EXECUTION


                           SECOND AMENDED AND RESTATED
                           LOAN AND SECURITY AGREEMENT

                                  By and Among

                   BOSTON BIOMEDICA, INC., BTRL CONTRACTS AND
        SERVICES, INC. and BBI-NORTH AMERICAN CLINICAL LABORATORIES, INC.

                                 as the Borrower

                                       and

                        THE FIRST NATIONAL BANK OF BOSTON

                                  as the Lender




                           Dated: As of August 2, 1995






             SECOND AMENDED AND RESTATED LOAN AND SECURITY AGREEMENT

                                TABLE OF CONTENTS



                                                                                                          Page
                                                                                                          ----
                                                                                                         
Preamble.........................................................................................            1

Section 1 - Definitions; Use of Terms; Incorporation by Reference................................            2


Section 2 - Establishment of Loan Account and Description of Loan Arrangement
                  and Credit Facilities..........................................................            7

2.1  Amounts and Types of Loans; Notes Evidencing Loans..........................................            7
2.2  Interest Rate on Loans......................................................................            8
2.3  Repayment of Loans..........................................................................            8
2.4  Security for the Loans......................................................................            8
2.5  Use of Proceeds ............................................................................            8
2.6  Loan Advances...............................................................................            8
2.7  Other Advances and Payments.................................................................            9
2.8  Loan Statements.............................................................................            9
2.9  Release of Guaranty.........................................................................           10
2.10 Review of  Line of Credit...................................................................           10

Section 3 - Security Interest in Collateral......................................................           10

3.1 Granting Clause; Description of Collateral...................................................           10
3.2 Certain Representations, Warranties, and Covenants Regarding the Collateral..................           12

    3.2.1  Lock Box Agreement....................................................................           12
    3.2.2  Schedules and Assignments of Account/Consents to Assignments..........................           12
    3.2.3  Bona Fide Accounts....................................................................           13
    3.2.4  Notification To Account Debtors and Others by Lender..................................           13
    3.2.5  Allowances and Adjustments............................................................           13
    3.2.6  Notification To Account Debtors by Borrower...........................................           14
    3.2.7  Title to Collateral...................................................................           14
    3.2.8  Actions To Maintain Perfection........................................................           14
    3.2.9  Lender's Payment of Taxes and Other Payments..........................................           14
    3.2.10 Verification..........................................................................           15
    3.2.11 Location of Collateral................................................................           15
    3.2.12 Powers of Attorney....................................................................           15
    3.2.13 Ratification and Indemnification Under Power of Attorney..............................           17
    3.2.14 Motor Vehicle Certificates of Title...................................................           17
    3.2.15 Audit Fees............................................................................           17
    3.2.16 Borrowing Base Determinations.........................................................           17

3.3  Inventory Collateral........................................................................           18
3.4  Equipment Collateral........................................................................           18

    3.4.1  Business Use; Purchase Money Acquisitions.............................................           18
    3.4.2  Fixtures..............................................................................           18

Section 4 - Representations, Covenants and Warranties............................................           19

4.1 General Representations, Covenants and Warranties............................................           19

    4.1.1 Business; Supplementary Information Regarding Borrower.................................           19
    4.1.2 Due Organization and Existence; Authorization..........................................           19
    4.1.3 Articles of Organization; Stock; Accurate Records......................................           20
    4.1.4 Binding Documents; Violation of Other Agreements.......................................           20
    4.1.5 Title To Assets; Security Interests and Mortgages; Leases;
                  Royalties; etc.................................................................           20
    4.1.6 Investments............................................................................           20
    4.1.7 Litigation; Outstanding Orders.........................................................           20
    4.1.8 Financial Statements Delivered.........................................................           21
    4.1.9 Current Stockholders...................................................................           21
    4.1.10 Other Liabilities; Tax Returns; No Adverse Changes....................................           21
    4.1.11 No Agency Between Borrower and Lender.................................................           21
    4.1.12 Regulation U..........................................................................           22
    4.1.13 ERISA.................................................................................           22
    4.1.14 Necessary Permits and Licenses........................................................           22
    4.1.15 Governmental Approvals Not Required...................................................           22
    4.1.16 Adequate Financing....................................................................           23
    4.1.17 No Event of Default...................................................................           23
    4.1.18 Compliance with Leases................................................................           23
    4.1.19 President and Chief Executive Officer; Major Stockholder..............................           23
    4.1.20 Compliance with Certain Environmental Laws............................................           23
    4.1.21 Recent Changes of Name or Structure...................................................           24
    4.1.22 Payment of Wages......................................................................           24

4.2 Certain Affirmative Covenants................................................................           24

    4.2.1 Payment of Obligations.................................................................           24
    4.2.2 Books and Records......................................................................           24
    4.2.3 Inspection.............................................................................           24
    4.2.4 Commercial Purposes....................................................................           25
    4.2.5 Notice of Adverse Matters..............................................................           25
    4.2.6 Principal Lending Business.............................................................           25





    4.2.7  Maintenance of Corporate Existence; Compliance with Laws..............................           25
    4.2.8  Payment of Taxes and Filing of Returns................................................           25
    4.2.9  Maintenance of Properties.............................................................           26
    4.2.10 Collection Costs; Legal Fees; etc.....................................................           26
    4.2.11 Insurance.............................................................................           26
    4.2.12 Further Agreements; Compliance with Other Obligations; Tax Returns;
                  Notice of Litigation and of Events of Default..................................           27
    4.2.13 Certain Environmental Matters.........................................................           28
    4.2.14 Changes in Master Exhibit.............................................................           29
    4.2.15 Government Approvals..................................................................           29
    4.2.16 Key Man Life Insurance................................................................           29

4.3  General Negative Covenants..................................................................           29

    4.3.1 Other Debt.............................................................................           29
    4.3.2 Payment of Dividends...................................................................           30
    4.3.3 Loans by the Borrower..................................................................           30
    4.3.4 Investments............................................................................           30
    4.3.5 Mergers, etc...........................................................................           30
    4.3.6 Sales of Assets........................................................................           30
    4.3.7 No Liens; Permitted Encumbrances ......................................................           30
    4.3.8 Continuance of Business................................................................           30

