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                                                                    EXHIBIT 10.1

                         EXECUTIVE EMPLOYMENT AGREEMENT

      This Executive Employment Agreement (this "AGREEMENT") is made and entered
into as of this 1st day of April, 2004 (the "EFFECTIVE DATE"), by and between
BioSource International, Inc., a Delaware corporation (the "COMPANY"), and Jozef
Vangenechten ("EXECUTIVE").

      1. ENGAGEMENT AND DUTIES.

            1.1 Commencing upon the Effective Date, and upon the terms and
subject to the conditions set forth in this Agreement, the Company hereby
engages and employs Executive as an officer of the Company, with the title and
designation of Executive Vice President-Commercial Operations of the Company.
Executive hereby accepts such engagement and employment.

            1.2 Executive's duties and responsibilities shall be those normally
and customarily vested in the office of Executive Vice President-Commercial
Operations of a corporation, subject to the supervision, direction and control
of the President of the Company. Specifically, Executive is responsible for the
Company's commercial operations in Foster City, Rockville and Hopkinton and the
Company's Camarillo based Sales and Marketing teams. In addition, Executive's
duties shall include those duties and services for the Company and its
affiliates as the President shall from time to time reasonably direct. Executive
shall report directly to the President.

            1.3 Executive agrees to devote his primary business time, energies,
skills, efforts and attention to his duties hereunder, and will not, without the
prior written consent of the Company, which consent will not be unreasonably
withheld, render any material services to any other business concern. Executive
will use his best efforts and abilities faithfully and diligently to promote the
Company's business interests.

            1.4 Except for routine travel incident to the business of the
Company, Executive shall perform his duties and obligations under this Agreement
principally from an office provided by the Company in Camarillo, California, or
such other location, as the President may from time to time determine.

      2. TERM OF EMPLOYMENT. Executive's employment pursuant to this Agreement
shall commence on the Effective Date and shall terminate on the earliest to
occur of the following:

            (a) the close of business on December 31, 2007;

            (b) the death of Executive;

            (c) delivery to Executive of written notice of termination by the
Company if Executive shall suffer a "permanent disability," which for purposes
of this Agreement shall mean a physical or mental disability which, in the
reasonable judgment of the President, is likely to render Executive unable to
perform his duties and obligations under this Agreement for 90 days in any
12-month period;

            (d) delivery to Executive of written notice of termination by the
Company "for cause," by reason of: (i) any act or omission knowingly undertaken
or omitted by Executive with the intent of causing damage to the Company, its
properties, assets or business or its stockholders, officers, directors or
employees; (ii) any act of Executive involving a material personal profit to
Executive, including, without limitation, any fraud, misappropriation or

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embezzlement, involving properties, assets or funds of the Company or any of its
subsidiaries; (iii) Executive's consistent failure to perform his normal duties
or any obligation under any provision of this Agreement, in either case, as
directed by the President; (iv) conviction of, or pleading nolo contendere to,
(A) any crime or offense involving monies or other property of the Company; (B)
any felony offense; or (C) any crime of moral turpitude; or (v) the chronic or
habitual use or consumption of drugs or alcoholic beverages; or

            (e) delivery to Executive of written notice of termination by the
Company "without cause";

            (f) termination by the Company, or one or more of its subsidiaries,
of any other written agreements entered into by the Company, or one or more of
its subsidiaries, on the one hand, and Executive and/or any entities controlled
by, or affiliated with, Executive, on the other hand, "for cause," as may be
defined therein;

            (g) termination by the Company, or one or more of its subsidiaries,
of any other written agreements entered into by the Company, or one or more of
its subsidiaries, on the one hand, and Executive and/or any entities controlled
by, or affiliated with, Executive, on the other hand, "without cause".

