Document:

Exhibit 4.3

Management Stock Purchase Plan

Plan Sponsor

Dart Industries Inc., a subsidiary of Tupperware Corporation
(the "Company"), will sponsor the Management Stock Purchase Plan
("MSPP") on behalf of the Company and its subsidiaries and affiliates
and their employees.

Purpose

The MSPP is designed to accomplish the following objectives:

     Significantly increase executive stock ownership;

     Reinforce importance of stock ownership guidelines for executives; and

     Provide a strong incentive for key executives to increase stock price.

Eligibility

The Compensation and Directors Committee of the Board of Directors
(the "Committee") of the Company determines which executives may participate
in the MSPP. The program is targeted at key executives who have an impact on
overall Company performance.

Plan Highlights

The MSPP is a one-time special opportunity for eligible executives to
purchase Tupperware Corporation stock using a loan provided to you by Dart
Industries Inc. or one of its foreign subsidiaries (the "Lender"), secured
by the shares purchased. For each share of stock you purchase through the
program, you will also receive two stock options from Tupperware Corporation.

Relevant Dates

You have been provided along with this Plan document a participation
interest letter, which is necessary for you to complete, sign, and return.
The participation interest letter should be received by the Company by
October 23, 2000. Promissory notes and security agreements will be provided
for execution in late October to early November 2000. Stock options shall be
granted at or around the date of the sale of the shares to participants,
subject to the discretion of the Committee to delay the grant of stock
stock options.  Stock options could be issued with exercise prices which
differ from the per share price at which shares were purchased.

Awards under the MSPP may be made subsequent to late October or early
November 2000 for executives who first become eligible for the MSPP
thereafter.

Stock Purchase Amount

The maximum number of shares that you can purchase through the MSPP
varies based on your position and salary. Your participation rate in
the program will be a multiple of your annual base salary. The maximum
number of shares that you can purchase through the Plan will equal the
number of shares (rounded to the nearest 100 shares) that equal the dollar
value of your committed participation. You have been provided along with
this Plan document a statement of personalized examples showing hypothetical
situations at your maximum MSPP participation rate.

Stock Options

For each share of stock you purchase, you will receive two stock options.
These stock options will be granted under the Tupperware Corporation 2000
Incentive Plan and will be provided in addition to the regular November
stock option awards. The features of the stock options received in
connection with the MSPP are as follows:

Grant Date

The Committee will determine the grant date of stock options, which is
expected to be as close as possible to the purchase date of shares.

Exercise Price

The Committee will determine the option exercise price, but it will be no
less than, and could be more than, the fair market value of the stock on the
grant date.

Vesting

Options will vest in a minimum of three years and a maximum of seven years.
Options may vest on any anniversary of the grant date, beginning with the
third anniversary and continuing through the seventh. The number of options
vesting on a particular anniversary of the grant date (beginning with the
third anniversary) will be determined as follows:

1.  The average closing share price for the 15 trading days preceding the
    anniversary date will be calculated.

2.  The average share price determined in Paragraph 1 will be used to
    determine the percentage increase, if any, in share price since the
    grant date. For instance, if the average share price calculated in
    Paragraph 1 is $30 and the option exercise price on the grant date is
    $20, the percentage increase will be 50%.

3.  The percentage increase, if any, calculated in Paragraph 2 will then
    be used to determine option vesting on each anniversary date (beginning
    with the third anniversary), as described more fully below.

4.  If the percentage of your options already vested is less than the
    percentage increase, if any, calculated in Paragraph 2, enough options
    will vest so that the percentage of your options vested equals the
    percentage increase, if any, in stock price calculated in Paragraph 2.
    For example, if the percentage increase in share price is 50% and only
    20% of your options are already vested, an additional 30% of your
    options will vest on this anniversary date.

5.  If the percentage of your options already vested is greater than or
    equal to the percentage increase, if any, in share price calculated in
    Paragraph 2, no options will vest on this anniversary date. For example,
    if the percentage increase is 50% and 75% of your options are already
    vested, no further options will vest on this anniversary date.

6.  Any remaining unvested options will vest on the seventh anniversary of
    the grant date, regardless of stock performance.