Section 5 - Financial and Reporting Covenants....................................................           31

5.1 Reporting Covenants..........................................................................           31

    5.1.1 Quarterly Financial Statements.........................................................           31
    5.1.2 Annual Financial Statements............................................................           32
    5.1.3 Monthly and Weekly Reports.............................................................           32
    5.1.4 Officer's Certificate..................................................................           33
    5.1.5 Other Information......................................................................           33

5.2  Financial Covenants.........................................................................           33

Section 6 - Events of Default....................................................................           35

Section 7 - Remedies.............................................................................           37

7.1 General Remedies.............................................................................           37
7.2 License .....................................................................................           39
7.3 No Duty of Preservation; Joint Property......................................................           39
7.4 Cumulative Remedies .........................................................................           39





Section 8 - Waiver; Termination .................................................................           40

8.1 Waiver By The Borrower.......................................................................           40
8.2 Lender's Option To Waive.....................................................................           40

Section 9 - Miscellaneous........................................................................           40

9.1 Deposits As Collateral; Set-Off..............................................................           40
9.2 Transfer of Collateral to Bank...............................................................           41
9.3 No Duty To Preserve or Collect...............................................................           41
9.4 Survival of Covenants; Binding Effect........................................................           41
9.5 Termination of Agreement.....................................................................           42
9.6 Conflict of Terms............................................................................           42
9.7 Prior Discussions; Amendments in Writing; Counterparts;
                  Filing As Financing Statement..................................................           42
9.8 General Indemnification......................................................................           43
9.9 Destruction of Documents; Jurisdiction.......................................................           43
9.10 Notices.....................................................................................           43
9.11Application of Proceeds......................................................................           44
9.12 Continuance of Defaults.....................................................................           44
9.13 Severability................................................................................           44
9.14 Headings....................................................................................           44
9.15 Governing Law; Sealed Instrument............................................................           45
9.16 Force Majeure...............................................................................           45
9.17 Interpretation of Agreement.................................................................           45








Master Exhibit


Exhibit 1.4.1              1994 BBI, BTRL and NACL Equipment Appraisal Report

Exhibit 1.8                Existing Government Contracts

Exhibit 3.2.1              Form of Lock Box Agreement

Exhibit 4.2.15(A)          Form of Collateral Assignment

Exhibit 4.2.15(B)          Form of Notice of Collateral Assignment

Exhibit 5.2.3              Calculation of Debt Service Ratios




             SECOND AMENDED AND RESTATED LOAN AND SECURITY AGREEMENT
             -------------------------------------------------------


         This Second  Amended and  Restated  Loan and Security  Agreement  (this
"Agreement")  is  dated  as of  August  2,  1995,  and  is by and  among  BOSTON
BIOMEDICA,  INC.  ("BBI"),  BTRL  CONTRACTS AND  SERVICES,  INC.  ("BTRL"),  and
BBI-NORTH AMERICAN CLINICAL LABORATORIES, INC. ("NACL"), formerly known as NORTH
AMERICAN  LABORATORY GROUP,  INC., each of which is a Massachusetts  corporation
validly  created,  legally  existing and in good standing  under the laws of the
Commonwealth of Massachusetts  and each of which has its "Notice Address" at 375
West Street, West Bridgewater, Massachusetts 02379 (BBI, BTRL and NACL, together
with their  respective  successors  and assigns,  are  collectively  referred to
herein as the  "Borrower")  and THE FIRST  NATIONAL  BANK OF BOSTON,  a national
banking   association   having  an  office  and  "Notice  Address"  at  Bank  of
Boston-Worcester   Tower,   P.O.  Box  15073,   100  Front  Street,   Worcester,
Massachusetts   01608-1438  (together  with  its  successors  and  assigns,  the
"Lender"),  successor-by-merger  to WORCESTER COUNTY  INSTITUTION FOR SAVINGS, a
Massachusetts savings bank ("WCIS").

         WHEREAS, the Borrower and the Lender entered into a certain amended and
restated loan  arrangement  (the "Loan  Arrangement")  as evidenced by a certain
Amended and Restated Loan and Security  Agreement dated as of June 18, 1993 (the
"Amended and Restated Agreement"),  which Loan Arrangement has been subsequently
amended by a certain letter  agreement dated August 26, 1993 ("Amendment No. 1")
by and  between  the  Borrower  and the  Lender,  further  amended  by a certain
Amendment No. 2 to Amended and Restated Loan Agreement dated as of July 29, 1994
("Amendment  No. 2") by and  between  the  Borrower  and the Lender and  further
amended by Amendment No. 3 to Amended and Restated  Loan and Security  Agreement
dated as of October 11, 1994 ("Amendment No. 3") by and between the Borrower and
the Lender (the  Amended and Restated  Agreement as amended by Amendment  No. 1,
Amendment No. 2 and Amendment No. 3 is sometimes  hereinafter referred to as the
"Amended Agreement"); and

         WHEREAS,  BTRL  and NACL are  each  wholly-owned  subsidiaries  of BBI,
formed to acquire  certain  assets  determined to be useful and necessary to the
business conducted by BBI; and

         WHEREAS,  the Borrower and the Lender  desire to again restate in their
entirety  all of the  provisions  of the  Loan  Arrangement,  to  amend  certain
provisions of the Loan Arrangement as more particularly described herein, and to
further increase the amount of credit available to the Borrower; and

         WHEREAS,  the Lender is willing to enter into this  Agreement and grant
such  financial  accommodations  to or  for  the  benefit  of  the  Borrower  in
accordance  with the terms of this Agreement only if the Borrower shall make and
enter into certain agreements, covenants,  representations and warranties as set
forth herein and as further set forth and contained in the Financing Instruments
(as  hereinafter  defined),  all of the terms and conditions of which  Financing
Instruments are hereby incorporated herein by reference;

