UNITED STATES

                       SECURITIES AND EXCHANGE COMMISSION

                             WASHINGTON, D.C. 20549



                                    FORM 8-K

                                 CURRENT REPORT


     PURSUANT TO SECTION 13 OR 15(D) OF THE SECURITIES EXCHANGE ACT OF 1934


                Date of Report (Date of earliest event reported)

                                  June 7, 2004


                          BIOSOURCE INTERNATIONAL, INC.
             (Exact name of registrant as specified in its charter)

            Delaware                 0-21930                     77-0340829
(State or other jurisdiction       (Commission                 (IRS Employer
      of incorporation)            File Number)              Identification No.)



        542 Flynn Road, Camarillo, California                       93012
       (Address of principal executive offices)                   (Zip Code)

       Registrant's telephone number, including area code: (805) 987-0086





ITEM 5. - OTHER EVENTS.

On June 7, 2004,  BioSource  International,  Inc.  (the  "Company")  and Genstar
Capital Partners II, L.P., an investor in the Company  ("Genstar"),  amended the
warrant  issued to Genstar on February  15,  2000 (the  "Genstar  Warrant"),  to
extend the  expiration  date of the Genstar  Warrant  from  February 15, 2005 to
February 15, 2007. In  consideration  for the Company's  agreement to extend the
expiration date of the Genstar Warrant,  Genstar agreed to increase the exercise
price per share underlying that warrant from $7.77 per share to $9.00 per share.
The  Company and Stargen II LLC,  another  investor in the Company  ("Stargen"),
executed a similar amendment to a warrant issued to Stargen on February 15, 2000
(the "Stargen  Warrant").  The amendments to the Genstar Warrant and the Stargen
Warrant are referred to in this report as the "Amendments."

The Company's Board of Directors appointed a Special Committee of its members to
negotiate the  Amendments  with Genstar and Stargen.  The Special  Committee was
comprised of Terrance  Bieker,  David Moffa, and John Overturf,  Jr.,  directors
independent  of, and having no financial or other interest in, either Genstar or
Stargen.

Copies  of the  Amendments  are  attached  hereto  as  Exhibits  10.1 and  10.2,
respectively, and are hereby incorporated herein by this reference.

ITEM 7. - FINANCIAL STATEMENTS, PRO FORMA FINANCIAL INFORMATION AND EXHIBITS.

         (a)      Financial Statements. None.

         (b)      Pro Forma Financial Information. None.

         (c)      Exhibits

                  10.1     Amendment  No. 1 to Warrant to Purchase  Common Stock
                           dated June 7, 2004,  by and  between  the Company and
                           Genstar Capital Partners II, L.P.

                  10.2     Amendment  No. 1 to Warrant to Purchase  Common Stock
                           dated June 7, 2004,  by and  between  the Company and
                           Stargen II LLC.





                                   SIGNATURES

         Pursuant to the  requirements  of the Securities  Exchange Act of 1934,
the  Registrant  has duly  caused  this report to be signed on its behalf by the
undersigned hereunto duly authorized.

                                BIOSOURCE INTERNATIONAL, INC.



June 8, 2004                   /S/ ALAN I. EDRICK
                               -------------------------------
                               Alan I. Edrick
                               Executive Vice President and
                               Chief Financial Officer





                                  EXHIBIT INDEX


EXHIBIT
NUMBER         DESCRIPTION
- -------        -----------

10.1           Amendment No. 1 to Warrant to Purchase Common Stock dated June 7,
               2004, by and between the Company and Genstar Capital Partners II,
               L.P.

10.2           Amendment No. 1 to Warrant to Purchase Common Stock dated June 7,
               2004, by and between the Company and Stargen II LLC.