Exhibit 99.1

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 Quarterly Report of Abgenix, Inc. (the “Company”) on Form 10-Q for the period ending June 30, 2002, as filed with the Securities and Exchange Commission on the date hereof (the “Report”), I hereby certify, pursuant to 18 U.S.C. § 1350, as adopted pursuant to § 906 of the Sarbanes-Oxley Act of 2002, that:

                (1)           The Report fully complies with the requirements of section 13(a) 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.

August 14, 2002
	/s/ RAYMOND M. WITHY
	Raymond M. Withy, Ph.D.
	President and Chief Executive Officer
	(Principal Executive Officer)