         NOW  THEREFORE,  in order to induce the Lender to lend certain sums, to
extend such additional credit and to grant financial  accommodations,  all to or
for  the  benefit  of  the  Borrower,   and  in  consideration  thereof  and  in
consideration of the mutual covenants herein  contained,  and for other good and
valuable  consideration,  the  receipt  and  sufficiency  of  which  are  hereby
acknowledged,  the Borrower  hereby  represents and warrants to the Lender,  and
hereby covenants and agrees with the Lender, all as follows:

                                    SECTION 1

                           DEFINITIONS; USE OF TERMS;
                           INCORPORATION BY REFERENCE
                           --------------------------

         In this Agreement:

         1.1 "Accounts" shall mean and refer to any and all of Borrower's rights
to payment  for goods  sold or leased or for  services  rendered,  which are not
evidenced by an  Instrument  or Chattel  Paper,  whether or not such





rights  have been earned by  performance,  and shall  include  all  receivables,
notes, drafts, acceptances, other forms of obligations and "accounts" as defined
in the UCC, all in whatever form and however arising or created;

         1.2 "Borrowing  Base" shall mean and refer to the lesser of the Line of
Credit Maximum Amount (defined below), or the Calculated Amount (defined below),
where:

                  1.2.1 "Line of Credit Maximum  Amount" shall mean and refer to
         the amount of THREE MILLION FIVE HUNDRED THOUSAND DOLLARS ($3,500,000);
         and

                  1.2.2  "Calculated  Amount" shall mean and refer to the sum of
        the following items:

                           1.2.2.1  Eighty  Percent  (80%) of the net  amount of
                  Eligible Accounts; plus

                           1.2.2.2  the  lesser  of Forty  percent  (40%) of all
                  Eligible  Inventory,  or One  Million  Five  Hundred  Thousand
                  Dollars ($1,500,000);

         1.3  "Eligible  Accounts"  shall  mean  and  refer to that  portion  of
Borrower's  Accounts which arise in the ordinary course of Borrower's  business,
which have been earned by performance and which are not:

                  1.3.1  outstanding more than ninety (90) days;

                  1.3.2 based on payment  terms other than those which are usual
        and customary to the Borrower's business;

                  1.3.3 due from any Account  Debtor  which holds or is entitled
         to any claim, counterclaim, setoff or chargeback or which has the right
         to return to the Borrower for credit or refund the goods giving rise to
         such Account;

                  1.3.4  based  on  any  sale  made  on,   so-called,   "delayed
        shipping", "bill and hold" or "dating" basis;

                  1.3.5  evidenced by a promissory note;

                  1.3.6 due from any  Person  employed  by, or any  salesman  or
        independent contractor of, the Borrower;

                  1.3.7 due from any  Guarantor  or any past,  present or future
        affiliate, parent or subsidiary of BBI, BTRL or NACL;

                  1.3.8  due from  Account  Debtors  with  respect  to which the
         Borrower is an Account  Debtor (to the extent of the amount  payable by
         Borrower);

                  1.3.9 based on delivery of goods on  consignment  or otherwise
         on "sale on approval",  "sale or return" or similar  terms  (whether or
         not compliance has been made with Section 2-326 of the UCC); or

                  1.3.10 determined by the Lender, in the exercise of reasonable
         judgment,  to be difficult to collect, to be of diminished or uncertain
         value,  or in  which  the  Lender  may not  have a  perfected  security
         interest pursuant to the provisions of the Financing Instruments.

         Notwithstanding  the foregoing,  if at any time, fifty percent (50%) or
         more of the Accounts due from any particular  patient Account Debtor of
         NACL remain unpaid (in whole or in part) after the passage of more




         than ninety (90) days from the  respective  dates of each such  patient
         Account invoice from NACL, then from and after such determination, none
         of the Accounts  (then  existing or  thereafter  arising) due from such
         patient  Account  Debtor shall be deemed to be Eligible  Accounts until
         such time as all patient  Accounts due from such patient Account Debtor
         are no more than  ninety  (90) days past due from date of  invoice as a
         result of actual payments received thereon.

         In addition,  Eligible  Accounts shall not include Accounts relating to
         Existing Government  Contracts (as hereinafter defined) until such time
         as the same have been novated  into the name of BTRL and are  otherwise
         in full compliance with 48 C.F.R.  ss.42.12 (1991) to the  satisfaction
         of Lender;

         Characterization  of any  account  due  from an  Account  Debtor  as an
         Eligible  Account shall not be deemed a determination  by the Lender as
         to its actual  value nor in any way  obligate  the Lender to accept any
         Account  subsequently  arising  from such  Account  Debtor to be, or to
         continue  to open  such  account  to be,  an  Eligible  Account;  it is
         Borrower's  responsibility to determine the creditworthiness of Account
         Debtors and all risks  concerning  the same and  collection of Accounts
         are with  Borrower.  All  Accounts  whether  or not  Eligible  Accounts
         constitute Collateral hereunder.

         1.4  "Eligible Equipment" shall mean

                  1.4.1    that  part  of  BBI's  Equipment  purchased  in  1994
                           appraised  by the  appraisal  dated  August  9,  1994
                           conducted by Frank Ronne & Associates, which Eligible
                           Equipment is listed in Exhibit 1.4.1 annexed hereto;

                  1.4.2    Equipment owned by BTRL (the "BTRL Equipment"), which
                           was  appraised  by  appraisal  dated  August  9, 1994
                           conducted by Frank Ronne & Associates, which Eligible
                           Equipment is listed in Exhibit 1.4.1 annexed hereto;

                  1.4.3    Equipment owned by NACL (the "NACL Equipment"), which
                           was  appraised  by  appraisal  dated  August  9, 1994
                           conducted by Frank Ronne & Associates, which Eligible
                           Equipment is listed in Exhibit 1.4.1 annexed  hereto;
                           and

                  1.4.4    Equipment  to be  purchased  by  the  Borrower  ("New
                           Eligible Equipment").

         1.5 "Eligible  Inventory" shall mean that part of BBI's Inventory which
the  Lender  determines,  from  time to time and in its sole  discretion,  to be
eligible for purposes of determining the Calculated Amount;

