<Page>


================================================================================

                       SECURITIES AND EXCHANGE COMMISSION
                             WASHINGTON, D.C. 20549
                                 --------------
                                   FORM 10-K/A

                                (Amendment No. 4)

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

                   FOR THE FISCAL YEAR ENDED DECEMBER 31, 2003

                                       OR

[ ]    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: 1-12091

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

                            MILLENNIUM CHEMICALS INC.
             (Exact name of registrant as specified in its charter)

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

<TABLE>
<S>                                                            <C>
               Delaware                                        22-3436215
    (State or other jurisdiction of              (I.R.S. Employer Identification No.)
    incorporation or organization)

     20 Wight Avenue, Suite 100                                  21030
            Hunt Valley, MD                                   (Zip Code)
(Address of principal executive offices)
</TABLE>

        Registrant's telephone number, including area code: 410-229-4400

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

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

                                               Name of each exchange
  Title of each class                           on which registered
-----------------------                       -----------------------
Common Stock, par value                       New York Stock Exchange
    $0.01 per share

           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 is required to file such reports) and (2) has been subject to such
filing requirements for the past 75 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]

         Indicate by check mark whether the registrant is an accelerated filer
(as defined in Rule 12b-2 of the Act). Yes [X] No [ ].

         The aggregate market value of voting stock held by non-affiliates as of
the last business day of the registrant's most recently completed second fiscal
quarter (based upon the closing price of $9.51 per common share as quoted on the
New York Stock Exchange), was approximately $593 million. For purposes of this
computation, the shares of voting stock held by directors, officers and employee
benefit plans of the registrant and its wholly-owned subsidiaries were deemed to
be stock held by affiliates. The number of shares of common stock outstanding at
March 5, 2004, was 64,605,553 shares, excluding 13,291,033 shares held by the
registrant, its subsidiaries and certain Company trusts that are not entitled to
vote.

Documents Incorporated by Reference

None.





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                                EXPLANATORY NOTE

      Millennium Chemicals Inc. (the "Company") filed Amendment No. 3
("Amendment No. 3") to its Annual Report on Form 10-K for the year ended
December 31, 2003 (the "Annual Report") to provide additional information
relating to the Company's material weakness in internal control over financial
reporting relating to the computation of deferred income taxes for the Company's
investment in Equistar Chemicals, LP; the analysis and re-computation performed
by the Company to correct such deferred income tax calculation; and the steps
the Company is taking to remediate such material weakness.

      This Amendment No. 4 to the Annual Report ("Amendment No. 4") contains the
text of Amendment No. 3 in its entirety apart from the explanatory note and
exhibits thereto. This Amendment No. 4 also includes as exhibits certificates
of each of the Chief Executive Officer and Chief Financial Officer that include
paragraphs 4 and 5, which were unintentionally omitted from the certificates
filed as exhibits to Amendment No. 3.


                                     PART II


Item 9A.  Controls and Procedures

(a)      The Company maintains disclosure controls and procedures that are
         designed to provide reasonable assurance that information required to
         be disclosed in the Company's filings under the Securities Exchange Act
         of 1934 is recorded, processed, summarized and reported within the
         periods specified in the rules and forms of the Securities and Exchange
         Commission (the "SEC") and that such information is accumulated and
         communicated to the Company's management, including its principal
         executive officer and principal financial officer, as appropriate, to
         allow timely decisions regarding required disclosure.

         As a result of tax integration activities that began in the second
         quarter of 2004 with respect to the Company's proposed business
         combination with Lyondell, the Company determined at the beginning of
         July 2004 that it had made errors in the computation of its tax basis
         in Equistar, which in turn had been used to compute the Company's
         deferred income taxes. In response to the determination that errors had
         been made, the Company performed a thorough analysis and re-computation
         of the Company's tax basis in Equistar. In late July 2004, the Company
         completed the analysis and re-computation necessary to verify and
         quantify the errors and prepare a restatement to correct the errors,
         which restatement was reflected in Amendment No. 2 to the Company's
         Annual Report on Form 10-K for the fiscal year ended December 31, 2003
         ("Amendment No. 2"), filed with the SEC on August 9, 2004.

