Exhibit 10.1


                             STOCK OPTION AGREEMENT
                          (NON-STATUTORY STOCK OPTION)

     This STOCK OPTION AGREEMENT (this "Option Agreement") is made and entered
into on the date set forth on the signature page hereof, by and between
BIOSOURCE INTERNATIONAL, INC. ( the "Company"), and James H. Chamberlain
("Optionee").

     The Board of Directors of the Company (the "Board") has authorized the
grant to Optionee of a non-statutory stock option to purchase shares of the
Company's Common Stock, par value $0.001 per share (the "Common Stock"), upon
the terms and subject to the conditions set forth in this Agreement.

     The Company and Optionee agree as follows:

     1. GRANT OF OPTION.

     The Company hereby grants to Optionee the right and option (the "Option"),
upon the terms and subject to the conditions set forth in this Agreement, to
purchase up to 50,000 shares of the Common Stock (the "Shares"), at an Option
Exercise Price (the "Exercise Price") of $2.6875 per share.

     2. TERM OF OPTION.

     The Option shall terminate and expire on the date (the "Option Expiration
Date") which is ten years from the date of this Option Agreement, unless sooner
terminated as provided herein.

     3. VESTING.

     The Option shall become immediately exercisable upon execution of this
Agreement.

     4. EXERCISE OF OPTION.

     There is no obligation to exercise the Option, in whole or in part. The
Option may be exercised, in whole or in part, only by delivery to the Company
of:

          (a) written notice of exercise in form and substance identical to
     Exhibit "A" attached to this Option Agreement stating the number of shares
     of Common Stock then being purchased (the "Purchased Shares"); and

          (b) payment of the Exercise Price of the Purchased Shares, either in
     cash, by check, or by transfer to the Company of issued and outstanding
     shares of Common Stock, or by any combination of the above methods of
     payment. If payment is made, in whole or in part, by transfer to the
     Company of issued and outstanding shares of Common Stock, the value of such
     shares shall be determined as follows: (i) if, at the time of payment, the
     Common Stock is traded on the National Market System or any national or
     regional stock exchange, the value of each share shall be the closing sale
     price of a share of Common Stock on the business day immediately preceding
     the payment or, if no sale was made on that date, on the most recent date
     when such a sale was made, as reported on the composite tape for securities
     transactions or similar source for reporting sales of the Common Stock;
     (ii) if, at the time of payment, quotations with respect to the Common
     Stock are made on the NASDAQ System, the value of each share


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     shall be the average of the closing bid and asked quotations of a share of
     Common Stock on the business day immediately preceding the payment or, if
     no quotations were made on that date, on the most recent date when such
     quotations were made; or (iii) if, at the time of payment, neither (i) nor
     (ii) above is applicable, the value of each share shall be the fair market
     value of each share, as determined by the Board or the Administrator.

     Following receipt of the notice and payment referred to above, the Company
shall issue and deliver to Optionee a stock certificate or stock certificates
evidencing the Purchased Shares; PROVIDED, HOWEVER, that the Company shall not
be obligated to issue a fraction or fractions of a share of its Common Stock,
and may pay to Optionee, in cash or by check, the fair market value of any
fraction or fractions of a share exercised by Optionee, which fair market value
shall be determined as set forth in the preceding paragraph.

     5. RESTRICTIONS ON PURCHASED SHARES.

     Optionee shall not sell, transfer (with or without consideration), assign,
pledge, hypothecate or otherwise dispose of (collectively, "Transfer") any of
the Purchased Shares unless and until ALL of the following have occurred:

          (a) The Purchased Shares are disposed of pursuant to and in conformity
     with an effective registration statement filed with the Securities and
     Exchange Commission (the "Commission") pursuant to the Securities Act of
     1933, as amended (the "Act"), or the proposed disposition will not result
     in a violation of the securities laws of any state of the United States;
     and

          (b) If requested by the Company, Optionee shall, prior to the transfer
     of such Purchased Shares, deliver to the Company a written opinion of
     counsel, satisfactory to the Company and its counsel, that the proposed
     disposition will comply with the requirements set forth in clause (a)
     above, in which case, the Company shall bear all reasonable costs of such
     counsel in preparing such opinion.

