EXHIBIT 32.2


                            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 BioSource  International,  Inc.  (the
"Company") on Form 10-K for the year ended September 30, 2003, as filed with the
Securities and Exchange Commission on the date hereof (the "Report"), I, Charles
C. Best, Chief Financial Officer of the Company,  certify, pursuant to 18 U.S.C.
Section 1350, as adopted  pursuant to Section 906 of the  Sarbanes-Oxley  Act of
2002, that, to the best of my knowledge:


         (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.


\S\ CHARLES C. BEST
- --------------------------
Charles C. Best
Chief Financial Officer

Date: March 29, 2004