      3. COMPENSATION; EXECUTIVE BENEFIT PLANS.

            3.1 The Company shall pay to Executive a net base salary in the US
(the "NET BASE SALARY") at an annual rate of $100,000 during each fiscal year of
this Agreement, subject to adjustment on an annual basis by the President. The
Net Base Salary shall be payable in installments throughout the year in the same
manner and at the same times the Company pays base salaries to other executive
officers of the Company. In the event that Executive's employment is terminated
pursuant to Section 2(e) or Section 2(g), above, the Company shall pay to
Executive $22,500 and the US$ equivalent of (euro)119,025 (the "Net SEVERANCE
PAYMENT"), subject to the provisions of Section 4 and Section 3.4 as it relates
to the gross-up for Social Security, Medicare, US Federal Income Tax and
California Income Tax, payable over a period of 9 months following the effective
date of such termination, and Executive shall retain only those options
described in Section 3.3, below, that have vested prior to the effective date of
such termination, provided, however, in the event that Executive's employment is
terminated pursuant to Section 2(g), and at the time of such termination, this
Agreement may also be terminated pursuant to Section 2(b), Section 2(c), or
Section 2(d), then Executive shall not be entitled to receive the Severance
Payment. The Net Severance Payment shall be adjusted in proportion to any
adjustment provided to the Net Base Salary from time to time. The Net Severance
Payment shall be payable in installments throughout the year in the same manner
and at the same times the Company pays base salaries to other executive officers
of the Company. Notwithstanding the foregoing, the Company shall not be
obligated to pay Executive the Net Severance Payment hereunder following the
termination of Executive's employment pursuant to Section 2(e) or Section 2(g),
above, from and after any time that Executive accepts an employment or
consulting position with any person or entity that is determined by the
President, in the exercise of his reasonable discretion, to be a competitor of
the Company.

            3.2 In addition to the Net Base Salary to be paid to Executive
hereunder, the Company shall pay a performance bonus (the "BONUS") determined in
accordance with a management incentive plan (the "MIP") to be approved in a
resolution adopted by the Compensation committee on an annual basis. The
management incentive plan will provide for the payment of an annual gross Bonus
equal to sixty-two thousand US dollars upon achieving

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the "target" objectives set forth in the MIP, and payments of such lesser or
greater amounts upon achieving results less than or greater than the "target"
objectives as shall be contained in the MIP. Any tax liability that may arise
from the payment of the Bonus by the Company to the Executive is the
responsibility of the Executive.

            3.3 Executive shall be granted an option to purchase 50,000 shares
of Common Stock at a per share exercise price equal to the "fair market value"
of such shares on the Effective Date (as defined in the Company's 2000 Stock
Incentive Plan (the "STOCK PLAN")). The Options shall be issued pursuant to the
terms of the Stock Plan, and shall vest as to 25% of the Options on the first
anniversary of the date of grant, and as to 1/48th of the Option on the last day
of each calendar month thereafter until fully vested. The option agreement will
provide for the acceleration of all vesting upon a change of control, as defined
in the option agreement, that occurs prior to the termination of this Agreement.
In addition, all previous grants of options to the Executive shall be modified
so that such options shall also accelerate and become fully vested upon a change
of control.

            3.4 Executive shall be entitled to reimbursement from the Company
for the reasonable costs and expenses which he incurs in connection with the
performance of his duties and obligations under this Agreement in a manner
consistent with the Company's practices and policies as adopted or approved from
time to time by the President for executive officers. The Company shall also
reimburse Executive for the cost of up to a total of six round trip coach
airline tickets to be used by members of the Executive's immediate family for
travel between the US and Belgium. In addition, the Company shall pay to
Executive $30,000 per annum for housing allowance, $3,400 per annum for US
health and dental insurance, $8,400 for Social Security and Medicare tax and the
US Federal and California tax gross-up of such payments and of the Net Base
Salary and of the Net Severance Payment. The Executive shall cooperate fully
with the Company to prepare the annual US State and Federal tax returns.

            3.5 The Company may deduct from any compensation payable to
Executive the minimum amounts sufficient to cover applicable federal, state
and/or local income tax withholding, old-age and survivors' and other social
security payments, state disability and other insurance premiums and payments,
but such deductions shall not result in a US tax expense to the Executive per
Section 3.4 above.