         1.6 "Equipment"  shall mean all motor vehicles  (whether or not subject
to motor vehicle  registration),  rolling stock,  machinery,  furniture,  office
equipment, plant equipment,  laboratory equipment, fixtures, tools, spare parts,
accessories, dies, molds and all other like goods, property and assets owned now
or hereafter by Borrower and used in the operation or  furtherance of Borrower's
business  (whether or not Eligible  Equipment or New  Eligible  Equipment);  and
"equipment" as defined in the UCC;

         1.7 "Equipment  Collateral"  shall mean all Equipment and all Documents
(whether negotiable or non-negotiable) which relate to Equipment;

         1.8 "Existing Government  Contracts" means the United States contracts,
subcontracts  and  agreements  relating  to BTRL which are listed on Exhibit 1.8
annexed hereto;

         1.9  "Financing  Instruments"  shall  mean  and  refer  to any  and all
agreements  (including  this  Agreement),   Instruments,  Documents,  and  other
writings including without  limitation,  security  agreements,  loan agreements,






notes,   guarantees,   mortgages,   deeds  of  trust,   collateral  assignments,
subordination agreements,  contracts,  notices, leases, financing statements and
all other written matter,  whether heretofore,  now, or hereafter executed by or
on behalf of the Borrower and  delivered  to the Lender in  connection  with the
transactions  described in this Agreement or contemplated hereby,  together with
all agreements and documents referred to therein or contemplated thereby;

         1.10  "GAAP"  shall  mean and refer to  generally  accepted  accounting
principles in the United States;

         1.11  "Inventory"  shall mean and refer to any and all of the following
owned  by  Borrower:  goods,  wares,  merchandise,   raw  materials,   supplies,
components,  work in process,  finished  goods and all  packaging,  advertising,
shipping material, labels and other devices, names, or marks affixed thereto for
purpose of selling the same; tangible personal property held by the Borrower for
processing,  sale,  license,  or lease,  or  furnished or to be furnished by the
Borrower  under  contracts  of sale or service or to be used or  consumed in the
Borrower's business (whether or not Eligible Inventory); items referred to above
which are in transit,  returned,  rejected,  repossessed or detained (whether or
not Eligible Inventory); and "inventory" as defined in the UCC;

         1.12 "Inventory  Collateral" shall mean all Inventory and all Documents
(whether negotiable or non-negotiable) which relate to Inventory;

         1.13 "IRC" shall mean and refer to the  Internal  Revenue Code of 1986,
as amended,  and  regulations as promulgated  and in effect,  from time to time,
thereunder;

         1.14 "Liens" shall mean and refer to any and all:  mortgages,  pledges,
security interests,  encumbrances,  liens, or charges of any kind including, but
not limited to,  agreements to give any of the foregoing;  conditional  sales or
other  title  retention  agreements  or  devices,  or any  leases in the  nature
thereof;  and the filing of, or agreement to give, any financing statement under
the Uniform Commercial Code of any jurisdiction;

         1.15  "Obligations"  shall mean and refer to any and all  indebtedness,
liabilities, duties, undertakings,  covenants and agreements (including those of
payment or of  performance)  of the  Borrower to the Lender,  all of every kind,
nature and  description,  and  arising  pursuant  to the terms of the  Financing
Instruments or otherwise, including, without limitation:

                  1.15.1  Borrower's  liability to repay the Loans  (hereinafter
         defined),  together  with the payment of all  interest and other monies
         due  pursuant  to the  terms  of any  and  all  notes,  and any and all
         substitutions,  renewals, extensions,  amendments and rewritings of the
         Loans  or  such  notes  and  all  present  and  future   advances  made
         thereunder;

                  1.15.2 the faithful performance and observance by the Borrower
         of all agreements, covenants and conditions contained in this Agreement
         and in each of the other Financing Instruments; and

                  1.15.3  any and all such  indebtedness,  liabilities,  duties,
         undertakings, covenants and agreements whether or not the same are: now
         existing or hereafter arising;  imposed by agreement or by operation of
         law;  due  or  not  due,   absolute  or   contingent,   liquidated   or
         unliquidated,   voluntary  or  involuntary;  evidenced  by  a  writing;
         presently  contemplated  by the  parties;  the  joint  or  the  several
         liabilities of the Borrower;  direct or indirect;  related or unrelated
         to the  transactions  described  in or  contemplated  by the  Financing
         Instruments;  liabilities  or  undertakings  of the Borrower as surety,
         guarantor or endorser with respect to  obligations of one or more other
         parties;  specifically  described  as secured or  unsecured;  hereafter
         acquired by Lender by  assignment,  other transfer or operation of law;
         the result of any transaction  whatsoever  between the Borrower and the
         Lender;  or by reason of any cause of action  which the Lender may have
         against the Borrower.







         1.16  "Persons"  shall  mean  and  refer  to any and  all  individuals,
corporations,  partnerships, joint stock associations, business or other trusts,
governments  or any agencies or  subdivisions  thereof,  joint ventures or other
entities or associations whatsoever;

         1.17 "UCC"  shall mean the  Uniform  Commercial  Code as in effect from
time to time in the Commonwealth of Massachusetts;

         1.18 The following terms shall have the respective meanings ascribed to
them  in  the  UCC:  "Account  Debtor",   "Chattel  Paper",  "Deposit  Account",
"Document", "Equipment", "General Intangibles" and "Instrument";

         1.19  Terms  defined   elsewhere  in  this  Agreement  shall  have  the
respective meanings ascribed to them where so defined;

         1.20 All exhibits to this Agreement are hereby  incorporated  herein by
reference;

         1.21 The use of the  singular  of terms which are defined in the plural
shall mean and refer to any one of the matters or items or entities  included in
such definition; and

         1.22 Use of the  connective  "or" is not intended to be exclusive;  the
term  "may  not"  is  intended  to be  prohibitive  and not  permissive;  use of
"includes"  and  "including"  is intended to be  interpreted  as  expansive  and
amplifying  and not as limiting in any way;  and  pronouns  used herein shall be
deemed to include the singular and the plural and all genders.

