SECURITIES AND EXCHANGE COMMISSION
                             WASHINGTON, D.C. 20549

                                    FORM 10-K

                  ANNUAL REPORT PURSUANT TO SECTION 13 OR 15(d)
                     OF THE SECURITIES EXCHANGE ACT OF 1934

For the fiscal year ended:                              Commission File Number:
     December 31, 2003                                          333-89080

                           STRUCTURED PRODUCTS CORP.,
                                  on behalf of

             CAST Step-Up Trust For Credit Suisse First Boston Notes

             (Exact name of registrant as specified in its charter)

           Delaware                                            13-3692801
(State or other jurisdiction of                            (I.R.S. Employer
incorporation or organization)                             Identification No.)

                              388 Greenwich Street
                            New York, New York 10013
               (Address of principal executive offices) (zip code)

Registrant's telephone number including area code:

                                  212-816-7496

Securities registered pursuant to Section 12(b) of the Act:

<TABLE>
<CAPTION>

Title of Each Class                            Name of Each Exchange on Which Registered
------------------------------------------     -----------------------------------------
<S>                                            <C>
CAST Step-Up Trust For Credit Suisse First     New York Stock Exchange
Boston Notes, Monthly-Pay Step-Up Class A
Certificates
</TABLE>


Securities registered pursuant to Section 12(g) of the Act:

                                      None

Indicate by check mark whether the Registrant has (1) 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 have filed such  reports)  and (2) has been  subject to such filing
requirements for the past 90 days.

                               Yes  X1          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. [ ]


---------------
1    Pursuant to staff  administrative  positions  established  in the no-action
     letter Corporate Asset Backed  Corporation  ("CABCO")  (available August 9,
     1995),  the  Depositor is not required to respond to various  items of Form
     10-K. Such items are designated herein as "Not Applicable".


                                       1

<PAGE>

As of the date of this report, all of the common stock of the Registrant is held
by Citigroup Global Markets Holding Company Inc.

Indicate  by check mark  whether  the  Registrant  is an  accelerated  filer (as
defined in Exchange Act Rule 12b-2).

                               Yes  __          No  X
                                                    -


                       Documents Incorporated by Reference
                       -----------------------------------

The distribution reports to security holders filed on Form 8-K during the fiscal
year in lieu of reports on Form 10-Q,  which  includes the reports filed on Form
8-K listed in Item 15(b) hereto.


                                Introductory Note
                                -----------------

Structured  Products Corp.  (the  "Depositor")  is the depositor  under the Base
Trust  Agreement,  dated as of December 15, 2000,  as  supplemented  by the CAST
Supplement  2003-5,  dated as of May 2, 2003,  by and between the  Depositor and
U.S. Bank Trust National Association, as Trustee (the "Trustee"),  providing for
the issuance of the CAST  Step-Up  Trust For Credit  Suisse First Boston  Notes,
Monthly-Pay  Step-Up  Class  A  Certificates  (the  "Certificates")  and  is the
depositor for the  Certificates  (the  "Registrant").  The  Certificates  do not
represent obligations of or interests in the Depositor or the Trustee.

The issuer(s) of the underlying  securities,  or guarantor thereof, or successor
thereto, as applicable,  is subject to the information reporting requirements of
the  Securities  Exchange Act of 1934,  as amended  (the  "Exchange  Act").  For
information on the issuer(s) of the underlying securities, or guarantor thereof,
or successor thereto, as applicable, please see its periodic and current reports
filed with the  Securities  and Exchange  Commission  (the  "Commission").  Such
reports and other information required to be filed pursuant to the Exchange Act,
by  the  issuer(s)  of the  underlying  securities,  or  guarantor  thereof,  or
successor  thereto,  as  applicable,  may be inspected  and copied at the public
reference  facilities  maintained by the  Commission at 450 Fifth Street,  N.W.,
Washington,  D.C. 20549.  The Commission also maintains a site on the World Wide
Web at  "http://www.sec.gov"  at which  users  can view and  download  copies of
reports,   proxy  and  information   statements  and  other   information  filed
electronically  through the Electronic  Data  Gathering,  Analysis and Retrieval
system,  or "EDGAR."  Neither the Depositor nor the Trustee has  participated in
the  preparation  of  such  reporting  documents,  or  made  any  due  diligence
investigation  with respect to the  information  provided  therein.  Neither the
Depositor  nor the Trustee has  verified the  accuracy or  completeness  of such
documents  or  reports.  There can be no  assurance  that events  affecting  the
issuer(s)  of the  underlying  securities,  or guarantor  thereof,  or successor
thereto, as applicable,  or the underlying  securities have not occurred or have
not yet been publicly  disclosed that would affect the accuracy or  completeness
of the publicly available  documents described above. The chart below lists each
trust,  the  issuer(s)  or  guarantor,  or  successor  thereto,  of the  related
underlying   security,   and  its  respective  Exchange  Act  file  numbers,  if
applicable.

