EXHIBIT 10.11
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                                  COMMON STOCK
                               PURCHASE AGREEMENT


                                     between


                             BOSTON BIOMEDICA, INC.


                                       and


                      G&G DIAGNOSTICS LIMITED PARTNERSHIP I




                            Dated as of June 5, 1990





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     COMMON STOCK  PURCHASE  AGREEMENT  dated as of June 5, 1990 between  BOSTON
BIOMEDICA,   INC.,  a  Massachusetts   corporation  (the  "Company"),   and  G&G
Diagnostics Limited Partnership I (the "Purchaser").

    WHEREAS,  the Company wishes to issue and sell to the Purchaser an aggregate
of 10,000 shares (the  "Shares") of the  authorized  but unissued  Common Stock,
$.01 par value, of the Company (the "Common Stock");

    WHEREAS,  the Company  wishes to grant the  Purchaser  an option to purchase
16,667 additional shares of Common Stock; and

    WHEREAS,  the  Purchaser  wishes to  purchase  the  Shares  on the terms and
subject to the conditions set forth in this Agreement;

    NOW,  THEREFORE,  in  consideration of the premises and the mutual covenants
contained in this Agreement, the parties agree as follows:


                                    ARTICLE I

                                   THE SHARES

     SECTION 1.01 Issuance,  Sale and Purchase of the Shares. The Company agrees
to issue and sell to the Purchaser and the Purchaser agrees to purchase from the
Company at the Closing (as defined in Section 1.03 hereof), 10,000 shares of the
Company's Common Stock for an aggregate purchase price of $150,000.00.

     SECTION 1.02 Grant of Option to Purchase  Additional  Shares. In connection
with the sale and purchase  described in Section 1.01 hereof, the Company agrees
to grant to the Purchaser an option to purchase up to 16,667 additional  shares,
exercisable  for a period  of two  years,  commencing  on the date  hereof  (the
"Option Period"), at a price of $20.00 per share during the first year following
the date  hereof  and at a price of $25.00  per share  during  the  second  year
following the date hereof; provided, however, that if the Company shall sell any
shares or equity-equivalents  (other than Reserved Employee Shares as defined in
Section  5.02 hereof or pursuant to Section  1.06  hereof) at a price lower than
$20.00 per share  during the first  year of the  Option  Period,  and (i) if the
Purchaser has not yet  exercised the option in full and the Purchaser  exercises
the  option in part or in full  within  thirty  (30) days  following  receipt of
notice  from the  Company of such sale,  or (ii) if the  Purchaser  has  already
exercised  the option in part or in full,  then (iii) the Company shall issue to
the Purchaser a sufficient number of shares of Common Stock as shall reduce (but
not  increase)  the cost per share paid by the  Purchaser  upon  exercise of the
option to such price at which such shares or equity-equivalents were issued; and
provided, further, that if the Company shall sell any shares or




                                     - 2 -

equity-equivalents  (other than Reserved  Employee  Shares as defined in Section
5.02  hereof) at a price lower than  $25.00 per share  during the second year of
the Option Period,  and (i) if the Purchaser has not yet exercised the option in
full and the  Purchaser  exercises  the option in part or in full within  thirty
(30) days following  receipt of notice from the Company of such sale, or (ii) if
the  Purchaser has already  exercised the option in part or in full,  then (iii)
the Company shall issue to the Purchaser a sufficient number of shares of Common
Stock as  shall  reduce  (but not  increase)  the  cost  per  share  paid by the
Purchaser  upon  exercise  of the option to such  price at which such  shares or
equity-equivalents were issued.

     SECTION 1.03  Closing.  The closing of the  purchase and sale  described in
Section 1.01 shall take place at 2:30 p.m.,  Boston time, on June 5, 1990, or at
such other date and time as may be agreed  upon  between the  Purchaser  and the
Company  (such  closing  being called the "Closing" and such date and time being
called the "Closing Date").

     SECTION  1.04  Payment and  Delivery.  At the  Closing,  the Company  shall
deliver to the  Purchaser  a  certificate  registered  in the  Purchaser's  name
representing  10,000 shares of Common  Stock.  As payment in full for the Shares
being purchased by and against delivery of the stock certificate therefore,  the
Purchaser  shall pay to the  Company by  certified  check or wire  transfer,  or
combination thereof, One Hundred Fifty Thousand Dollars ($150,000.00).

     SECTION 1.05 Price Protection.

    (a) If the Company  shall  within  three years after the Closing  Date issue
additional  shares of Common  Stock or other  securities  convertible  into,  or
exercisable or exchangeable  for Common Stock (other than the Reserved  Employee
Shares described in Section 5.02 below) at a price per  common-equivalent  share
of less  than the price per share  paid for the  Shares by the  Purchaser  under
Section 1.01 hereof,  the Company shall issue to the Purchaser at no cost to the
Purchaser a sufficient number of shares of Common Stock as shall reduce (but not
increase)  the cost per share paid by the  Purchaser  for the Shares  (which for
purposes of this Section 1.05 shall  include any shares  issued  pursuant to the
option in Section  1.02) to such price at which such  Common  Stock  equivalents
were issued.

    (b) Any  Shares of Common  Stock  issued  under this  Section  1.05 shall be
included within the definition of Shares.

     SECTION 1.06 Additional Investments. The Purchaser hereby acknowledges that
within the six month period  following the Closing  Date,  the Company may issue
and sell up to an  additional  30,000  shares of Common  Stock  and  options  to
purchase  50,001  shares of Common Stock or an aggregate of 80,001  Common Stock
equivalents for the purpose of raising additional equity





                                      - 3 -




capital.  In connection with such issuance and sale, the Company shall not grant
any new  investors  any  rights  which  are  superior  to those  granted  to the
Purchaser under this Agreement  without  securing for the Purchaser the right to
participate  in such  superior  rights pro rata with such new  investors  on the
basis of the  total  dollar  amount  invested  by the  Purchaser  and each  such
investor.  Conversely, such new investors shall have the right to participate on
a similar pro rata basis with the  Purchaser  in  connection  with the rights of
Purchaser under the Registration Rights Agreement (as hereinafter defined),  and
the rights granted under Sections 5.01(a) (the Purchaser's  right of approval to
be  exercised  by  one  representative  of all  such  investors,  including  the
Purchaser), 5.02, and 5.11 (the nominee referred to therein being the nominee of
the Purchaser and the new  investors) of this  Agreement.  The Purchaser and the
Company each agrees to execute and deliver any and all such further  instruments
and waivers  which may be  reasonably  necessary  to carry out the intent of the
parties under this Section 1.06.


                                   ARTICLE II

                  REPRESENTATIONS AND WARRANTIES OF THE COMPANY

    The Company  represents  and warrants to the Purchaser  that,  except as set
forth in the  Disclosure  Schedule  attached  as  Schedule  I (which  Disclosure
Schedule makes explicit  reference to the particular  representation or warranty
as to which  exception is taken,  which in each case shall  constitute  the sole
representation and warranty as to which such exception shall apply):

     SECTION 2.01 Organization,  Qualifications and Corporate Power. The Company
is a corporation duly incorporated,  validly existing and in good standing under
the laws of the Commonwealth of Massachusetts  and is duly licensed or qualified
to transact  business as a foreign  corporation  and is in good standing in each
jurisdiction  in  which  the  nature  of the  business  transacted  by it or the
character of the  properties  owned or leased by it requires  such  licensing or
qualification  except where the failure to be so licensed or qualified would not
have  a  material  adverse  effect  on the  business,  operations  or  financial
condition of the Company.  The Company has the corporate  power and authority to
own and hold its properties and to carry on its business as now conducted and as
proposed to be conducted,  to execute,  deliver and perform this Agreement,  the
Registration Rights Agreement with the Purchaser in the form attached as Exhibit
A (the "Registration Rights Agreement") and the Stock Restriction Agreement with
the  Purchaser  and the other party thereto named in paragraph (h) of Article IV
of this  Agreement,  in the form  attached as Exhibit B (the "Stock  Restriction
Agreement"),  and to issue,  sell and  deliver  the  Shares.  The Company has no
subsidiaries.







                                      - 4 -



     SECTION 2.02 Authorization of Agreements, Etc.

          (a) The execution and delivery by the Company of this  Agreement,  the
Registration  Rights  Agreement  and  the  Stock  Restriction   Agreement,   the
performance  by the Company of its  obligations  hereunder and  thereunder,  the
issuance,  sale and  delivery  of the Shares  have been duly  authorized  by all
requisite  corporate action and will not violate any provision of law, any order
of any court or other agency of government,  the Articles of Organization of the
Company,  as amended (the "Charter") or the By-laws of the Company,  as amended,
or any provision of any  indenture,  agreement or other  instrument to which the
Company, any of its subsidiaries or any of their respective properties or assets
is bound, or conflict with, result in a breach of or constitute (with due notice
or lapse of time or both) a default under any such indenture, agreement or other
instrument,  or result  in the  creation  or  imposition  of any  lien,  charge,
restriction,  claim or  encumbrance  of any  nature  whatsoever  upon any of the
properties or assets of the Company or any of its subsidiaries.  No provision of
the Stock Restriction Agreement violates, conflicts with, results in a breach of
or  constitutes  (with due notice or lapse of time or both) a default  under any
indenture,  agreement  or other  instrument  to which the  Company or any of its
subsidiaries  is bound or,  to the best of the  Company's  knowledge,  any other
indenture,  agreement or instrument  (regardless,  in each such case, of whether
any such violation, conflict, breach or default relates to the Company or any of
its  subsidiaries or to another party to any such indenture,  agreement or other
instrument).

          (b)  The  Shares  have  been  duly  authorized  and,  when  issued  in
accordance  with  this  Agreement,  will  be  validly  issued,  fully  paid  and
nonassessable  shares of Common  Stock and will be free and clear of all  liens,
charges, restrictions, claims and encumbrances imposed by or through the Company
except as set forth in the Registration Rights Agreement.  The issuance, sale or
delivery of the Shares is not subject to any preemptive right of stockholders of
the  Company  or to any right of first  refusal  or other  right in favor of any
person.

     SECTION 2.03 Validity.  This Agreement has been duly executed and delivered
by the Company and  constitutes the legal,  valid and binding  obligation of the
Company,  enforceable  in accordance  with its terms.  The  Registration  Rights
Agreement and the Stock  Restriction  Agreement,  when executed and delivered in
accordance  with this Agreement,  will  constitute the legal,  valid and binding
obligations  of the Company,  enforceable  in accordance  with their  respective
terms.

     SECTION 2.04 Authorized  Capital Stock. The authorized capital stock of the
Company consists of 1,000,000 shares of Common Stock.  Immediately  prior to the
Closing,  163,787 shares of Common Stock will be validly issued and outstanding,
fully paid







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and  nonassessable.  The  stockholders  of record and holders of  subscriptions,
warrants,  options,  convertible  securities,  and other rights  (contingent  or
other) to purchase or otherwise  acquire equity  securities of the Company,  and
the  number  of shares of  Common  Stock and the  number of such  subscriptions,
warrants,  options,  convertible securities, and other such rights held by each,
are  as set  forth  in the  attached  Schedule  II.  The  designations,  powers,
preferences, rights, qualifications,  limitations and restrictions in respect of
each class and series of  authorized  capital  stock of the  Company  are as set
forth in the  Charter,  a copy of which is  attached  as Exhibit C, and all such
designations,  powers,  preferences,  rights,  qualifications,  limitations  and
restrictions  are valid,  binding and  enforceable  and in  accordance  with all
applicable laws.  Except as set forth in the attached Schedule II, (i) no person
owns of  record  or is known to the  Company  to own  beneficially  any share of
Common Stock, (ii) no subscription,  warrant,  option,  convertible security, or
other  right  (contingent  or other) to  purchase or  otherwise  acquire  equity
securities  of the Company is authorized  or  outstanding  and (iii) there is no
commitment by the Company to issue  shares,  subscriptions,  warrants,  options,
convertible securities,  or other such rights or to distribute to holders of any
of its equity  securities  any  evidence  of  indebtedness  or asset.  Except as
provided  for in the Charter or as set forth in the  attached  Schedule  II, the
Company has no obligation (contingent or other) to purchase, redeem or otherwise
acquire  any of its  equity  securities  or any  interest  therein or to pay any
dividend or make any other distribution in respect thereof. Except for the Stock
Restriction  Agreement,  to the best of the  Company's  knowledge  there  are no
voting  trusts  or  agreements,  stockholders'  agreements,  pledge  agreements,
buy-sell  agreements,  rights of first  refusal,  preemptive  rights or  proxies
relating to any securities of the Company or any of its subsidiaries (whether or
not the Company or any of its subsidiaries is a party thereto).