                                    SECTION 2

                        ESTABLISHMENT OF LOAN ACCOUNT AND
             DESCRIPTION OF LOAN ARRANGEMENTS AND CREDIT FACILITIES
             ------------------------------------------------------

         Upon  all  the  terms  and  conditions  established  by  the  Financing
Instruments,  the  Lender and the  Borrower  agree to enter  into  certain  loan
transactions,  pursuant to which the Lender agrees to lend (or otherwise  extend
credit or provide other financial  accommodations)  to or for the benefit of the
Borrower,  and the Borrower agrees to borrow (or otherwise guarantee,  undertake
to repay or be  liable  for) the  amount  and the  Obligations  described  below
(altogether,  the  "Loans"),  and the Lender hereby opens for and in the name of
the Borrower one or more loan  accounts  for the purposes of  administering  the
following Loans:

         2.1 Amounts and Type of Loans;  Notes Evidencing  Loans. The respective
amounts and types of the Loans shall be:

                  2.1.1  a  Three   Million   Five  Hundred   Thousand   Dollars
         ($3,500,000)  term revolving line of credit (the "Line of Credit") (the
         authorized  maximum principal amount  outstanding from time to time, of
         which  shall not exceed the  Borrowing  Base),  which is  evidenced  by
         Borrower's  Second Amended and Restated Term Revolving  Promissory Note
         (the "Line of Credit  Note")  dated of even date  herewith  in the face
         amount of the Line of Credit Maximum Amount;

                  2.1.2 a term loan in the  original  principal  amount of Eight
         Hundred  Forty-nine  Thousand  Dollars  ($849,000)  (the  "Amended  and
         Restated Term Loan"),  evidenced by the Borrower's Amended and Restated
         Term  Promissory  Note (the  "Amended  and  Restated  Term Note") dated
         October 11, 1994;






                  2.1.3 a term  loan in the  original  principal  amount  of Two
         Hundred  Thousand  Dollars   ($200,000)  (the  "$200,000  Term  Loan"),
         evidenced by the Borrower's  Term  Promissory  Note (the "$200,000 Term
         Note") dated October 11, 1994 in the face amount of the full  principal
         thereof; and

                  2.1.4 a term loan in the  original  principal  amount of Three
         Hundred Fifty Thousand  Dollars  ($350,000) (the "$350,000 Term Loan"),
         evidenced by the Borrower's  Term  Promissory  Note (the "$350,000 Term
         Note")  dated of even  date  herewith  in the face  amount  of the full
         principal thereof.

(The Line of Credit Note,  the Amended and Restated Term Note, the $200,000 Term
Note  and the  $350,000  Term  Note  may each be  referred  to as a  "Note"  and
collectively as the "Notes".)

         2.2 Interest Rate on Loans. The principal amount outstanding, from time
to time,  of each of the Loans  shall  bear  interest  at the  respective  rates
applicable to each Loan in accordance with the provisions of the Notes.

         2.3  Repayment of Loans.  Principal  and interest of the Loans shall be
paid to the Lender in accordance with the provisions of the Notes.

         2.4  Security  for the Loans.  All of the Loans shall be secured by the
security  interests  granted  in the  Collateral  (as  hereinafter  defined)  as
provided by this Agreement.

         2.5  Use of Proceeds.  The proceeds of the Loans shall be used:

                  2.5.1 with respect to the Line of Credit,  for working capital
         purposes;

                  2.5.2 with  respect to the  Amended  and  Restated  Term Loan,
         advances up to the full amount of the  Amended and  Restated  Term Note
         have  been  made  for  the  purchase  by  the  Borrower  of  laboratory
         equipment,  furniture and computer equipment,  and to pay down the Line
         of Credit;

                  2.5.3 with respect to the $200,000  Term Loan,  advances up to
         the full amount of the  $200,000  Term Loan have been made for purposes
         of the  purchase  and  installation  by BBI,  BTRL and NACL of Eligible
         Equipment; and

                  2.5.4 with respect to the $350,000 Term Loan,  advances  shall
         be made at the request of the  Borrower  from time to time for a period
         of six (6) months from the date hereof for  purposes of the purchase of
         New Eligible Equipment, but such advances shall not exceed seventy-five
         percent (75%) of the purchase price of such New Eligible Equipment.

         2.6 Loan  Advances.  After  the  date  hereof,  Loans  shall be made by
advances by the Lender to one or more of the accounts maintained by the Borrower
pursuant to Section  4.2.6 hereof  (hereafter,  the "Main  Operating  Account").
Subject  to the terms and  conditions  hereof,  the Lender may make Loans to the
Borrower (i) to cover checks drawn by Borrower on the Main Operating Account and
(ii) to cover  other  authorized  charges  whether  given to the Lender  orally,
telephonically  or in writing and (iii) to cover  other  charges due and payable
hereunder.  As an  accommodation  to the Borrower,  and to facilitate  the "zero
balance account" relationship  contemplated by this Agreement,  and to avoid the
necessity  that the Lender  communicate  with the Borrower  each time checks are
presented for payment against the Main Operating Account,  the Borrower requests
the Bank to make a Loan charged to the Loan Account  sufficient  to cover checks
and other authorized  charges on each occasion that the same are presented.  All
actions of the Lender in  connection  with the  ordinary  administration  of the
foregoing are hereby  ratified and confirmed and shall be conclusive and binding
upon the  Borrower.  Each request by the Borrower to Lender for an advance under
the Line of Credit or the $350,000 Term Loan shall  constitute a  representation
by  the  Borrower  that  as of  the  date  of  such  request  (a)  each  of  the
representations and warranties set






forth  herein  are  true,  (b) the  Borrower  is in  compliance  with all of the
covenants,  terms and conditions hereof, and (c) no event or circumstances exist
which constitute or with the lapse of time or notice,  or both, would constitute
or result in the occurrence of an Event of Default (as hereinafter defined).

