a claim would impede the assessment or collection of U.S. tax
on excess inclusion income,  contrary to the  congressional  purpose of assuring
that such income will be taxable in all events. See, e.g., sections  860E(a)(1),
(b), (e) and 860G(b) of the Code.

<PAGE>

     The Treasury and the IRS have learned that certain  taxpayers  transferring
noneconomic residual interests to foreign branches have attempted to rely on the
formula  test to obtain  safe  harbor  treatment  in an  effort  to  impede  the
assessment or collection of U.S. tax on excess  inclusion  income.  Accordingly,
the  final  regulations  provide  that if a  noneconomic  residual  interest  is
transferred  to a  foreign  permanent  establishment  or  fixed  base  of a U.S.
taxpayer,  the transfer is not eligible for safe harbor  treatment  under either
the asset  test or the  formula  test.  The  final  regulations  also  require a
transferee  to  represent  that it will not cause  income  from the  noneconomic
residual  interest to be attributable to a foreign  permanent  establishment  or
fixed base.

     Section 1.860E-1(c)(8) provides computational rules that a taxpayer may use
to  qualify  for  safe  harbor   status   under  the   formula   test.   Section
1.860E-1(c)(8)(i)  provides that the transferee is presumed to pay tax at a rate
equal to the highest rate of tax specified in section 11(b).  Some  commentators
were  concerned that this presumed rate of taxation was too high because it does
not take into  consideration  taxpayers  subject to the alternative  minimum tax
rate. In light of the comments received,  this provision has been amended in the
final regulations to allow certain transferees that compute their taxable income
using the alternative  minimum tax rate to use the alternative  minimum tax rate
applicable to corporations.

     Additionally,  Sec. 1.860E-1(c)(8)(iii) provides that the present values in
the  formula  test  are to be  computed  using  a  discount  rate  equal  to the
applicable  Federal  short-term  rate prescribed by section  1274(d).  This is a
change  from  the  proposed   regulation  and  Rev.  Proc.   2001-12.  In  those
publications  the  provision  stated that "present  values are computed  using a
discount rate equal to the applicable Federal rate prescribed in section 1274(d)
compounded  semiannually"  and that "[a] lower  discount rate may be used if the
transferee can demonstrate that it regularly borrows, in the course of its trade
or  business,  substantial  funds at such  lower  rate from an  unrelated  third
party." The IRS and the Treasury  Department  have learned  that,  based on this
provision,  certain taxpayers have been attempting to use unrealistically low or
zero interest rates to satisfy the formula test,  frustrating  the intent of the
test.  Furthermore,  the  Treasury  Department  and the IRS believe  that a rule
allowing  for a rate  other than a rate based on an  objective  index  would add
unnecessary complexity to the safe harbor. As a result, the rule in the proposed
regulations  that  permits a transferee  to use a lower  discount  rate,  if the
transferee can demonstrate that it regularly  borrows  substantial funds at such
lower rate, is not included in the final regulations; and the Federal short-term
rate  has  been  substituted  for  the  applicable  Federal  rate.  To  simplify
taxpayers' computations, the final regulations allow use of any of the published
short-term  rates,  provided  that  the  present  values  are  computed  with  a
corresponding  period  of  compounding.  With the  exception  of the  provisions
relating to transfers to foreign  branches,  these  changes  generally  have the
proposed  applicability  date of February 4, 2000,  but  taxpayers may choose to
apply the interest  rate formula set forth in the proposed  regulation  and Rev.
Proc. 2001-12 for transfers occurring before August 19, 2002.

     It is anticipated  that when final  regulations are adopted with respect to
FASITs,  Sec.  1.860H-6(g)  of the  proposed  regulations  will  be  adopted  in


<PAGE>

substantially  its  present  form,  with the result  that the final  regulations
contained  in this  document  will  also  govern  transfers  of FASIT  ownership
interests with substantially the same applicability date as is contained in this
document.