      4. EXCHANGE RATE CORRECTION. During the term of his employment hereunder,
Executive's Net Base Salary of $100,000 shall be paid in two portions: $30,000
and the US$ equivalent of (euro)56,000, adjusted on a monthly basis, up or down,
to reflect the change in exchange rate between the US dollar and the Euro. Such
adjustment shall be calculated on a prospective monthly basis on the last day of
each successive month and shall not be modified retrospectively. The initial
(euro)56,000 portion of the Net Base Salary is based upon an exchange rate of
1.25 US dollar to 1 Euro. The exchange rate used for calculating the (euro)
equivalent of the $70,000 portion of the Net Base Salary for each prospective
monthly period shall be the actual exchange rate on the last business day of
each preceding month in accordance with the historical practice of the Company
or its subsidiaries. In the event that the Company is required to pay the Net
Severance Payment in accordance with the provisions of Section 3.1, the portion
of the Net Severance Payment including the US$ equivalent of (euro)119,000 shall
be adjusted on a monthly basis, up or down, to reflect the change in exchange
rate between the US dollar and the Euro. During the period in which the Net
Severance Payment is being paid, the adjustment to the US$ equivalent of
(euro)119,000 shall be calculated on a prospective monthly basis on the last day
of each successive month during such period and shall not be modified
retrospectively. The initial (euro)119,000 portion of the Net Severance Payment
is based upon an exchange rate of 1.25 US dollar to 1 Euro. The exchange rate
used for calculating the (euro)119,000 portion of the


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Net Severance Payment for each prospective monthly period during the period in
which the Net Severance Payment is being paid shall be the actual exchange rate
on the last business day of each preceding month during such period in
accordance with the historical practice of the Company or its subsidiaries.

      5. CONFIDENTIALITY OF PROPRIETARY INFORMATION AND MATERIAL.

            5.1 Industrial Property Rights. For the purpose of this Agreement,
"INDUSTRIAL PROPERTY RIGHTS" shall mean all of the Company's patents,
trademarks, trade names, inventions, copyrights, know-how or trade secrets,
formulas and science, now in existence or hereafter developed or acquired by the
Company or for its use, relating to any and all products and services which are
developed, formulated and/or manufactured by the Company.

            5.2 Trade Secrets. For the purpose of this Agreement, "TRADE
SECRETS" shall mean any formula, pattern, device, or compilation of information
that is used in the Company's business and gives the Company an opportunity to
obtain an advantage over its competitors who do not know and/or do not use it.
This term includes, but is not limited to, information relating to the marketing
of the Company's products and services, including price lists, pricing
information, customer lists, customer names, the particular needs of customers,
information relating to their desirability as customers, financial information,
intangible property and other such information which is not in the public
domain.

            5.3 Technical Data. For the purpose of this Agreement, "TECHNICAL
DATA" shall mean all information of the Company in written, graphic or tangible
form relating to any and all products which are developed, formulated and/or
manufactured by the Company, as such information exists as of the Effective Date
or is developed by the Company during the term hereof.

            5.4 Proprietary Information. For the purpose of this Agreement,
"PROPRIETARY INFORMATION" shall mean all of the Company's Industrial Property
Rights, Trade Secrets and Technical Data. Proprietary Information shall not
include any information which (i) was lawfully in the possession of Executive
prior to Executive's employment with the Company, (ii) may be obtained by a
reasonably diligent businessperson from readily available and public sources of
information, (iii) is lawfully disclosed to Executive after termination of
Executive's employment by a third party which does not have an obligation to the
Company to keep such information confidential, or (iv) is independently
developed by Executive after termination of Executive's employment without
utilizing any of the Company's Proprietary Information.

            5.5 Agreement Not To Copy Or Use. Executive agrees, at any time
during the term of his employment and for a period of five years thereafter, not
to copy, use or disclose (except as required by law after first notifying the
Company and giving it an opportunity to object) any Proprietary Information
without the Company's prior written permission. The Company may withhold such
permission as a matter within its sole discretion during the term of this
Agreement and thereafter.

      6. RETURN OF CORPORATE PROPERTY AND TRADE SECRETS. Upon any termination of
this Agreement, Executive shall turn over to the Company all property, writings
or documents then in his possession or custody belonging to or relating to the
affairs of the Company or comprising or relating to any Proprietary Information.

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      7. DISCOVERIES AND INVENTIONS.

            7.1 Disclosure. Executive will promptly disclose in writing to the
Company complete information concerning each and every invention, discovery,
improvement, device, design, apparatus, practice, process, method, product or
work of authorship, whether patentable or not, made, developed, perfected,
devised, conceived or first reduced to practice by Executive, whether or not
during regular working hours (hereinafter referred to as "DEVELOPMENTS"), either
solely or in collaboration with others, (a) prior to the term of this Agreement
while working for the Company, (b) during the term of this Agreement or (c)
within six months after the term of this Agreement, if relating either directly
or indirectly to the business, products, practices, techniques or confidential
information of the Company.