The following examples illustrate the vesting procedure:

Date               Stock      Increase in    Options vesting   Total options
                   price*     stock price    on this date      vested
                              since grant
                              date

                          Example 1: Fast Stock Growth

Grant date           $20          N/A             N/A               None
Third anniversary    $30          50%             50%               50%
Fourth anniversary   $35          75%             25%               75%
Fifth anniversary    $45         125%             25%              100%

                          Example 2: Slow Stock Growth

Grant date           $20         N/A              N/A              None
Third anniversary    $24         20%              20%              20%
Fourth anniversary   $22         10%              None             20%
Fifth anniversary    $30         50%              30%              50%
Sixth anniversary    $35         75%              25%              75%
Seventh anniversary  $35         75%              25%             100%

     * Stock prices shown for the grant anniversary dates are the
       average closing prices for the 15 trading days prior to the
       anniversary date.

Term of Option

The term of each option shall be ten years, subject to the provisions of
the Tupperware Corporation 2000 Incentive Plan.

Restrictions on Sale of Shares

Since a primary objective of the Plan is to significantly increase executive
stock ownership, 50% of the net shares (after exercise price and taxes) that
you receive when you exercise your MSPP options cannot be sold until your
MSPP loan is fully repaid, except to the extent that the Company permits you
to sell such shares to satisfy a required loan repayment. Upon exercise of
an MSPP option, the Company will retain a share certificate representing such
amount of net shares, although you will have full voting and dividend rights
to the shares. Such shares are not being held as collateral for the loan.
The Company will deliver to you a certificate representing the remaining 50%
amount of the net shares, which may be sold at any time after exercise,
subject to the customary trading restrictions.

Loan

If you participate in the MSPP, you will receive a loan for the purchase of
your shares from the Lender. The features of the loan are as follows:

Amount of Loan

The loan will be for 100% of the purchase price of your shares on the loan
date.

Interest Rate

The interest rate will be the Applicable Federal Rate ("AFR") in effect
on the loan date. Interest will be compounded quarterly. The AFR is published
by the U.S. Internal Revenue Service. Under current U.S. tax rules, if the
loan interest rate is lower than the AFR, the interest rate would be
considered a below market rate and some taxable income would be imputed to
you as a result of receiving the loan. By using the AFR, taxable imputed
income is avoided. Outside the U.S., other tax-related rules may apply.

Payment of Interest

Interest on the loan shall be accrued quarterly and shall be paid in
accordance with the repayment schedule discussed below. Any remaining
interest due after the application of cash dividends shall be added to the
loan amount.

Security

The loan is secured with the stock purchased through the MSPP. The Company
has recourse to your purchased stock and to your individual general assets
for repayment of up to 100% of the principal and interest owed. The share
certificates will be held by the Lender in Orlando, Florida.

Release of Shares

Each time you pay principal and the associated interest on your loan, a
portion of your stock equal to the percentage of the principal being repaid
will be released. Once your loan is fully repaid, all shares will be
released. While shares are unreleased, two special provisions apply to them:

Sale of Shares. At your request, you can direct the Lender to sell a portion
of the shares and apply the proceeds to satisfy a required repayment.
Otherwise, unreleased shares cannot be sold.

Dividends on Shares. Any cash dividends paid on an unreleased share will
automatically be applied to reducing your loan interest. Once a share is
released, dividends paid on that share will be paid directly to you.

Repayment Schedule

Your loan will be repaid in three installment payments (other than
application of cash dividends and any prepayments):

The first repayment will be made on the fifth anniversary of the loan date
(approximately October 31, 2005) and will be for 25% of the principal (plus
associated interest).

The second repayment will be made on the sixth anniversary of the loan date
(approximately October 31, 2006) and will be for 25% of the principal (plus
associated interest).

The third and final repayment will be made on the eighth anniversary of the
loan date (approximately October 31, 2008) and will be for 50% of the
principal (plus associated interest).

If you wish, you can accelerate this repayment schedule. Any prepayment will
be applied first to associated interest, and then to principal installments
in the order of their maturities. Shares will be released proportionately as
principal repayments are made.

Application of Annual Bonus to Interest

You may decide to direct a portion of your annual cash bonus toward repayment
of the interest on your loan. Executives are encouraged to use 10% of their
net annual cash bonus after taxes to avoid large amounts of interest
compounding on the loan.

Supplemental Cash Bonus

In order to limit your risk if the stock price declines, the Company also may
pay a supplemental cash bonus. The supplemental cash bonus, if any, will not
be paid directly to you. Rather, the bonus will be applied to your loan at
the required repayment date. The amount of the supplemental cash bonus,
if any, at each of the three repayment dates will be determined as follows:

1.   The percentage decline in stock price from the price of the stock at the
     time of purchase to the repayment date will be calculated.

