EXHIBIT 99.1


                                  CERTIFICATION
            PURSUANT TO SECTION 906 OF THE SARBANES-OXLEY ACT OF 2002
        (SUBSECTIONS (a) AND (b) OF SECTION 1350, CHAPTER 63 OF TITLE 18,
                               UNITED STATES CODE)

     Pursuant to section 906 of the  Sarbanes-Oxley Act of 2002 (subsections (a)
and (b) of section 1350,  chapter 63 of Title 18,  United States Code),  each of
the  undersigned   officers  of  BioSource   International,   Inc.,  a  Delaware
corporation (the  "Company"),  does hereby certify with respect to the Quarterly
Report of the Company on Form 10-Q for the quarter  ended  September 30, 2002 as
filed with the Securities and Exchange  Commission  (the "10-Q Report") that, to
the best of the undersigned's knowledge:

     (1)  the 10-Q 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 10-Q Report fairly presents,  in all
          material respects,  the financial  condition and results of operations
          of the Company.





Date:  November 11, 2002                        /s/ LEONARD M. HENDRICKSON
                                                --------------------------
                                                   Leonard M. Hendrickson
                                                   President and
                                                   Chief Executive Officer








Date:  November 11, 2002                        /s/ CHARLES C. BEST
                                                -------------------
                                                   Charles C. Best
                                                   Executive Vice President and
                                                   Chief Financial Officer