Cell Genesys (CEGE) 10-Q 2002 Q3 Quarterly report

Exhibit 99.1

CERTIFICATION OF CHIEF EXECUTIVE OFFICER AND CHIEF FINANCIAL OFFICER

PURSUANT TO

18 U.S.C. SECTION 1350,

AS ADOPTED PURSUANT TO

SECTION 906 OF THE SARBANES-OXLEY ACT OF 2002

I, Stephen A. Sherwin, certify, pursuant to 18 U.S.C. Section 1350, as adopted pursuant to Section 906 of the Sarbanes-Oxley Act of 2002, that the Quarterly Report of Cell Genesys, Inc. Form 10-Q for the quarterly period ended June 30, 2002 fully complies with the requirements of Section 13(a) or 15(d) of the Securities Exchange Act of 1934 and that information contained in such Form 10-Q fairly presents in all material respects the financial condition and results of operations of Cell Genesys, Inc.

Date: August 14, 2002

By:/s/ Stephen A. Sherwin
Name: Stephen A. Sherwin, M.D.
Title: Chief Executive Officer

I, Matthew J. Pfeffer, certify, pursuant to 18 U.S.C. Section 1350, as adopted pursuant to Section 906 of the Sarbanes-Oxley Act of 2002, that the Quarterly Report of Cell Genesys, Inc. Form 10-Q for the quarterly period ended June 30, 2002 fully complies with the requirements of Section 13(a) or 15(d) of the Securities Exchange Act of 1934 and that information contained in such Form 10-Q fairly presents in all material respects the financial condition and results of operations of Cell Genesys, Inc.

Date: August 14, 2002

By: /s/ Matthew J. Pfeffer
Name: Matthew J. Pfeffer
Title: Chief Financial Officer