2.   A percentage of the principal due on the repayment date equal to the
     percentage decline in stock price will be paid as a supplemental cash
     bonus which will be applied to your loan. For instance, if the stock
     price on a repayment date has declined 10%, 10% of the principal due on
     that repayment date will be paid as a supplemental cash bonus and will
     be applied to your loan.

3.   The total amount that may be paid as a supplemental cash bonus (and
     applied to your loan) on any repayment date will not exceed 25% of the
     principal due on that date.

4.   A supplemental cash bonus can only be paid on required loan repayments.
     Required loan repayments are those made on the regularly scheduled
     repayment dates (at the end of years 5, 6, and 8) or on a date on which
     a repayment is required because of termination of employment (other than
     voluntary termination or termination for cause). A supplemental cash
     bonus will not be paid when repayments are made voluntarily on other
     dates or when repayments are required because of voluntary termination
     or termination for cause or upon default.

If Your Employment Ends

If your employment ends, the loan repayment and option vesting and expiration
provisions will change as summarized in the following table:

<TABLE>

<CAPTION>
Reason for            Loan Repayment                       Options*<F1>
leaving               Date                      Vesting             Expiration
<S>                   <C>                    <C>                  <C>
Retirement at age     Earlier of scheduled   Options continue     Options expire
55 through 60 with    date or 2 years        to vest for 1 year   2 years after
at least 10 years     after retirement       after retirement     retirement
of service

Retirement after      Earlier of scheduled   Options continue     Options expire
age 60 with at        date or 6 years        to vest for 6 years  6 years after
least 15 years        after retirement       after retirement     retirement
of service

Disability            Earlier of scheduled   Options continue     Options expire
                      date or 3 years        to vest for 3 years  3 years after
                      after disability       after disability     disability

Death                 Earlier of scheduled   Options vest         Options expire
                      date or 3 years        immediately          3 years after
                      after death                                 death, unless
                                                                  death occurs
                                                                  during retire-
                                                                  ment, in which
                                                                  case the
                                                                  retirement
                                                                  provisions
                                                                  control

Voluntary            Immediately upon        No further          Options expire
termination          termination             options vest        30 days after
                                                                 termination

Involuntary          Immediately upon        Options continue    Options expire
termination          termination             to vest for 1 year  1 year after
other than                                   after termination   termination
for cause

Termination          Immediately upon        No further          Options expire
for cause            termination             options vest        immediately
                                                                 upon
                                                                 termination
<FN>
<F1>
     *In no case will an option remain exercisable beyond the maximum
     10-year term under the Tupperware Corporation 2000 Incentive Plan
     or the remaining term of the option. These vesting and expiration
     terms are conditioned upon the provisions of the Tupperware
     Corporation 2000 Incentive Plan.
</FN>
</TABLE>

Tax and Financial Planning Considerations

You should consult with a professional financial adviser to be sure you
understand how participating in the MSPP may affect your taxes and overall
financial plan.

For More Information

Questions should be directed to the Senior Vice President, Human Resources
in Orlando, Florida.

This document is intended to provide you with a summary of the MSPP and is
not to be construed as a contract or a promise to pay an award nor does it
imply or guarantee participation in subsequent years. The Committee reserves
the right to interpret, define, change, or cancel provisions of this program
at any time. The Committee may also need to modify provisions to comply with
local regulatory requirements for participants who reside outside the U.S.
The stock option matters discussed above as part of the program are
governed by the provisions of Tupperware Corporation's 2000 Incentive Plan,
which is administered by the Committee. In instances of question or conflict,
the provisions of Tupperware Corporation's 2000 Incentive Plan will govern
stock options granted under this program.EXHIBIT 4.1

                          SECURITIES PURCHASE AGREEMENT

     THIS SECURITIES PURCHASE AGREEMENT (this "AGREEMENT") is executed this 15th
day of September, 2000 to be effective as of August 9, 2000, between BioSource
International, Inc., a Delaware corporation (the "COMPANY"), and GENSTAR CAPITAL
PARTNERS II, L.P. (together with such other persons to whom this right may be
assigned under Section 4.5, below, the "PURCHASER").

     WHEREAS, the Company and Purchaser are executing and delivering this
Agreement in reliance upon the exemption from securities registration afforded
by Rule 506 under Regulation D as promulgated by the United States Securities
and Exchange Commission (the "COMMISSION") under Section 4(2) of the Securities
Act of 1933, as amended (the "SECURITIES ACT"); and

     WHEREAS, subject to the terms and conditions set forth in this Agreement,
the Company desires to issue and sell to Purchaser, and Purchaser desires to
acquire from the Company, 300,000 shares of the Company's Common Stock, par
value $0.001 per share (the "COMMON STOCK"), at a price of $15.00 per share,
subject to adjustment as set forth in Section 1.1, below.