         The restatement of prior periods' financial statements that resulted
         from the analysis and re-computation discussed above decreased the
         Company's liability for deferred income taxes and shareholders' deficit
         at December 31, 2003 and 2002 by $15 million. The restatement similarly
         decreased liabilities for deferred income taxes and increased
         shareholders' equity at December 31, 2001 and 2000 by $15 million. The
         restatement did not affect the Company's cash flow or operating income
         in any year.

         The errors corrected in the restatement were the result of (i) an
         incorrect computation by the Company in 1998 of the Company's original
         tax basis in the net assets it contributed to Equistar upon the joint
         venture's formation in December 1997 and (ii) incorrect computations by
         the Company for 1998 and 1999 of changes in the amount of such tax
         basis. The Company also discovered a de minimis error made in 2001. The
         Company believes that the errors were attributable to a material
         weakness in internal control over financial reporting relating to the
         computation by the Company of deferred income taxes for the Company's
         investment in Equistar. The material weakness consisted of (i)
         inadequate review and verification by the Company in 1998 of tax basis
         data relating to net assets contributed by the Company to Equistar in
         December 1997, and (ii) incorrect interpretation by the Company of
         Equistar tax return information provided by the "tax matters partner"
         of Equistar and used by Millennium to compute changes in its tax basis
         in Equistar for 1998 and 1999. Under Equistar's partnership agreement,
         Lyondell serves as the tax matters partner and, as such, prepares and
         files Equistar's tax returns.

         In order to remediate the material weakness in internal control over
         financial reporting, the Company is documenting the procedures used
         to analyze and re-compute the Company's tax basis in Equistar in July
         2004 for implementation with respect to the third quarter of 2004 and
         subsequent reporting periods. These procedures include (i) the detailed
         review by the Company's Director-Tax and its Vice President-Tax of
         estimates of tax return data provided quarterly by Equistar's tax
         matters partner, (ii) followed by discussions of the results of such
         review with the tax matters partner to confirm the correctness of the
         Company's interpretation of the estimated tax return data provided by
         the tax matters partner and (iii) thereafter, review of the results of
         these procedures by the Company's Corporate Controller and Chief
         Financial Officer. Although these procedures will be implemented for
         the third quarter of 2004, the material weakness will not be considered
         remediated until these procedures operate for a period of time, are
         tested and it is concluded that such procedures are operating
         effectively.

         In March 2004, prior to the initial filing of the Company's Annual
         Report on Form 10-K for the fiscal year ended December 31, 2003, the
         Company completed an evaluation under the supervision and with the
         participation of the Company's management, including the Company's
         principal executive officer and


                                       2




<Page>


         principal financial officer, of the effectiveness of the design and
         operation of the Company's disclosure controls and procedures as of
         December 31, 2003. Based on this evaluation, the Company's principal
         executive officer and principal financial officer concluded that the
         Company's disclosure controls and procedures were effective at the
         reasonable assurance level as of December 31, 2003. However, as a
         result of the Company's decision to restate its financial statements,
         the Company completed in early August 2004, prior to filing Amendment
         No. 2, a second evaluation under the supervision and with the
         participation of the Company's management, including the Company's
         principal executive officer and principal financial officer, of the
         effectiveness of the design and operation of the Company's disclosure
         controls and procedures as of December 31, 2003. Based on this second
         evaluation, the Company's principal executive officer and principal
         financial officer concluded that, solely as a result of the material
         weakness referred to above, the Company's disclosure controls and
         procedures were not effective at the reasonable assurance level as of
         December 31, 2003. However, as a result of the analysis and
         re-computation discussed above, management believes that the financial
         statements included in Amendment No. 2 fairly present in all material
         respects the Company's financial condition, results of operations and
         cash flows for the fiscal periods presented.

(b)      There were no changes in the Company's internal control over financial
         reporting that occurred during the most recent fiscal quarter covered
         by this Annual Report that have materially affected, or are reasonably
         likely to materially affect, the Company's internal control over
         financial reporting.

         As a result of Section 404 of the Sarbanes-Oxley Act of 2002 and the
         rules issued thereunder (the "Section 404 Requirements"), the Company
         will be required to include in its Annual Report on Form 10-K for the
         year ending December 31, 2004 a report on management's assessment of
         the effectiveness of the Company's internal control over financial
         reporting. As part of the process of preparing for compliance with the
         Section 404 Requirements, in 2003, the Company initiated a review of
         its internal control over financial reporting. This review is being
         conducted under the direction of senior management. As a result,
         management has made improvements to the Company's internal control
         through the date of the filing of this Amendment No. 3 as part of its
         normal review process. The Company's management does not believe these
         changes have materially affected, or are reasonably likely to
         materially affect, the Company's internal control over financial
         reporting. The Company anticipates that improvements will continue to
         be made as part of the ongoing review.






