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      AS FILED WITH THE SECURITIES AND EXCHANGE COMMISSION ON JULY 27, 2004
                                                   1933 ACT FILE NO. 333-_______
                                                   1940 ACT FILE NO. 811 - 03763

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                       SECURITIES AND EXCHANGE COMMISSION
                             WASHINGTON, D.C. 20549

                                   ----------

                            REGISTRATION STATEMENT ON
                                    FORM S-6

                                   ----------

                FOR REGISTRATION UNDER THE SECURITIES ACT OF 1933
                     OF SECURITIES OF UNIT INVESTMENT TRUSTS
                            REGISTERED ON FORM N-8B-2

A.      EXACT NAME OF TRUST: CLAYMORE SECURITIES DEFINED PORTFOLIOS, SERIES 187

B.      NAME OF DEPOSITOR: CLAYMORE SECURITIES, INC.

C.      COMPLETE ADDRESS OF DEPOSITOR'S PRINCIPAL EXECUTIVE OFFICES:

                            Claymore Securities, Inc.
                              210 North Hale Street
                             Wheaton, Illinois 60187

D.      NAME AND COMPLETE ADDRESS OF AGENT FOR SERVICE:

  Copies to:

     NICHOLAS DALMASO, ESQ.            ERIC F. FESS
     Senior Managing Director and
     General Counsel
     Claymore Securities, Inc.        Chapman and Cutler LLP
     210 North Hale Street            111 West Monroe Street
     Wheaton, Illinois 60187          Chicago, Illinois 60603
     (630) 784-6300                   (312) 845-3000

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        It is proposed that this filing will become effective (check appropriate
box)

/ /     immediately upon filing pursuant to paragraph (b)

/ /     on (date) pursuant to paragraph (b)

/ /     60 days after filing pursuant to paragraph (a)

/ /     on (date) pursuant to paragraph (a) of rule 485 or 486

/ /     This post-effective amendment designates a new effective date for a
        previously filed post-effective amendment.

E.      TITLE OF SECURITIES BEING REGISTERED: Units of fractional undivided
beneficial interest.

F.      APPROXIMATE DATE OF PROPOSED SALE TO PUBLIC: As soon as practicable
after the effective date of the Registration Statement.

/ /     Check box if it is proposed that this filing will become effective on
        (date) at (time) pursuant to Rule 487.

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The registration hereby amends this Registration Statement on such date or dates
as may be necessary to delay its effective date until the registrant shall file
a further amendment which specifically states that this Registration Statement
shall thereafter become effective in accordance with Section 8(a) of the
Securities Act of 1933 or until the Registration Statement shall become
effective on such date as the Commission, acting pursuant to said Section 8(a)
may determine.

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                   PRELIMINARY PROSPECTUS DATED JULY 27, 2004

                              SUBJECT TO COMPLETION


[LOGO OMITTED]

Claymore Securities Defined Portfolios, Series 187

Equity Dividend Income Portfolio (5-year), Series 9

Small-Cap Core Portfolio, Series 2


     Final prospectuses for prior Series of the Claymore Securities Defined
Portfolios are hereby incorporated by reference and used as part of a
preliminary prospectus for Claymore Securities Defined Portfolios, Series 187
(the "TRUST"). The final prospectus for the Trust is expected to be
substantially similar to the previous prospectuses. However, specific
information with respect to the Trust, including pricing, the size and
composition of the Trust's portfolio, the number of units of the Trust, dates
and summary information regarding the characteristics of securities to be
deposited in the Trust is not now available and will be different from that
shown since Trust has a unique portfolio. Accordingly, the information contained
herein with regard to the previous Trust should be considered as being included
for informational purposes only.

     The Securities and Exchange Commission has not approved or disapproved
these securities or passed upon the adequacy of this Prospectus. Any
representation to the contrary is a criminal offense.

     The information in this Prospectus is not complete and may be changed. We
may not sell these securities until the registration statement filed with the
Securities and Exchange Commission is effective. This Prospectus is not an offer
to sell the securities and it is not soliciting an offer to buy these securities
in any state where the offer or sale is not permitted.

Incorporated herein by reference are the prospectuses from Claymore Securities
Defined Portfolios, Series 167 (Registration No. 333-111746) dated January 15,
2004 and Claymore Securities Defined Portfolios, Series 177 (Registration No.
333-114530) dated May 5, 2004 which shall be used as a preliminary prospectus
for Claymore Securities Defined Portfolios, Series 187. The final prospectus for
Claymore Securities Defined Portfolios, Series 167, was filed on January 16,
2004 and the final prospectus for Claymore Securities Defined Portfolios, Series
177, was filed on May 6, 2004

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                       CONTENTS OF REGISTRATION STATEMENT

        A.  Bonding Arrangements of Depositor:

        The Depositor has obtained the following Securities Dealer Blanket Bond
for its officers, directors and employees:

<Table>
<Caption>
              INSURER/POLICY NO.                              AMOUNT
              ------------------                              ------
                                                         
        National Union Fire Insurance
     Company of Pittsburgh, Pennsylvania                    $ 250,000
                  959-9000
</Table>

        This Registration Statement comprises the following papers and
documents.

