SECURITIES AND EXCHANGE COMMISSION

                             Washington, D.C. 20549


                                    FORM 10-K/A

[X]      Annual  report  pursuant  to  Section  13 or  15(d)  of the Securities
         Exchange   Act  of  1934   for   the    period  from October 1, 2001
         (Commencement of Operations) to December 31, 2001

[  ]     Transition report pursuant to Section 13 or 15(d) of the
         Securities Exchange Act of 1934 for the transition period from   to


                        Commission File Number 333-61840-08

               CREDIT SUISSE FIRST BOSTON MORTGAGE SECURITIES CORP.
             (Exact name of registrant as specified in its charter)

         Delaware                                            13-3320910
(State or other jurisdiction of                           I.R.S. Employer
incorporation or organization)                            Identification No.)

11 Madison Ave.
New York, New York                                             10010
(Address of Principal Executive Offices)                      (Zip Code)

       Registrant's telephone number, including area code :(212)325-2000


         CREDIT SUISSE FIRST BOSTON MORTGAGE SECURITIES CORP.
                         CSFB
        MORTGAGE PASS-THROUGH CERTIFICATES, SERIES 2001-S23
       (Title of each class of securities covered by this Form)

Securities registered pursuant to Section 12(b) of the Act:  None
Securities registered pursuant to Section 12(g) of the Act:  None

Indicate by check mark whether the registrant (1) has filed all reports required
to be filed by Section 13 or 15(d) of the Securities Exchange Act of 1934 during
the  preceding 12 months (or for such  shorter  period that the  registrant  was
required  to file  such  reports),  and  (2) has  been  subject  to such  filing
requirements for the past 90 days. Yes [X] No [ ]

Indicate by check mark if disclosure of delinquent  filers  pursuant to Item 405
of Regulation  S-K is not contained  herein,  and will not be contained,  to the
best of registrant's  knowledge,  in definitive proxy or information  statements
incorporated by reference in Part III of this Form 10-K or any amendment to this
Form 10-K. [X]

Documents incorporated by reference:  None

                                   Page 1 of 5
             This report consists 12 of consecutively numbered pages.


<PAGE>

                        AMENDMENT NUMBER 1 OF 1

                                  -2-

<PAGE>

CREDIT SUISSE FIRST BOSTON MORTGAGE SECURITIES CORP.
CSFB
MORTGAGE PASS-THROUGH CERTIFICATES, SERIES 2001-S23
-----------------------------------------------------------------------

PART IV

Item 14. Exhibits, Financial Statement Schedules and Reports on Form 8-K

(a) The following documents are filed as part of this report:

    (1) Financial Statements:
         Omitted.

    (2)  Financial Statement Schedules:
         Omitted.

    (3)  Exhibits:

   Annual  Servicer  Statement of  Compliance,  filed as Exhibit 99.1 hereto.
   Annual Statement of  Independent  Accountants  Report for the Servicer,
           filed as Exhibit 99.2 hereto.

(b)   Reports on Form 8-K: The  following  Current  Reports on Form 8-K were
      filed by the Registrant during the last quarter of 2001.

      Current  Reports   on Form 8-K,   dated   November 26,  2001, December 26,
     2001,  and  January  25,  2002,   were filed for the  purpose of filing the
     Monthly  Statement  sent to the  Holders of the  Offered  Certificates  for
     payments made on the same dates.  The items reported in such Current Report
     were Item 5 (Other Events).


(c)   Exhibits to this report are listed in Item (14)(a)(3) above.

                                      -3-
<PAGE>


SIGNATURE

Pursuant to the  requirements of Section 13 or 15(d) of the Securities  Exchange
Act of 1934,  the  registrant  has duly  caused  this report to be signed on its
behalf by the undersigned thereunto duly authorized.


                                    JPMORGAN CHASE BANK,
                                    not in its individual capacity but solely
                                    as Trustee under the Agreement
                                    referred to herein



Date:  August 21, 2002              By:  /s/ Thomas M. Britt
                                    -----------------------------
                                    Thomas M. Britt
                                    Trust Officer



                                      -4-
<PAGE>


                                 EXHIBIT INDEX

Exhibit     Description                                                 Page

 99.1       Servicer's Annual Statement of Compliance                    6
            and Officers' Certification

 99.2       Servicer's Annual Independent Accountant's Report            10



                                      -5-
<PAGE>

                                EXHIBIT 99.1

        Servicer's Annual Statement of Compliance
        and Officers' Certification

                                      -6-

<PAGE>
Wilshire Financial Services Group Inc.
1776 SW Madison Street
Portland, Oregon  97205

Tel:    503.223.5600
Fax:    503.952.7476
www.wfsg.com


MANAGEMENT'S ASSERTION ON MINIMUM SERVICING STANDARDS

As of and for the year ended December 31, 2001,  Wilshire Credit Corporation has
complied in all material respects with the minimum servicing standards set forth
in the Mortgage  Banker's  Association of America's  Uniform Single  Attestation
Program for Mortgage  Bankers.  As of and for this same period,  Wilshire Credit
Corporation had in effect a fidelity bond in the amount of $10,000,000.00 and an
errors and omission policy in the amount of $5,000,000.00.

