<PAGE>


                       SECURITIES AND EXCHANGE COMMISSION
                             WASHINGTON, D. C. 20549

                           --------------------------

                                    FORM 8-K

                                 CURRENT REPORT

                       Pursuant to Section 13 or 15(d) of
                       The Securities Exchange Act of 1934

                            -------------------------

      Date of Report (Date of earliest event reported): September 15, 2006

                          MERRILL LYNCH DEPOSITOR, INC.
                     (on behalf of PPLUS TRUST SERIES CMT-1)
             (Exact name of registrant as specified in its charter)


        Delaware                001-32142                   13-3891329
    (State or other       (Commission File #)           (I. R. S. Employer
    jurisdiction of                                     Identification No.)
     incorporation)

 World Financial Center,                                     10080
   New York,  New York                                    (Zip Code)
  (Address of principal
   executive offices)

                           --------------------------

       Registrant's telephone number, including area code: (212) 449-1000

                      INFORMATION TO BE INCLUDED IN REPORT


Check the appropriate box below if the Form 8-K filing is intended to
simultaneously satisfy the filing obligation of the registrant under any of the
following provisions (see General Instruction A.2.):

[ ]      Written communications pursuant to Rule 425 under the Securities Act
         (17 CFR 230.425)

[ ]      Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17
         CFR 240.14a-12)

[ ]      Pre-commencement communications pursuant to Rule 14d-2(b) under the
         Exchange Act (17 CFR 240.14d-2(b))

[ ]      Pre-commencement communications pursuant to Rule 13e-4(c) under the
         Exchange Act (17 CFR 240.13e-4(c))


<PAGE>

Section 1.        Registrant's Business and Operations

                  Not applicable.

Section 2.        Financial Information

                  Not applicable.

Section 3.        Securities and Trading Markets

                  Not applicable.

Section 4.        Matters Related to Accountants and Financial Statements

                  Not applicable.

Section 5.        Corporate Governance and Management

                  Not applicable.

Section 6.        Asset-Backed Securities

                  Not applicable.

Section 7.        Regulation FD

                  Not applicable.

Section 8.        Other Events

         Item 8.01         Other events

              99.1         Distribution to holders of the PPLUS Trust
                           Certificates Series CMT-1 on September 15, 2006.


                                    For information with respect to the
                           underlying securities held by PPLUS Trust Series
                           CMT-1, please refer to Comcast Corporation's
                           (Commission file number 000-50093) periodic reports,
                           including annual reports on Form 10-K, quarterly
                           reports on Form 10-Q and current reports on Form 8-K,
                           and other information on file with the Securities and
                           Exchange Commission (the "SEC"). You can read and
                           copy these reports and other information at the
                           public reference facilities maintained by the SEC at
                           Room 1580, 100 F Street, NE, Washington, D.C. 20549.
                           You may obtain copies of this material for a fee by
                           writing to the SEC's Public Reference Section of the
                           SEC at 100 F Street, NE, Washington, D.C. 20549. You
                           may obtain information about the operation of the
                           Public Reference Room by calling the SEC at
                           1-800-SEC-0330. You can also access some of this
                           information electronically by means of the SEC's
                           website on the Internet at http://www.sec.gov, which
                           contains reports, proxy and information statements
                           and other information that the underlying securities
                           guarantors' and underlying securities issuer have
                           filed electronically with the SEC.

                                    Although we have no reason to believe the
                           information concerning the underlying securities, the
                           underlying guarantees, the underlying securities
                           issuer or the underlying securities guarantors
                           contained in the underlying securities issuer's or
                           the underlying securities guarantors' Exchange Act
                           reports is not reliable, neither the depositor nor
                           the trustee participated in the preparation of such
                           documents or made any due diligence inquiry with
                           respect to the information provided therein. No
                           investigation with respect to the underlying
                           securities issuer or the underlying securities
                           guarantors (including, without limitation, no
                           investigation as to their respective financial
                           condition or creditworthiness), the underlying
                           securities or the underlying guarantees has been
                           made. You should obtain and evaluate the same
                           information concerning the underlying securities
                           issuer and the underlying securities guarantors as
                           you would obtain and evaluate if you were investing
                           directly in the underlying securities and the
                           underlying guarantees or in other securities issued
                           by the underlying securities issuer or the underlying
                           securities guarantors. There can be no assurance that
                           events affecting the underlying securities, the
                           underlying guarantees, the underlying securities
                           issuer or the underlying securities guarantors have
                           not occurred or have not yet been publicly disclosed
                           which would affect the accuracy or completeness of
                           the publicly available documents described above.