     NOW, THEREFORE, in consideration of the promises and mutual covenants and
agreements hereinafter contained, the Company and Purchaser hereby agree as
follows:

                                   ARTICLE I.

                         PURCHASE AND SALE OF THE SHARES

     1.1 PURCHASE AND SALE. Subject to the terms and conditions set forth
herein, the Company shall issue and sell to Purchaser, and Purchaser shall
purchase from the Company on the Closing Date (as defined below), 300,000 shares
of Common Stock (subject to adjustment as set forth in this Section 1.1, the
"SHARES"), at a price per Share of $15.00; PROVIDED, that if the closing price
for the Company's Common Stock on the date that Russell Hays commences
employment with the Company (currently contemplated to be September 18, 2000) is
less than $15.00 per share (such lesser price, the "ADJUSTED PURCHASE PRICE"),
the Shares shall equal, and Purchaser shall purchase, that number of shares of
Common Stock as are equal to the product of $4,500,000 divided by the Adjusted
Purchase Price, at a price per Share equal to the Adjusted Purchase Price.

     1.2 CLOSING. The closing of the purchase and sale of the Shares (the
"CLOSING") shall take place at the offices of Troop Steuber Pasich Reddick &
Tobey, LLP, 2029 Century Park East, 24th Floor, Los Angeles, California, 90067,
or by transmission by facsimile and overnight courier, immediately following the
date that Russell Hays commences employment with the Company, or such later date
or different location as the parties shall agree (the "CLOSING DATE"). At the
Closing:

<PAGE>

          (a) Purchaser shall deliver, as directed by the Company, an aggregate
payment of $4,500,000 in United States dollars (the "PURCHASE PRICE") in
immediately available funds to an account or accounts designated in writing by
the Company; and

          (b) The Company shall instruct its transfer agent to immediately
deliver to Purchaser a stock certificate or certificates, in definitive form,
registered in the name of Purchaser, representing the Shares.

                                  ARTICLE II.

                         REPRESENTATIONS AND WARRANTIES

     2.1 REPRESENTATIONS, WARRANTIES AND AGREEMENTS OF THE COMPANY. The Company
hereby makes the following representations and warranties to Purchaser:

          (a) ORGANIZATION AND QUALIFICATION. The Company is a corporation duly
incorporated, validly existing and in good standing under the laws of the State
of Delaware, with the requisite corporate power and authority to own and use its
properties and assets and to carry on its business as currently conducted.

          (b) AUTHORIZATION, VALIDITY AND ISSUANCE OF SHARES. The Company has
the requisite corporate power and authority to enter into and perform its
obligations under this Agreement and to issue and sell the Shares in accordance
with the terms hereof. The execution, delivery and performance of this Agreement
by the Company and the consummation of the transactions contemplated hereby
(including, without limitation, the issuance of the Shares) have been duly
authorized by the Company's Board of Directors and no further consent or
authorization of the Company, its Board of Directors or its stockholders is
required, and the Company has duly executed and delivered this Agreement. This
Agreement constitutes the valid and binding obligation of the Company,
enforceable against the Company in accordance with its terms, subject to
applicable bankruptcy, insolvency, reorganization, moratorium, fraudulent
transfer and other laws affecting creditors' rights and remedies generally and
to general principles of equity (regardless of whether enforcement is sought in
a proceeding at law or in equity). The Shares are and at all times will
hereafter continue to be duly authorized. Upon receipt by the Company of the
Purchase Price, the Shares will be validly issued, fully paid and
non-assessable, free and clear of all taxes, liens, claims, encumbrances and
Company rights of first refusal, other than taxes, liens, claims and
encumbrances created by Purchaser and will not be subject to any preemptive
rights, rights of first refusal or other similar rights of stockholders of the
Company and will not impose personal liability on the holder thereof.