     SECTION  2.05  Financial  Statements.  The  Company  has  furnished  to the
Purchaser  the  audited  consolidated  balance  sheet  of the  Company  and  its
subsidiaries as of December 31, 1988 and the related consolidated  statements of
income,  stockholders' equity and cash flows of the Company and its subsidiaries
for the year ended December 31, 1988, the unaudited  consolidated  balance sheet
of the Company and its  subsidiaries  as of December 31,  1989,  and the related
consolidated  statements of income,  stockholders'  equity and cash flows of the
Company and its  subsidiaries  for the year ended  December  31,  1989,  and the
unaudited  consolidated  balance sheet of the Company and its subsidiaries as of
April 30, 1990 (the "Balance Sheet") and the related  consolidated  statement of
income,  for the four month  period  ended April 30,  1990.  All such  financial
statements have been prepared in accordance with generally  accepted  accounting
principles  consistently  applied and fairly present the consolidated  financial
position  of the  Company  and its  subsidiaries  as of  December  31,  1988 and
December 31,






                                      - 6 -



1989,  respectively,  and the consolidated  results of their operations and cash
flows for the years ended December 31, 1988 and December 31, 1989, respectively.
Since the date of the Balance Sheet, (i) there has been no change in the assets,
liabilities  or financial  condition of the Company and its  subsidiaries  (on a
consolidated  basis) from that reflected in the Balance Sheet except for changes
in the  ordinary  course  of  business  which  in the  aggregate  have  not been
materially  adverse  and  (ii)  none  of  the  business,  prospects,   financial
condition,  operations,  property or affairs of the Company and its subsidiaries
(on a  consolidated  basis)  has  been  materially  adversely  affected  by  any
occurrence or  development,  individually  or in the  aggregate,  whether or not
insured against.

     SECTION 2.06 Events Subsequent to the Date of the Balance Sheet.  Since the
date of the Balance  Sheet,  the  Company has not (i) issued any stock,  bond or
other corporate security, (ii) borrowed any amount or incurred or become subject
to any liability (absolute,  accrued or contingent),  except current liabilities
incurred and liabilities  under contracts entered into in the ordinary course of
business,  (iii)  discharged or satisfied any lien or encumbrance or incurred or
paid any obligation or liability  (absolute,  accrued or contingent)  other than
current liabilities shown on the Balance Sheet and current liabilities  incurred
since the date of the Balance  Sheet in the ordinary  course of  business,  (iv)
declared or made any payment or  distribution  to  stockholders  or purchased or
redeemed  any  share of its  capital  stock or other  security,  (v)  mortgaged,
pledged or subjected to lien any of its assets,  tangible or  intangible,  other
than liens of current real  property  taxes not yet due and payable,  (vi) sold,
assigned or transferred any of its tangible assets except in the ordinary course
of business,  or cancelled any debt or claim, (vii) sold, assigned,  transferred
or granted any exclusive  license with respect to any patent,  trademark,  trade
name, service mark,  copyright,  trade secret or other intangible asset,  (viii)
suffered any loss of property or waived any right of  substantial  value whether
or not in the  ordinary  course of  business,  (ix) made any  change in  officer
compensation  except in the ordinary course of business and consistent with past
practice,  (x) made any material  change in the manner of business or operations
of the Company,  (xi) entered into any transaction except in the ordinary course
of  business  or as  otherwise  contemplated  hereby or (xii)  entered  into any
commitment (contingent or otherwise) to do any of the foregoing.

     SECTION  2.07  Litigation;  Compliance  with Law.  Except  with  respect to
Intellectual  Property  (as  such  term  is  defined  in  Section  2.14  of this
Agreement),  which  matters are  separately  discussed  in Section  2.14 of this
Agreement,  there is no (i) action,  suit,  claim,  proceeding or  investigation
pending  or,  to the best of the  Company's  knowledge,  threatened  against  or
affecting the Company, at law or in equity, or before or by any Federal,  state,
municipal or other governmental department, com-






                                      - 7 -



mission,  board, bureau,  agency or instrumentality,  domestic or foreign,  (ii)
arbitration   proceeding  relating  to  the  Company  pending  under  collective
bargaining  agreements or otherwise or (iii) governmental inquiry pending or, to
the best of the Company's knowledge, threatened against or affecting the Company
(including without limitation any inquiry as to the qualification of the Company
to hold or receive any license or permit),  and there is no basis for any of the
foregoing.  The  Company is not in  default  with  respect  to any order,  writ,
injunction  or decree known to or served upon the Company of any court or of any
Federal, state, municipal or other governmental department,  commission,  board,
bureau,  agency or instrumentality,  domestic or foreign.  There is no action or
suit by the Company  pending or threatened  against  others.  To the best of the
Company's  knowledge the Company has complied with all laws, rules,  regulations
and orders applicable to its business, operations,  properties, assets, products
and  services,  and the Company has all  necessary  permits,  licenses and other
authorizations  required to conduct its business as conducted and as proposed to
be conducted  except where the failure to comply or obtain such permit,  license
or other authorization would not have a material adverse effect on the business,
operations  or financial  condition of the  Company.  There is no existing  law,
rule,  regulation  or order,  and the Company is not aware of any proposed  law,
rule,  regulation or order,  whether  Federal or state,  which would prohibit or
restrict the Company from, or otherwise  materially adversely affect the Company
in,  conducting its business in any  jurisdiction  in which it is now conducting
business or in which it proposes to conduct business.

     SECTION 2.08 Proprietary  Information of Third Parties.  To the best of the
Company's knowledge,  no third party has claimed or has reason to claim that any
person  employed by or  affiliated  with the Company has (a)  violated or may be
violating any of the terms or conditions of his employment,  non-competition  or
non-disclosure  agreement  with  such  third  party,  (b)  disclosed  or  may be
disclosing  or  utilized or may be  utilizing  any trade  secret or  proprietary
information  or  documentation  of such third party or (c)  interfered or may be
interfering in the employment  relationship  between such third party and any of
its present or former employees.  No third party has requested  information from
the Company which suggests that such a claim might be contemplated.  To the best
of the Company's knowledge, no person employed by or affiliated with the Company
has  employed  or  proposes  to employ any trade  secret or any  information  or
documentation  proprietary  to any  former  employer,  and to  the  best  of the
Company's  knowledge,  no person  employed by or affiliated with the Company has
violated any confidential  relationship  which such person may have had with any
third party,  in connection  with the  development,  manufacture  or sale of any
product  or  proposed  product  or the  development  or sale of any  service  or
proposed service of the Company,  and the Company has no reason to believe there
will be any such employment or violation. To the best of the Company's







                                      - 8 -



knowledge,  none of the execution or delivery of this Agreement, or the carrying
on of the  business  of the  Company  as  officers,  employees  or agents by any
officer,  director or key  employee of the  Company,  or the conduct or proposed
conduct of the business of the Company, will conflict with or result in a breach
of the terms,  conditions  or  provisions  of or  constitute a default under any
contract, covenant or instrument under which any such person is obligated.

     SECTION 2.09 Title to  Properties.  The Company and its  subsidiaries  have
good and marketable title to their respective properties and assets reflected on
the Balance Sheet or acquired by them since the date of the Balance Sheet (other
than  properties and assets disposed of in the ordinary course of business since
the date of the Balance Sheet),  and all such properties and assets are free and
clear  of  mortgages,  pledges,  security  interests,  liens,  charges,  claims,
restrictions and other  encumbrances,  except for liens for or current taxes not
yet due and payable and minor  imperfections  of title,  if any, not material in
nature or amount and not materially  detracting  from the value or impairing the
use of the property  subject  thereto or impairing  the  operations  or proposed
operations of the Company and its subsidiaries.

     SECTION  2.10  Leasehold  Interests.  Each lease or  agreement to which the
Company is a party under which it is a lessee of any property, real or personal,
is a  valid  and  subsisting  agreement  without  any  default  of  the  Company
thereunder  and,  to the best of the  Company's  knowledge,  without any default
thereunder of any other party  thereto.  No event has occurred and is continuing
which,  with due notice or lapse of time or both,  would constitute a default or
event of default by the  Company  under any such lease or  agreement  or, to the
best of the  Company's  knowledge,  by any other party  thereto.  The  Company's
possession  of such  property  has not been  disturbed  and,  to the best of the
Company's  knowledge,  no claim has been asserted against the Company adverse to
its rights in such leasehold interests.

     SECTION 2.11  Insurance.  The Company holds valid policies  covering all of
the insurance required to be maintained by it under Section 5.04.

     SECTION 2.12 Taxes. The Company has filed all tax returns,  Federal, state,
county and local, required to be filed by it, and the Company has paid all taxes
shown to be due by such  returns  as well as all other  taxes,  assessments  and
governmental  charges  which  have  become  due or  payable,  including  without
limitation  all taxes which the Company is  obligated  to withhold  from amounts
owing to employees,  creditors and third parties. All such taxes with respect to
which the Company has become obligated pursuant to elections made by the Company
in accordance  with  generally  accepted  practice  have been paid.  The Federal
income tax  returns of the  Company  have  never  been  audited by the  Internal
Revenue







                                      - 9 -



Service. No deficiency  assessment with respect to or proposed adjustment of the
Company's  Federal,  state,  county or local taxes is pending or, to the best of
the Company's  knowledge,  threatened.  There is no tax lien, whether imposed by
any Federal,  state,  county or local taxing authority,  outstanding against the
assets,  properties  or business of the Company.  Neither the Company nor any of
its stockholders has ever filed (a) an election  pursuant to Section 1362 of the
Internal  Revenue  Code of 1986,  as amended (the  "Code"),  that the Company be
taxed as an S corporation or (b) consent pursuant to Section 341(f) of the Code,
relating to collapsible corporations.

     SECTION 2.13 Other Agreements. Except as set forth in the attached Schedule
III(A),  the Company is not a party to or otherwise bound by any written or oral
contract  or  instrument  or other  restriction  involving  payment by or to the
Company of an amount greater than $25,000 which individually or in the aggregate
could materially adversely affect the business, prospects,  financial condition,
operations,  property  or  affairs  of the  Company.  Except as set forth in the
attached  Schedule  III(B),  the Company is not a party to or otherwise bound by
any written or oral:

          (a) distributor, dealer, manufacturer's representative or sales agency
        contract or agreement  which is not  terminable on less than ninety (90)
        days' notice without cost or other  liability to the Company (except for
        contracts  which, in the aggregate,  do not involve payment by or to the
        Company of amounts greater than $25,000);

          (b) sales contract which entitles any customer to a rebate or right of
        set-off,  to return any product to the Company after acceptance  thereof
        or to delay  the  acceptance  thereof,  involving  payment  by or to the
        Company of an amount greater than $25,000;

          (c)  contract  with any labor  union  (and,  to the  knowledge  of the
        Company,  no organizational  effort is being made with respect to any of
        its employees);

          (d)  contract or other  commitment  with any supplier  containing  any
        provision permitting any party other than the Company to renegotiate the
        price or other  terms,  or  containing  any  pay-back  or other  similar
        provision,  upon the  occurrence of a failure by the Company to meet its
        obligations  under the contract when due or the  occurrence of any other
        event,  involving payment by or to the Company of an amount greater than
        $25,000;

          (e) contract for the future purchase of fixed assets or for the future
        purchase of  materials,  supplies or  equipment  in excess of its normal
        operating requirements which involves the actual or potential payment by
        the Company of an amount greater than $25,000;








                                     - 10 -



           (f) contract  for the  employment  of any officer,  employee or other
        person  (whether  by  oral  or  written  agreement)  on a  full-time  or
        consulting basis which is not terminable on notice without cost or other
        liability to the  Company,  except  normal  severance  arrangements  and
        accrued vacation pay;


           (g)  bonus,  pension,  profit-sharing,  retirement,  hospitalization,
        insurance,  stock  purchase,  stock  option or other  plan,  contract or
        understanding pursuant to which benefits are provided to any employee of
        the Company (other than group  insurance  plans  applicable to employees
        generally);


           (h)  agreement or indenture  relating to the borrowing of money or to
        the  mortgaging or pledging of, or otherwise  placing a lien or security
        interest on, any asset of the Company;

           (i) guaranty of any obligation for borrowed money or otherwise;

           (j)  voting  trust  or  agreement,  stockholders'  agreement,  pledge
        agreement,  buy-sell  agreement or first  refusal or  preemptive  rights
        agreement relating to any securities of the Company;

           (k) agreement,  or group of related agreements with the same party or
        any group of affiliated parties, under which the Company has advanced or
        agreed to advance money or has agreed to lease any property as lessee or
        lessor;

           (l) agreement or obligation  (contingent or otherwise) to issue, sell
        or otherwise  distribute or to repurchase or otherwise acquire or retire
        any share of its capital stock or any of its other equity securities;

           (m)  assignment,  license or other agreement with respect to any form
        of intangible property;

           (n) agreement under which it has granted any person any  registration
        rights, other than the Registration Rights Agreement;


           (o) agreement  under which it has limited or restricted  its right to
        compete with any person in any respect;

           (p) other contract or group of related  contracts with the same party
        involving more than $25,000 or continuing over a period of more than six
        months from the date or dates thereof (including  renewals or extensions
        optional with another  party),  which  contract or group of contracts is
        not terminable by the Company without penalty upon notice of thirty (30)
        days or less,  but excluding  any contract or group of contracts  with a
        customer of the Company for the sale,







                                     - 11 -



        lease or rental of the  Company's  products or services if such contract
        or group of  contracts  was entered  into by the Company in the ordinary
        course of business; or

          (q) other contract,  instrument,  commitment,  plan or arrangement,  a
        copy of which  would be  required  to be filed with the  Securities  and
        Exchange  Commission (the  "Commission") as an exhibit to a registration
        statement on Form S-1 if the Company were  registering  securities under
        the Securities Act of 1933, as amended (the "Securities Act").