     Any attempted Transfer which is not in full compliance with this Paragraph
5 shall be null and void AB INITIO, and of no force or effect.


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     6. ADJUSTMENTS UPON RECAPITALIZATION.

          Subject to any required action by the stockholders of the Company:

          (a) If outstanding shares of the Common Stock shall be subdivided into
     a greater number of shares of the Common Stock, or a dividend in Shares of
     Common Stock or other securities of the Company convertible into or
     exchangeable for shares of the Common Stock (in which latter event the
     number of shares of Common Stock issuable upon the conversion or exchange
     of such securities shall be deemed to have been distributed) shall be paid
     in respect of the shares of Common Stock, the Exercise Price in effect
     immediately prior to such subdivision or at the record date of such
     dividend shall, simultaneously with the effectiveness of such subdivision
     or immediately after the record date of such dividend, be proportionately
     reduced, and conversely, if the outstanding shares of Common Stock shall be
     combined into a smaller number of shares of Common Stock, the Exercise
     Price in effect immediately prior to such combination shall, simultaneously
     with the effectiveness of such combination, be proportionately increased.

          (b) In the event the Company at any time, or from time to time, shall
     make or issue, or fix a record date for the determination of holders of
     shares of Common Stock entitled to receive, a dividend or other
     distribution payable in securities or the Company other than shares of
     Common Stock or securities convertible into or exchangeable for shares of
     Common Stock then and in each such event, provision shall be made so that
     the holder of the Option shall receive upon exercise thereof, in addition
     to the number of shares receivable thereupon, the amount of securities of
     the Company which he or she would have received had his or her Option been
     exercised on the date of such event and had thereafter, during the period
     from the date of such event to and including the date of exercise, retained
     such securities receivable by him or her as aforesaid during such period,
     giving application to all adjustments called for during such period under
     this Paragraph 6 with respect to the rights of the holder of the Option.

          (c) When any adjustment is required to be made in the Exercise Price,
     the number of Shares purchasable upon the exercise of the Option shall be
     adjusted to that number of Shares determined by (i) multiplying an amount
     equal to the number of Shares purchasable on the exercise of the Option
     immediately prior to such adjustment by the Exercise Price in effect
     immediately prior to such adjustment, and then (ii) dividing that product
     by the Exercise Price in effect immediately after such adjustment.

          (d) In case of any capital reorganization, any reclassification of the
     Common Stock (other than a change in par value or recapitalization
     described in Paragraph 6(a) or 6(b) of this Agreement), or the
     consolidation of the Company with, or a sale of substantially all of the
     assets of the Company to (which sale is followed by a liquidation or
     dissolution of the Company), or merger of the Company with, another person
     where, in each such case, the Company is the "surviving corporation," as
     defined in Paragraph 6(j) below, Optionee shall thereafter be entitled upon
     exercise of the Option to purchase the kind and number of shares of stock
     or other securities or property of the surviving corporation receivable
     upon such event by a holder of the number of shares of the Common Stock
     which the Option entitles Optionee to purchase from the Company any
     immediately prior to such event; and in any such case, appropriate
     adjustment shall be made in the application of the provisions set forth in
     this Agreement with respect to Optionee's rights and interests thereafter,
     to the end that the provisions set forth in this Agreement (including the
     specified changes and other adjustments to the Exercise Price) shall
     thereafter be applicable in relation to any shares or other property
     thereafter purchasable upon exercise of the Option.