          (c) CAPITALIZATION. The capitalization of the Company as of the date
hereof is set forth on Schedule 2(c), including the authorized capital stock,
the number of shares issued and outstanding, the number of shares issuable and
reserved for issuance pursuant to the Company's stock option plans, the number
of shares issuable and reserved for issuance pursuant to securities exercisable
for, or convertible into or exchangeable for any shares of capital stock. All of
such outstanding shares of the Company's capital stock have been, or upon
issuance will be, validly issued, fully paid and nonassessable. Except as set
forth on Schedule 2(c), no shares of capital stock of the Company (including the
Shares) are subject to preemptive rights or any

                                     Page 2
<PAGE>

other similar rights of the shareholders of the Company or any liens or
encumbrances. Except for the Shares and as disclosed in Schedule 2(c), as of the
date of this Agreement, (i) there are no outstanding securities, options,
warrants, scrip, rights to subscribe to, calls or commitments of any character
whatsoever to which the Company is a party relating to the issuance by the
Company of securities or rights convertible into or exercisable or exchangeable
for, any shares of capital stock of the Company, or arrangements by which the
Company is or may become bound to issue additional shares of capital stock of
the Company, and (ii) there are no agreements or arrangements under which the
Company is obligated to register the sale of any of its securities under the
Securities Act.

          (d) ACKNOWLEDGMENT REGARDING THE PURCHASER'S PURCHASE OF THE
SECURITIES. The Company acknowledges and agrees that Purchaser is not acting as
a financial advisor or acting as a fiduciary of the Company (or in any similar
capacity) with respect to this Agreement or the transactions contemplated
hereby, and the relationship between the Company and Purchaser is "arms length"
and that any statement made by Purchaser or any of its representatives or agents
in connection with this Agreement and the transactions contemplated hereby is
not advice or a recommendation and is merely incidental to Purchaser's purchase
of the Shares and has not been relied upon by the Company, its officers or
directors in any way. The Company further represents to Purchaser that the
Company's decision to enter into this Agreement has been based solely on an
independent evaluation by the Company and its representatives.

          (e) PRIVATE OFFERING; SOLICITATION. The Company and all persons acting
on its behalf have not (i) made, directly or indirectly, and will not make,
offers or sales of any securities or solicited any offers to buy any security
under circumstances that would require registration of the Shares or the
issuance of such securities under the Securities Act, (ii) distributed any
offering materials in connection with the offering and sale of the Shares, any
amendments and any supplements thereto, or (iii) solicited any offer to buy or
sell the Shares by means of any form of general solicitation or advertising (as
those terms are used in Rule 502(c) of Regulation D under the Exchange Act) in a
manner which would require registration under the Securities Act. Subject to the
accuracy and completeness of the representations and warranties of Purchaser
contained in Section 2.2 hereof, the offer, issuance and sale by the Company to
Purchaser of the Shares is exempt from the registration requirements of the
Securities Act.

     2.2 REPRESENTATIONS AND WARRANTIES OF PURCHASER. Purchaser hereby
represents and warrants to the Company as follows:

          (a) ORGANIZATION; AUTHORITY. Purchaser is a limited partnership duly
formed, validly existing and in good standing under the laws of the State of
Delaware with the requisite power and authority to enter into and to consummate
the transactions contemplated hereby and otherwise to carry out its obligations
hereunder. The purchase by Purchaser of the Shares hereunder has been duly
authorized by all necessary action on the part of Purchaser. This Agreement has
been duly executed and delivered by Purchaser and constitutes the valid and
legally binding obligation of Purchaser, enforceable against Purchaser in
accordance with its terms, except as such enforceability may be limited by
applicable bankruptcy, insolvency, reorganization, moratorium, liquidation or
similar laws relating to, or affecting generally the enforcement of, creditors'
rights and remedies or by other equitable principles of general

                                     Page 3
<PAGE>

application, and except that rights to indemnification and contribution may be
limited by federal or state securities laws or public policy relating thereto.

          (b) INVESTMENT INTENT. Purchaser is acquiring the Shares for its own
account and not with a present view to or for distributing or reselling the
Shares or any part thereof or interest therein in violation of the Securities
Act; provided, however, that by making the representations herein, Purchaser
does not agree to hold any of the Shares for any minimum or other specific term
and reserves the right to dispose of the Shares at any time in accordance with
or pursuant to a registration statement or an exemption under the Securities
Act.

          (c) PURCHASER STATUS. At the time Purchaser was offered the Shares and
at the Closing Date, (i) it was and will be an "accredited investor" as defined
in Rule 501 under the Securities Act and (ii) Purchaser, either alone or
together with its representatives, had and will have such knowledge,
sophistication and experience in business and financial matters so as to be
capable of evaluating the merits and risks of the prospective investment in the
Shares.