               The Facing Sheet
               The Prospectus
               The Signatures
               Consents of Counsel

        The following exhibits:

1.1     Reference Trust Agreement (to be supplied by amendment).

1.1.1   Standard Terms and Conditions of Trust (Reference is made to Exhibit
        1.1.1 to Amendment No.1 to the Registration Statement on Form S-6 for
        Claymore Securities Defined Portfolios, Series 116 (File No. 333-72828
        filed on December 18, 2001).

2.1     Code of Ethics (Reference is made to Exhibit 2.1 to the Registration
        Statement on Form S-6 for Claymore Securities Deferred Portfolios,
        Series 171 (File No. 333-112575 filed on February 19, 2004).

3.1     Opinion of counsel as to legality of the securities being registered
        including a consent to the use of its name in the Registration Statement
        (to be supplied by amendment).

3.2     Opinion of counsel as to Federal Income tax status of the securities
        being registered including a consent to the use of its name in the
        Registration Statement (to be supplied by amendment).

3.3     Opinion of counsel as to New York Income tax status of the securities
        being registered including a consent to the use of its name in the
        Registration Statement (to be supplied by amendment).

3.4     Opinion of counsel as to the Trustee and the Trust (s) including a
        consent to the use of its name in the Registration Statement (to be
        supplied by amendment).

4.1     Consent of Independent Auditors (to be supplied by amendment).

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                                   SIGNATURES

     Pursuant to the requirements of the Securities Act of 1933, the Registrant,
Claymore Securities Defined Portfolios, Series 187 has duly caused this
Registration Statement to be signed on its behalf by the undersigned thereunto
duly authorized, in the City of Wheaton, and State of Illinois, on the 27th day
of July, 2004.

                                     CLAYMORE SECURITIES DEFINED PORTFOLIOS,
                                       SERIES 187, Registrant

                                     By:  CLAYMORE SECURITIES, INC., Depositor


                                        By:   /s/ Nicholas Dalmaso
                                            -----------------------------
                                                    Nicholas Dalmaso


     Pursuant to the requirements of the Securities Act of 1933, this
Registration Statement has been signed below on July 26, 2004 by the following
persons, who constitute a majority of the Board of Directors of Claymore
Securities, Inc.

   SIGNATURE*           TITLE**                      DATE

                                                   ) By:  /s/ Nicholas Dalmaso
                                                   )      ----------------------
                                                   )           Nicholas Dalmaso
                                                   )           Attorney-in-Fact*
                                                   )
DAVID HOOTEN*           Chairman of the Board of   )      July 27, 2004
                        Directors                  )

/S/ CHARLES MILLINGTON  Chief Financial Officer           July 27, 2004
- ----------------------
    CHARLES MILLINGTON

/S/ NICHOLAS DALMASO    Executive Vice President,         July 27, 2004
- ----------------------  Secretary, Treasurer and
    NICHOLAS DALMASO    Director


- ----------
*    An executed copy of the related power of attorney was filed as Exhibit 6.0
     to Registration Statement No. 333-98345 on August 22, 2002.

**   The titles of the persons named herein represent their capacity in and
     relationship to Claymore Securities, Inc., the Depositor.

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                         CONSENT OF INDEPENDENT AUDITORS

     The consent of Grant Thronton LLP to the use of its report and to the
reference to such firm in the Prospectus included in the Registration Statement
will be filed as Exhibit 4.1 to the Registration Statement.

                        CONSENT OF CHAPMAN AND CUTLER LLP

     The consent of Chapman and Cutler LLP to the use of its name in the
Prospectus included in the Registration Statement will be contained in its
opinions to be filed as Exhibits 3.1 and 3.2 to the Registration Statement.

                      CONSENT OF EMMET, MARVIN & MARTIN LLP

     The consent of Emmet, Marvin & Martin LLP to the use of its name in the
Prospectus included in the Registration Statement will be contained in its
opinions to be filed as Exhibits 3.3 and 3.4 to the Registration Statement.

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                                   MEMORANDUM

     Re:   Claymore Securities Defined Portfolios, Series 187

     The list of securities comprising the trust of the fund, the evaluation,
record and distribution dates and other changes pertaining specifically to the
new series, such as size and number of units of the trust in the fund and the
statement of financial condition of the new fund will be filed by amendment.

                                    1940 ACT

                              FORMS N-8A AND N-8B-2

     Form N-8A and Form N-8B-2 were filed in respect of Claymore Securities
Defined Portfolios, Series 116 (and subsequent series) (File No. 811-03763).

                                    1933 ACT

                                  THE INDENTURE

     The form of the proposed Standard Terms and Conditions of Trust is expected
to be in all respects consistent with the form of the Standard Terms and
Conditions of Trust dated December 18, 2001 relative to Claymore Securities
Defined Portfolios, Series 116.

                                                 CHAPMAN AND CUTLER LLP

Chicago, Illinois
July 27, 2004

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