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          (e) A consolidation of the Company with, or a sale of substantially
     all of the assets of the Company to (which sale is followed by a
     liquidation or dissolution of the Company), or the Merger of the Company
     with, any other person (other than a consolidation, sale or merger in which
     the Company is the "Surviving Corporation," as defined in Paragraph 6 (j)
     below) shall cause the Option to terminate on the Effective Date of such
     consolidation, sale or merger; PROVIDED, HOWEVER, that the Optionee shall
     have the right during a ten day period ending on the fifth day prior to
     such consolidation, sale or merger to exercise the Option, in whole or in
     part, without regard to the installment provision set forth in Paragraph 3
     of this Option Agreement; but any exercise of the Option which except for
     the provisions of this Paragraph 6(e) would not then be exercisable, shall
     be conditioned upon the actual occurrence of such consolidation, sale or
     merger, and if such consolidation, sale of merger is abandoned or otherwise
     does not occur, for any reason, the Optionee's exercise of the Option
     during such ten day period shall be null and void, and of no force and
     effect; PROVIDED, FURTHER, that if such consolidation, sale or merger is to
     be consummated, in whole or in part, by the tender of Common Stock to the
     Surviving Corporation, the Optionee hereby agrees to tender the Shares
     issued upon exercise of his or her Option to the Surviving Corporation, if
     so directed by the board of directors of the Company, and to vote such
     Shares for or against such consolidation, sale or merger, as directed by
     the board of directors of the Company. For purposes of this Paragraph 6(e)
     and subject to the previous sentence, any exercise of the Option by
     optionee pursuant to this Paragraph 6 shall be deemed to occur immediately
     prior to the consummation of such consolidation, sale or merger.

          (f) If the Company is dissolved or liquidated then the Option shall
     terminate on the effective date of such dissolution or liquidation;
     PROVIDED, HOWEVER, the Optionee shall have the right during a ten day
     period ending on the fifth day prior to such dissolution or liquidation to
     exercise his or her Option in whole or in part, without regard to any of
     the installment provisions set forth in Paragraph 3 of this Agreement; but
     the exercise of the Option which except for the provisions of this
     Paragraph 6(f) would not then be exercisable, shall be conditioned upon the
     actual occurrence of such dissolution or liquidation, and if such
     dissolution or liquidation were not to occur, the Optionee's exercise of
     the Option during such ten day period shall be null and void, and of no
     force and effect. For purposes of the this Paragraph 6(f) and subject to
     the previous sentence, any exercise of the Option by Optionee pursuant to
     this Paragraph 6(f) shall be deemed to occur immediately prior the
     consummation of such dissolution or liquidation.

          (g) To the extent that the foregoing adjustments relate to stock or
     securities of the Company, such adjustments shall be made by the
     Administrator, and its determination shall be final, binding and
     conclusive.

          (h) The provisions of this Paragraph 6 are intended to be exclusive,
     and Optionee shall have no other rights upon the occurrence of any of the
     events described in this Paragraph 6.

          (i) The grant of the Option shall not affect in any way the right or
     power of the Company to make adjustments, reclassifications,
     reorganizations or changes in its capital or business structure, or to
     merge, consolidate, dissolve or liquidate, or to sell or transfer all or
     any part of its business or assets.

          (j) The determination as to which party is the "surviving corporation"
     in a consolidation, sale or merger shall be made on the basis of the
     relative equity interests of the stockholders in the corporation existing
     after the consolidation, sale or merger, as follows: If following any
     consolidation, sale or merger the holders of outstanding voting securities
     of the Company prior to the consolidation, sale or merger own equity
     securities possessing more than 50% of the voting power of the


                                  EX-10-1 - 4
<PAGE>


     corporation existing after the consolidation, sale or merger, then for
     purposes of this Agreement, the Company shall be the surviving corporation.
     In all other cases, the Company shall not be the surviving corporation. In
     making the determination of ownership by the stockholders of a corporation,
     immediately after a consolidation, sale or merger, of securities pursuant
     to this Paragraph 6(j), securities which they owned immediately prior to
     such consolidation, sale or merger as stockholders of another party to the
     transaction shall be disregarded.

     7. WAIVER OF RIGHTS TO PURCHASE STOCK.

          By signing this Agreement, Optionee acknowledges and agrees that
     neither the Company nor any other person or entity is under any oral
     obligation to sell or transfer to Optionee any option or equity security of
     the Company. By signing this Agreement, Optionee specifically waives all
     rights which he or she may have had prior to the date of this Agreement
     under any oral agreement or promise by the Company to receive any option or
     equity security of the Company.