          (d) RELIANCE. Purchaser understands and acknowledges that (i) the
Shares are being offered and sold to Purchaser without registration under the
Securities Act in a private placement that is exempt from the registration
provisions of the Securities Act under Section 4(2) of the Securities Act or
Regulation D promulgated thereunder and (ii) the availability of such exemption
depends in part on, and the Company will rely upon the accuracy and truthfulness
of, the representations set forth in this Section 2.2 and Purchaser hereby
consents to such reliance.

          (e) INFORMATION. Purchaser and its advisors, if any, have been
furnished with all materials relating to the business, finances and operations
of the Company and materials relating to the offer and sale of the Shares which
have been requested by Purchaser or its advisors. Purchaser and its advisors, if
any, have been afforded the opportunity to ask questions of the Company.
Purchaser understands that its investment in the Shares involves a significant
degree of risk, including the risk of a total loss of investment.

          (f) GOVERNMENTAL REVIEW. Purchaser understands that no United States
federal or state agency or any other government or governmental agency or
authority has passed upon or made any recommendation or endorsement of the
Shares.

          (g) OTHER AGREEMENTS. Purchaser has not, directly or indirectly, made
any agreements with the Company relating to the terms and conditions of the
transactions contemplated by this Agreement except for the Investor Rights
Agreement dated as of February 15, 2000 by and among the Company, Purchaser and
Stargen II LLC (the "INVESTOR RIGHTS AGREEMENT") and as otherwise set forth in
this Agreement.

        The Company acknowledges and agrees that Purchaser makes no
representations or warranties with respect to the transactions contemplated
hereby other than those specifically set forth in this Section 2.2. Purchaser
acknowledges and agrees that the Company makes no representations or warranties
with respect to the transactions contemplated hereby other than those
specifically set forth in Section 2.1 hereof.

                                     Page 4
<PAGE>

                                  ARTICLE III.

                                OTHER AGREEMENTS

     3.1 TRANSFER RESTRICTIONS; LEGEND.

          (a) TRANSFER RESTRICTIONS. Purchaser understands that (i) except as
provided in the Investor Rights Agreement, the Shares have not been and are not
being registered under the Securities Act or any state securities laws, and may
not be transferred unless (A) subsequently registered thereunder, or (B)
Purchaser shall have delivered to the Company an opinion of counsel reasonably
acceptable to the Company (which opinion shall be in form, substance and scope
customary for opinions of counsel in comparable transactions) to the effect that
the Shares to be sold or transferred may be sold or transferred under an
exemption from such registration, or (C) sold under Rule 144 promulgated under
the Securities Act (or a successor rule), or (D) sold or transferred to an
affiliate of Purchaser or a partner or member of Purchaser pursuant to an
exemption under the Securities Act; and (ii) neither the Company nor any other
person is under any obligation to register such Shares under the Securities Act
or any state securities laws or to comply with the terms and conditions of any
exemption thereunder, in each case, other than pursuant to the Investor Rights
Agreement.

          (b) LEGEND. Purchaser understands that the Shares and, until such time
as the Shares have been registered under the Securities Act as contemplated by
the Investor Rights Agreement or otherwise may be sold by Purchaser under Rule
144, the certificates for the Shares may bear a restrictive legend in
substantially the following form:

          The securities represented by this certificate have not been
          registered under the Securities Act of 1933, as amended, or the
          securities laws of any state of the United States. The securities
          represented hereby may not be offered or sold in the absence of an
          effective registration statement for the securities under applicable
          securities laws unless offered, sold or transferred under an available
          exemption from the registration requirements of those laws.

          The legend set forth above shall be removed and the Company shall
issue a certificate without such legend to the holder of any Shares upon which
it is stamped, if (i) the sale of such Shares is registered under the Securities
Act or (ii) in connection with the resale of such Shares, such holder provides
the Company with an opinion of counsel, in form, substance and scope customary
for opinions of counsel in comparable transactions, or a "no action" letter from
the staff of the Commission, in either case to the effect that a public sale or
transfer of such Shares may be made without registration under the Securities
Act or (iii) when such Shares may be sold by a person who is not an "affiliate"
of the Company under Rule 144(k). Purchaser agrees to sell all Shares, including
those represented by a certificate(s) from which the legend has been removed,
pursuant to an effective registration statement or under an exemption from the
registration requirements of the Securities Act. The Company acknowledges that
Purchaser may distribute the Shares to its partners in accordance with the terms
of its organizational documents

                                     Page 5
<PAGE>

and the legend set forth above shall be removed for Shares held by holders who
can sell such Shares pursuant to Rule 144(k).