The  Company,  and to the best of the  Company's  knowledge,  each  other  party
thereto have in all material respects performed all the obligations  required to
be performed by them to date,  have received no notice of default and are not in
default (with due notice or lapse of time or both) under any material  provision
of any lease,  agreement  or  contract  now in effect to which the  Company is a
party or by which it or its  property  may be bound.  The Company has no present
expectation or intention of not fully performing all its obligations  under each
such lease, contract or other agreement, and the Company has no knowledge of any
breach or anticipated breach by the other party to any contract or commitment to
which the Company is a party.  The Company is in full compliance with all of the
terms and provisions of its Charter and By-laws, as amended.

     SECTION 2.14 Patents,  Trademarks,  Etc. The Company has no patents, patent
rights  or patent  applications.  Set  forth in  Schedule  I is a list and brief
description of all trademarks,  trademark  applications,  service marks, service
mark  applications,  trade names and copyrights,  and all  applications for such
which are in the process of being  prepared,  owned by or registered in the name
of the  Company,  or of which the  Company is a licensor or licensee or in which
the Company has any right, and in each case a brief description of the nature of
such  right.  No claim is pending  or, to the best of the  Company's  knowledge,
threatened  to the effect that the  operations  of the Company  infringe upon or
conflict with the asserted rights of any other person under any patents,  patent
applications,  trademarks,  trademark applications,  service marks, service mark
applications, trade names, copyrights,  manufacturing processes, formulae, trade
secrets and know how (collectively,  "Intellectual  Property"),  and the Company
has not been notified as to any basis for any such claim (whether or not pending
or  threatened).  No claim is pending or  threatened to the effect that any such
Intellectual  Property  owned or licensed by the  Company,  or which the Company
otherwise has the right to use, is invalid or unenforceable by the Company,  and
the Company has not been notified as to any basis for any such claim (whether or
not  pending  or  threatened).  To the  best  of the  Company's  knowledge,  all
technical  information  developed by and  belonging to the Company which has not
been  patented  has been kept  confidential.  The  Company  has not  granted  or
assigned to any other person or entity any right to manufacture, have







                                     - 12 -



manufactured,  assemble or sell the products or proposed  products or to provide
the services or proposed services of the Company.

     SECTION 2.15 Loans and Advances.  The Company does not have any outstanding
loans or advances to any person and is not  obligated  to make any such loans or
advances,  except,  in each case,  for  advances to  employees of the Company in
respect of reimbursable  business expenses anticipated to be incurred by them in
connection with their performance of services for the Company.

     SECTION  2.16  Assumptions,  Guaranties,  Etc.  of  Indebtedness  of  Other
Persons. The Company has not assumed,  guaranteed,  endorsed or otherwise become
directly  or  contingently  liable  on  any  indebtedness  of any  other  person
(including,  without  limitation,  liability by way of agreement,  contingent or
otherwise,  to purchase,  to provide  funds for  payment,  to supply funds to or
otherwise  invest in the debtor,  or otherwise  to assure the  creditor  against
loss),  except for  guaranties  by  endorsement  of negotiable  instruments  for
deposit or collection in the ordinary course of business.

     SECTION 2.17 Significant  Customers and Suppliers.  No customer or supplier
which was  significant to the Company during the period covered by the financial
statements  referred  to in Section  2.05 or which has been  significant  to the
Company  thereafter,  has  terminated,   materially  reduced  or  threatened  to
terminate or materially  reduce its  purchases  from or provision of products or
services to the Company,  as the case may be. For purposes of this Section 2.17,
a customer is  significant  to the Company if it accounts  for or is expected to
account for five percent  (5%) or more of the  Company's  annual  revenues and a
supplier is  significant  to the  Company if it  accounts  for or is expected to
account for supply purchases by the Company in excess of $25,000 per year.

     SECTION  2.18  Governmental  Approvals.  Subject  to  the  accuracy  of the
representations  and  warranties  of the  Purchaser set forth in Article III, no
registration  or filing with,  or consent or approval of or other action by, any
Federal,  state or other  governmental  agency or  instrumentality is or will be
necessary for the valid  execution,  delivery and  performance by the Company of
this  Agreement,  the  Registration  Rights  Agreement or the Stock  Restriction
Agreement, the issuance, sale and delivery of the Shares, other than (i) filings
pursuant to state  securities  laws (all of which  filings have been made by the
Company) in connection  with the sale of the Shares and (ii) with respect to the
Registration  Rights  Agreement,  the registration of the shares covered thereby
with the Commission and filings pursuant to state securities laws.

     SECTION  2.19  Disclosure.  Neither  this  Agreement,  nor any  Schedule or
Exhibit to this Agreement,  nor the Business Plan of the Company dated March 31,
1989 (the "Business Plan"), contains






                                     - 13 -



an untrue  statement of a material  fact or omits a material  fact  necessary to
make the statements  contained herein or therein not misleading  except that the
Company makes no  representations or warranties as to third party marketing data
contained in the Business Plan. None of the statements,  documents, certificates
or  other  items  prepared  or  supplied  by the  Company  with  respect  to the
transactions contemplated hereby contains an untrue statement of a material fact
or omits a material fact necessary to make the statements  contained therein not
misleading.  There  is no  fact  which  the  Company  has not  disclosed  to the
Purchaser and its counsel and of which the Company is aware which materially and
adversely  affects  or could  materially  and  adversely  affect  the  business,
prospects, financial condition,  operations,  property or affairs of the Company
or any of its  subsidiaries.  The  financial  projections  and  other  estimates
contained  in the  Business  Plan  were  prepared  by the  Company  based on the
Company's  experience in the industry and on  assumptions of fact and opinion as
to future events which the Company,  at the date of the issuance of the Business
Plan,  believed  to be  reasonable,  but which the  Company  cannot and does not
assure or guarantee the  attainment  of in any manner.  As of the date hereof no
facts have come to the  attention of the Company  which  would,  in its opinion,
require  the  Company  to revise or  amplify  the  assumptions  underlying  such
projections and other estimates or the conclusions derived therefrom.

     SECTION  2.20  Offering of the  Shares.  Neither the Company nor any person
authorized or employed by the Company as agent,  broker,  dealer or otherwise in
connection  with the  offering  or sale of the  Shares  or any  security  of the
Company  similar  to the  Shares  has  offered  the  Shares or any such  similar
security  for sale to,  or  solicited  any  offer to buy the  Shares or any such
similar  security  from,  or otherwise  approached  or  negotiated  with respect
thereto  with,  any person or  persons,  and  neither the Company nor any person
acting on its behalf has taken or will take any other action (including, without
limitation,  any offer,  issuance or sale of any  security of the Company  under
circumstances  which might  require the  integration  of such  security with the
Shares under the Securities  Act or the rules and  regulations of the Commission
thereunder),  in either case so as to subject the offering,  issuance or sale of
the Shares to the registration provisions of the Securities Act.

     SECTION  2.21  Brokers.  The  Company  has  no  contract,   arrangement  or
understanding  with any  broker,  finder or similar  agent  with  respect to the
transactions contemplated by this Agreement.

     SECTION  2.22  Officers.  Set forth in Schedule I is a list of the names of
the officers of the Company,  together with the title or job  classification  of
each such person and the total compensation  anticipated to be paid to each such
person by the Company and its  subsidiaries in 1990. None of such persons has an
employment agreement, whether oral or written, with the


                                     - 14 -



Company or any of its  subsidiaries,  which is not  terminable  on notice by the
Company or such  subsidiary  without  cost or other  liability to the Company or
such subsidiary other than voluntary payment of reasonable severance.

     SECTION 2.23 Transactions With Affiliates.  No director,  officer, employee
or  stockholder of the Company,  or member of the family of any such person,  or
any corporation, partnership, trust or other entity in which any such person, or
any member of the family of any such person, has a substantial interest or is an
officer, director, trustee, partner or holder of more than 5% of the outstanding
capital stock thereof, is a party to any transaction with the Company, including
any contract,  agreement or other  arrangement  providing for the employment of,
furnishing  of  services  by,  rental  of  real or  personal   property  from or
otherwise requiring payments to any such person or firm.

     SECTION  2.24  Employees.  Each of the  officers of the  Company,  each key
employee  and each other  employee now employed by the Company who has access to
confidential  information  of the Company has executed a Employee  Nondisclosure
Developments  Agreements  substantially  in the form of Exhibit D (collectively,
the "Employee Nondisclosure and Developments Agreements"), and such agreement is
in full force and effect.  No officer or key employee of the Company has advised
the Company (orally or in writing) that he intends to terminate  employment with
the  Company.  To the best of the  Company's  knowledge  it has  complied in all
material  respects with all applicable laws relating to the employment of labor,
including  provisions  relating to wages,  hours, equal opportunity,  collective
bargaining  and the payment of Social  Security  and other  taxes,  and with the
Employee Retirement Income Security Act of 1974, as amended.

     SECTION 2.25 U.S. Real Property Holding Corporation. The Company is not now
and has never been a "United  States  real  property  holding  corporation",  as
defined  in  Section  897(c)(2)  of  the  Code  and  Section  1.897-2(b)  of the
Regulations promulgated by the Internal Revenue Service.


                                   ARTICLE III

                 REPRESENTATIONS AND WARRANTIES OF THE PURCHASER

    The Purchaser represents and warrants to the Company that:

            (a) it is an  "accredited  investor"  within the meaning of Rule 501
       under the Securities  Act and was not organized for the specific  purpose
       of acquiring the Shares;

            (b) it has  sufficient  knowledge  and  experience  in  investing in
       companies  similar  to the  Company  in terms of the  Company's  stage of
       development so as to be able to evaluate







                                     - 15 -



       the risks and  merits of its  investment  in the  Company  and it is able
       financially to bear the risks thereof;

            (c) it has had an  opportunity  to discuss the  Company's  business,
       management  and  financial  affairs with the  Company's  management,  the
       officers  of  the  Company  have  made  available  any  and  all  written
       information  which the  Purchaser  has requested and have answered to the
       Purchaser's satisfaction all inquiries made by the Purchaser;

            (d) the Shares being  purchased by it are being acquired for its own
       account for the purpose of investment  and not with a view to or for sale
       in connection with any distribution thereof;

            (e) it  understands  that (i) the  Shares  have not been  registered
       under the  Securities  Act by reason of their  issuance in a  transaction
       exempt from the registration  requirements of the Securities Act pursuant
       to  Section  4(2)  thereof  or  Rule  505 or 506  promulgated  under  the
       Securities  Act,  based in part on the bona fide nature of its investment
       intent as  expressed  herein,  (ii) the Shares must be held  indefinitely
       unless  a  subsequent   disposition   thereof  is  registered  under  the
       Securities Act or is exempt from such registration, (iii) the Shares will
       bear a legend to such effect and (iv) the Company will make a notation on
       its transfer books to such effect;

            (f) it has the power and authority to enter into this  Agreement and
       to perform all of its obligations hereunder; and

            (g)  it has no  contract,  arrangement  or  understanding  with  any
       broker,  finder  or  similar  agent  with  respect  to  the  transactions
       contemplated by this Agreement.

                                   ARTICLE IV

                          CONDITIONS TO THE OBLIGATIONS
                                OF THE PURCHASER

    The  obligation  of the  Purchaser  to purchase and pay for the Shares being
purchased  by it on  the  Closing  Date  is,  at  its  option,  subject  to  the
satisfaction, on or before the Closing Date, of the following conditions:

            (a) Opinion of Company's Counsel.  The Purchaser shall have received
       from Brown, Rudnick,  Freed & Gesmer, counsel for the Company, an opinion
       dated the Closing  Date,  substantially  in the form  attached  hereto as
       Exhibit E.