     8. INVESTMENT INTENT.

          Optionee represents and agrees that if he or she exercises the Option
     in whole or in part, he or she will acquire the Shares upon such exercise
     for the purpose of investment and not with a view to the distribution of
     such Shares, and that upon each exercise of the Option he or she will
     furnish to the Company a written statement to such effect.

     9. LEGEND ON STOCK CERTIFICATES.

          Optionee agrees that the Company may place on each certificate
     representing the Purchased Shares the following legend:

               THE SECURITIES EVIDENCED BY THIS CERTIFICATE HAVE NOT BEEN
          REGISTERED UNDER THE SECURITIES ACT OF 1933, AS AMENDED ("THE ACT"),
          HAVE BEEN TAKEN FOR INVESTMENT, AND MAY NOT BE SOLD, TRANSFERRED,
          ASSIGNED, PLEDGED, HYPOTHECATED OR OTHERWISE DISPOSED OF EXCEPT IN
          ACCORDANCE WITH THE ACT AND THE RULES AND REGULATIONS OF THE
          SECURITIES AND EXCHANGE COMMISSION THEREUNDER.

     10. NO RIGHTS AS STOCKHOLDER.

          Optionee shall have no rights as a stockholder with respect to the
     Shares until the date of the issuance to Optionee of a stock certificate or
     stock certificates evidencing such Shares. Except as may be provided in
     Paragraph 6 of this Agreement, no adjustment shall be made for dividends
     (ordinary or extraordinary, whether in cash, securities or other property)
     or distributions or other rights for which the record date is prior to the
     date such stock certificate is issued.

     11. MODIFICATION.

          The Board or the Administrator may modify, extend or renew the Option
     or accept the surrender of, and authorize the grant of a new option in
     substitution for, the Option (to the extent not previously exercised).


                                  EX-10-1 - 5
<PAGE>


     12. WITHHOLDING.

          (a) The Company shall be entitled to require as a condition of
     delivery of any Purchased Shares upon exercise of any Option that the
     Optionee agree to remit, at the time of such delivery or at such later date
     as the Company may determine, an amount sufficient to satisfy all federal,
     state and local withholding tax requirements relating thereto, and Optionee
     agrees to take such other action required by the Company to satisfy such
     withholding requirements.

          (b) With the consent of the Administrator, and in accordance with any
     rules and procedures from time to time adopted by the Administrator,
     Optionee may elect to satisfy his or her obligations under Paragraph 12(a)
     above by (i) directing the Company to withhold a portion of the Shares
     otherwise deliverable (or to tender back to the Company a portion of the
     Shares issued where the Optionee (a "Section 16(b) Recipient") is required
     to report the ownership of the Shares pursuant to Section 16(a) of the
     Securities Exchange Act of 1934, as amended, and has not made an election
     under Section 83(b) of the Code (a "Withholding Right")); or (ii) tendering
     other shares of the Common Stock of the Company which are already owned by
     Optionee which in all cases have a fair market value (as determined in
     accordance with the provisions of Paragraph 4(b) hereof) on the date as of
     which the amount of tax to be withheld is determined (the "Tax Date") equal
     to the amount of taxes to be paid by such method.

          (c) To exercise a Withholding Right, the Optionee must follow the
     election procedures set forth below, together with such additional
     procedures and conditions set forth in this Option Agreement or otherwise
     adopted by the Administrator:

               (A) the Optionee must deliver to the Company his or her written
          notice of election (the "Election") and specify whether all or a
          stated percentage of the applicable taxes will be paid in accordance
          with Paragraph 12(b) above and whether the amount so paid shall be
          made in accordance with the "flat" withholding rates for supplemental
          wages or as determined in accordance with Optionee's form W-4 (or
          comparable state or local form);

               (B) unless disapproved by the Administrator as provided in
          Subsection (iii) below, the Election once made will be irrevocable;
          and

               (C) no Election is valid unless the Administrator has the right
          and power, in its sole discretion, with or without cause or reason
          therefor, to consent to the Election, to refuse to consent to the
          Election, or to disapprove the Election; and if the Administrator has
          not consented to the Election on or prior to the Tax Date, the
          Election will be deemed approved.