     3.2 REGISTRATION RIGHTS PURSUANT TO THE INVESTOR RIGHTS AGREEMENT. Each of
the Company and Purchaser hereby agrees that the Shares shall constitute
"Registrable Securities" as that term is defined in the Investor Rights
Agreement, that the Shares shall be subject to the terms of the Investor Rights
Agreement in all respects and that Purchaser shall be entitled to all of the
rights, benefits and privileges under the Investor Rights Agreement with respect
to the Shares, and the parties agree to cause the Investor Rights Agreement to
be amended to reflect such agreement.

     3.3 EXPENSES. The Company shall reimburse Purchaser for the out-of-pocket
expenses reasonably incurred by it and its affiliates and advisors in connection
with the negotiation, preparation, execution and delivery of this Agreement, the
Amendment to the Investor Rights Agreement and any other agreements to be
executed in connection herewith, including, without limitation, its reasonable
attorneys' fees and expenses.

                                  ARTICLE IV.

                                  MISCELLANEOUS

     4.1 ENTIRE AGREEMENT. This Agreement contains the entire understanding of
the parties with respect to the subject matter hereof and supersede all prior
agreements and understandings, oral or written, with respect to such matters.

     4.2 NOTICES. Any notices, consents, waivers or other communications
required or permitted to be given under the terms of this Agreement must be in
writing and will be deemed to have been delivered (i) upon receipt, when
delivered personally, (ii) upon receipt, when sent by facsimile, PROVIDED
confirmation of transmission is mechanically or electronically generated and
kept on file by the sending party (if received by or before 5:30 p.m. where such
notice is received) or the first (1st) business day following such delivery (if
received after 5:30 p.m. where such notice is received) or (iii) one (1)
business day after deposit with a nationally recognized overnight courier, in
each case properly addressed to the party to receive the same. The addresses and
facsimile numbers for such communications shall be:

                      (i)    If to the Company:

                             BioSource International, Inc.
                             542 Flynn Road
                             Camarillo, CA  93012
                             Telephone:  (805) 987-0086
                             Attention:  Chief Executive Officer
                             Facsimile:  (805) 383-5382

                                     Page 6
<PAGE>

                      with a copy to:

                             Troop Steuber Pasich Reddick & Tobey, LLP
                             2029 Century Park East, 24th Floor
                             Los Angeles, CA 90067
                             Attention:  Scott W. Alderton, Esq.
                             Facsimile: (310) 728-2222

                      (iii)  If to Purchaser, to:

                             GENSTAR CAPITAL LLC
                             555 California Street, Suite 4850
                             San Francisco, CA  94104
                             Telecopy No.:  (415) 834-2383
                             Attention: Jean-Pierre L. Conte

                      with a copy to:

                             Latham & Watkins
                             505 Montgomery Street, Suite 1900
                             San Francisco, CA 94111-2562
                             Facsimile No.: (415) 395-8095
                             Attention:  Scott Haber, Esq.

Each party shall provide written notice to the other parties of any change in
address or facsimile number in accordance with the provisions hereof.

     4.3 AMENDMENTS; WAIVERS. No provision of this Agreement may be waived or
amended except in a written instrument signed, in the case of an amendment, by
both the Company and Purchaser or, in the case of a waiver, by the party against
whom a waiver of any such provision is sought. No waiver of any default with
respect to any provision, condition or requirement of this Agreement shall be
deemed to be a continuing waiver in the future or a waiver of any other
provision, condition or requirement hereof, nor shall any delay or omission of
any party to exercise any right hereunder in any manner impair the exercise of
any such right accruing to it thereafter.

     4.4 HEADINGS. The titles and headings contained herein are for convenience
only, do not constitute a part of this Agreement and shall not be deemed to
limit or affect any of the provisions hereof.

     4.5 SUCCESSORS AND ASSIGNS. The rights and obligations of Purchaser under
this Agreement may be assigned in whole of in part to any partner, member,
officer, director or "affiliate" (as defined in Rule 144 of the rules and
regulations of the Commission) of Purchaser; provided such assignee is an
"accredited investor" (as defined in Rule 501 of the rules and regulations of
the Commission), and agrees to be bound by and fully perform all of Purchaser's
obligations hereunder with respect to such assignment. This Agreement shall be
binding upon and inure to the benefit of the parties and their successors and
permitted assigns. If and to the

                                     Page 7
<PAGE>

extent that any of Purchaser's successors or permitted assigns does not
constitute an "Exempt Person" as that term is defined in Section 1 of the Rights
Agreement dated as of February 25, 1999 between the Company and U.S. Stock
Transfer Corporation, as rights agent, as amended by the Rights Agreement
Amendment dated as of January 10, 2000 (as so amended, the "RIGHTS AGREEMENT"),
then the Company shall immediately amend the Rights Agreement to specifically
provide that such successors or permitted assigns are included within the
definition of "Exempt Person" thereunder.