/s/  Jay H. Memmott
Jay H. Memmott
President/CEO
March 22, 2002


/s/  Bruce A. Weinstein
Bruce A. Weinstein
Chief Financial Officer
March 22, 2002

                                        -7-

<PAGE>
Wilshire Credit Corporation
1776 SW Madison Street
Portland, Oregon  97205

Tel:    (503) 223-5600
        (800) 776-0100
Fax:    (503) 223-8799



ANNUAL SERVICING CERTIFICATION

In connection with those loans serviced by us we hereby certify that:

1. All real estate taxes,  special assessments and any charges that might become
a lien upon the property and which come due in the first calendar year have been
paid.

2. All FHA  insurance  premiums  or  private  mortgage  insurance  premiums,  if
applicable, have been paid and are in full force and effect.

3. An extended mortgage  impairment policy is in force,  adequately insuring all
loans in which Investor Savings has an interest.

4. All interest and/or monthly payment  adjustments for ARM loans have been made
in accordance with the mortgage terms.

5. Any exceptions to this  certification  are listed on an attachment along with
an explanation concerning their completion. If there are none listed, it will be
considered that there are no exceptions.

6. If applicable,  all property inspections have been completed according to the
provisions of the servicing agreement.

7.  We have a complete Disaster Recovery Plan in place.



WILSHIRE CREDIT CORPORATION
By:  /s/  Jay Memmott
Title:  President

March 22, 2002


                                        -8-

<PAGE>
OLYMPUS Servicing, LP
9600 Great Hills Trail, Suite #200W
Austin, TX  78759

Tel:  512.349.8300
Fax:  512.349.8371
www.OlympusServicing.com


OFFICER CERTIFICATE


A review of the  activities of the Servicer  during the preceding  calendar year
and of its  performance  under  servicing  agreements,  including this Servicing
Agreement has been made under such officer's supervision and to the best of such
officer's knowledge.

Based on such review,  the Servicer has compiled in all material  respects  with
the minimum  servicing  standards  set forth in the Uniform  Single  Attestation
Program for Mortgage  Bankers and has fulfilled all of its material  obligations
in all material respects throughout such year.


/s/  Jeff Neal
Jeff Neal
Chief Operating Officer


                                        -9-

<PAGE>


                                EXHIBIT 99.2

        Servicer's Annual Independent Accountant's Report



                                      -10-
<PAGE>
Deloitte & Touche LLP
Suite 3900
111 S.W. Fifth Avenue
Portland, Oregon 97204-3642

Tel: (503) 222-1341
Fax: (503) 324-2172


INDEPENDENT ACCOUNTANTS' REPORT

To Wilshire Credit Corporation:

We have examined management's assertion about Wilshire Credit Corporation's (the
"Company"),  a majority-owned  subsidiary of Wilshire  Financial  Services Group
Inc., compliance with the minimum servicing standards identified in the Mortgage
Bankers Association of America's Uniform Single Attestation Program for Mortgage
Bankers (USAP) as of and for the year ended  December 31, 2001,  included in the
accompanying  management assertion.  Management is responsible for the Company's
compliance with those minimum  servicing  standards.  Our  responsibility  is to
express an opinion on management's assertion about the entity's compliance based
on our examination.

Our  examination  was  made in  accordance  with  standards  established  by the
American  Institute of Certified Public Accountants and,  accordingly,  included
examining,  on a test basis,  evidence about the Company's  compliance  with the
minimum  servicing   standards  and  performing  such  other  procedures  as  we
considered  necessary  in the  circumstances.  We believe  that our  examination
provides a reasonable basis for our opinion.  Our examination does not provide a
legal  determination  on the  Company's  compliance  with the minimum  servicing
standards.

In our  opinion,  management's  assertion  that the  Company  complied  with the
aforementioned minimum servicing standards as of and for the year ended December
31, 2001 is fairly stated, in all material respects.



/s/ Deloitte & Touche LLP
------------------------------

March 22, 2002


                                        -11-

<PAGE>
KPMG
111 Congress Avenue, Suite 1100
Austin, TX  78701

Tel:  512.320.5200
Fax:  512.320.5100


INDEPENDENT ACCOUNTANTS' REPORT

General and Limited Partners
Olympus Servicing L.P.

We have examined management's assertion, included in the accompanying Management
Assertion,  that Olympus  Servicing  L.P.  complied  with the minimum  servicing
standards set forth in the Mortgage  Bankers  Association  of America's  Uniform
Single  Attestation  program for  Mortgage  Bankers as of and for the year ended
December  31, 2001.  Management  is  responsible  for Olympus  Servicing  L.P.'s
compliance with those minimum  servicing  standards.  Our  responsibility  is to
express an opinion on management's assertion about the Partnership's  compliance
based on our examination.

Our examination was made in accordance with attestations  standards  established
by the American  Institute of Certified  Public  Accountants  and,  accordingly,
included  examining,  on a test basis,  evidence about Olympus  Servicing L.P.'s
compliance with the minimum servicing  standards  specified above and performing
such other  procedures  as we  considered  necessary  in the  circumstances.  We
believe that our examination  provides a reasonable  basis for our opinion.  Our
examination does not provide a legal  determination on Olympus  Servicing L.P.'s
compliance with the minimum servicing standards.

In our opinion, management's assertion that Olympus Servicing L.P. complied with
the  aforementioned  minimum  servicing  standards  as of and for the year ended
December 31, 2001 is fairly stated, in all material respects.


/s/  KPMG LLP

January 25, 2002




                                        -12-