     Effect on Other Documents

     Rev.  Proc.  2001-12  (2001-3  I.R.B.  335) is obsolete  for  transfers  of
noneconomic residual interests in REMICs occurring on or after August 19, 2002.

     Special Analyses

     It is hereby  certified that these  regulations will not have a significant
economic impact on a substantial number of small entities. This certification is
based  on the  fact  that it is  unlikely  that a  substantial  number  of small
entities will hold REMIC residual interests. Therefore, a Regulatory Flexibility
Analysis  under  the  Regulatory  Flexibility  Act (5 U.S.C.  chapter  6) is not
required.  It  has  been  determined  that  this  Treasury  decision  is  not  a
significant regulatory action as defined in Executive Order 12866.  Therefore, a
regulatory assessment is not required. It also has been determined that sections
553(b) and 553(d) of the  Administrative  Procedure Act (5 U.S.C.  chapter 5) do
not apply to these regulations.

     Drafting Information

     The principal author of these regulations is Courtney Shepardson.  However,
other  personnel  from the IRS and  Treasury  Department  participated  in their
development.

     List of Subjects

     26 CFR Part 1

     Income taxes, Reporting and record keeping requirements.

     26 CFR Part 602

     Reporting and record keeping requirements.

     Adoption of Amendments to the Regulations

     Accordingly, 26 CFR parts 1 and 602 are amended as follows:

     PART 1--INCOME TAXES

     Paragraph 1. The authority citation for part 1 continues to read in part as
follows:

     Authority: 26 U.S.C. 7805 * * *

<PAGE>

                                                                     Exhibit K

                                   [Reserved]




<PAGE>

                                                                     Exhibit L


                  [FORM OF RULE 144A INVESTMENT REPRESENTATION]

             Description of Rule 144A Securities, including numbers:



                            _______________________
                            _______________________
                            _______________________





     The undersigned  seller,  as registered  holder (the "Seller"),  intends to
transfer the Rule 144A Securities  described above to the undersigned buyer (the
"Buyer").

     1. In connection  with such transfer and in accordance  with the agreements
pursuant  to which the Rule 144A  Securities  were  issued,  the  Seller  hereby
certifies  the  following  facts:  Neither  the Seller nor anyone  acting on its
behalf has offered, transferred, pledged, sold or otherwise disposed of the Rule
144A  Securities,  any interest in the Rule 144A Securities or any other similar
security to, or solicited any offer to buy or accept a transfer, pledge or other
disposition  of  the  Rule  144A  Securities,  any  interest  in the  Rule  144A
Securities  or any other  similar  security  from,  or otherwise  approached  or
negotiated  with respect to the Rule 144A  Securities,  any interest in the Rule
144A Securities or any other similar security with, any person in any manner, or
made any general  solicitation  by means of general  advertising or in any other
manner,  or taken any other action,  that would constitute a distribution of the
Rule 144A  Securities  under the  Securities  Act of 1933, as amended (the "1933
Act"),  or that  would  render the  disposition  of the Rule 144A  Securities  a
violation of Section 5 of the 1933 Act or require registration pursuant thereto,
and that the Seller has not offered the Rule 144A Securities to any person other
than the Buyer or  another  "qualified  institutional  buyer" as defined in Rule
144A under the 1933 Act.

     2. The Buyer warrants and  represents  to, and covenants  with, the Seller,
the  Trustee,  the Trust and the Master  Servicer (as defined in Section 1.01 of
the Pooling and Servicing  Agreement (the  "Agreement")  dated as of February 1,
2004 among Washington Mutual Mortgage  Securities Corp., as Depositor and Master
Servicer,  Citibank,  N.A., as Trustee,  and Christiana Bank & Trust Company, as
Delaware trustee) pursuant to Section 5.01(f) of the Agreement, as follows:

     a.  The  Buyer  understands  that the Rule  144A  Securities  have not been
registered under the 1933 Act or the securities laws of any state.

     b. The Buyer considers  itself a substantial,  sophisticated  institutional
investor having such knowledge and experience in financial and business  matters
that it is capable of evaluating  the merits and risks of investment in the Rule
144A Securities.

     c. The Buyer has received and  reviewed  the Private  Placement  Memorandum
dated as of February 24, 2004 relating to the Rule 144A  Securities and has been
furnished with all  information  regarding the Rule 144A  Securities that it has
requested from the Seller, the Trustee, the Company or the Master Servicer.