     4.6 NO THIRD-PARTY BENEFICIARIES. This Agreement is intended for the
benefit of the parties hereto and their respective permitted successors and
assigns and is not for the benefit of, nor may any provision hereof be enforced
by, any other Person.

     4.7 GOVERNING LAW. This Agreement shall be governed by and construed and
enforced in accordance with the internal laws of the State of California without
regard to the principles of conflicts of law thereof. Each party hereby
irrevocably submits to the nonexclusive jurisdiction of the State or Federal
courts sitting in the County of Los Angeles for the adjudication of any dispute
hereunder or in connection herewith or with any transaction contemplated hereby
or discussed herein, and hereby irrevocably waives, and agrees not to assert in
any suit, action or proceeding, any claim that it is not personally subject to
the jurisdiction of any such court, or that such suit, action or proceeding is
improper. Each party hereby irrevocably waives personal service of process and
consents to process being served in any such suit, action or proceeding by
mailing a copy thereof to such party at the address for such notices to it under
this Agreement and agrees that such service shall constitute good and sufficient
service of process and notice thereof. Nothing contained herein shall be deemed
to limit in any way any right to serve process in any manner permitted by law.
EACH PARTY HEREBY IRREVOCABLY WAIVES ANY RIGHT IT MAY HAVE, AND AGREES NOT TO
REQUEST, A JURY TRIAL FOR THE ADJUDICATION OF ANY DISPUTE HEREUNDER OR IN
CONNECTION HEREWITH OR ARISING OUT OF THIS AGREEMENT OR ANY TRANSACTION
CONTEMPLATED HEREBY.

     4.8 SURVIVAL. The representations and warranties of the Company and
Purchaser contained in Sections 2.1 and 2.2 and the agreements and covenants set
forth in Article III, shall survive the Closing and any sale of the Shares
regardless of any investigation made by or on behalf of Purchaser or by or on
behalf of the Company, except that, in the case of representations and
warranties such survival shall be limited to the period of one (1) year
following the Closing Date on which they were made or deemed to have been made
(other than with respect to any claim by a third party against the party to this
Agreement who seeks to assert a claim based on such representations and
warranties).

     4.9 COUNTERPARTS. This Agreement may be executed in two or more
counterparts, all of which when taken together shall be considered one and the
same agreement and shall become effective when counterparts have been signed by
each party and delivered to the other parties, it being understood that both
parties need not sign the same counterpart. In the event that any signature is
delivered by facsimile transmission, such signature shall create a valid and
binding obligation of the party executing (or on whose behalf such signature is
executed) the same with the same force and effect as if such facsimile signature
page were an original thereof.

                                     Page 8
<PAGE>

     4.10 SEVERABILITY. In case any one or more of the provisions of this
Agreement shall be invalid or unenforceable in any respect, the validity and
enforceability of the remaining terms and provisions of this Agreement shall not
in any way be affected or impaired thereby and the parties will attempt to agree
upon a valid and enforceable provision which shall be a reasonable substitute
therefor, and upon so agreeing, shall incorporate such substitute provision in
this Agreement.

     4.11 FURTHER ASSURANCES. Each party shall do and perform, or cause to be
done and performed, all such further acts and things, and shall execute and
deliver all such other agreements, certificates, instruments and documents, as
the other parties may reasonably request in order to carry out the intent and
accomplish the purposes of this Agreement and the consummation of the
transactions contemplated hereby.

     4.12 FEES AND EXPENSES. Except as set forth in Section 3.3 hereof, each
party shall pay the fees and expenses of its advisers, counsel, accountants and
other experts, if any, and all other expenses incurred by such party incident to
the negotiation, preparation, execution, delivery and performance of this
Agreement.

                            [SIGNATURE PAGE FOLLOWS]

                                     Page 9
<PAGE>

     IN WITNESS WHEREOF, the parties hereto have caused this Securities Purchase
Agreement to be duly executed by their respective authorized persons as of the
date first indicated above.

                                        BIOSOURCE INTERNATIONAL, INC.

                                        By:     /s/ JAMES CHAMBERLAIN
                                           -------------------------------------
                                           James Chamberlain
                                           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

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