Exhibit 99.4


                            CERTIFICATION PURSUANT TO
                             18 U.S.C. SECTION 1350,
                             AS ADOPTED PURSUANT TO
                  SECTION 906 OF THE SARBANES-OXLEY ACT OF 2002

In connection with the Annual Report of Wyeth (the "Company") on Form 10-K/A for
the fiscal year ended December 31, 2001, as filed with the Securities and
Exchange Commission on December 23, 2002 (the "Report"), I, Robert Essner, Chief
Executive Officer of the Company, certify, pursuant to 18 U.S.C. ss. 1350, as
adopted pursuant to ss. 906 of the Sarbanes-Oxley Act of 2002, that:

(1) The Report fully complies with the requirements of section 13(a) or 15(d) of
the Securities Exchange Act of 1934; and

(2) The information contained in the Report fairly presents, in all material
respects, the financial condition and results of operations of the Company.





Dated:  December 23, 2002                By /s/    Robert Essner
                                           -----------------------------
                                                   Robert Essner
                                           President and Chief Executive
                                                      Officer