                                       3





<Page>




                                     PART IV

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

(a) The Following Documents are Filed as Part of This Report:


1.    Supplemental Financial Information. The Supplemental Financial Information
relating to Equistar consists of the following:


      Supplemental Financial Information.

      The Supplemental Financial Information relating to Equistar consists of
the following:

<TABLE>
<CAPTION>
                                                                                              Page of
                                                                                            This Report
                                                                                          ----------------
<S>                                                                                              <C>
       Financial Statements of Equistar:
          Report of PricewaterhouseCoopers LLP..........................................         F-1
          Consolidated Statements of Income--Years Ended December 31, 2003, 2002,
          and 2001......................................................................         F-2
          Consolidated Balance Sheets--December 31, 2003 and 2002.......................         F-3
          Consolidated Statements of Cash Flows--Years Ended December 31, 2003, 2002
            and 2001....................................................................         F-4
          Consolidated Statements of Partners' Capital--Years Ended December 31, 2003,
            2002 and 2001...............................................................         F-5
          Notes to Consolidated Financial Statements....................................     F-6 to F-23
</TABLE>



2. Financial Statement Schedule.

Financial Statement Schedule II -- Valuation and Qualifying Accounts, located on
page S-1 of Amendment No. 2 to the Annual Report on Form 10-K/A, should be
read in conjunction with the Financial Statements included in Item 8 of
Amendment No. 2 to the Annual Report on Form 10-K/A. Schedules, other than
Schedule II, are omitted because of the absence of the conditions under which
they are required or because the information called for is included in the
Consolidated Financial Statements of the Company or the Notes thereto.



3. Exhibits.


<TABLE>
<CAPTION>
     Exhibit
     Number                                           Description of Document
     -------                                          -----------------------
<S>              <C>
       3.1(a)    Amended and Restated Certificate of Incorporation of the
                 Company (Filed as Exhibit 3.1 to the Company's Registration
                 Statement on Form 10 (File No. 1-12091) (the "Form 10"))*

       3.1(b)    Certificate of Elimination of Series A Junior Preferred Stock
                 of Millennium Chemicals Inc. (Filed as Exhibit 3.1(b) to the
                 Company's Annual Report on Form 10-K for the year ended
                 December 31, 2002 (the "2002 Form 10-K")) *

       3.2       By-laws of the Company (as amended on February 4, 2002) (Filed
                 as Exhibit 3.2 to the Company's Annual Report on Form 10-K for
                 the year ended December 31, 2001 (the "2001 Form 10-K"))*

       4.1(a)    Form of Indenture, dated as of November 27, 1996, among
                 Millennium America (formerly named Hanson America Inc.), the
                 Company and The Bank of New York, as Trustee, in respect of the
                 7% Senior Notes due November 15, 2006 and the 7.625% Senior
                 Debentures due November 15, 2026
</TABLE>



                                      4



<Page>



<TABLE>
<S>              <C>
                 (Filed as Exhibit 4.1 to the Registration Statement of the
                 Company and Millennium America on Form S-1 (Registration No.
                 333-15975) (the "Form S-1"))*

       4.1(b)    First Supplemental Indenture dated as of November 21, 1997
                 among Millennium America, the Company and The Bank of New York,
                 as Trustee (Filed as Exhibit 4.1(b) to the Company's Annual
                 Report on Form 10-K for the year ended December 31, 1997 (the
                 "1997 Form 10-K"))*

       4.2       Indenture, dated as of June 18, 2001, among Millennium America
                 as Issuer, the Company as Guarantor, and The Bank of New York,
                 as Trustee (including the form of 9 1/4% Senior Notes due 2008
                 and the Note Guarantee) (Filed as Exhibit 4.1 to the
                 Registration Statement of the Company and Millennium America
                 (Registration Nos. 333-65650 and 333-65650-1) on Form S-4 (the
                 "Form S-4"))*