               (D) If the Optionee on the date of delivery of the Election to
          the Company is a Section 16(b) Recipient, the following additional
          provisions will apply:

                    (i) the Election cannot be made during the six calendar
               month period commencing with the date of 9rant of the Withholding
               Right (even if the Option to which such Withholding Right relates
               has been granted prior go such date); and

                    (ii) the Election must be made any day six calendar months
               or more prior to the Tax Date.


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     13. CHARACTER OF OPTION.

          The Option is intended to constitute a non-statutory stock option and
     does not constitute an "incentive stock option" as that term is defined in
     Section 422 of the Code.

     14. GENERAL PROVISIONS.

          (a) FURTHER ASSURANCES. Optionee shall promptly take all actions and
     execute all documents requested by the Company which the Company deems to
     be reasonably necessary to effectuate the terms and intent of this Option
     Agreement.

          (b) NOTICES. All notices, requests, demands and other communications
     under this Option Agreement shall be in writing and shall be given to the
     parties hereto as follows:

               (i) If to the Company, to:

                   BIOSOURCE INTERNATIONAL, INC.
                   820 Flynn Road
                   Camarillo, California 93012

               (ii) If to Optionee, to the address set forth in the records of
          the Company,

or at such other address or addresses as may have been furnished by such either
party in writing to the other party hereto. Any such notice, request, demand or
other communication shall be effective (i) if given by mail, 72 hours after such
communication is deposited in the mail by first-class certified mail, return
receipt requested, postage prepaid, addressed as aforesaid, or (ii) if given by
any other means, when delivered at the address specified in this subparagraph
(b).

          (c) TRANSFER OF RIGHTS UNDER THIS OPTION AGREEMENT. The Company may at
     any time transfer and assign its rights and delegate its obligations under
     this Option Agreement to any other person, corporation, firm or entity,
     including its officers, directors and stockholders, with or without
     consideration.

          (d) OPTION NON-TRANSFERABLE. Optionee may not sell, transfer, assign
     or otherwise dispose of the Option except by will or the laws of descent
     and distribution, and only Optionee may exercise the Option during his or
     her lifetime.

          (e) SUCCESSORS AND ASSIGNS. Except to the extent specifically limited
     by the terms and provisions of this Option Agreement, this Option Agreement
     shall be binding upon and inure to the benefit of the parties hereto and
     their respective successors, assigns, heirs and personal representatives.

          (f) GOVERNING LAW. This Option Agreement shall be governed by and
     construed in accordance with the laws of the State of California applicable
     to contracts made in, and to be performed within, that State.

          (g) ATTORNEYS' FEES. In the event that any action, suit or other
     proceeding is instituted upon any breach of this Option Agreement, the
     prevailing party shall be paid by the other party thereto an amount equal
     to all of the prevailing party's costs and expenses, including attorneys'
     fees incurred


                                  EX-10-1 - 7
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     in each and every such action, suit or proceeding (including any and all
     appeals or petitions therefrom). As used in this Option Agreement,
     "attorneys' fees" shall mean the full and actual cost of any legal services
     actually performed in connection with the matter involved calculated on the
     basis of the usual fee charged by the attorney performin9 such services and
     shall not be limited to "reasonable attorneys' fees" as defined in any
     statute or rule of court.

          (h) MISCELLANEOUS. Titles and captions contained in this Option
     Agreement are inserted for convenience of reference only and do not
     constitute a part of this Option Agreement for any other purpose. Except as
     specifically provided herein, neither this Option Agreement nor any right
     pursuant hereto or interest herein shall be assignable to any of the
     parties hereto without the prior written consent of the other party hereto.


                                  EX-10-1 - 8
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     IN WITNESS WHEREOF, the parties hereto have entered into and executed this
Option Agreement as of the date set forth below.

DATED: May 19, 1993


                                        BIOSOURCE INTERNATIONAL, INC.



                                         By: /S/ ANNA ANDERSON
                                             -----------------------------------
                                             Its: CHIEF FINANCIAL OFFICER


                                        OPTIONEE


                                        By:  /S/ JAMES CHAMBERLAIN
                                             -----------------------------------
                                             James H. Chamberlain


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