<PAGE>

     d.  Neither  the  Buyer  nor  anyone  acting  on its  behalf  has  offered,
transferred,  pledged,  sold or otherwise  disposed of the Rule 144A Securities,
any interest in the Rule 144A  Securities or any other  similar  security to, or
solicited any offer to buy or accept a transfer,  pledge or other disposition of
the Rule 144A Securities,  any interest in the Rule 144A Securities or any other
similar security from, or otherwise approached or negotiated with respect to the
Rule 144A  Securities,  any  interest in the Rule 144A  Securities  or any other
similar  security  with,  any  person  in  any  manner,   or  made  any  general
solicitation  by means of general  advertising or in any other manner,  or taken
any  other  action,  that  would  constitute  a  distribution  of the Rule  144A
Securities  under the 1933 Act or that would render the  disposition of the Rule
144A Securities a violation of Section 5 of the 1933 Act or require registration
pursuant  thereto,  nor will it act, nor has it  authorized or will it authorize
any person to act, in such manner with respect to the Rule 144A Securities.

     e. The Buyer is a "qualified  institutional  buyer" as that term is defined
in Rule  144A  under the 1933 Act and has (1)  completed  either of the forms of
certification  to that  effect  attached  hereto  as  Annex 1 or Annex 2, or (2)
obtained the waiver of the Company with respect to Annex 1 and Annex 2  pursuant
to Section  5.01(f) of the Agreement.  The Buyer is aware that the sale to it is
being  made in  reliance  on Rule  144A.  The Buyer is  acquiring  the Rule 144A
Securities for its own account or the accounts of other qualified  institutional
buyers,  understands  that such Rule 144A  Securities may be resold,  pledged or
transferred  only  (i)  to a  person  reasonably  believed  to  be  a  qualified
institutional  buyer that  purchases for its own account or for the account of a
qualified institutional buyer to whom notice is given that the resale, pledge or
transfer  is being made in reliance  on Rule 144A,  or (ii)  pursuant to another
exemption from registration under the 1933 Act.

     f. The Buyer is not  affiliated  with  (i) the  Trustee or (ii) any  Rating
Agency that rated the Rule 144A Securities.

     g. If applicable, the Buyer has complied, and will continue to comply, with
the guidelines  established by Thrift Bulletin 13a issued April 23, 1998, by the
Office of Regulatory Activities of the Federal Home Loan Bank System.

     3. This  document  may be executed in one or more  counterparts  and by the
different  parties  hereto on  separate  counterparts,  each of  which,  when so
executed, shall be deemed to be an original; such counterparts,  together, shall
constitute one and the same document.


     IN WITNESS  WHEREOF,  each of the parties has executed  this document as of
the date set forth below.



____________________              ____________________
Print Name of Seller              Print Name of Buyer


By:_________________              By:_________________
      Name:                         Name:
      Title:                        Title:


<PAGE>

Taxpayer Identification:________________  Taxpayer Identification:_____________
No.:____________________________________  No.:_________________________________
Date:___________________________________  Date:________________________________


<Page>

                                                           Annex 1 to Exhibit L

            QUALIFIED INSTITUTIONAL BUYER STATUS UNDER SEC RULE 144A

             [For Buyers Other Than Registered Investment Companies]



     The  undersigned  hereby  certifies as follows in connection  with the Rule
144A Investment Representation to which this Certification is attached:

     1. As indicated  below,  the undersigned is the President,  Chief Financial
Officer, Senior Vice President or other executive officer of the Buyer.