       4.3       Indenture, dated as of November 25, 2003, among the Company as
                 Issuer, Millennium America as Guarantor, and the Bank of New
                 York, as Trustee, in respect to the 4% Convertible Senior
                 Debentures due November 15, 2023 (Filed as Exhibit 4.1 to the
                 Company's Current Report on Form 8-K dated November 25, 2003)*

      10.1       Form of Indemnification Agreement, dated as of September 30,
                 1996, between Hanson and the Company (Filed as Exhibit 10.8 to
                 the Form 10)*

      10.2       Form of Tax Sharing and Indemnification Agreement, dated as of
                 September 30, 1996, between Hanson, Millennium Overseas
                 Holdings Ltd., Millennium America Holdings Inc. (formerly HM
                 Anglo American Ltd.), Hanson North America Inc. and the Company
                 (Filed as Exhibit 10.9(a) to the Form 10)*

      10.3(a)    Deed of Tax Covenant, dated as of September 30, 1996, between
                 Hanson, Millennium Overseas Holdings Ltd., Millennium Inorganic
                 Chemicals Limited (formerly SCM Chemicals Limited), SCMC
                 Holdings B.V. (formerly Hanson SCMC B.V.), Millennium Inorganic
                 Chemicals Ltd. (formerly SCM Chemicals Ltd.), and the Company
                 (the "Deed of Tax Covenant") (Filed as Exhibit 10.9(b) to the
                 Form 10)*

      10.3(b)    Amendment to the Deed of Tax Covenant dated January 28, 1997
                 (Filed as Exhibit 10.9(c) to the Company's Annual Report on
                 Form 10-K for the year ended December 31, 1996 (the "1996 Form
                 10-K"))*

      10.4(a)    Credit Agreement, dated June 18, 2001, among Millennium America
                 Inc., as Borrower, Millennium Inorganic Chemicals Limited, as
                 Borrower, certain borrowing subsidiaries of Millennium
                 Chemicals Inc., from time to time party thereto, Millennium
                 Chemicals Inc., as Guarantor, the lenders from time to time
                 party thereto, Bank of America, N.A., as Syndication Agent and
                 The Chase Manhattan Bank as Administrative Agent and collateral
                 agent (Filed as Exhibit 10.1 to the Form S-4)*

      10.4(b)    First Amendment, dated as of December 14, 2001, to the Credit
                 Agreement dated as of June 18, 2001, with Bank of America, N.A.
                 and JP Morgan Chase Bank and the lenders party thereto (Filed
                 as Exhibit 99.1 to the Company's Current Report on Form 8-K
                 dated December 18, 2001)*

      10.4(c)    Second Amendment, dated as of June 19, 2002, to the Credit
                 Agreement dated as of June 18, 2001, with the Bank of America,
                 N.A. and JP Morgan Chase Bank and the lenders party thereto
                 (Filed as Exhibit 10.1 to the Company's Quarterly Report on
                 Form 10-Q for the quarter ended June 30, 2002 (the "June 30,
                 2002, Form 10-Q"))*

      10.4(d)    Third Amendment, dated as of April 25, 2003, to the Credit
                 Agreement dated as of June 18, 2001, with the Bank of America,
                 N.A. and JP Morgan Chase Bank and the lenders party thereto
                 (Filed as Exhibit 10.1 to the Company's Quarterly Report on
                 Form 10-Q for the quarter ended March 31, 2003)*

      10.4(e)    Fourth Amendment, dated as of November 18, 2003, to the Credit
                 Agreement dated as of June 18, 2001, with the Bank of America,
                 N.A. and JP Morgan Chase Bank and the lenders party thereto
                 (Filed as Exhibit 10.1 to the Company's Quarterly Report on
                 Form 10-Q for the quarter ended March 31, 2003)*

      10.5       Form of Change in Control Agreements between Millennium America
                 Holdings Inc., (or certain of its subsidiaries), and each of
                 Robert E. Lee, C. William Carmean, Timothy E. Dowdle, Marie S.
                 Dreher, John E. Lushefski and Myra J. Perkinson (Filed as
                 Exhibit 10.7 to the 2002 Form 10-K)*'D'

</TABLE>



                                        5



<Page>



<TABLE>
<S>              <C>
      10.6(a)    Millennium Chemicals Inc. Annual Performance Incentive Plan
                 (Filed as Exhibit 10.23 to the Form 10)*'D'

