Document:

EXHIBIT 4.6

                                SECOND AMENDMENT
                                       TO
                            INVESTOR RIGHTS AGREEMENT

        THIS SECOND AMENDMENT (this "SECOND AMENDMENT"), dated as of September
28, 2000, by and among BIOSOURCE INTERNATIONAL, INC., a corporation organized
under the laws of the State of Delaware (the "COMPANY"); GENSTAR CAPITAL
PARTNERS II, L.P., a Delaware limited partnership ("GENSTAR CAPITAL PARTNERS");
STARGEN II LLC, a Delaware limited liability company ("STARGEN"); RUSSELL D.
HAYS, an individual ("HAYS"); GEORGE UVEGES, an individual ("UVEGES");
JEAN-PIERRE L. CONTE, an individual ("CONTE"); RICHARD F. HOSKINS, an individual
("HOSKINS"); RICHARD D. PATERSON, an individual ("PATERSON"); and ROBERT J.
WELTMAN, an individual ("WELTMAN" and, together with Conte, Hoskins and
Paterson, the "NEW INVESTORS" and, together with Conte, Hoskins, Paterson, Hays,
Uveges, Genstar Capital Partners and Stargen, the "INVESTORS").

                                    RECITALS

        WHEREAS, the Company, Genstar Capital Partners, Stargen, Hays and Uveges
are parties to that certain Investor Rights Agreement dated February 15, 2000,
as amended by the Amendment to Investor Rights Agreement dated as of September
18, 2000 (as so amended, the "AGREEMENT," capitalized terms used herein and not
otherwise defined herein shall have the respective meanings set forth in the
Agreement);

        WHEREAS, the Company, on the one hand, and Genstar Capital Partners and
the New Investors, on the other hand, have entered into that certain purchase
agreement dated September 15, 2000, as amended on September 28, 2000 (as so
amended, the "PURCHASE Agreement"), pursuant to which the Company has agreed,
upon the terms and subject to the conditions contained therein, to issue and
sell to Genstar Capital Partners and the New Investors an aggregate of 300,000
shares of the Company's Common Stock, par value $0.001 per share (the "SHARES");
and

        WHEREAS, in connection with the transactions contemplated by the
Purchase Agreement, the Company and the Investors desire to amend the Agreement
to provide to Genstar Capital Partners and the New Investors, upon closing of
the purchase of the Shares pursuant to the Purchase Agreement, certain
registration rights with respect to the Shares under the Securities Act, and
applicable state securities laws.

                                    AGREEMENT

        NOW, THEREFORE, in consideration of the premises and the mutual
covenants contained herein and other good and valuable consideration, the
receipt and sufficiency of which are hereby acknowledged, the Company and the
Investors, intending to be legally bound, hereby agree as follows:

     1. AMENDMENT TO DEFINITIONS. Section 1(b) of the Agreement is hereby
amended to read as follows:

          (b) "REGISTRABLE SECURITIES" means (i) the shares of Common Stock of
     the Company issued to Genstar Capital Partners and the Investors pursuant
     to certain purchase agreements dated September 15, 2000 and September 18,
     2000, respectively, by and among

<PAGE>

     the Company, Genstar Capital Partners and the New Investors, on the one
     hand, and the Company, Russell D. Hays and George Uveges, on the other
     hand, and (ii) the shares of Common Stock of the Company issued or issuable
     to Genstar Capital Partners and Stargen upon conversion of the Series B
     Shares or upon exercise of the Warrants and any shares of capital stock
     issued or issuable, from time to time (with any adjustments), as a
     distribution on or in exchange for or otherwise with respect to the
     foregoing.

          Section 1 of the Agreement is hereby amended to add the following new
     subsections:

          (d) "INVESTORS" shall mean each of Genstar Capital Partners II, L.P.
     ("Genstar Capital Partners"), Stargen II LLC ("Stargen"), Russell D. Hays,
     George Uveges, Jean-Pierre L. Conte, Richard F. Hoskins, Richard D.
     Paterson and Robert J. Weltman; PROVIDED, HOWEVER, that none of Russell D.
     Hays, George Uveges, Jean-Pierre L. Conte, Richard F. Hoskins, Richard D.
     Paterson or Robert J. Weltman shall be deemed to be an "Investor" under
     Sections 10, 11, 12 or 13 of this Agreement.

          (e) "NEW INVESTORS" shall mean each of Jean-Pierre L. Conte, Richard
     F. Hoskins, Richard D. Paterson and Robert J. Weltman.

     2. JOINDER. The Company and the Investors hereby agree that (i) the New
Investors shall be deemed to be parties to the Agreement; and (ii) Genstar
Capital Partners and the New Investors shall be entitled to all of the rights,
benefits and privileges of Investors, and shall observe all of the obligations
of Investors, under the Agreement with respect to the Shares held by each of
them; PROVIDED, HOWEVER, that none of the New Investors shall be deemed to be an
"Investor" under Sections 10, 11, 12 or 13 of the Agreement, nor shall any of
the New Investors be entitled to any of the rights, benefits or privileges
inuring to the benefit of "Investors" under Sections 10, 11, 12 or 13 of the
Agreement, such rights, benefits and privileges being reserved for the exclusive
benefit of Genstar Capital Partners and Stargen.