     2. In  connection  with  purchases by the Buyer,  the Buyer is a "qualified
institutional  buyer" as that term is defined in Rule 144A under the  Securities
Act of 1933 ("Rule  144A")  because  (i) the  Buyer owned  and/or  invested on a
discretionary basis $______________________ (the Buyer must own and/or invest on
a discretionary  basis at least $100,000,000 in securities unless the Buyer is a
dealer,  and, in that case, the Buyer must own and/or invest on a  discretionary
basis at least $10,000,000 in securities) in securities (except for the excluded
securities  referred to below) as of the end of the Buyer's  most recent  fiscal
year (such amount being  calculated in  accordance  with Rule 144A) and (ii) the
Buyer satisfies the criteria in the category marked below.

     ___  Corporation,  etc.  The  Buyer is a  corporation  (other  than a bank,
savings and loan association or similar  institution),  Massachusetts or similar
business trust,  partnership,  or charitable  organization  described in Section
501(c)(3) of the Internal Revenue Code.

     ___ Bank. The Buyer (a) is a national bank or banking institution organized
under the laws of any State, territory or the District of Columbia, the business
of which is substantially  confined to banking and is supervised by the State or
territorial  banking  commission  or similar  official  or is a foreign  bank or
equivalent institution, and (b) has an audited net worth of at least $25,000,000
as demonstrated in its latest annual  financial  statements,  a copy of which is
attached hereto.

     ___  Savings  and Loan.  The Buyer (a) is a savings  and loan  association,
building  and loan  association,  cooperative  bank,  homestead  association  or
similar  institution,  which is  supervised  and  examined by a State or Federal
authority having  supervision over any such institutions or is a foreign savings
and loan association or equivalent  institution and (b) has an audited net worth
of  at  least  $25,000,000  as  demonstrated  in  its  latest  annual  financial
statements.

     ___ Broker-Dealer.  The Buyer is a dealer registered pursuant to Section 15
of the Securities
         Exchange Act of 1934.

     ___ Insurance Company.  The Buyer is an insurance company whose primary and
predominant  business  activity is the writing of insurance or the reinsuring of
risks underwritten by insurance companies and which is subject to supervision by
the  insurance  commissioner  or a  similar  official  or  agency  of a State or
territory or the District of Columbia.

     ___ State or Local Plan. The Buyer is a plan  established and maintained by
a State, its political  subdivisions,  or any agency or  instrumentality  of the
State or its political subdivisions, for the benefit of its employees.



                                     L-1-1
<PAGE>

     ___ ERISA Plan. The Buyer is an employee benefit plan within the meaning of
Section 3(3) of the Employee  Retirement Income Security Act of 1974, as amended
("ERISA") and is subject to the fiduciary responsibility provisions of ERISA.

     ___ Investment Adviser. The Buyer is an investment adviser registered under
the Investment Advisers Act of 1940.

     ___ SBIC. The Buyer is a Small Business  Investment Company licensed by the
U.S.  Small  Business  Administration  under Section  301(c) or (d) of the Small
Business Investment Act of 1958.

     ___  Business  Development  Company.  The Buyer is a  business  development
company as defined in Section 202(a)(22) of the Investment Advisers Act of 1940.

     ___ Trust Fund.  The Buyer is a trust fund whose trustee is a bank or trust
company  and  whose  participants  are  exclusively  (a) plans  established  and
maintained  by  a  State,   its  political   subdivisions,   or  any  agency  or
instrumentality of the State or its political  subdivisions,  for the benefit of
its  employees,  or (b) employee  benefit plans within the meaning of Title I of
the Employee  Retirement  Income  Security Act of 1974,  but is not a trust fund
that includes as participants individual retirement accounts or H.R. 10 plans.

