Exhibit 31.1


                      CERTIFICATION PURSUANT TO SECTION 302
                        OF THE SARBANES-OXLEY ACT OF 2002


I, Robert E. Lee, President and Chief Executive Officer of Millennium Chemicals
Inc., certify that:

     1. I have reviewed this annual report on Form 10-K of Millennium Chemicals
Inc. as filed with the Securities and Exchange Commission on March 12, 2004 and
as amended by Amendment No. 1 to the Annual Report on Form 10-K, filed with the
Securities and Exchange Commission on April 27, 2004, Amendment No. 2 to the
Annual Report on Form 10-K, filed with the Securities and Exchange Commission on
August 9, 2004 and this Amendment No. 3 to the Annual Report on Form 10-K, filed
with the Securities and Exchange Commission on the date hereof; and

     2. Based on my knowledge, this annual report, as amended, 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 with respect to the period covered by
this annual report.

Date: September 23, 2004

                                            /s/ ROBERT E. LEE
                                           -----------------------------
                                           Robert E. Lee
                                           President and Chief Executive Officer
                                           (Principal Executive Officer)