            (b)  Representations  and  Warranties  to be True and  Correct.  The
       representations and warranties contained in Arti-







                                     - 16 -



       cle II shall be true,  complete and correct on and as of the Closing Date
       with the same effect as though such  representations  and  warranties had
       been made on and as of such date,  and the President and Treasurer of the
       Company shall have certified to such effect to the Purchaser in writing.

            (c) Performance.  The Company shall have performed and complied with
       all agreements contained herein required to be performed or complied with
       by it prior to or at the Closing Date, and the President and Treasurer of
       the Company  shall have  certified  to the  Purchaser  in writing to such
       effect and to the further  effect that all of the conditions set forth in
       this Article IV have been satisfied.

            (d) All  Proceedings  to be  Satisfactory.  All  corporate and other
       proceedings   to  be  taken  by  the  Company  in  connection   with  the
       transactions contemplated hereby and all documents incident thereto shall
       be  satisfactory  in form and substance to the Purchaser and its counsel,
       and  the   Purchaser  and  its  counsel  shall  have  received  all  such
       counterpart  originals or certified or other copies of such  documents as
       they reasonably may request.

            (e) Supporting  Documents.  The Purchaser and its counsel shall have
       received copies of the following documents:

          (i) (A) the Charter, certified as of a recent date by the Secretary of
          State of the Commonwealth of Massachusetts,  (B) a certificate of said
          Secretary  dated as of a recent date as to the due  incorporation  and
          good  standing of the Company,  the payment of all excise taxes by the
          Company  and listing  all  documents  of the Company on file with said
          Clerk  and  (C) a  certificate  of  the  Secretary  of  State  of  the
          jurisdiction of  incorporation  of each of the Company's  subsidiaries
          dated  as of a  recent  date  as to the  due  incorporation  and  good
          standing of such subsidiary;

          (ii) a certificate  of the Clerk or an Assistant  Clerk of the Company
          dated the Closing Date and certifying:  (A) that attached thereto is a
          true and  complete  copy of the By-laws of the Company as in effect on
          the date of such  certification;  (B) that attached  thereto is a true
          and complete copy of all resolutions adopted by the Board of Directors
          or the stockholders of the Company authorizing the execution, delivery
          and performance of this Agreement,  the Registration  Rights Agreement
          and the Stock Restriction Agreement and issuance, sale and delivery of
          the Shares, and that all such resolutions are in full force and effect
          and  are  all  the   resolutions   adopted  in  connection   with  the
          transactions contemplated by this Agreement, the







                                     - 17 -



          Registration Rights Agreement and the Stock Restriction Agreement; (C)
          that the  Charter  has not  been  amended  since  the date of the last
          amendment referred to in the certificate  delivered pursuant to clause
          (i)(B) above; and (D) to the incumbency and specimen signature of each
          officer of the Company  executing  this  Agreement,  the  Registration
          Rights  Agreement  or  the  Stock  Restriction  Agreement,  the  stock
          certificates representing the Shares and any certificate or instrument
          furnished  pursuant hereto,  and a certification by another officer of
          the Company as to the incumbency and signature of the officer  signing
          the certificate referred to in this clause (ii); and

          (iii) such additional  supporting documents and other information with
          respect to the  operations and affairs of the Company as the Purchaser
          or its counsel reasonably may request.

            (f) Registration  Rights Agreement.  The Company shall have executed
       and delivered the Registration Rights Agreement.

            (g) Board of Directors. The By-laws of the Company shall provide, in
       addition to any  provisions  required by law,  that any two directors may
       call a meeting of the Board.

            (h) Stock Restriction  Agreement.  The Stock  Restriction  Agreement
       shall have been  executed  and  delivered  by the  Company and Richard T.
       Schumacher.

            (i)  Non-Competition  Agreements.  Each officer of the Company shall
       have entered  into a  Non-Competition  Agreement  with the Company in the
       form   attached  as  Exhibit  F   (collectively,   the   "Non-Competition
       Agreements"), and copies thereof shall have been delivered to counsel for
       the Purchaser.

            (j) Charter.  The Charter shall read in its entirety as set forth in
       Exhibit C.

            (k) Employee Agreements.  Copies of the Employee  Non-disclosure and
       Development  Agreements  shall have been  delivered  to  counsel  for the
       Purchaser.

            (1) Preemptive  Rights.  All  stockholders of the Company having any
       preemptive, first refusal or other rights with respect to the issuance of
       the Shares shall have irrevocably waived the same in writing.

            (m) Percentage  Ownership.  The Company shall have sufficient  Stock
       outstanding  so that the  purchase of shares by the  Purchaser  shall not
       result in aggregate ownership by







                                     - 18 -



       the Purchaser of twenty percent (20%) or more of the equity securities of
       the Company.

            (n) Fees of  Purchaser's  Counsel.  The  Company  shall have paid in
       accordance  with Section 6.01 the fees and  disbursements  of Purchaser's
       counsel invoiced at the Closing.

All such documents  shall be satisfactory in form and substance to the Purchaser
and its counsel.


                                    ARTICLE V

                            COVENANTS OF THE COMPANY

    The  Company  covenants  and agrees with the  Purchaser  that until the date
which is the  earlier of (i) five (5) years  after the  Closing  Date under this
Agreement;  (ii) the effective date of the registration under the Securities Act
of an underwritten public offering of securities of the Company of $2,000,000 or
more;  or (iii) such time as the number of Shares owned by the  Purchaser  shall
drop below five  percent (5%) of the  outstanding  shares of Common Stock of the
Company:

     SECTION 5.01 Financial Statements,  Reports, Etc. The Company shall furnish
to the Purchaser:

          (a) within  ninety  (90) days after the end of each fiscal year of the
       Company a consolidated  balance sheet of the Company and its subsidiaries
       as of the end of such fiscal year and the related consolidated statements
       of income,  stockholders'  equity and cash flows for the fiscal year then
       ended,   prepared  in  accordance  with  generally  accepted   accounting
       principles  and  certified by a firm of  independent  public  accountants
       selected by the Board of  Directors  of the  Company and  approved by the
       nominee of the Purchaser;

          (b) within  forty-five  (45) days after the end of each fiscal quarter
       in each fiscal  year  (other than the last fiscal  quarter in each fiscal
       year), a consolidated  balance sheet of the Company and its  subsidiaries
       and the  related  consolidated  statements  of income  and  stockholders'
       equity,  unaudited but prepared in  accordance  with  generally  accepted
       accounting principles and certified by the Chief Financial Officer of the
       Company,  such  consolidated  balance  sheet  to be as of the end of such
       fiscal quarter and such consolidated statements of income,  stockholders'
       equity and cash flows to be for such  fiscal  quarter  and for the period
       from the beginning of the fiscal year to the end of such fiscal  quarter,
       in each case with comparative  statements for the corresponding period in
       the prior fiscal year;







                                     - 19 -



          (c) at the  time  of  delivery  of  each  annual  financial  statement
      pursuant to Section 5.01(a), a certificate executed by the Chief Financial
      Officer of the Company stating that such officer has caused this Agreement
      to be reviewed  and has no  knowledge of any default by the Company in the
      performance  or observance of any of the  provisions of this Agreement or,
      if such officer has such knowledge, specifying such default and the nature
      thereof;

          (d) within  thirty (30) days prior to the start of each  fiscal  year,
      consolidated capital and operating expense budgets,  cash flow projections
      and income and loss  projections  for the Company and its  subsidiaries in
      respect  of such  fiscal  year,  all  itemized  in  reasonable  detail and
      prepared  on  a  monthly  basis,  and,  promptly  after  preparation,  any
      revisions to any of the foregoing;

          (e) promptly  following  receipt by the Company,  each audit  response
      letter,  accountant's management letter and other written report submitted
      to the Company by its independent public accountants in connection with an
      annual  or  interim  audit  of  the  books  of the  Company  or any of its
      subsidiaries;

          (f) promptly after the  commencement  thereof,  notice of all actions,
      suits,  claims,  proceedings,  investigations  and  inquiries  of the type
      described  in Section  2.07 that  could  materially  adversely  affect the
      Company or any of its subsidiaries;

          (g) promptly upon sending,  making  available or filing the same,  all
      press releases, reports and financial statements that the Company sends or
      makes  available  to its  stockholders  or  directors  or  files  with the
      Commission; and

          (h) promptly,  from time to time, such other information regarding the
      business, prospects, financial condition,  operations, property or affairs
      of the Company  and its  subsidiaries  as such  Purchaser  reasonably  may
      request.

    Notwithstanding  the  foregoing,  if the Company,  using its best efforts is
unable to deliver the  materials  specified  in  paragraphs  (a) and (d) of this
Section 5.01 within the specified time period,  the Purchaser  shall accept such
materials if delivered in the case of Section  5.01(a) within one hundred twenty
(120) days after the end of the fiscal  year and in the case of Section  5.01(d)
within thirty (30) days after the end of the fiscal year.

     SECTION  5.02  Right of First  Refusal.  The  Company  shall,  prior to any
issuance by the  Company of any of its  securities  (other than debt  securities
with no equity feature), offer to the Purchaser by written notice the right, for
a period of thirty







                                     - 20 -



(30) days, to purchase all of such securities for cash at an amount equal to the
price or  other  consideration  for  which  such  securities  are to be  issued;
provided,  however,  that the first refusal rights of the Purchaser  pursuant to
this Section 5.02 shall not apply to securities  issued (A) as a stock  dividend
or upon any subdivision of shares of Common Stock,  provided that the securities
issued  pursuant to such stock dividend or subdivision are limited to additional
shares of Common  Stock,  (B)  pursuant  to  subscriptions,  warrants,  options,
convertible securities, or other rights which are listed in Schedule II as being
outstanding on the Closing Date, (C) solely in consideration for the acquisition
(whether by merger or  otherwise) by the Company or any of its  subsidiaries  of
all or  substantially  all of the  stock or  assets  of any  other  entity,  (D)
pursuant to a firm commitment  underwritten public offering, (E) pursuant to the
exercise  of options to  purchase  Common  Stock  granted  to  employees  of the
Company, not to exceed in the aggregate that number of shares that is 20% of the
Common Stock  outstanding at any time  (appropriately  adjusted to reflect stock
splits, stock dividends, combinations of shares and the like with respect to the
Common  Stock)  less the number of shares (as so  adjusted)  issued  pursuant to
options granted to current or former employees,  consultants or directors of the
Company,  outstanding  on the date of this  Agreement  and listed in Schedule II
pursuant  to clause  (B) above (the  shares  exempted  by this  clause (E) being
hereinafter referred to as the "Reserved Employee Shares"),  (F) within a period
of six months  following  the  Closing  Date for the  purpose of raising  equity
capital  for the  Company but not to exceed  30,000  shares of Common  Stock and
options to purchase  50,001  shares of Common  Stock or an  aggregate  of 80,001
Common  Stock  equivalents,  (G) upon the  exercise  of any right  which was not
itself in violation of the terms of this Section 5.02, and (H) at any time after
the date which is five (5) years  from the date of the  Closing.  The  Company's
written notice to the Purchaser  shall  describe the  securities  proposed to be
issued by the  Company and specify  the  number,  price and payment  terms.  The
Purchaser  may accept the  Company's  offer as to all, but not less than all, of
the  securities  offered  to it by  written  notice  thereof  given by it to the
Company  prior to the  expiration of the  aforesaid  thirty (30) day period,  in
which event the Company shall  promptly  sell and the Purchaser  shall buy, upon
the terms  specified,  the number of  securities  agreed to be  purchased by the
Purchaser.  The Company  shall be free at any time prior to one  hundred  twenty
(120) days after the date of its notice of offer to the Purchaser,  to offer and
sell to any third party or parties the number of such  securities  not agreed by
the  Purchaser to be  purchased  by it, at a price and on payment  terms no less
favorable  to the Company  than those  specified  in such notice of offer to the
Purchaser. However, if such third party sale or sales are not consummated within
such one  hundred  twenty  (120) day  period,  the  Company  shall not sell such
securities  as shall not have been  purchased  within such period  without again
complying with this Section 5.02.







                                     - 21 -



     SECTION 5.03 Corporate Existence. The Company shall maintain and cause each
of its subsidiaries to maintain their respective corporate existence, rights and
franchises in full force and effect.