     3. The term  "securities" as used herein does not include (i) securities of
issuers that are affiliated with the Buyer,  (ii) securities that are part of an
unsold  allotment  to or  subscription  by the Buyer,  if the Buyer is a dealer,
(iii) bank deposit notes and certificates of deposit,  (iv) loan participations,
(v) repurchase  agreements,  (vi)  securities  owned but subject to a repurchase
agreement and (vii) currency, interest rate and commodity swaps.

     4. For purposes of  determining  the aggregate  amount of securities  owned
and/or invested on a discretionary  basis by the Buyer,  the Buyer used the cost
of such  securities  to the  Buyer  and did not  include  any of the  securities
referred to in the preceding  paragraph.  Further, in determining such aggregate
amount,  the Buyer may have included  securities  owned by  subsidiaries  of the
Buyer,  but only if such  subsidiaries  are  consolidated  with the Buyer in its
financial  statements  prepared in accordance with generally accepted accounting
principles  and if the  investments of such  subsidiaries  are managed under the
Buyer's direction.  However, such securities were not included if the Buyer is a
majority-owned,  consolidated  subsidiary of another enterprise and the Buyer is
not itself a reporting company under the Securities Exchange Act of 1934.

     5.  The  Buyer  acknowledges  that  it  is  familiar  with  Rule  144A  and
understands  that the seller to it and other parties related to the Certificates
are relying and will continue to rely on the statements  made herein because one
or more sales to the Buyer may be in reliance on Rule 144A.


                                     L-1-2
<PAGE>

                               Will the Buyer be purchasing the Rule 144A
    _____          _______
    Yes               No      Securities only for the Buyer's own account?

     6. If the answer to the foregoing  question is "no", the Buyer agrees that,
in connection  with any purchase of securities sold to the Buyer for the account
of a third party (including any separate  account) in reliance on Rule 144A, the
Buyer will only  purchase for the account of a third party that at the time is a
"qualified  institutional  buyer"  within the meaning of Rule 144A. In addition,
the Buyer agrees that the Buyer will not purchase  securities  for a third party
unless the Buyer has  obtained a current  representation  letter from such third
party or taken other  appropriate  steps  contemplated  by Rule 144A to conclude
that  such  third  party   independently  meets  the  definition  of  "qualified
institutional buyer" set forth in Rule 144A.

     7. The Buyer will notify each of the parties to which this certification is
made of any changes in the information and conclusions herein. Until such notice
is given,  the  Buyer's  purchase  of Rule 144A  Securities  will  constitute  a
reaffirmation of this certification as of the date of such purchase.



                             _____________________________________________
                                   Print Name of Buyer


                              By:_________________________________________
                                   Name:
                                   Title:

                              Date:_______________________________________

                                     L-1-3
<PAGE>



                                                         ANNEX 2 TO EXHIBIT L

            QUALIFIED INSTITUTIONAL BUYER STATUS UNDER SEC RULE 144A

              [For Buyers That Are Registered Investment Companies]



     The  undersigned  hereby  certifies as follows in connection  with the Rule
144A Investment Representation to which this Certification is attached:

     1. As indicated  below,  the undersigned is the President,  Chief Financial
Officer or Senior Vice  President  of the Buyer or, if the Buyer is a "qualified
institutional  buyer" as that term is defined in Rule 144A under the  Securities
Act of 1933  ("Rule  144A")  because  Buyer  is part of a Family  of  Investment
Companies (as defined below), is such an officer of the Adviser.

     2. In  connection  with  purchases  by  Buyer,  the  Buyer is a  "qualified
institutional  buyer" as  defined in SEC Rule 144A  because  (i) the Buyer is an
investment company registered under the Investment Company Act of 1940, and (ii)
as marked below, the Buyer alone, or the Buyer's Family of Investment Companies,
owned at least  $100,000,000 in securities  (other than the excluded  securities
referred to below) as of the end of the Buyer's  most recent  fiscal  year.  For
purposes  of  determining  the  amount of  securities  owned by the Buyer or the
Buyer's Family of Investment Companies, the cost of such securities was used.