         2.7 Other  Advances  and  Payments.  Whether or not the  entire  amount
available  under  the Line of Credit  shall  have  been  advanced  to or for the
benefit  of the  Borrower,  and  whether or not the Loans  shall be payable  (by
maturity or by  acceleration)  or an Event of Default shall have occurred  under
this Agreement, the Lender shall be entitled (but shall not be obligated and may
not be required) to make, at its sole discretion,  additional advances from time
to time:

                  2.7.1 in payment or reimbursement,  as the case may be, of any
         and  all  payments  made  or  amounts  owing   pursuant  to  applicable
         provisions of the Financing Documents;

                  2.7.2 to pay the Lender's usual and customary  charges for (a)
         services rendered by it to the Borrower at the Borrower's request which
         charges relate to the Obligations;  and (b) charges otherwise  required
         to be paid by the Borrower pursuant to this Agreement; and

                  2.7.3  otherwise  to or for the  benefit of the  Borrower,  as
         requested  or consented  to by the  Borrower,  as the Lender may in its
         discretion deem proper or expedient;

and each such additional advance shall be a part of the Obligations and shall at
all times be subject to the terms and  conditions of this  Agreement and secured
as provided in the Financing Instruments.

         2.8 Loan Statements. All advances to or for the benefit of the Borrower
pursuant  to this  Agreement  shall be charged to the loan  account or  accounts
opened in the Borrower's  name on the Lender's  books.  The Lender  periodically
shall  render to the  Borrower  statements  of such loan  account  or  accounts,
setting  forth the daily loan  balance  and total  accrued  interest  during the
subject  period,  which,  when so  rendered,  shall be  considered  prima  facie
evidence  of the  correctness  thereof  except  to the  extent  that the  Lender
receives  written  notice of any  exceptions  proposed by the Borrower  within a
reasonable  time,  but in no event later than one hundred twenty (120) days from
the date of such statement. If for any reason the Borrower has not paid interest
charges and/or any fees for services, expenses incurred or other charges owed to
the Lender by the Borrower, the Lender, at its option and discretion, may at any
time or times debit such  charges,  expenses,  and fees to the  Borrower's  loan
account and such amounts shall be added to the principal amount thereof,  or the
Lender  may  debit  such  interest,  charges  and  fees,  and any  other  unpaid
Obligations  then due,  to any deposit or other  account of the  Borrower at the
Lender.  Such debits shall not constitute a waiver of any Event of Default.  Any
item received in payment towards the Borrower's  outstanding  indebtedness which
requires  clearance or payment  shall not be  considered  to have been  credited
until final clearance and final payment.







         2.9  Additional  Term  Loan.  Provided  that  there  exists no Event of
Default  hereunder,  and no event shall have occurred  which with the passage of
time or the  giving  of  notice,  or both,  could  become  an  Event of  Default
hereunder,  the Lender agrees to provide the Borrower,  by January 1, 1996, with
an  additional  term loan in an  original  principal  amount  not to exceed  One
Hundred Thousand  Dollars  ($100,000) for purposes of paying down the balance of
the Line of Credit  then  outstanding.  Such  additional  term loan shall have a
five-year term and shall be upon such additional  terms, and shall bear interest
at a rate,  as shall  be  determined  by the  Lender  in its  sole and  absolute
discretion.

         2.10 Review of Line of Credit. The Lender agrees (a) to review the Line
of Credit  annually on or before  July 30 of each year  commencing  in 1996,  to
determine  whether the  Maturity  Date (as  defined in the Line of Credit  Note)
thereof  will be  extended  for an  additional  twelve-month  period  beyond the
Maturity  Date  then  in  effect;  and  (b)  to  notify  the  Borrower  of  such
determination  in  accordance  with  the  notice  provisions  of the  Agreement.
Notwithstanding  the foregoing,  any  determination  by the Lender to extend the
Maturity Date shall not be binding and enforceable  against the Lender until the
execution of an Extension Agreement, executed by the parties hereto.

                                    SECTION 3

                         SECURITY INTEREST IN COLLATERAL
                         -------------------------------

         3.1 Granting  Clause;  Description of  Collateral.  As security for the
prompt  and  full  repayment  (and  performance  as  the  case  may  be)  of the
Obligations,  the Borrower  hereby  grants to the Lender a  continuing  security
interest in and to all of the  Borrower's  present and future  right,  title and
interest in and to the  following  assets and  property,  and each item thereof,
whether now or  hereafter  existing,  owned or acquired by  Borrower,  or now or
hereafter arising or due or to become due, wherever such assets and property may
be  located,   together  with  all   substitutions,   replacements,   additions,
accessions,  products and proceeds (of every kind and nature, cash and non-cash,
including,  without  limitation,  insurance  proceeds and proceeds  which may be
property of any type  described  below) of or to any of the  following,  (all of
which, together with any other property in which the Lender may in the future be
granted a security interest to secure the Obligations,  is collectively included
within the meaning of "Collateral" as used herein):

                  3.1.1 all Inventory and all Documents  (whether  negotiable or
         non-negotiable);

                  3.1.2 all  Accounts  (whether  or not  Eligible  Accounts  for
         purposes of determining  the Borrowing Base  hereunder);  all rights of
         Borrower to draw under letters of credit; and all rights of Borrower in
         and to the  Inventory  which gave rise to any  Account,  and all liens,
         guaranties and security  granted to or held by Borrower with respect to
         Accounts or other  obligations  owing to Borrower (all of the foregoing
         are collectively referred to herein as the "Receivables Collateral");

                  3.1.3 all contract rights, including,  without limitation, all
         rights to payment under Existing Government Contracts and contracts not
         yet earned by performance and not evidenced by an Instrument or Chattel
         Paper;

                  3.1.4 all General  Intangibles,  including without  limitation
         all goodwill,  customer  lists,  judgments,  licenses,  permits,  trade
         names, logos, trademarks,  service marks, patents, patent applications,
         copyrights,   blueprints,   drawings,   designs,   papers,   rights  to
         performance,   intellectual   property,   trade  secrets,   proprietary
         processes,  developmental  ideas and concepts,  and proprietary rights,
         information and property of any kind and nature;