<PAGE>

Section 9.        Financial Statements and Exhibits

         Item 9.01         Financial Statements and Exhibits

                  (a)      Financial statements of business acquired.

                           Not Applicable.

                  (b)      Pro forma financial information.

                           Not Applicable.

                  (c)      Shell company transactions

                           Not Applicable.

                  (d)      Exhibits.

                           99.1     Trustee's report in respect of the September
                                    15, 2006 distribution to holders of the
                                    PPLUS Trust Certificates Series CMT-1.

<PAGE>

                                   SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, the
registrant has duly caused this report to be signed on its behalf by the
undersigned, hereunto duly authorized.


                                  MERRILL LYNCH DEPOSITOR, INC.

Date: 9/26/06                     By: /s/ Jason Liddell
                                      --------------------------------------
                                  Name:  Jason Liddell
                                  Title: Vice President


<PAGE>


                                  EXHIBIT INDEX


99.1     Trustee's report in respect of the September 15, 2006 distribution to
         holders of the PPLUS Trust Certificates Series CMT-1.
[{"type": "8-K", "sequence": "1", "filename": "b415023_8k.txt", "description": "FORM 8-K", "secsgml_size_bytes": 8346}]
{"company-data": {"conformed-name": "MERRILL LYNCH DEPOSITOR INC PPLUS TRUST SERIES CMT-1", "cik": "0001286189", "assigned-sic": "6189", "irs-number": "133891329", "state-of-incorporation": "DE", "fiscal-year-end": "1231"}, "filing-values": {"form-type": "8-K", "act": "34", "file-number": "001-32142", "film-number": "061110159"}, "business-address": {"street1": "WORLD FINANCIAL CENTER", "city": "NEW YORK", "state": "NY", "zip": "10281"}, "mail-address": {"street1": "4 WORLD FINANCIAL CENER", "street2": "NORTH TOWER", "city": "NEW YORK", "state": "NY", "zip": "10080"}}
SECURITIES AND EXCHANGE COMMISSION
                             WASHINGTON, D. C. 20549

                           --------------------------

                                    FORM 8-K

                                 CURRENT REPORT

                       Pursuant to Section 13 or 15(d) of
                       The Securities Exchange Act of 1934

                            -------------------------

      Date of Report (Date of earliest event reported): September 15, 2006

                          MERRILL LYNCH DEPOSITOR, INC.
                     (on behalf of PPLUS TRUST SERIES CMT-1)
             (Exact name of registrant as specified in its charter)

        Delaware                001-32142                   13-3891329
    (State or other       (Commission File #)           (I. R. S. Employer
    jurisdiction of                                     Identification No.)
     incorporation)

 World Financial Center,                                     10080
   New York,  New York                                    (Zip Code)
  (Address of principal
   executive offices)

                           --------------------------

       Registrant's telephone number, including area code: (212) 449-1000

                      INFORMATION TO BE INCLUDED IN REPORT

Check the appropriate box below if the Form 8-K filing is intended to
simultaneously satisfy the filing obligation of the registrant under any of the
following provisions (see General Instruction A.2.):

[ ]      Written communications pursuant to Rule 425 under the Securities Act
         (17 CFR 230.425)

[ ]      Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17
         CFR 240.14a-12)

[ ]      Pre-commencement communications pursuant to Rule 14d-2(b) under the
         Exchange Act (17 CFR 240.14d-2(b))

[ ]      Pre-commencement communications pursuant to Rule 13e-4(c) under the
         Exchange Act (17 CFR 240.13e-4(c))
Section 1.        Registrant's Business and Operations

                  Not applicable.