            7.2 Assignment. Executive, to the extent that he has the legal right
to do so, hereby acknowledges that any and all Developments are the property of
the Company and hereby assigns and agrees to assign to the Company any and all
of Executive's right, title and interest in and to any and all of such
Developments; provided, however, that, in accordance with California Labor Code
Sections 2870 and 2872, the provisions of this Section 7.2 shall not apply to
any Development that the Executive developed entirely on his own time without
using the Company's equipment, supplies, facilities or trade secret information
except for those Developments that either:

                  (a) relate at the time of conception or reduction to practice
of the Development to the Company's business, or actual or demonstrably
anticipated research or development of the Company; or

                  (b) result from any work performed by Executive for the
Company.

            7.3 Assistance of Executive. Upon request and without further
compensation therefore, but at no expense to Executive, and whether during the
term of this Agreement or thereafter, Executive will do all reasonable lawful
acts, including, but not limited to, the execution of papers and lawful oaths
and the giving of testimony, that, in the reasonable opinion of the Company, its
successors and assigns, may be necessary or desirable in obtaining, sustaining,
reissuing, extending and enforcing United States and foreign Letters Patent,
including, but not limited to, design patents, on any and all Developments and
for perfecting, affirming and recording the Company's complete ownership and
title thereto, subject to the proviso in Section 7.2 hereof, and Executive will
otherwise reasonably cooperate in all proceedings and matters relating thereto.

            7.4 Records. Executive will keep complete and accurate accounts,
notes, data and records of all Developments in the manner and form requested by
the Company. Such accounts, notes, data and records shall be the property of the
Company, subject to the proviso in Section 7.2 hereof, and, upon request by the
Company, Executive will promptly surrender the same to it or, if not previously
surrendered upon its request or otherwise, Executive will surrender the same,
and all copies thereof, to the Company upon the conclusion of his employment.

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            7.5 Obligations, Restrictions and Limitations. Executive understands
that the Company may enter into agreements or arrangements with agencies of the
United States Government and that the Company may be subject to laws and
regulations which impose obligations, restrictions and limitations on it with
respect to inventions and patents which may be acquired by it or which may be
conceived or developed by employees, consultants or other agents rendering
services to it. Executive agrees that he shall be bound by all such obligations,
restrictions and limitations applicable to any such invention conceived or
developed by him during the term of this Agreement and shall take any and all
further action which may be required to discharge such obligations and to comply
with such restrictions and limitations.

      8. NON-SOLICITATION COVENANT.

            8.1 Nonsolicitation and Noninterference. During the term of this
Agreement and for a period of two years thereafter, Executive shall not (a)
induce or attempt to induce any employee of the Company to leave the employ of
the Company or in any way interfere adversely with the relationship between any
such employee and the Company, (b) induce or attempt to induce any employee of
the Company to work for, render services or provide advice to or supply
confidential business information or trade secrets of the Company to any third
person, firm or corporation or (c) induce or attempt to induce any customer,
supplier, licensee, licensor or other business relation of the Company to cease
doing business with the Company or in any way interfere with the relationship
between any such customer, supplier, licensee, licensor or other business
relation and the Company.

            8.2 Indirect Solicitation. Executive agrees that, during the term of
this Agreement and the period covered by Section 8.1 hereof, he will not,
directly or indirectly, assist or encourage any other person in carrying out,
directly or indirectly, any activity that would be prohibited by the provisions
of Section 8.1 if such activity were carried out by Executive, either directly
or indirectly; and, in particular, Executive agrees that he will not, directly
or indirectly, induce any employee of the Company to carry out, directly or
indirectly, any such activity.

      9. INJUNCTIVE RELIEF. Executive hereby recognizes, acknowledges and agrees
that in the event of any breach by Executive of any of his covenants,
agreements, duties or obligations contained in Sections 5, 6, 7 and 8 of this
Agreement, the Company would suffer great and irreparable harm, injury and
damage, the Company would encounter extreme difficulty in attempting to prove
the actual amount of damages suffered by the Company as a result of such breach,
and the Company would not be reasonably or adequately compensated in damages in
any action at law. Executive therefore covenants and agrees that, in addition to
any other remedy the Company may have at law, in equity, by statute or
otherwise, in the event of any breach by Executive of any of his covenants,
agreements, duties or obligations contained in Sections 5, 6, 7 and 8 of this
Agreement, the Company shall be entitled to seek and receive temporary,
preliminary and permanent injunctive and other equitable relief from any court
of competent jurisdiction to enforce any of the rights of the Company, or any of
the covenants, agreements, duties or obligations of Executive hereunder, and/or
otherwise to prevent the violation of any of the terms or provisions hereof, all
without the necessity of proving the amount of any actual damage to the Company
or any affiliate thereof resulting therefrom; provided, however, that nothing
contained in this Section 9 shall be deemed or construed in any manner
whatsoever as a waiver by the Company of any of the rights which the Company may
have against Executive at law, in equity, by statute or otherwise arising out
of, in connection with or resulting from the breach by Executive of any of his
covenants, agreements, duties or obligations hereunder.