     SECTION 5.04 Properties,  Business,  Insurance.  The Company shall maintain
and cause each of its subsidiaries to maintain as to their respective properties
and business,  with financially sound and reputable insurers,  insurance against
such  casualties and  contingencies  and of such types and in such amounts as is
customary for companies similarly  situated,  which insurance shall be deemed by
the Company to be  sufficient.  The Company shall also maintain in effect a "key
person" life insurance policy, payable to the Company, on the life of Richard T.
Schumacher (so long as he remains an employee of the Company),  in an amount not
less than  $2,000,000.  If the Company shall  maintain life  insurance  policies
payable to the Company on the life of Mr.  Schumacher  in an amount in excess of
$2,000,000,  then on the death of Mr.  Schumacher,  nothing in this Section 5.04
shall restrict the Company's use of insurance  proceeds in excess of $2,000,000.
The Company shall not cause or permit any  assignment  or change in  beneficiary
and shall not borrow against any such policy.  The Company will add one designee
of the  Purchaser as a notice  party for any such policy and shall  request that
the issuer of such  policy  provide  such  designee  with ten (10) days'  notice
before such policy is  terminated  (for failure to pay premiums or otherwise) or
assigned or before any change is made in the beneficiary thereof.

     SECTION 5.05 Inspection,  Consultation and Advice. The Company shall permit
and cause each of its  subsidiaries  to permit the Purchaser and such persons as
it may designate,  at the Purchaser's  expense,  to visit and inspect any of the
properties  of the Company and its  subsidiaries,  examine  their books and take
copies and extracts therefrom, discuss the affairs, finances and accounts of the
Company  and  its  subsidiaries  with  their  officers,   employees  and  public
accountants (and the Company hereby  authorizes said accountants to discuss with
the  Purchaser and such  designees  such affairs,  finances and  accounts),  and
consult with and advise the management of the Company and its subsidiaries as to
their  affairs,  finances  and  accounts,  all  at  reasonable  times  and  upon
reasonable notice.

     SECTION 5.06 Restrictive Agreements Prohibited. Neither the Company nor any
of its  subsidiaries  shall become a party to any  agreement  which by its terms
restricts the Company's  performance of this Agreement,  the Registration Rights
Agreement, the Stock Restriction Agreement or the Charter.

     SECTION  5.07  Transactions   with  Affiliates.   Except  for  transactions
contemplated  by  this  Agreement  or as  otherwise  approved  by the  Board  of
Directors,  neither the Company nor any of its subsidiaries shall enter into any
transaction with any







                                     - 22 -



director, officer, employee or holder of more than 5% of the outstanding capital
stock of any class or  series  of  capital  stock of the  Company  or any of its
subsidiaries,  member of the  family  of any such  person,  or any  corporation,
partnership,  trust or other entity in which any such  person,  or member of the
family of any such person, is a director, officer, trustee, partner or holder of
more than 5% of the outstanding  capital stock thereof,  except for transactions
on customary terms related to such person's employment.

     SECTION 5.08 Use of Proceeds.  The Company  shall use the proceeds from the
sale of the Shares in accordance with Exhibit G.

     SECTION 5.09 Board of Directors  Meetings.  The Company  shall use its best
efforts to ensure that meetings of its Board of Directors are held at least four
times each year and at least once each quarter.

     SECTION  5.10  Compensation.  The Company  shall not pay to its  management
compensation in excess of that  compensation  customarily  paid to management in
companies of similar size, of similar maturity, and in similar businesses.

     SECTION 5.11  By-laws.  The Company shall at all times cause its By-laws to
provide  that,  (i) the number of  directors  constituting  the entire  Board of
Directors  is six (6),  and (ii)  unless  otherwise  required by the laws of the
Commonwealth of  Massachusetts  any two directors shall have the right to call a
meeting of the Board of Directors  or  stockholders.  The Company  shall use its
best efforts to ensure that at all times a nominee of the  Purchaser  shall have
been elected and shall hold office as one of the directors. The Company shall at
all times maintain  provisions in its By-laws and/or  Charter  indemnifying  all
directors  against  liability and absolving all directors  from liability to the
Company and its  stockholders to the maximum extent  permitted under the laws of
the Commonwealth of Massachusetts.

     SECTION 5.12 Performance of Contracts. The Company shall not amend, modify,
terminate,  waive or otherwise  alter,  in whole or in part, any of the Employee
Nondisclosure  and  Developments  Agreements  or the  Non-Competition  Agreement
without the approval of the Company's Board of Directors.

     SECTION 5.13 Vesting of Reserved  Employee  Shares.  The Company  shall not
grant to any of its employees options to purchase Reserved Employee Shares which
will  become  exercisable  at a rate in excess of 20% per annum from the date of
such grant  without the approval of the Company's  Board of  Directors.  Nothing
contained  in this  Section 5.13 shall  prohibit  the  immediate  vesting of all
options to purchase  Reserved Employee Shares in the event of the sale of all or
substantially all of the assets







                                     - 23 -



of the  Company,  a merger  or  consolidation  with and into  another  entity or
entities,  or any similar  transaction  in which there is a change in control of
the Company.

     SECTION  5.14  Employee  Nondisclosure  and  Developments  Agreements.  The
Company shall use its best efforts to obtain and shall cause its subsidiaries to
use their best  efforts to obtain an  Employee  Nondisclosure  and  Developments
Agreement in substantially  the form of Exhibit D from all future officers,  key
employees and other employees who will have access to  confidential  information
of the Company upon their employment by the Company or any of its subsidiaries.

     SECTION 5.15 Mergers,  Sale of Assets,  Etc. of  Subsidiaries.  The Company
shall not permit any  subsidiary to consolidate or merge into or with or sell or
transfer all or substantially all its assets, except that any subsidiary may (i)
consolidate  or  merge  into or with or sell or  transfer  assets  to any  other
subsidiary,  or (ii)  merge  into or sell or  transfer  assets  to the  Company,
without the approval of the Company's Board of Directors.

     SECTION 5.16  Maintenance of Ownership of  Subsidiaries.  The Company shall
not sell or otherwise  transfer any shares of capital  stock of any  subsidiary,
except to the Company or another subsidiary,  or permit any subsidiary to issue,
sell or otherwise  transfer any shares of its capital stock or the capital stock
of any  subsidiary,  except to the  Company or another  subsidiary,  without the
approval of the Company's Board of Directors.

     SECTION 5.17  Distributions by  Subsidiaries.  The Company shall not permit
any subsidiary to purchase or set aside any sums for the purchase of, or pay any
dividend  or make any  distribution  on,  any  shares of its  stock,  except for
dividends or other  distributions  payable to the Company or another subsidiary,
without the approval of the Company's Board of Directors.

     SECTION 5.18  Compliance  with Laws. The Company shall use its best efforts
to comply, and cause each subsidiary to comply, with all applicable laws, rules,
regulations  and orders,  noncompliance  with which could  materially  adversely
affect its business or condition, financial or otherwise.

     SECTION  5.19  Keeping of Records and Books of Account.  The Company  shall
keep, and cause each subsidiary to keep,  adequate records and books of account,
in which complete  entries will be made in accordance  with  generally  accepted
accounting   principles   consistently   applied,   reflecting   all   financial
transactions of the Company and such  subsidiary,  and in which, for each fiscal
year,   all  proper   reserves  for   depreciation,   depletion,   obsolescence,
amortization,  taxes,  bad debts  and  other  purposes  in  connection  with its
business shall be made.







                                     - 24 -



     SECTION 5.20 Change in Nature of Business.  The Company  shall not make, or
permit any subsidiary to make, any material change in the nature of its business
as set forth in the Business Plan without the approval of the Company's Board of
Directors.

     SECTION 5.21 U.S. Real Property Interest Statement.  Upon a written request
by the  Purchaser,  the  Company  shall  provide  the  Purchaser  with a written
statement   informing  the  Purchaser   whether  its  interest  in  the  Company
constitutes a U.S. real property  interest.  The Company's  determination  shall
comply with the requirements of Treasury Regulation section 1.897-2(h)(1) or any
successor  regulation,  and the  Company  shall  provide  timely  notice  to the
Internal  Revenue  Service,  in  accordance  with and to the extent  required by
Treasury Regulation section 1.897-2(h)(2) or any successor regulation, that such
statement has been made. The Company's  written statement to the Purchaser shall
be delivered to the Purchaser  within ten (10) days of the  Purchaser's  written
request  therefor.  The  Company's  obligation  to  furnish a written  statement
pursuant to this Section  5.24 shall  continue  notwithstanding  the fact that a
class  of  the  Company's  stock  may  be  regularly  traded  on an  established
securities market.

     SECTION 5.22 Changes in Outstanding  Equity  Securities.  The Company shall
not repurchase  outstanding  equity securities or otherwise adjust the number of
equity  securities  outstanding if such repurchase or adjustment would result in
the  Purchaser's   aggregate  investments  in  the  securities  of  the  Company
accounting for 20% or more of the equity  securities of the Company,  unless the
Company shall offer to repurchase a sufficient  number of shares of Common Stock
from the Purchaser as shall be necessary to reduce the aggregate  investments in
the  securities of the Company to less than 20% of the equity  securities of the
Company at the same time and on the same  terms and  conditions  as the  Company
repurchases outstanding equity securities from other security holders.

     SECTION 5.23 Delayed  Commencement  of Certain  Covenants.  Notwithstanding
anything to the contrary in this Article V or in this Agreement  generally,  the
covenants set forth in Section 5.01, 5.02, 5.04, 5.11, 5.15, 5.16, 5.17 and 5.21
shall  not  commence  and  the  Company  shall  have no  obligations  whatsoever
thereunder  unless  and until  either  (i) within a period of two years from the
Closing Date, the Company  receives not less than $100,000 from the Purchaser in
consideration of the issuance and sale to the Purchaser of additional  shares of
Common Stock or Common Stock  equivalents,  whether  pursuant to the exercise of
the option  referred to in Section 1.02 or pursuant to  purchases of  additional
securities directly from the Company, or (ii) within a period of six months from
the Closing  Date,  the  company  has  received  not less than an  aggregate  of
$500,000  from the sale of  securities  referred to in Section  1.06 or from the
Purchaser pursuant to clause (i), above. The date on which the earlier of







                                     - 25 -



the two  events set forth in clause (i) and clause  (ii),  above,  shall  occur,
provided such occurrence takes place within the respective time periods also set
forth in said clauses, shall be referred to as the "Effective Date."

                                  ARTICLE V(A)
                                  ------------

                  RIGHT OF FIRST REFUSAL FOR PURCHASER'S SHARES
                  ---------------------------------------------

    At anytime after the Closing Date, the Purchaser shall, prior to any sale or
transfer  of any of the  Company's  securities  held by it (other  than sales or
transfers to Irwin J.  Gruverman,  G.D.  Searle & Co., or any  affiliate of G.D.
Searle & Co.),  offer the Company by written  notice the right,  for a period of
thirty (30) days, to purchase all of such securities for cash at an amount equal
to the price or other  consideration for which such securities are to be sold or
transferred.  The  Purchaser's  written notice to the Company shall describe the
type  and  number  of  securities  proposed  to be  sold or  transferred  by the
Purchaser  and  specify the number,  price and  payment  terms.  The Company may
accept the Purchaser's offer as to all, but not less than all, of the securities
offered to it by written  notice  thereof given by it to the Purchaser  prior to
the  expiration  of the  aforesaid  thirty (30) day  period,  in which event the
Purchaser  shall  promptly  sell and the  Company  shall  buy,  upon  the  terms
specified,  the number of securities agreed to be purchased by the Company.  The
Purchaser shall be free at any time prior to one hundred twenty (120) days after
the date of its notice of offer to the Company to sell and transfer to any third
party or parties the number of such  securities  not agreed by the Company to be
purchased  by it,  at a price  and on  payment  terms no less  favorable  to the
Purchaser than those specified in such notice of offer to the Company.  However,
if such third party sale or transfer is not consummated  within such one hundred
twenty  (120)  day  period,  the  Purchaser  shall  not  sell or  transfer  such
securities  as shall not have been  purchased  with such  period  without  again
complying with this Article V(A).


                                   ARTICLE VI

                                  MISCELLANEOUS

     SECTION  6.01  Expenses.  Each party  hereto  will pay its own  expenses in
connection with the transactions  contemplated hereby,  provided,  however, that
the Company  shall pay the fees and  disbursements  of the  Purchaser's  special
counsel,  Testa,  Hurwitz & Thibeault,  in connection with such transactions and
the subsequent amendment or enforcement thereof up to $3,000.

     SECTION  6.02   Survival  of   Agreements.   All   covenants,   agreements,
representations  and  warranties  made  herein  or in  the  Registration  Rights
Agreement, the Stock Restriction Agreement,







                                     - 26 -



or any  certificate or instrument  delivered to the Purchaser  pursuant to or in
connection with this Agreement,  the Registration  Rights Agreement or the Stock
Restriction  Agreement,  shall  sur- vive the  execution  and  delivery  of this
Agreement,   the  Registration   Rights  Agreement  and  the  Stock  Restriction
Agreement,  the issuance,  sale and delivery of the Shares,  and all  statements
contained  in any  certificate  or other  instrument  delivered  by the  Company
hereunder or thereunder or in connection  herewith or therewith  shall be deemed
to constitute representations and warranties made by the Company.