      10.6(b)    Amendment Number 1 dated January 20, 1997, to the Millennium
                 Chemicals Inc. Annual Performance Plan (Filed as Exhibit
                 10.23(b) to the 1996 Form 10-K)*'D'

      10.6(c)    Amendment Number 2 dated January 23, 1998, to the Millennium
                 Chemicals Inc. Annual Performance Incentive Plan (Filed as
                 Exhibit 10.23(c) to the 1997 Form 10-K)*'D'

      10.6(d)    Amendment Number 3 dated January 22, 1999, to the Millennium
                 Chemicals Inc. Annual Performance Incentive Plan (Filed as
                 Exhibit 10.20(d) to the 1998 Form 10-K)*'D'

      10.6(e)    Amendment Number 4 dated as of June 1, 2002, to the Millennium
                 Chemicals Inc. Annual Performance Incentive Plan (Filed as
                 Exhibit 10.9(e) to the 2002 Form 10-K)*'D'

      10.7(a)    Millennium Chemicals Inc. Long Term Stock Incentive Plan (Filed
                 as Exhibit 10.25 to the Form 10)*'D'

      10.7(b)    Amendment Number 1 to the Millennium Chemicals Inc. Long Term
                 Stock Incentive Plan (Filed as Exhibit 10.6 to the Company's
                 Quarterly Report on Form 10-Q for the quarter ended September
                 30, 1997)*'D'

      10.7(c)    Amendment dated July 24, 1997 to the Millennium Chemicals Inc.
                 Long Term Stock Incentive Plan (Filed as Exhibit 10.25(c) to
                 the 1997 Form 10-K)*'D'

      10.7(d)    Amendments dated January 23, 1998 and December 10, 1998, to the
                 Millennium Chemicals Inc. Long Term Stock Incentive Plan (Filed
                 as Exhibit 10.23(d) to the 1998 Form 10-K)*'D'

      10.7(e)    Amendment dated as of November, 2002, to the Millennium
                 Chemicals Inc. Long Term Stock Incentive Plan*'D' (Filed as
                 Exhibit 10.7(e) to the Company's Amendment No. 1 to the Annual
                 Report on Form 10-K for the year ended December 31, 2003 (the
                 "2003 Form 10-K/A")

      10.8(a)    Amended and Restated Millennium Chemicals Inc. Supplemental
                 Executive Retirement Plan (Filed as Exhibit 10.11(a) to the
                 2002 Form 10-K)*'D'

      10.8(b)    Millennium Chemicals Inc. 2003 Supplemental Executive
                 Retirement Plan (Filed as Exhibit 10.11(b) to the 2002 Form
                 10-K)*'D'

      10.9(a)    Millennium Chemicals Grandfathered Supplemental Executive
                 Retirement Plan (Filed as Exhibit 10.15(b) to the 2000 Form
                 10-K)*'D'

      10.9(b)    Amendment dated as of November, 2002, to the Millennium
                 Chemicals Grandfathered Supplemental Executive Retirement
                 Plan*'D' (Filed as Exhibit 10.9(b) to the 2003 Form 10-K/A)

      10.10(a)   Millennium Petrochemicals Grandfathered Supplemental Executive
                 Retirement Plan (Filed as Exhibit 10.16 to the 2000 Form
                 10-K)*'D'

      10.10(b)   Amendment dated as of November, 2002, to the Millennium
                 Petrochemicals Grandfathered Supplemental Executive Retirement
                 Plan*'D' (Filed as Exhibit 10.10(b) to the 2003 Form 10-K/A)

      10.11(a)   Millennium Inorganic Chemicals Grandfathered Supplemental
                 Executive Retirement Plan (Filed as Exhibit 10.17 to the 2000
                 Form 10-K)*'D'

      10.11(b)   Amendment dated as of November, 2002, to the Millennium
                 Inorganic Chemicals Inc. Grandfathered Supplemental Executive
                 Retirement Plan*'D' (Filed as Exhibit 10.11(b) to the 2003 Form
                 10-K/A)

      10.12(a)   Millennium Specialty Chemicals Grandfathered Supplemental
                 Executive Retirement Plan (Filed as Exhibit 10.18 to the 2000
                 Form 10-K)*'D'

      10.12(b)   Amendment dated as of November, 2002, to the Millennium
                 Specialty Chemicals Inc. Grandfathered Supplemental Executive
                 Retirement Plan*'D' (Filed as Exhibit 10.12(b) to the 2003 Form
                 10-K/A)