     ____ The Buyer owned  $___________________  in  securities  (other than the
excluded  securities referred to below) as of the end of the Buyer's most recent
fiscal year (such amount being calculated in accordance with Rule 144A).

     ____ The Buyer is part of a Family of Investment  Companies  which owned in
the aggregate  $______________ in securities (other than the excluded securities
referred  to below) as of the end of the Buyer's  most recent  fiscal year (such
amount being calculated in accordance with Rule 144A).

     3. The term "Family of  Investment  Companies"  as used herein means two or
more  registered  investment  companies  (or series  thereof) that have the same
investment  adviser or  investment  advisers that are  affiliated  (by virtue of
being majority owned  subsidiaries  of the same parent or because one investment
adviser is a majority owned subsidiary of the other).

     4. The term  "securities" as used herein does not include (i) securities of
issuers that are affiliated  with the Buyer or are part of the Buyer's Family of
Investment Companies, (ii) bank deposit notes and certificates of deposit, (iii)
loan  participations,  (iv)  repurchase  agreements,  (v)  securities  owned but
subject to a repurchase agreement and (vi) currency, interest rate and commodity
swaps.

     5. The Buyer is familiar  with Rule 144A and  understands  that each of the
parties to which this  certification  is made are relying  and will  continue to
rely on the  statements  made herein because one or more sales to the Buyer will
be in reliance on Rule 144A.  In addition,  the Buyer will only purchase for the
Buyer's own account.

     6.  The  undersigned  will  notify  each  of  the  parties  to  which  this
certification is made of any changes in the information and conclusions  herein.
Until such notice,  the Buyer's purchase of Rule 144A Securities will constitute
a reaffirmation of this  certification by the undersigned as of the date of such
purchase.

                                     L-2-1
<PAGE>




                                                   Print Name of Buyer


                                  By:
                                       Name:
                                       Title:

                                  Date:


                                  IF AN ADVISER:


                                                   Print Name of Buyer


                                  By:
                                       Name:
                                       Title:

                                  Date:

(SEAL)



                                     L-2-2
<PAGE>

                                                                   Exhibit M




                                                      [Date]

[Company]

Re:  Pooling and Servicing  Agreement  dated as of February 1, 2004 by and among
     Washington  Mutual  Mortgage  Securities  Corp.,  as  Depositor  and Master
     Servicer,  Citibank, N.A., as Trustee, and Christiana Bank & Trust Company,
     as Delaware  trustee,  relating to Washington  Mutual  Mortgage  Securities
     Corp. WaMu Mortgage Pass-Through Certificates, Series 2004-S1

Ladies and Gentlemen:

     In  accordance  with  Section  2.02  of  the  above-captioned  Pooling  and
Servicing Agreement, the undersigned,  as [Trustee] [Initial Custodian],  hereby
certifies that,  except as noted on the attachment  hereto,  as to each Mortgage
Loan listed in the Mortgage Loan Schedule  (other than any Mortgage Loan paid in
full or listed on the attachment hereto) it has reviewed the documents delivered
to it pursuant to Section 2.01 of the Pooling and  Servicing  Agreement  and has
determined that (i) all documents required (in the case of instruments described
in clauses (X)(iv) and (Y)(ix) of the definition of "Mortgage File," known by it
to be required)  pursuant to the definition of "Mortgage  File" and Section 2.01
of the Pooling and Servicing  Agreement to have been executed and received as of
the date  hereof are in its  possession  and (ii) all such  documents  have been
executed  and relate to the  Mortgage  Loans  identified  in the  Mortgage  Loan
Schedule. The [Trustee] [Initial Custodian] has made no independent  examination
of  such  documents  beyond  the  review  specifically  required  in  the  above
referenced  Pooling and  Servicing  Agreement  and has relied upon the purported
genuineness  and due  execution  of any such  documents  and upon the  purported
genuineness of any signature thereon. The [Trustee] [Initial Custodian] makes no
representations as to: (i) the validity, legality, enforceability or genuineness
of any of the  documents  contained in each Mortgage File or any of the Mortgage
Loans  identified on the Mortgage  Loan  Schedule,  or (ii) the  collectability,
insurability, effectiveness or suitability of any such Mortgage Loan.