     SECTION 6.03 Brokerage.  Each party hereto will indemnify and hold harmless
the  others  against  and in  respect  of  any  claim  for  brokerage  or  other
commissions  relative  to this  Agreement  or to the  transactions  contemplated
hereby,  based in any way on agreements,  arrangements or understandings made or
claimed to have been made by such party with any third party.

     SECTION  6.04  Parties in  Interest.  All  representations,  covenants  and
agreements  contained  in this  Agreement  by or on behalf of any of the parties
hereto  shall bind and inure to the  benefit of the  respective  successors  and
assigns of the parties hereto whether so expressed or not.  Without limiting the
generality of the  foregoing,  all  representations,  covenants and agree- ments
benefiting the Purchaser shall inure to the benefit of any qualified  subsequent
holder from time to time of the Shares.  For  purposes of this  Section 6.04 the
term  qualified  subsequent  holder  shall  include  G.D.  Searle  & Co.  or any
affiliate, the General Partner of the Purchaser or any individual or entity that
purchases 100% of the shares purchased by the Purchaser under this Agreement.

     SECTION  6.05   Notices.   All  notices,   requests,   consents  and  other
communications hereunder shall be in writing and shall be delivered in person or
mailed by certified or registered mail, return receipt requested,  or telexed in
the case of non-U.S. residents, addressed as follows:

           (a) if to the Company,  at Boston  Biomedica,  Inc., 375 West Street,
       West Bridgewater,  Massachusetts 02379, Attention: President, with a copy
       to Steven R. London, Esq., Brown, Rudnick,  Freed & Gesmer, One Financial
       Center, Boston, MA 02111; and

           (b) if to the Purchaser,  at G&G  Diagnostics  Corp.,  90 Oak Street,
       Newton,  Massachusetts 02164, Attention:  Irwin J. Gruverman, with a copy
       to Katherine M. Todd, Esq., Testa,  Hurwitz & Thibeault,  Exchange Place,
       53 State Street, Boston, Massachusetts 02109;

or, in any such case,  at such other  address  or  addresses  as shall have been
furnished in writing by such party to the others.







                                     - 27 -



     SECTION  6.06  Governing  Law.  This  Agreement  shall be  governed  by and
construed in accordance with the laws of the Commonwealth of Massachusetts.

     SECTION 6.07 Entire Agreement. This Agreement,  including the Schedules and
Exhibits  hereto,  constitutes the sole and entire agreement of the parties with
respect to the subject  matter  hereof.  All Schedules  and Exhibits  hereto are
hereby incorporated herein by reference.

     SECTION 6.08  Counterparts.  This  Agreement may be executed in two or more
counterparts,  each of  which  shall be  deemed  an  original,  but all of which
together shall constitute one and the same instrument.

     SECTION 6.09 Amendments. This Agreement may not be amended or modified, and
no provisions  hereof may be waived,  without the written consent of the Company
and the holders of at least two-thirds of the outstanding shares of Common Stock
issued as Shares under this Agreement.

     SECTION 6.10  Severability.  If any  provision of this  Agreement  shall be
declared void or unenforceable by any judicial or administrative  authority, the
validity  of any  other  provision  and of the  entire  Agreement  shall  not be
affected thereby.

     SECTION 6.11 Titles and  Subtitles.  The titles and subtitles  used in this
Agreement are for convenience only and are not to be considered in construing or
interpreting any term or provision of this Agreement.

     SECTION  6.12  Certain  Defined  Terms.  As  used in  this  Agreement,  the
following  terms shall have the following  meanings (such meanings to be equally
applicable to both the singular and plural forms of the terms defined):

          (a)   "person"   shall  mean  an   individual,   corporation,   trust,
        partnership,  joint  venture,  unincorporated  organization,  government
        agency or any agency or political subdivision thereof, or other entity.

          (b)  "subsidiary"  shall mean, as to the Company,  any  corporation of
        which more than 50% of the  outstanding  stock  having  ordinary  voting
        power to elect a majority of the Board of Directors of such  corporation
        (irrespective  of whether or not at the time stock of any other class or
        classes of such  corporation  shall have or might have  voting  power by
        reason of the happening of any  contingency)  is at the time directly or
        indirectly owned by the Company,  or by one or more of its subsidiaries,
        or by the Company and one or more of its subsidiaries.







                                     - 28 -



        IN WITNESS  WHEREOF,  the Company and the  Purchaser  have executed this
Agreement as of the day and year first above written.

                                                      BOSTON BIOMEDICA, INC.



                                                      By:/s/Richard T. Shumacher
                                                         -----------------------
[Corporate Seal]                                      Title: President
                                                             -------------------
ATTEST:



/s/Signature Unreadable
- -----------------------
Clerk
                                                     G&G DIAGNOSTICS LIMITED
                                                     PARTNERSHIP I



                                                     By: /s/Signature Unreadable
                                                         -----------------------
                                                         General Partner




                               AMENDMENT NO. 1 TO
                         COMMON STOCK PURCHASE AGREEMENT
                                      WITH
                             BOSTON BIOMEDICA, INC.

                                   Dated as of
                                December 5, 1990











                               AMENDMENT NO. 1 TO
                         COMMON STOCK PURCHASE AGREEMENT

      This  Amendment  No. 1 (the  "Amendment")  to the  Common  Stock  Purchase
Agreement,  dated  June  5,  1990  by and  between  Boston  Biomedica,  Inc.,  a
Massachusetts   corporation   (the  "Company")  and  G&G   Diagnostics   Limited
Partnership  I (the  "Purchaser")  (the  "Purchase  Agreement")  is  made  as of
December 5, 1990, by and between the Company,  the Purchaser and G&G Diagnostics
Limited Partnership II (the "Additional Purchaser").

     WHEREAS, the Company wishes to issue and sell to the Additional  Purchaser,
and Additional  Purchaser  wishes to purchase from the Company,  an aggregate of
10,000 shares (the "New Shares") of Common Stock,  $.01 par value per share (the
"Common Stock"), of the Company; and

     WHEREAS,  the Company  wishes to grant the  Additional  Purchaser an option
(the "New Option") to purchase 16,667 shares of Common Stock; and

     WHEREAS,  the  Additional  Purchaser  wishes to purchase the New Shares and
accept the New Option subject to substantially  the same terms and conditions as
are set forth in the Purchase Agreement; and

     WHEREAS,  the parties hereto wish to amend the Purchase  Agreement pursuant
to Section 6.09 thereof, as hereinafter provided;

     NOW THEREFORE,  in  consideration  of the payments  provided herein and for
other good and valuable  consideration,  the receipt and sufficiency of which is
hereby acknowledged, the parties hereby agree as follows:

I.   THE NEW SHARES AND NEW OPTION
     -----------------------------

          1.1  Issuance,  Sale and  Purchase of New Shares and New  Option.  The
parties  hereby  agree that the Company  shall issue and sell to the  Additional
Purchaser and the  Additional  Purchaser  shall purchase from the Company at the
Second  Closing (as defined in Section 1.3 hereof) 10,000 shares of Common Stock
having  the  rights  and  privileges  set  forth in the  Company's  Articles  of
Organization,  as amended,  for an aggregate  purchase price of $150,000.00.  In
connection  with the sale and  purchase  described  in Section 1.1  hereof,  the
Company agrees to grant to the Additional  Purchaser an option to purchase up to
16,667 additional shares,  exercisable for a period of two years,  commencing on
the date hereof (the "New Option  Period") at a price of $20.00 per share during
the first year following the







                                      - 2 -



date hereof and at a price of $25.00 per share during the second year  following
the date hereof; provided, however, that if the Company shall sell any shares or
equity-equivalents  (other than Reserved  Employee  Shares as defined in Section
5.02 of the  Purchase  Agreement  or  pursuant to Section  1.06 of the  Purchase
Agreement,  as amended by Section  1.5  hereof) at a price lower than $20.00 per
share during the first year of the New Option Period,  and (i) if the Additional
Purchaser  has not yet  exercised  the New  Option  in full  and the  Additional
Purchaser  exercises  the New Option in part or in full within  thirty (30) days
following  receipt  of notice  from the  Company  of such  sale,  or (ii) if the
Additional  Purchaser  has already  exercised the New Option in part or in full,
then (iii) the Company  shall  issue to the  Additional  Purchaser a  sufficient
number of shares of Common Stock as shall reduce (but not increase) the cost per
share paid by the  Additional  Purchaser upon exercise of the New Option to such
price at which such shares or  equity-equivalents  were  issued;  and  provided,
further, that if the Company shall sell any shares or equity-equivalents  (other
than  Reserved  Employee  Shares as  defined  in  Section  5.02 of the  Purchase
Agreement)  at a price lower than $25.00 per share during the second year of the
New Option Period, and (i) if the Additional Purchaser has not yet exercised the
New Option in full and the Additional Purchaser exercises the New Option in part
or in full within thirty (30) days following  receipt of notice from the Company
of such sale, or (ii) if the Additional  Purchaser has already exercised the New
Option in part or in full,  then (iii) the Company shall issue to the Additional
Purchaser a sufficient number of shares of Common Stock as shall reduce (but not
increase) the cost per share paid by the  Additional  Purchaser upon exercise of
the New  Option to such price at which such  shares or  equity-equivalents  were
issued.

          1.2 Second Closing,  Payment and Delivery. The closing of the purchase
and sale  described  in Section  1.1 shall  take place at the  offices of Testa,
Hurwitz & Thibeault, 53 State Street, Boston, Massachusetts 02109 at 10:00 a.m.,
Boston time, on December , 1990, or at such other date and time and place as may
be agreed upon between the  Additional  Purchaser  and the Company (such closing
being  called the  "Second  Closing")  and such date and time  being  called the
"Second Closing Date"). At the Second Closing,  the Company shall deliver to the
Additional Purchaser a certificate registered in the Additional Purchaser's name
representing  10,000  shares of Common  Stock.  As  payment  in full for the New
Shares  being  purchased  by  and  against  delivery  of the  stock  certificate
therefore,  the Additional Purchaser shall pay to the Company by certified check
or wire transfer,  or combination  thereof,  One Hundred Fifty Thousand  Dollars
($150,000.00).

          1.3 Definitions.  The parties further agree that the New Shares issued
hereunder  shall be deemed to be "Shares"  for all  purposes  under the Purchase
Agreement and to the same extent







                                      - 3 -



as if such shares had been originally  issued under the Purchase  Agreement.  In
addition,  all references in the Purchase  Agreement to the "Purchaser" shall be
deemed to refer to the Purchaser and the Additional Purchaser.

          1.4 Price  Protection.  The provisions of Section 1.05 of the Purchase
Agreement  shall apply to the New Shares  purchased by the Additional  Purchaser
under the Amendment to the same extent as if the New Shares had been  originally
issued under the Purchase  Agreement except that for purposes of determining the
three-year  period during which such price protection  provisions shall apply to
the New Shares the "Closing Date" shall be the Second Closing Date as defined in
Section 1.3 hereof.

          1.5  Additional  Investments.  After the  purchase  by the  Additional
Purchaser of the New Shares, the number of shares of Common Stock and options to
purchase  Common Stock which the Company may issue and sell  pursuant to Section
1.06 of the  Purchase  Agreement  shall be reduced  to 20,000  shares and 33,334
shares  respectively  or an aggregate of 53,334  Common  Stock  equivalents.  In
addition,  Section  1.06 of the  Purchase  Agreement  shall be  amended  so that
reference to the "Closing Date" shall be changed to the "Second Closing Date" as
defined in Section 1.3 hereof.

II. REPRESENTATIONS AND WARRANTIES OF THE COMPANY.
    ----------------------------------------------

     The Company represents and warrants to the Additional Purchaser that except
as set forth in the  Supplemental  Disclosure  Schedule  attached  as  Exhibit A
hereto,  the  representations  and  warranties  in  Article  II of the  Purchase
Agreement shall be true and correct on the Second Closing Date.

III. REPRESENTATIONS AND WARRANTIES OF THE ADDITIONAL PURCHASER.
     -----------------------------------------------------------

     The Additional  Purchaser  represents and warrants to the Company that each
of the  representations and warranties of the Purchaser set forth in Article III
to the Purchase  Agreement shall be true on the Second Closing Date with respect
to the Additional Purchaser.