      10.13(a)   Millennium Chemicals Inc. Salary and Bonus Deferral Plan (Filed
                 as Exhibit 10.30 to the 1996 Form 10-K)*'D'

      10.13(b)   Amendment Number 1 dated January 23, 1998, to the Millennium
                 Chemicals Inc. Salary and Bonus Deferral Plan (Filed as Exhibit
                 10.30(b) to the 1997 Form 10-K)*'D'

      10.13(c)   Amendment Number 2 dated January 22, 1999, to the Millennium
                 Chemicals Inc. Salary and Bonus
</TABLE>


                                      6





<Page>


<TABLE>

<S>              <C>
                 Deferral Plan (Filed as Exhibit 10.28(c) to the 1998 Form 10-K)*'D'

      10.13(d)   Amendment Number Three to the Millennium Chemicals Inc. Salary
                 and Bonus Deferral Plan dated November 2002 (Filed as Exhibit
                 10.19(d) to the 2002 Form 10-K)*'D'

      10.14(a)   Millennium Chemicals Inc. Supplemental Savings and Investment
                 Plan (Filed as Exhibit 10.29 to the 1998 Form 10-K)*'D'

      10.14(b)   Amendment to the Millennium Chemicals Inc. Supplemental Savings
                 and Investment Plan (Filed as Exhibit 10.20(b) to the 2002 Form
                 10-K)*'D' (Filed as Exhibit 10.14(b) to the 2003 Form 10-K/A)

      10.15      Millennium Chemicals Inc. 2003 Long Term Incentive Plan*'D'

      10.16      Millennium Chemicals Inc. 2004 Long Term Incentive Plan*'D'

      10.17      Millennium Chemicals Inc. 2003 Executive Long Term Executive Plan*'D'

      10.18      Millennium Chemicals Inc. 2004 Executive Long Term Incentive Plan*'D'

      10.19(a)   Millennium America Holdings Inc. Long Term Incentive Plan and
                 Executive Long Term Incentive Plan Trust Agreement (Filed as
                 Exhibit 10.23 to the 2000 Form 10-K)*'D'

      10.19(b)   Amendment Number 1 to the Millennium America Holdings Inc. Long
                 Term Incentive Plan Trust Agreement (Filed as Exhibit 10.23(b)
                 to the 2002 Form 10-K)*'D'

      10.20(a)   Millennium Chemicals Inc. Omnibus Incentive Compensation Plan
                 (Filed as Exhibit 10.24 to the 2000 Form 10-K)*'D'

      10.20(b)   Form of Stock Option Agreement under Omnibus Incentive
                 Compensation Plan (Filed as Exhibit 10.24(b) to the 2001 Form
                 10-K)*'D'

      10.20(c)   Amendment to Millennium Chemicals Inc. 2001 Omnibus Incentive
                 Compensation Plan (Filed as Exhibit 10.24(c) to the 2002 Form
                 10-K)*'D'

      10.20(d)   Amendment dated as of November, 2002, to the Millennium
                 Chemicals Inc. 2001 Omnibus Incentive Compensation Plan*'D'
                 (Filed as Exhibit 10.20(d) to the 2003 Form 10-K/A)

      10.20(e)   Form of Millennium Chemicals Inc. 2001 Omnibus Incentive
                 Compensation Plan Restricted Stock Award Agreement for
                 Non-Employee Directors*'D'

      10.20(f)   Form of Millennium Chemicals Inc. 2001 Omnibus Incentive
                 Compensation Plan Performance Unit Award Agreement for
                 International Officers and Key Employees*'D'

      10.20(g)   Form of Millennium Chemicals Inc. 2001 Omnibus Incentive
                 Compensation Plan Restricted Stock Award Agreement for
                 International Officers and Key Employees*'D'

      10.20(h)   Form of Millennium Chemicals Inc. 2001 Omnibus Incentive
                 Compensation Plan Restricted Stock Award Agreement for Officers
                 and Key Employees*'D'

      10.21(a)   Master Transaction Agreement between the Company and Lyondell
                 (Filed as an Exhibit to the Company's Current Report on Form
                 8-K dated July 25, 1997)*

      10.21(b)   First Amendment to Master Transaction Agreement between
                 Lyondell and the Company (Filed as an Exhibit to the Company's
                 Current Report on Form 8-K dated October 17, 1997)*