     3. ENTIRE AGREEMENT. This Amendment supersedes the Agreement solely with
respect to the subject matter herein. All terms and provisions of the Agreement
not affected by this Amendment remain binding and enforceable between Investors
and the Company.

                  [REMAINDER OF PAGE INTENTIONALLY LEFT BLANK]

                                     Page 2
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        IN WITNESS WHEREOF, the parties have caused this Amendment to be duly
executed as of the date first above written.

                                            BIOSOURCE INTERNATIONAL, INC.

                                            By:/S/ RUSSELL D. HAYS
                                               ----------------------
                                               RUSSELL D. HAYS
                                               President and Chief
                                               Executive Officer

                                            GENSTAR CAPITAL PARTNERS II, L.P.

                                            By: Genstar Capital LLC
                                                 Its General Partner

                                            By: /S/ JEAN-PIERRE L. CONTE
                                                ------------------------
                                                Jean-Pierre L. Conte
                                                Managing Director

                                            STARGEN II LLC

                                            By: /S/ JEAN-PIERE L. CONTE
                                                -----------------------
                                                Jean-Pierre L. Conte
                                                Managing Director

                                            /S/ RUSSELL D. HAYS
                                            ---------------------------
                                            Russell D. Hays

                                            /S/ GEORGE UVEGES
                                            ---------------------------
                                            George Uveges

                                            /s/ RICHARD F. HOSKINS
                                            ---------------------------
                                            Richard F. Hoskins

                                     Page 3
<PAGE>

                                            /s/ RICHARD D. PATERSON
                                            ---------------------------
                                            Richard D. Paterson

                                            /s/ ROBERT J. WELTMAN
                                            ---------------------------
                                            Robert J. Weltman

                                     Page 4EXHIBIT 4.7

                           RIGHTS AGREEMENT AMENDMENT

        Rights Agreement Amendment, dated as of January 10, 2000 (this
"Amendment"), to the Rights Agreement dated as of February 25, 1999 (the "Rights
Agreement"), between Biosource International, Inc., a Delaware corporation (the
"Company") and U.S. Stock Transfer Corporation, as Rights Agent (the "Rights
Agent").

        The Company and the Rights Agent have heretofore executed and delivered
the Rights Agreement. Pursuant to Section 26 of the Rights Agreement, the
Company and the Rights Agent may from time to time supplement or amend the
Rights Agreement in accordance with the provisions of Section 26 thereof.

        In consideration of the foregoing premises and mutual agreements set
forth in the Rights Agreement and this Amendment, the parties hereto agree as
follows:

        1. The definition of "Exempt Person" in Section 1 of the Rights
Agreement is hereby amended and restated to read in its entirety as follows:

        "Exempt Person" shall include (i) the Company, (ii) any Subsidiary (as
hereinafter defined) of the Company, (iii) any employee benefit plan of the
Company or any of its Subsidiaries, or any entity holding shares of Common Stock
which was organized, appointed or established by the Company or any Subsidiary
of the Company for or pursuant to the terms of any such plan and (iv) Genstar
Capital Partners II, L.P., Stargen II LLC and their respective Affiliates
(collectively the "Genstar Capital Group")."

        2. Section 3(a) of the Rights Agreement is further amended by adding a
new sentence as the final sentence thereto, which shall read in its entirety as
follows:

              "Notwithstanding anything in this Rights Agreement to the
contrary, a Distribution Date shall not be deemed to have occurred solely as a
result of (i) the approval, execution or delivery of that certain Securities
Purchase Agreement, dated as of January 10, 2000, by and between the Company and
the GenStar Capital Group, or any of the agreements or instruments required to
be executed and delivered in connection with the transactions contemplated
therein (collectively, the "Genstar Capital Agreements"), or (ii) the
consummation of the transactions contemplated by the Genstar Capital Agreements
or the performance of the terms of the Genstar Capital Agreements."

        3. This Amendment shall be governed by and construed in accordance with
the laws of the State of Delaware.

        4. This Amendment may be executed in any number of counterparts and each
of such counterparts shall for all purposes be deemed an original, and all such
counterparts shall together constitute but one and the same instrument.

        5. Except as expressly set forth herein, this Amendment shall not by
implication or otherwise alter, modify, amend or in any way affect any of the
terms, conditions, obligations, covenants or agreements contained in the Rights
Agreement, all of which are ratified and affirmed in all respects and shall
continue in full force and effect.

<PAGE>

        IN WITNESS WHEREOF, the parties hereto have caused this Amendment to be
duly executed as of the day and year first above written.

                               BIOSOURCE INDUSTRIES, INC.

                               By:     /s/ JAMES H. CHAMBERLAIN
                                   ---------------------------------------
                                     James H. Chamberlain
                                     President and Chief Executive Officer

                               U.S. STOCK TRANSFER CORPORATION

                               By:   /S/ ENRIQUE ARTAZA
                                   ----------------------------------------
                               Name:  Enrique Artaza
                               Title: Sr. Vice President

                                     Page 2

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