--------------------------------------------------- ----------------------------
Underlying Securities Issuer(s) or Guarantor, or     Exchange Act File Number
                successor thereto
--------------------------------------------------- ----------------------------
Credit Suisse First Boston (USA), Inc.              001-06862
--------------------------------------------------- ----------------------------


                                       2

<PAGE>


                                     PART I
                                     ------

Item 1.   Business
-------   --------

          None

Item 2.   Properties
-------   ----------

          None

Item 3.   Legal Proceedings
-------   -----------------

          None

Item 4.   Submission of Matters To A Vote of Security Holders
-------   ---------------------------------------------------

          None

                                     PART II
                                     -------

Item 5.   Market for Registrant's Common Equity and Related Stockholder Matters
-------   ---------------------------------------------------------------------

          The  Certificates  representing  investors'  interest in the Trust are
          represented  by one or more  physical  Certificates  registered in the
          name of Cede & Co., the nominee of The Depository Trust Company.

          The Certificates are listed on the New York Stock Exchange.



Item 6.   Selected Financial Data
-------   -----------------------

              None

Item 7.   Management's  Discussion  and  Analysis  of  Financial  Condition  and
-------   ----------------------------------------------------------------------
          Results of Operations
          ---------------------

              Not Applicable

Item 7A.  Quantitative and Qualitative Disclosures About Market Risk
--------  ----------------------------------------------------------

          None

Item 8.   Financial Statements and Supplementary Data
-------   -------------------------------------------

          None

Item 9.   Changes  In and  Disagreements  With  Accountants  on  Accounting  and
-------   ----------------------------------------------------------------------
          Financial Disclosure
          --------------------

          None

                                    PART III
                                    --------

Item 10.  Directors and Executive Officers of the Registrant
--------  --------------------------------------------------

          None

                                       3

<PAGE>

Item 11.  Executive Compensation
--------  ----------------------

          Not Applicable

Item 12.  Security Ownership of Certain Beneficial Owners and Management
--------  --------------------------------------------------------------

          Information  required by Item 201(d) of Regulation S-X: Not applicable
          Information required by Item 403 of Regulation S-X: None

Item 13.  Certain Relationships and Related Transactions
--------  ----------------------------------------------

          None

Item 14.  Controls and Procedures
--------  -----------------------

          Not Applicable

                                     PART IV
                                     -------

Item 15.  Exhibits, Financial Schedules and Reports on Form 8-K
--------  -----------------------------------------------------

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

     3.   Exhibits:

          99.1 Certification  by Assistant Vice President and Finance Officer of
               the  Registrant  pursuant to 15 U.S.C.  Section  7241, as adopted
               pursuant to Section 302 of the Sarbanes-Oxley Act of 2002.

          99.2 Annual Compliance Report by Trustee.

(b)  The following  reports on Form 8-K were filed during the period  covered by
     this report and are hereby incorporated by reference:

-------------- ----- -----------------------------------------------------------
               1.    Trustee's Distribution Statement for the June 15, 2003
                     Distribution Date filed on Form 8-K on June 27, 2003.
-------------- ----- -----------------------------------------------------------
               2.    Trustee's Distribution Statement for the July 15, 2003
                     Distribution Date filed on Form 8-K on July 25, 2003.
-------------- ----- -----------------------------------------------------------
               3.    Trustee's  Distribution  Statement  for the August 15, 2003
                     Distribution Date filed on Form 8-K on August 27, 2003.
-------------- ----- -----------------------------------------------------------
               4.    Trustee's Distribution Statement for the September 15, 2003
                     Distribution Date filed on Form 8-K on September 24, 2003.
-------------- ----- -----------------------------------------------------------
               5.    Trustee's  Distribution  Statement for the October 15, 2003
                     Distribution Date filed on Form 8-K on October 22, 2003.
-------------- ----- -----------------------------------------------------------
               6.    Trustee's  Distribution Statement for the November 15, 2003
                     Distribution Date filed on Form 8-K on November 20, 2003.
-------------- ----- -----------------------------------------------------------
               7.    Trustee's  Distribution Statement for the December 15, 2003
                     Distribution Date filed on Form 8-K on December 22, 2003.
-------------- ----- -----------------------------------------------------------


(c)  See item 15(a)(3) above.


                                       4

<PAGE>



                                   SIGNATURES
                                   ----------



     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.

                                              Structured Products Corp., as
                                              depositor for the Trust
                                              (the "Registrant")




Dated:  March 29, 2004                          By: /s/ Mark C. Graham
                                                --------------------------------
                                                Name:   Mark C. Graham
                                                Title:  Assistant Secretary,
                                                        Assistant Vice President
                                                        and Finance Officer


                                       5

<PAGE>


                                                                    Exhibit 99.1


                                  CERTIFICATION
                                  -------------


I, John W. Dickey, certify that:

1. I have reviewed this annual report on Form 10-K,  and all reports on Form 8-K
containing  distribution  or  servicing  reports  filed in  respect  of  periods
included in the year covered by this annual report of Structured Products Corp.,
on behalf of CAST Step-Up Trust For Credit Suisse First Boston Notes;

2. Based on my knowledge,  the  information in these reports,  taken as a whole,
does not  contain  any untrue  statement  of a material  fact or omit to state a
material  fact  necessary  to  make  the  statements   made,  in  light  of  the
circumstances  under which such  statements  were made, not misleading as of the
last day of the period covered by this annual report;

3. Based on my knowledge,  the distribution or servicing information required to
be provided to the depositor by the trustee under the pooling and servicing,  or
similar, agreement, for inclusion in these reports is included in these reports;
and

4. I am responsible for reviewing the activities  performed by the depositor and
the trustee  under the pooling and  servicing,  or similar,  agreement and based
upon  my  knowledge  and  the  annual  compliance  review  required  under  that
agreement,  and except as disclosed in the reports,  the  depositor  and trustee
have each fulfilled its obligations under that agreement.

In giving the  certifications  above,  I have  reasonably  relied on information
provided to me by the following  unaffiliated  parties: U.S. Bank Trust National
Association.


                                              By: /s/ John W. Dickey
                                                --------------------------------
                                                Name:  John W. Dickey
                                                Title: Assistant Vice President
                                                       and Finance Officer
                                                Date:  March 29, 2004


                                       6

<PAGE>


                                                                    Exhibit 99.2


                            ANNUAL COMPLIANCE REPORT
                            ------------------------

         The  undersigned,   being  an  officer  of  U.S.  Bank  Trust  National
Association,  as trustee (the "Trustee"), with respect to CAST Step-Up Trust For
Credit Suisse First Boston Notes, on whose behalf Structured  Products Corp. has
prepared this annual report on Form 10-K for the fiscal year ended  December 31,
2003 (the "Annual Report"), certifies as follows:

1. The Trustee is the trustee under the trust agreement.

2. Based on my  knowledge,  for the periods  included in the year covered by the
Annual  Report,  the  Trustee  has  fulfilled  its  obligations,  including  any
servicing obligations, under the trust agreement.



                                               /s/    Marlene Fahey
                                              ----------------------------------
                                              Name:   Marlene Fahey
                                              Title:  Vice President
                                              Date:   March 29, 2004


                                       7

<PAGE>



                                  EXHIBIT INDEX

Exhibit                                                                     Page
-------                                                                     ----

 99.1     Certification   by  Assistant  Vice  President  and  Finance       6
          Officer  of the  Registrant  pursuant  to 15 U.S.C.  Section
          7241,   as  adopted   pursuant   to   Section   302  of  the
          Sarbanes-Oxley Act of 2002.

 99.2     Annual  Compliance  Report by Trustee  pursuant to 15 U.S.C.       7
          Section 7241.





                                       8