     Capitalized  words  and  phrases  used  herein  shall  have the  respective
meanings  assigned  to  them  in  the  above-captioned   Pooling  and  Servicing
Agreement.




                               as [Trustee] [Initial Custodian]


                          By:
                               Name:
                               Title:


<PAGE>

                                   EXHIBIT N

                             BENEFIT PLAN AFFIDAVIT

Citibank, N.A., as Trustee (the "Trustee")
111 Wall Street, 14th Floor, Zone 3
New York, New York 10005
Attn:  Structured Finance Group, Washington Mutual 2004-S1

Washington Mutual Mortgage Securities Corp. ("Washington Mutual")
75 North Fairway Drive
Vernon Hills, IL  60061

RE:  CLASS [B-4] [B-5] [B-6] CERTIFICATES (THE "PURCHASED  CERTIFICATES") ISSUED
     BY WaMu  MORTGAGE  PASS-THROUGH  CERTIFICATES  SERIES  2004-S1  TRUST  (THE
     "TRUST")

     Under penalties of perjury, I, _____________________,  declare that, to the
best of my knowledge and belief, the following representations are true, correct
and complete; and

     1. That I am the _______________ of  __________________  (the "Purchaser"),
whose taxpayer  identification  number is ___________,  and on behalf of which I
have the authority to make this affidavit.

     2. That the Purchaser is acquiring a Purchased Certificate  representing an
interest in the assets of the Trust.

     3. That the Purchaser satisfies the condition in the paragraph marked below
[mark one paragraph only]:

     ___ The Purchaser is not an employee  benefit plan or other plan subject to
the prohibited transaction provisions of the Employee Retirement Income Security
Act of 1974, as amended,  or Section 4975 of the Internal  Revenue Code of 1986,
as amended (a "Plan"),  or any other person (including an investment  manager, a
named  fiduciary or a trustee of any Plan) acting,  directly or  indirectly,  on
behalf of, or purchasing  any of the Purchased  Certificates  with "plan assets"
of, any Plan within the meaning of the Department of Labor ("DOL") regulation at
29 C.F.R. Section 2510.3-101.

     ___ The Purchaser is an insurance  company,  the source of funds to be used
by it to acquire or hold the  Purchased  Certificate  is an  "insurance  company
general  account"  (within  the  meaning  of DOL  Prohibited  Transaction  Class
Exemption  ("PTCE")  95-60),  and the  conditions  in Sections I and III of PTCE
95-60 have been satisfied.

     ___ The  Purchaser  has  delivered to  Washington  Mutual and the Trustee a
Benefit Plan  Opinion (as defined in Section  1.01 of the Pooling and  Servicing
Agreement,  dated as of February 1, 2004, by and among  Washington  Mutual,  the
Trustee and the Delaware Trustee thereunder, and relating to the Trust).



                                     N-1
<PAGE>

IN WITNESS WHEREOF, the Purchaser has caused this instrument to be duly executed
on  its   behalf,   by  its  duly   authorized   officer   this   _____  day  of
__________________, 20__.

[Purchaser]

By:
      Its:


                                     N-2
<PAGE>

Personally appeared before me  ______________________,  known or proved to me to
be  the  same  person  who  executed  the  foregoing  instrument  and  to  be  a
________________  of the Purchaser,  and  acknowledged to me that (s)he executed
the  same as  his/her  free  act and  deed  and as the  free act and deed of the
Purchaser.