Section 2.        Financial Information

                  Not applicable.

Section 3.        Securities and Trading Markets

                  Not applicable.

Section 4.        Matters Related to Accountants and Financial Statements

                  Not applicable.

Section 5.        Corporate Governance and Management

                  Not applicable.

Section 6.        Asset-Backed Securities

                  Not applicable.

Section 7.        Regulation FD

                  Not applicable.

Section 8.        Other Events

         Item 8.01         Other events

              99.1         Distribution to holders of the PPLUS Trust
                           Certificates Series CMT-1 on September 15, 2006.

                                    For information with respect to the
                           underlying securities held by PPLUS Trust Series
                           CMT-1, please refer to Comcast Corporation's
                           (Commission file number 000-50093) periodic reports,
                           including annual reports on Form 10-K, quarterly
                           reports on Form 10-Q and current reports on Form 8-K,
                           and other information on file with the Securities and
                           Exchange Commission (the "SEC"). You can read and
                           copy these reports and other information at the
                           public reference facilities maintained by the SEC at
                           Room 1580, 100 F Street, NE, Washington, D.C. 20549.
                           You may obtain copies of this material for a fee by
                           writing to the SEC's Public Reference Section of the
                           SEC at 100 F Street, NE, Washington, D.C. 20549. You
                           may obtain information about the operation of the
                           Public Reference Room by calling the SEC at
                           1-800-SEC-0330. You can also access some of this
                           information electronically by means of the SEC's
                           website on the Internet at http://www.sec.gov, which
                           contains reports, proxy and information statements
                           and other information that the underlying securities
                           guarantors' and underlying securities issuer have
                           filed electronically with the SEC.

                                    Although we have no reason to believe the
                           information concerning the underlying securities, the
                           underlying guarantees, the underlying securities
                           issuer or the underlying securities guarantors
                           contained in the underlying securities issuer's or
                           the underlying securities guarantors' Exchange Act
                           reports is not reliable, neither the depositor nor
                           the trustee participated in the preparation of such
                           documents or made any due diligence inquiry with
                           respect to the information provided therein. No
                           investigation with respect to the underlying
                           securities issuer or the underlying securities
                           guarantors (including, without limitation, no
                           investigation as to their respective financial
                           condition or creditworthiness), the underlying
                           securities or the underlying guarantees has been
                           made. You should obtain and evaluate the same
                           information concerning the underlying securities
                           issuer and the underlying securities guarantors as
                           you would obtain and evaluate if you were investing
                           directly in the underlying securities and the
                           underlying guarantees or in other securities issued
                           by the underlying securities issuer or the underlying
                           securities guarantors. There can be no assurance that
                           events affecting the underlying securities, the
                           underlying guarantees, the underlying securities
                           issuer or the underlying securities guarantors have
                           not occurred or have not yet been publicly disclosed
                           which would affect the accuracy or completeness of
                           the publicly available documents described above.
Section 9.        Financial Statements and Exhibits

         Item 9.01         Financial Statements and Exhibits

                  (a)      Financial statements of business acquired.

                           Not Applicable.

                  (b)      Pro forma financial information.

                           Not Applicable.

                  (c)      Shell company transactions

                           Not Applicable.

                  (d)      Exhibits.

                           99.1     Trustee's report in respect of the September
                                    15, 2006 distribution to holders of the
                                    PPLUS Trust Certificates Series CMT-1.
SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, the
registrant has duly caused this report to be signed on its behalf by the
undersigned, hereunto duly authorized.

                                  MERRILL LYNCH DEPOSITOR, INC.

Date: 9/26/06                     By: /s/ Jason Liddell
                                      --------------------------------------
                                  Name:  Jason Liddell
                                  Title: Vice President
EXHIBIT INDEX

99.1     Trustee's report in respect of the September 15, 2006 distribution to
         holders of the PPLUS Trust Certificates Series CMT-1.