Cell Genesys (CEGE) 10-Q 2009 Q3 Quarterly report

Exhibit 32.1

CERTIFICATION OF CHIEF EXECUTIVE 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, to my knowledge, the Quarterly Report of Cell Genesys, Inc. on Form 10-Q for the quarterly period ended June 30, 2009 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.

Dated: August 5, 2009

By:	/s/    STEPHEN A. SHERWIN, M.D.
Name:	Stephen A. Sherwin, M.D.
Title:	Chairman of the Board and Chief Executive Officer

This certification accompanies this Report on Form 10-Q pursuant to Section 906 of the Sarbanes-Oxley Act of 2002 and shall not, except to the extent required by such Act, be deemed filed by the Company for purposes of Section 18 of the Securities Exchange Act of 1934, as amended (the “Exchange Act”). Such certification will not be deemed to be incorporated by reference into any filing under the Securities Act of 1933, as amended, or the Exchange Act, except to the extent that the Company specifically incorporates it by reference.

A signed original of this written statement required by Section 906 has been provided to Cell Genesys, Inc. and will be retained by Cell Genesys, Inc. and furnished to the Securities and Exchange Commission on request.