     SUBSCRIBED and SWORN to before me this day of ____________, 20__.


         Notary Public

                                      N-3
<page>
                                                                       Exhibit O

                             BENEFIT PLAN AFFIDAVIT

Citibank, N.A., as Trustee (the "Trustee")
111 Wall Street, 14th Floor, Zone 3
New York, New York 10005
Attn:  Structured Finance Group, Washington Mutual 2004-S1

Washington  Mutual  Mortgage  Securities  Corp.  ("Washington  Mutual")
75 North
Fairway Drive Vernon Hills, IL 60061

     RE: CLASS [B-1] [B-2] [B-3]  CERTIFICATES  (THE  "PURCHASED  CERTIFICATES")
ISSUED BY WaMu  MORTGAGE  PASS-THROUGH  CERTIFICATES  SERIES  2004-S1 TRUST (THE
"TRUST")

     Under penalties of perjury, I, _____________________,  declare that, to the
best of my knowledge and belief, the following representations are true, correct
and complete; and

     1. That I am the _______________ of  __________________  (the "Purchaser"),
whose taxpayer  identification  number is ___________,  and on behalf of which I
have the authority to make this affidavit.

     2. That the Purchaser is acquiring a Purchased Certificate  representing an
interest in the assets of the Trust.

     3. That the Purchaser satisfies the condition in the paragraph marked below
[mark one paragraph only]:

     ___ The  Purchaser is not an employee  benefit or other plan subject to the
prohibited transaction provisions of the Employee Retirement Income Security Act
of 1974, as amended  ("ERISA"),  or Section 4975 of the Internal Revenue Code of
1986,  as amended (a  "Plan"),  or any other  person  (including  an  investment
manager,  a named  fiduciary or a trustee of any such Plan) acting,  directly or
indirectly,  on behalf of or  purchasing  the Purchased  Certificate  with "plan
assets"  of, any Plan  within the  meaning of the  Department  of Labor  ("DOL")
regulation at 29 C.F.R. Section 2510.3-101.

     ___ The Purchaser is an insurance  company,  the source of funds to be used
by it to acquire or hold the  Purchased  Certificate  is an  "insurance  company
general  account"  (within  the  meaning  of DOL  Prohibited  Transaction  Class
Exemption  ("PTCE")  95-60),  and the  conditions  in Sections I and III of PTCE
95-60 have been satisfied.

     ___  The  Purchased   Certificate  was  rated  "BBB-"  or  better  (or  its
equivalent)  by at least one of the Rating  Agencies (as defined in Section 1.01
of  the  Pooling  and  Servicing  Agreement  (the  "the  Pooling  and  Servicing
Agreement"),  dated as of February 1, 2004, by and among Washington  Mutual, the
Trustee and the Delaware Trustee  thereunder,  and relating to the Trust) at the
time of  Purchaser's  acquisition  of the  Purchased  Certificate  (or  interest
therein).

     ___ The  Purchaser  has  delivered to  Washington  Mutual and the Trustee a
Benefit Plan  Opinion (as defined in Section  1.01 of the Pooling and  Servicing
Agreement).

                                     O-1
<PAGE>

     IN WITNESS  WHEREOF,  the Purchaser  has caused this  instrument to be duly
executed  on its  behalf,  by its duly  authorized  officer  this  _____  day of
__________________, 20__.

[Purchaser]

     By:
         Its:
                                     O-2
<PAGE>

  Personally  appeared before me  ______________________,  known or
proved to me to be the same person who executed the foregoing  instrument and to
be a  ________________  of the  Purchaser,  and  acknowledged  to me that  (s)he
executed  the same as his/her  free act and deed and as the free act and deed of
the Purchaser.

     SUBSCRIBED and SWORN to before me this day of ____________, 20__.


     Notary Public




                                      O-3