                  3.1.5 all Equipment,  whether or not Eligible Equipment or New
         Eligible Equipment;






                  3.1.6 all items of tangible and intangible  personal  property
         of any and every kind and description which are not otherwise described
         in this subsection 3.1;

                  3.1.7 all Instruments  (whether  negotiable or non-negotiable,
         and  regardless  of their  being  attached to Chattel  Paper),  Chattel
         Paper,  policies and certificates of insurance,  securities,  deposits,
         Deposit Accounts, money, cash and other property;

                  3.1.8 all liens,  guarantees,  rights, remedies and privileges
         pertaining to any of the Collateral, including the right of stoppage in
         transit;

                  3.1.9  all  federal,  state,  and  local  tax  refunds  and/or
         abatements to which the Borrower is, or becomes, entitled no matter how
         or when arising,  including  but not limited to any loss  carryback tax
         refunds;

                  3.1.10 all books,  records and information  relating to any of
         the Collateral or the operation of the Borrower's  business in whatever
         medium  the same may be  stored,  contained,  recorded  or  maintained,
         including without  limitation all electronically  recorded  information
         and all  rights of  access  to such  books,  records  and  information,
         computer software and information (and all rights,  programs,  manuals,
         storage,  backup,  service  contracts,  licenses  and source codes with
         respect  thereto),  and all  property in which such books,  records and
         information are stored, contained, recorded or maintained; and

                  3.1.11 all insurance proceeds,  refunds,  and premium rebates,
         whether  arising out of insurance  relating to any of the  foregoing or
         otherwise.

         3.2 Certain  Representations,  Warranties,  and Covenants Regarding the
Collateral. In addition to the warranties,  representations and covenants of the
Borrower set forth  elsewhere in this Agreement,  the Borrower hereby  warrants,
represents, and covenants as follows:

                  3.2.1 Lock Box Agreement.  The Borrower  shall  hereafter make
         collection of all  Receivables  Collateral in accordance with the terms
         and  provisions  of the form of Lock Box Agreement  attached  hereto as
         Exhibit  3.2.1  (the  "Lock  Box  Agreement"),  and  shall  immediately
         instruct its Account Debtors to remit all payments,  including  without
         limitation all checks, drafts, cash,  instruments,  and other items and
         forms of payment which represent, or constitute proceeds or collections
         of,  the  Receivables  Collateral,  in  accordance  with the  terms and
         provisions  of the Lock  Box  Agreement.  Upon  receipt,  Lender  shall
         deposit all such  Receivables  Collateral in a collateral  account with
         the Lender (the  "Collateral  Account"),  subject to the  provisions of
         this  subsection  3.2.1.  After  allowing  two (2)  business  days  for
         collection  of checks and other  instruments,  Lender  will credit (but
         conditional upon final  collection) such payments to Borrower's Line of
         Credit loan account (except foreign  collection items received by check
         of a foreign bank drawn on U.S.  Dollars  which shall be credited  when
         actually received in immediately  available funds by the Lender).  Such
         credits  shall be  conditional  upon  final  payment in cash or solvent
         credits of the items  giving rise to them.  If any item is not so paid,
         the Lender, in its discretion, whether or not the item is returned, may
         either reverse any credit given for the item or charge it to Borrower's
         Deposit Account.  Any surplus remaining in the Collateral Account after
         payment of any then due amounts under the Loans shall be then deposited
         in  Borrower's  Deposit  Account  and may be used  by  Borrower  in its
         discretion subject to the terms and conditions of this Agreement.

                  3.2.2  Schedules  and  Assignments  of   Accounts/Consents  to
         Assignments.  As and to the  extent  the  Lender  may from time to time
         request,   the  Borrower   shall  provide  the  Lender  with  schedules
         describing  all Accounts  created or acquired by the Borrower,  and the
         Borrower shall execute and deliver written assignments of such Accounts
         to the Lender,  including without limitation the Collateral





         Assignments  contemplated  by Section  4.2.15  hereof when  applicable,
         provided,  however,  that the Borrower's failure to execute and deliver
         such  schedules  and/or  assignments  shall  not  affect  or limit  the
         Lender's  security  interest  or other  rights in and to each  Account.
         Together with each schedule so  requested,  the Borrower  shall furnish
         its sales and cash  journals or  equivalents  acceptable to the Lender,
         and shall warrant the genuineness  thereof. the Borrower shall also, on
         request of the Lender,  furnish the Lender with the  original  shipping
         and/or delivery receipts for all merchandise sold.

                  3.2.3 Bona Fide Accounts.  The Borrower  hereby  warrants that
         all Accounts are and will be bona fide existing  obligations created by
         the sale and delivery of  merchandise  (not on consignment or approval)
         or the  rendition of services to  customers  in the ordinary  course of
         business,  free of Liens,  and  unconditionally  owed to the  Borrower,
         without  defense,  offset  or  counterclaim,  or that in the  event the
         Borrower  becomes aware of the existence of a claim of defense,  offset
         or  counterclaim,  the Borrower will promptly notify the Lender of such
         status of any such Account,  and the portion of such Account subject to
         defense,  offset or counterclaim shall be excluded from  classification
         as an Eligible  Account until such time as the Lender is satisfied that
         such  Account  is no  longer  subject  to claim of  defense,  offset or
         counterclaim.

                  3.2.4  Notification  To  Account  Debtors  and  Others  by the
         Lender.  The Lender or the Lender's  designee may, at any time or times
         thereafter,  with notice to the Borrower  (given  before,  concurrently
         with or within a  reasonably  prompt  time  thereafter,  except that no
         notice  shall be required if an Event of Default  has  occurred  and is
         continuing),  notify  customers  or Account  Debtors  of the  Borrower,
         either in the name of the Lender or the  Borrower,  that  Accounts have
         been  assigned  to the Lender  and of the  Lender's  security  interest
         therein,  and may instruct such  customers and Account  Debtors to make
         payment  directly  to  the  Lender  or  such  other  address  as may be
         specified by the Lender,  and the Lender may collect  directly from the
         obligors  thereon  all  amounts  due  on  account  of any or all of the
         Collateral  and may charge the  collection  costs and  expenses  to the
         Borrower,  and the Lender may, at any time or times,  advise any Person
         of the Lender's security interest in and to the Collateral.