      10.22      Amended and Restated Limited Partnership Agreement of Equistar
                 Chemicals, LP dated as of November 6, 2002 (Filed as Exhibit
                 10.26 to the Company's Current Report on Form 8-K dated
                 November 25, 2002 (the "November 26, 2002 Form 8-K"))*

      10.23(a)   Asset Contribution Agreement (the "Millennium Asset
                 Contribution Agreement") among Millennium Petrochemicals,
                 Millennium Petrochemicals LP LLC and Equistar (Filed as an
                 Exhibit to the Company's Current Report on Form 8-K dated
                 December 10, 1997)*

      10.23(b)   First Amendment to the Millennium Asset Contribution Agreement
                 dated as of May 15, 1998 (Filed as Exhibit 10.23(b) to the 1999
                 Form 10-K)*

      10.23(c)   Second Amendment to the Asset Contribution Agreement among
                 Millennium Chemicals Inc., Millennium Petrochemicals LP LLC,
                 and Equistar Chemicals, LP (Filed as Exhibit 10.27(c) to the
                 2002 Form 10-K)*

      10.24      Amended and Restated Parent Agreement among Lyondell, the
                 Company and Equistar, dated as of November 6, 2002, (Filed as
                 Exhibit 10.29 to the November 26, 2002 8-K)*

</TABLE>



                                      7



<Page>


<TABLE>
<S>              <C>
      21.1       Subsidiaries of the Company*

      23.2       Consent of PricewaterhouseCoopers LLP (Filed as Exhibit 23.2 to
                 the Company's Amendment No. 2 to the Annual Report on Form 10-K
                 for the year ended December 31, 2003 ("10-K Amendment No.2"))*

      31.1       Certificate of Principal Executive Officer pursuant to Section
                 302 of the Sarbanes-Oxley Act of 2002**

      31.2       Certificate of Principal Financial Officer pursuant to Section
                 302 of the Sarbanes-Oxley Act of 2002**

      32.1       Certificate of Principal Executive Officer pursuant to Section
                 906 of the Sarbanes-Oxley Act of 2002* (Furnished, not filed,
                 in accordance with Item 601(b)(32)(ii) of Regulation S-K, 17
                 CFR 229.601(b)(32)(ii) with the 10-K Amendment No. 2)

      32.2       Certificate of Principal Financial Officer pursuant to Section
                 906 of the Sarbanes-Oxley Act of 2002* (Furnished, not filed,
                 in accordance with Item 601(b)(32)(ii) of Regulation S-K, 17
                 CFR 229.601(b)(32)(ii) with the 10-K Amendment No.2)

      99.1       Information relevant to forward-looking statements*
</TABLE>

In addition, the Company hereby agrees to furnish to the Securities and Exchange
Commission, upon request, a copy of any instrument not listed above that defines
the rights of the holders of long-term debt of the Company and its subsidiaries.

-----------------
    *  Incorporated by reference.
   **  Filed or furnished herewith.
  'D'  Management contract or compensatory plan or arrangement required to be
filed pursuant to Item 14(c).

(b)    Reports on Form 8-K

Current Reports on Form 8-K dated November 18, 2003, November 20, 2003, November
25, 2003, December 15, 2003 and February 4, 2004 were filed or furnished during
the quarter ended December 31, 2003 and through March 12, 2004, the date the
original Annual Report on Form 10-K was filed with the Securities and Exchange
Commission.



                                      8




<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.

                                    MILLENNIUM CHEMICALS INC.

                                    By:          /s/ ROBERT E. LEE
                                        ----------------------------------------
                                                     Robert E. Lee
                                                     President and
                                                Chief Executive Officer

September 24, 2004













                                       9






<Page>




                                  Exhibit Index
                                  -------------

<TABLE>
<CAPTION>
     Exhibit
     Number                  Description of Document
     -------                 -----------------------
<S>             <C>
     31.1       Certificate of Principal Executive Officer pursuant to Section
                302 of the Sarbanes-Oxley Act of 2002

     31.2       Certificate of Principal Financial Officer pursuant to Section
                302 of the Sarbanes-Oxley Act of 2002

</TABLE>






                                     10


                           STATEMENT OF DIFFERENCES

The dagger symbol shall be expressed as.....................................'D'