IV. CONDITIONS TO THE OBLIGATIONS OF THE ADDITIONAL PURCHASER.
    ----------------------------------------------------------

     The obligation of the Additional  Purchaser to purchase the New Shares from
the Company is subject to the  satisfaction on or before the Second Closing Date
of the following conditions, all or any of which may be waived in writing by the
Additional Purchaser:

      (a)   Representations   and  Warranties.   Subject  to  any   supplemental
information  set forth in  Exhibit  A, the  representations  and  warranties  in
Article II of the Purchase







                                      - 4 -



Agreement  shall be true,  complete and correct on and as of the Second  Closing
Date with the same effect as though then made,  and the  President and Treasurer
of the Company shall have certified to such effect to the  Additional  Purchaser
in writing.

       (b)  Performance.  The Company shall have performed and complied with all
agreements  contained  herein  required to be performed  or complied  with by it
prior to or at the Second  Closing Date,  and the President and Treasurer of the
Company  shall have  certified  to the  Additional  Purchaser in writing to such
effect and to the further  effect that all of the  conditions  set forth in this
Article IV have been satisfied.

       (c)  All  Proceedings  to  be  Satisfactory.   All  corporate  and  other
proceedings  to be taken by the  Company  in  connection  with the  transactions
contemplated  hereby and all documents incident thereto shall be satisfactory in
form  and  substance  to the  Additional  Purchaser  and  its  counsel,  and the
Additional  Purchaser and its counsel  shall have received all such  counterpart
originals or certified or other copies of such documents as they  reasonably may
request.

      (d) Supporting  Documents.  The Additional Purchaser and its counsel shall
have received  copies of the documents  specified in Article IV paragraph (e) of
the Purchase Agreement.

       (e) Registration  Rights  Agreement.  The Company,  the Purchaser and the
Additional  Purchaser  shall have  executed  and  delivered  an amendment to the
Registration  Rights  Agreement in  substantially  the form  attached  hereto as
Exhibit B.

      (f) Stock  Restriction  Agreement.  The Company and Richard T.  Schumacher
shall  have  executed  and  delivered  an  amendment  to the  Stock  Restriction
Agreement in substantially the form attached hereto as Exhibit C.

      (g)  Preemptive  Rights.  All  stockholders  of  the  Company  having  any
preemptive,  first  refusal or other  rights with respect to the issuance of the
New Shares shall have irrevocably waived the same in writing.

      (h)  Percentage  Ownership.   The  Company  shall  have  sufficient  Stock
outstanding so that the purchase of shares by the Additional Purchaser shall not
result in aggregate  ownership by the Purchaser and the Additional  Purchaser of
twenty percent (20%) or more of the equity securities of the Company.

      (i)  Fees  of  Counsel.   The  Company   shall  have  paid  the  fees  and
disbursements  of counsel to the  Purchaser  and  Additional  Purchaser,  Testa,
Hurwitz & Thibeault,  as invoiced at the Second Closing for services rendered to
the Purchaser and the Additional Purchaser.







                                      - 5 -



V.   COVENANTS OF THE COMPANY
     ------------------------

     The Company covenants and agrees with the Additional Purchaser that it will
observe,  perform and comply with each of the covenants of the Company set forth
in Article V of the Purchase Agreement,  provided,  however,  that clause (F) of
Section 5.02 of the Purchase Agreement shall be amended so that reference to the
"Closing  Date"  shall be changed  to the  "Second  Closing  Date" as defined in
Section  1.3  hereof  and the  number of shares of Common  Stock and  options to
purchase  Common  Stock which the  Company  may issue and sell  pursuant to such
clause shall be reduced to 20,000  shares and 33,334 shares  respectively  or an
aggregate of 53,334 Common Stock equivalents.

VI. MISCELLANEOUS
    -------------
          6.1 Except where  context  otherwise  requires all  references  to the
Purchaser in the Purchase  Agreement  shall be deemed to refer to the  Purchaser
and the Additional Purchaser, collectively or individually, as applicable.

          6.2.  The  Purchase  Agreement  shall  remain in full force and effect
except as amended hereby.

          6.3. From and after the date hereof,  the parties hereto shall execute
and deliver such instruments, amendments and other documents as may be necessary
to effectuate fully the purposes of this Amendment.

          6.4.  This  Amendment  may be  executed  in  any  number  of  separate
counterparts  with  the  same  effect  as if all  parties  had  signed  the same
document. All such counterparts shall be construed together and shall constitute
one and the same instrument.


     [The Remainder of this Page is Intentionally Left Blank]







                                      - 6 -



            IN WITNESS  WHEREOF,  the parties have executed this Amendment No. 1
to the Common Stock Purchase Agreement as of the date first written above.


                                                   BOSTON BIOMEDICA, INC.



                                                   By: /s/ Richard T. Shumacher
                                                       ------------------------
                                                   Title: President
                                                          ---------------------


                                                   G&G DIAGNOSTICS LIMITED
                                                   PARTNERSHIP I


                                                   By: /s/ Irwin J. Gruverman
                                                      -------------------------
                                                      General Partner


                                                   G&G DIAGNOSTICS LIMITED
                                                   PARTNERSHIP II


                                                   By: /s/ Irwin J. Gruverman
                                                       ------------------------
                                                       General Partner









                                                                       Exhibit A

                        SUPPLEMENTAL DISCLOSURE SCHEDULE

Section 2.04    Authorized Capital Stock
- ------------    ------------------------

Immediately prior to the Second Closing,  175,454 shares of Common Stock will be
issued and outstanding.

See attached Schedule II.


Section 2.05    Financial Statements
- ------------    --------------------

1.      The Company sold 10,000  shares of its Common Stock and granted  options
        to  purchase  16,667  additional  shares of Common  Stock to G&G Limited
        Partnership I for $150,000 on June 5, 1990.

2.      On  September  7,  1990,  the  Company  amended  its Loan  and  Security
        Agreement  with Worcester  County  Institution  for Savings  ("WCIS") to
        increase its revolving line of credit to $500,000.  On the same day, the
        Company  amended and  restated  its  Revolving  Demand Note with WCIS to
        increase the principal sum to $500,000.


Section 2.06    Events Subsequent to Date of Balance Sheet
- ------------    ------------------------------------------

See Section 2.05.


Section 2.09    Title to Properties
- ------------    -------------------

1.      WCIS has a perfected  security  interest in all assets of the Company to
        secure the obligations of the Company  pursuant to its Loan and Security
        Agreement  dated August 17, 1988 and amendments  thereto dated September
        7, 1990.

2.      Bank of New England has a security interest in a $15,000  Certificate of
        Deposit of the Company to secure a Secured  Time Note,  the  outstanding
        balance of which is approximately $13,000.

3.      North Easton Savings Bank has a security interest in the following items
        presently owned by the Company:

        a.   1989 Chevrolet Nova
        b.   1988 Chevrolet Corsica
        c.   Desk Top Publishing System
        d.   Toshiba Copier











November 30, 1990





Mr. Irwin J. Gruverman, General Partner
G & G Diagnostics Limited Partnership I                     [COPY]
90 Oak Street
Newton, MA 02164

Dear Irv:

Pursuant  to your  request,  please  find  below a detailed  description  of our
intended use of the  proceeds  from the  upcoming  sale of common stock  (10,000
shares: $150,000) to G & G Diagnostics Limited Partnership I.




I.    Marketing and Sales
      -------------------
                                                                         
      1.  full-time sales representative                                    $30,000

      2.  full time sales support person                                     24,000

      3.  American Association of Blood Banks Meeting
           a.  booth space                                                    3,000
           b.  travel, lodging and entertainment expenses                    10,000
           c.  promotional materials -                                       10,000
              (poster, pamphlet, PERFORMANCE Panel  Handouts)

      4.  Promotional material (sales catalogue, pamphlets, etc.)            12,000

      5.  Direct mail (postage, labels, brochures)                            6,000

      6.  Miscellaneous                                                      10,000


II.  Research and Development/Production
     -----------------------------------
       1.  Preparation of new PERFORMANCE Panels for release during          45,000
           first two quarters of 1991  (anti-HTLV,  HIV Antigen,  HLA,
           False Positive  anti-HIV 1, anti-HIV 2, Low Titer anti-HIV 1)




Sincerely,

/s/ Ric
- ---------------------
Richard T. Schumacher
President


RTS/cjk



          BBI                BOSTON BIOMEDICA, INC.
                    375 WEST STREET - WEST BRIDGEWATER MA 02379
            Tel (508) 580-1900 - Telex 5106012210 - FAX (508) 580-2202












                              AMENDED AND RESTATED
                           STOCK RESTRICTION AGREEMENT

    This Amended and Restated Stock Restriction  Agreement (this "Agreement") is
made and entered into as of this 5th day of December,  1990, by and among Boston
Biomedica,  Inc.,  a  Massachusetts  corporation  (the  "Company"),  Richard  T.
Schumacher (the  "Stockholder"),  and G&G Diagnostics  Limited Partnership I and
G&G Diagnostics  Limited Partnership II (each an "Investor" and collectively the
"Investors").

     WHEREAS,  the Stockholder is the holder of an aggregate of 82,500 shares of
common stock, $.01 par value, of the Company (the "Common Stock");

     WHEREAS,  the Investors have acquired shares of Common Stock of the Company
pursuant to the terms of a Common Stock Purchase Agreement dated June 5, 1990 as
amended on the date hereof  between the Company and the Investors (the "Purchase
Agreement"); and

     WHEREAS,  it is a  condition  to the  obligations  of the  Investors  under
Amendment No. 1 to the Purchase Agreement that this Agreement be executed by the
parties hereto,  and the parties are willing to execute this Agreement and to be
bound by the provisions hereof;

      NOW,  THEREFORE,  in  consideration  of the foregoing,  the agreements set
forth below,  and the parties'  desire to provide for continuity of ownership of
the Company to further the  interests  of the Company and its present and future
stockholders, the parties hereby agree with each other as follows:

     1. Certain Defined Terms.  As used in this  Agreement,  the following terms
shall have the following respective meanings:

          (a) "Stock" shall mean and include all shares of Common Stock, and all
other  securities  of the  Company  which may be issued  in  exchange  for or in
respect  of  shares  of  Common  Stock  (whether  by way of stock  split,  stock
dividend, combination, reclassification, reorganization, or any other means).

          (b)  "Shares"  shall mean and include all shares of Stock now owned or
hereafter acquired by either the Stockholder or the Investor.

          (c) "Effective  Date" shall have the meaning set forth in Section 5.23
of the Purchase Agreement.







                                      - 2 -


    2. Prohibited Transfers. After the Effective Date, the Stockholder shall not
sell, assign, transfer, pledge,  hypothecate,  mortgage,  encumber or dispose of
all or any of his Shares except to the Company or as expressly  provided in this
Agreement.  Notwithstanding  the foregoing,  the Stockholder may transfer all or
any of his Shares (i) by way of gift to any member of his family or to any trust
for the benefit of any such family member or the Stockholder,  provided that any
such transferee  shall agree in writing with the Company and the Investor,  as a
condition  to  such  transfer,  to be  bound  by all of the  provisions  of this
Agreement to the same extent as if such transferee were the Stockholder, (ii) by
will  or the  laws of  descent  and  distribution,  in  which  event  each  such
transferee shall be bound by all of the provisions of this Agreement to the same
extent as if such transferee  were the  Stockholder.  Notwithstanding  Section 3
below the Stockholder may pledge not more than 50% of the Shares held by him for
purposes of obtaining  personal  financing.  As used herein,  the word  "family"
shall  include any spouse,  lineal  ancestor or  descendant,  brother or sister,
niece or nephew.

    3.   Right of First Refusal on Dispositions.
         ---------------------------------------

          (a) If at any time after the Effective Date the Stockholder desires to
sell for cash or cash  equivalents  all or any part of his Shares  pursuant to a
bona fide offer from a third party (the "Proposed Transferee"),  the Stockholder
shall  submit a written  offer (the  "Offer") to sell such Shares (the  "Offered
Shares") to the  Investor on terms and  conditions,  including  price,  not less
favorable to the Investors than those on which the Stockholder  proposes to sell
such Offered  Shares to the Proposed  Transferee.  The Offer shall  disclose the
identity of the Proposed Transferee, the Offered Shares proposed to be sold, the
total  number  of Shares  owned by the  Stockholder,  the terms and  conditions,
including  price, of the proposed sale, and any other material facts relating to
the proposed sale. The Offer shall further state that the Investors may acquire,
in accordance with the provisions of this Agreement, all, but not less than all,
of the  Offered  Shares for the price and upon the other  terms and  conditions,
including deferred payment (if applicable), set forth therein.

          (b) The Investors shall have the absolute right to purchase all of the
Offered  Shares.  To the extent that the  Investors as a group may purchase all,
but not less than all, of the Offered Shares,  the Investors may determine among
themselves the number of such Offered Shares to be purchased by each Investor.