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      10. MISCELLANEOUS.

            10.1 Arbitration. The parties agree that they will use their best
efforts to amicably resolve any dispute arising out of or relating to this
Agreement. Any controversy, claim or dispute that cannot be so resolved shall be
settled by final binding arbitration in accordance with the rules of the
American Arbitration Association and judgment upon the award rendered by the
arbitrator or arbitrators may be entered in any court having jurisdiction
thereof. Any such arbitration shall be conducted in Los Angeles County or
Ventura County, California, or such other place as may be mutually agreed upon
by the parties. Within fifteen (15) days after the commencement of the
arbitration, each party shall select one person to act arbitrator, and the two
arbitrators so selected shall select a third arbitrator within ten (10) days of
their appointment. Each party shall bear its own costs and expenses and an equal
share of the arbitrator's expenses and administrative fees of arbitration.

            10.2 Notices. All notices, requests and other communications
(collectively, "NOTICES") given pursuant to this Agreement shall be in writing,
and shall be delivered by personal service or by United States first class,
registered or certified mail (return receipt requested), postage prepaid,
addressed to the party at the address set forth below:

                 If to Company:

                          BioSource International, Inc.
                          542 Flynn Road
                          Camarillo, CA 93012
                          Attn: President

                  If to Executive, at the address maintained for Executive in
the Company's payroll records.

            Any Notice shall be deemed duly given when received by the addressee
thereof, provided that any Notice sent by registered or certified mail shall be
deemed to have been duly given three days from date of deposit in the United
States mails, unless sooner received. Either party may from time to time change
its address for further Notices hereunder by giving notice to the other party in
the manner prescribed in this section.

            10.3 Entire Agreement. This Agreement contains the sole and entire
agreement and understanding of the parties with respect to the entire subject
matter of this Agreement, and any and all prior agreements, discussions,
negotiations, commitments and understandings, whether oral or otherwise, related
to the subject matter of this Agreement are hereby merged herein. No
representations, oral or otherwise, express or implied, other than those
contained in this Agreement have been relied upon by any party to this
Agreement.

            10.4 Attorneys' Fees. If any action, suit or other proceeding is
instituted to remedy, prevent or obtain relief from a default in the performance
by any party of its obligations under this Agreement, the prevailing party shall
recover all of such party's costs and reasonable attorneys' fees incurred in
each and every such action, suit or other proceeding, including any and all
appeals or petitions there from.

            10.5 Governing Law. THIS AGREEMENT SHALL BE GOVERNED BY AND
CONSTRUED IN ACCORDANCE WITH THE LAWS OF THE STATE OF CALIFORNIA, WITHOUT REGARD
TO CONFLICTS OF LAW PRINCIPLES THEREOF.

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            10.6 Captions. The various captions of this Agreement are for
reference only and shall not be considered or referred to in resolving questions
of interpretation of this Agreement.

            10.7 Counterparts. This Agreement may be executed in any number of
counterparts, each of which shall be deemed to be an original, but all of which
together shall constitute one and the same instrument.

            10.8 Business Day. If the last day permissible for delivery of any
Notice under any provision of this Agreement, or for the performance of any
obligation under this Agreement, shall be other than a business day, such last
day for such Notice or performance shall be extended to the next following
business day (provided, however, under no circumstances shall this provision be
construed to extend the date of termination of this Agreement).

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      In witness whereof, the parties have executed this Agreement as of the
date first set forth above.

Company:                                       Executive:

BIOSOURCE INTERNATIONAL, INC.                  JOZEF VANGENECHTEN

By:_________________________________           By: _____________________________

   Terrance J. Bieker, President and CEO

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