          (c) If an Investor  desires to purchase all or any part of the Offered
Shares,  said Investor shall  communicate in writing its election to purchase to
the Stockholder,  which  communication  shall state the number of Offered Shares
said Investor desires to







                                       -3-



purchase and shall be delivered  in person or mailed to the  Stockholder  at the
address set forth in accordance  with Section 11 below within thirty days of the
date the Offer was made.  Such  communication  shall,  when taken in conjunction
with the Offer, be deemed to constitute a valid, legally binding and enforceable
agreement for the sale and purchase of such Offered Shares. Sales of the Offered
Shares to be sold to  purchasing  Investors  pursuant to this Section 3 shall be
made at the offices of the Company on the 45th day  following the date the Offer
was made (or if such 45th day is not a business day, then on the next succeeding
business  day).  Such sales shall be effected by the  Stockholder's  delivery to
each purchasing Investor of a certificate or certificates evidencing the Offered
Shares to be  purchased by it, duly  endorsed  for  transfer to such  purchasing
Investor,  against  payment to the Stockholder of the purchase price therefor by
such purchasing Investor.

          (d) If the  Investors do not purchase all of the Offered  Shares,  the
Offered  Shares  not so  purchased  may be sold by the  Stockholder  at any time
within 90 days after the date the Offer was made,  subject to the  provisions of
Sections 4, 5 and 6. Any such sale shall be to the Proposed  Transferee,  at not
less than the price  and upon  other  terms  and  conditions,  if any,  not more
favorable  to the Proposed  Transferee  than those  specified in the Offer.  Any
Offered  Shares not sold within such 90-day period shall  continue to be subject
to the  requirements  of a prior offer  pursuant  to this  Section 3. If Offered
Shares are sold  pursuant to this Section 3 to any  purchaser who is not a party
to this Agreement,  the Offered Shares so sold shall no longer be subject to any
of the restrictions imposed by this Agreement.

          (e) The Investors'  right of first refusal  provided in this Section 3
shall not apply with respect to sales of Shares to the Company.

     4.   Right of Participation in Sales.
          --------------------------------

          (a) If at any time after the Effective Date the Stockholder desires to
sell all or any part of the Shares  owned by him to any  person or entity  other
than one or more of the Investors (the "Purchaser"), each of the Investors shall
have the  right to sell to the  Purchaser,  as a  condition  to such sale by the
Stockholder, at the same price per share and on the same terms and conditions as
involved  in such sale by the  Stockholder,  the same  percentage  of the Shares
owned  by such  Investor  as the  Shares  to be sold by the  Stockholder  to the
Purchaser  represents  with  respect  to the  Shares  owned  by the  Stockholder
immediately  prior to the sale of any of his  Shares to the  Purchaser.  For the
purposes of this  Section 4, all of the stock which an Investor has the right to
acquire from the Company upon the conversion, exercise or exchange of any of the
securities of the Company then owned by such Investor.







                                      - 4 -


          (b) Each  Investor  wishing to so  participate  in any sale under this
Section 4 it shall notify the  Stockholder  in writing of such intention as soon
as practicable after receipt of the Offer made pursuant to Section 3, and in any
event within  twenty days after the date the Offer was made.  Such  notification
shall be  delivered in person or mailed to such  Stockholder  at the address set
forth in accordance with Section 11 below.

          (c) The Stockholder and each participating  Investor shall sell to the
Purchaser  all,  or at the  option  of the  Purchaser,  any  part of the  Shares
proposed  to be sold by them at not less than the price and upon other terms and
conditions,  if any, not more favorable to the Purchaser than those in the Offer
provided by the Stockholder under Section 3 above;  provided,  however, that any
purchase of less than all of such Shares by the Purchaser shall be made from the
Stockholder  and each  participating  Investor  pro rata based upon the relative
amount of the Shares that the  Stockholder and each  participating  Investor are
otherwise entitled to sell pursuant to Section 4(a).

           (d) Any Shares sold by the  Stockholder  pursuant  to this  Section 4
shall no longer be subject to the restrictions imposed by this Agreement and any
Shares sold by a  participating  Investor  pursuant  to this  Section 4 shall no
longer be entitled to the benefits conferred by this Agreement.

           (e) The  Investors'  right to  participate  in sales pursuant to this
Section 4 shall not apply with respect to sales of Shares to the Company.

     5. Election of Directors.  After the Effective Date, the Stockholder agrees
to vote all his Shares at all  elections of directors of the Company so that the
Board of Directors of the Company shall consist of six members.  The Stockholder
further  agrees to vote his Shares to cause and  maintain  the  election  to the
Board of Directors of the Company of the person designated by the Investor.

     6. Sales Before the Effective Date. If the Stockholder shall sell,  assign,
transfer or otherwise dispose of all or any of his Shares prior to the Effective
Date to any  Purchaser  who is not a party to this  Agreement the Shares so sold
shall continue to be subject to the  restrictions  of this Agreement  (including
but not limited to the  restrictions on transfer in Sections 2, 3, and 4 and the
voting provisions of Section 5).

     7. Term.  This  Agreement  shall  terminate  (a)  immediately  prior to the
consummation of the first firm commitment  underwritten public offering pursuant
to an  effective  registration  statement  on Form S-1 (or its then  equivalent)
under the  Securities  Act of 1933, as amended,  pursuant to which the aggregate
price paid by the public for the  purchase of Stock is at least  $5,000,000,  or
(b) the fifth anniversary of the Second Closing Date, whichever occurs first.







                                      - 5 -


     8. Failure to Deliver Shares. If the Stockholder  becomes obligated to sell
any Shares to an  Investor  or the  Company  under this  Agreement  and fails to
deliver  such  Shares  in  accordance  with the  terms of this  Agreement,  such
Investor or the Company,  as the case may be, may, at its option, in addition to
all other remedies it may have,  send to the  Stockholder the purchase price for
such Shares as is herein specified.  Thereupon,  the Company upon written notice
to  the  Stockholder,   (a)  shall  cancel  on  its  books  the  certificate  or
certificates  representing  the Shares to be sold and (b) shall  issue,  in lieu
thereof,  in the name of such Investor or the Company, as the case may be, a new
certificate or certificates  representing such Shares,  and thereupon all of the
Stockholder's rights in and to such Shares shall terminate.

     9.  Specific  Enforcement.   The  Stockholder  expressly  agrees  that  the
Investors and the Company will be  irreparably  damaged if this Agreement is not
specifically  enforced.  Upon a  breach  or  threatened  breach  of  the  terms,
covenants and/or conditions of this Agreement by the Stockholder,  the Investors
and the Company shall, in addition to all other remedies,  each be entitled to a
temporary or permanent  injunction,  without showing any actual damage, and/or a
decree for specific performance, in accordance with the provisions hereof.

     10.  Legend.  Each  certificate  evidencing  any of the Shares shall bear a
legend substantially as follows:

              "The shares represented  by this  certificate   are   subject   to
              restrictions   on  transfer  and  may  not  be  sold,   exchanged,
              transferred, pledged, hypothecated or otherwise disposed of except
              in accordance  with and subject to all the terms and conditions of
              a certain Stock Restriction  Agreement dated as of June 5, 1990, a
              copy of which  the  Company  will  furnish  to the  holder of this
              certificate upon request and without charge."

     11.  Notices.  Notices  given  hereunder  shall be deemed to have been duly
given on the date of  personal  delivery or on the date of postmark if mailed by
certified or  registered  mail,  return  receipt  requested,  to the party being
notified at his or its address specified on the applicable signature page hereto
or such other address as the addressee may subsequently notify the other parties
of in writing.

     12. Entire Agreement and Amendments.  This Agreement constitutes the entire
agreement of the parties with respect to the subject  matter  hereof and neither
this  Agreement nor any  provision  hereof may be waived,  modified,  amended or
terminated  except by a written  agreement signed by the parties hereto.  To the
extent  any  term or  other  provision  of any  other  indenture,  agreement  or
instrument  by which any party hereto is bound  conflicts  with this  Agreement,
this Agreement shall have precedence over such conflicting term or provision.







                                      - 6 -


     13. Governing Law; Successors and Assigns. This Agreement shall be governed
by the laws of the Commonwealth of  Massachusetts  and shall be binding upon the
heirs,  personal  representatives,  executors,  administrators,  successors  and
assigns of the parties.

     14.  Waivers.  No  waiver  of any  breach  or  default  hereunder  shall be
considered valid unless in writing,  and no such waiver shall be deemed a waiver
of any subsequent breach or default of the same or similar nature.

     15.  Severability.  If any provision of this Agreement  shall be held to be
illegal,   invalid   or   unenforceable,    such   illegality,   invalidity   or
unenforceability shall attach only to such provision and shall not in any manner
affect or render illegal,  invalid or unenforceable  any other provision of this
Agreement,  and this  Agreement  shall be  carried  out as if any such  illegal,
invalid or unenforceable provision were not contained herein.

     16.  Captions.  Captions are for convenience  only and are not deemed to be
part of this Agreement.

     17.  Continuation of Employment.  Nothing in this Agreement shall create an
obligation  on the  Company  or  the  Investor  to  continue  the  Stockholder's
employment with the Company.

     18.   Counterparts.   This  Agreement  may  be  executed  in  two  or  more
counterparts,  each of  which  shall be  deemed  an  original,  but all of which
together shall constitute one and the same instrument.

     IN WITNESS  WHEREOF,  this  Agreement  has been executed as of the date and
year first above written.

                                          COMPANY:

                                          BOSTON BIOMEDICA, INC.


                                          By: /s/Richard T. Shumacher
                                              -------------------------
                                          Title: President
                                                 ----------------------
                                          Address: 375 West Street
                                                   West Bridgewater,
                                                   MA 02379







                                      - 7 -



                                           INVESTORS:

                                           G&G DIAGNOSTICS LIMITED
                                           PARTNERSHIP I



                                           By: /s/ Irwin J. Gruverman
                                               --------------------------
                                           Title: General Partner

                                           Address: 90 Oak Street
                                                    Newton, MA 02164


                                           G&G DIAGNOSTICS LIMITED
                                           PARTNERSHIP II


                                           By: /s/ Irwin J. Gruverman
                                               --------------------------
                                           Title: General Partner

                                           Address: 90 Oak Street
                                                    Newton, MA 02164


                                           STOCKHOLDER:



                                           /s/Richard T. Shumacher
                                           ------------------------------
                                           Richard T. Schumacher

                                           Address: 375 West St.
                                           W. Bridgewater, MA 02379









                                 AMENDMENT NO. 1
                                       TO
                          REGISTRATION RIGHTS AGREEMENT

                                December 5, 1990


     This Amendment No. 1 (the "Amendment") to the Registration Rights Agreement
dated as of June 5, 1990 (the "Agreement") by and among Boston Biomedica,  Inc.,
a  Massachusetts   corporation  (the  "Company")  and  G&G  Diagnostics  Limited
Partnership  I (the  "Purchaser")  is made as of December 5, 1990 by and between
the Company,  the  Purchaser and G&G  Diagnostics  Limited  Partnership  II (the
"Additional Purchaser").

     WHEREAS,  the Additional  Purchaser has agreed to purchase shares of Common
Stock, $.0l par value ("Common Stock"), of the Company pursuant to Amendment No.
1 to the  Common  Stock  Purchase  Agreement  of June  5,  1990  (the  "Purchase
Agreement")  between the Company,  the Purchaser and the  Additional  Purchaser,
dated the date hereof; and

     WHEREAS,  as an inducement to the  Additional  Purchaser to consummate  the
transactions  contemplated  by the  Purchase  Agreement,  the  Company  and  the
Purchaser have agreed to make the Additional Purchaser a party to the Agreement;

     NOW  THEREFORE,  in  consideration  of the foregoing and the agreements set
forth below, the parties hereby agree and consent to the following:

     As of the date  hereof,  the  following  terms as used in the  Registration
Rights Agreement of June 5, 1990 shall have the following respective meanings:

           "Registrable  Shares" shall mean all shares of Common Stock issued or
           issuable to the Purchaser and the  Additional  Purchaser  pursuant to
           the Purchase Agreement and any amendment thereto whether purchased or
           issued pursuant to the equity provisions thereof.


      [The Remainder of This Page Intentionally Left Blank.]







                                      - 2 -



     IN WITNESS  WHEREOF,  this  Amendment  has been executed as of the date and
year first above written.

                                                    BOSTON BIOMEDICA, INC.




                                                    By:/s/Richard T. Shumacher
                                                       ------------------------
                                                    Title: President
                                                          ---------------------

AGREED TO AND ACCEPTED as of
the date first above written.


G&G Diagnostics Limited
Partnership I


By: /s/ Irwin J. Gruverman
    -----------------------
Title: General Partner



G&G Diagnostic Limited
Partnership II


By: /s/ Irwin J. Gruverman
    -----------------------
Title: General Partner