                  3.2.5 Allowances and  Adjustments.  Unless and until otherwise
         directed by the Lender acting in its sole discretion,  the Borrower may
         grant such  allowances or other  adjustments to Account  Debtors as may
         reasonably accord with sound business  practice;  provided however that
         no extension of time for payment shall be granted  without the Lender's
         prior written  consent and provided that the Borrower shall furnish the
         Lender with all reports required hereby with respect to such allowances
         and adjustments.  If any Inventory is returned to or repossessed by the
         Borrower (other than for any routine  warranty,  modification or repair
         service) or is downgraded in quality or has its marketability adversely
         affected, or is detained from or refused entry to the United States, or
         required  to be removed  from the United  States,  the  Borrower  shall
         report any such  occurrence to the Lender in writing in accordance with
         the  provisions  hereof,  and if within three (3) days after receipt by
         the Lender of such written  report  thereof,  the Lender fails to issue
         specific  instructions to the Borrower  concerning such Inventory,  the
         Borrower shall have the right to dispose of the same in accordance with
         sound business  practices,  subject,  however, to the Lender's security
         interest  therein and in any  Collateral  arising from the  disposition
         thereof.  Upon the  occurrence  of an Event of Default,  the Lender may
         settle or adjust disputes and claims directly with customers or Account
         Debtors  for  amounts  and  upon  terms  which  the  Lender   considers
         advisable,  and in all cases the Lender will credit the Borrower's Line
         of Credit loan account with only the net amounts received by the Lender
         in payment of such Accounts.

                  3.2.6 Notification To Account Debtors by the Borrower.  At the
         request  of the Lender  made at any time or times,  the  Borrower  will
         provide written  notifications to any or all of the Borrower's  Account
         Debtors concerning the Lender's security interest in the Collateral and
         will request that such Account Debtors forward payment thereof directly
         to the Lender or as the Lender may direct.






                  3.2.7 Title to  Collateral.  Except for the security  interest
         hereby granted or previously granted and the Permitted Encumbrances (as
         hereinafter defined), the Borrower is and shall remain the owner of the
         Collateral  free from all  Liens,  and the  Borrower  will  defend  the
         Collateral  against  all claims and  demands of all persons at any time
         claiming the same or any interest therein,  and, except with respect to
         the Permitted Encumbrances,  no financing statement covering any of the
         Collateral  is on file in any public  office in any  jurisdiction.  The
         Borrower will promptly upon learning  thereof  report to the Lender all
         matters  materially  adversely  affecting the value,  collectibility or
         enforceability of any Collateral. The Borrower does not have presently,
         and  shall  not  have   hereafter,   possession  of  any  Inventory  on
         consignment.

                  3.2.8  Actions  To  Maintain  Perfection.  From  time to time,
         whether or not  requested  by the Lender,  the  Borrower  will take all
         steps and actions necessary in order to create,  confirm and maintain a
         valid and  perfected  security  interest  in favor of the Lender in the
         Collateral,  subject only to the Permitted Encumbrances,  and will join
         with the Lender in taking any such actions reasonably  requested by the
         Lender,  including without  limitation  executing one or more financing
         statements in form satisfactory to the Lender, and will pay the cost of
         filing the same in all public offices  wherever filing is deemed by the
         Lender to be  necessary  for the purpose of  creating,  perfecting,  or
         maintaining  the  perfection  or  priority  of the  security  interests
         granted herein;  and the Borrower will from time to time at the request
         of the Lender  also do, or execute and  deliver,  such  additional  and
         further  acts,  things,   assurances  and  instruments  as  are  deemed
         desirable by the Lender in order to more  completely vest in and assure
         to the Lender all of its rights hereunder and in or to the Collateral.

                  3.2.9  Lender's  Payment of Taxes and Other  Payments.  At the
         Lender's option, the Lender may at any time or times (but shall have no
         obligation to):

                           3.2.9.1 discharge taxes, Liens, or security interests
                  or other encumbrances (other than Permitted Encumbrances,  and
                  other than taxes being  contested in good faith in  accordance
                  with and to the extent permitted by this Agreement,  unless in
                  either  case an Event of Default  shall have  occurred  and be
                  continuing)  at any time  levied,  placed or  assessed  on the
                  Collateral;

                           3.2.9.2 pay for  insurance on the  Collateral  if the
                  Borrower shall at any time fail to maintain such insurance, or
                  if the Lender  shall at any time  receive  notice or otherwise
                  become  aware that such  insurance  may be cancelled or become
                  cancelable within twenty (20) days; and

                           3.2.9.3 pay for the maintenance  and  preservation of
                  the Collateral.

         The Borrower shall  reimburse the Lender on demand for any payment made
         or  expense   incurred  by  the  Lender   pursuant  to  the   foregoing
         authorization,  and such  obligation  to  reimburse  the  Lender  shall
         constitute part of the Obligations secured by this Agreement.

                  3.2.10 Verification. The Borrower hereby authorizes the Lender
         to  verify  the  Collateral,   and  any  portion   thereof,   including
         verification  with Account  Debtors,  and with the  Borrower's  billing
         companies,  collection  agencies,  and accountants at any time and from
         time to time, and to sign the Borrower's  name to any notice to Account
         Debtors or any notice relative to such verification of Collateral.

                  3.2.11  Location  of  Collateral.  Such of the  Collateral  as
         constitutes  tangible  property  will  be  kept  at  all  times  at the
         Borrower's  Notice  Address or at the Maryland  Office (as  hereinafter
         defined) or the Connecticut Office (as hereinafter  defined),  wherever
         the same is  currently  located.  The  Borrower  will not  remove  such
         Collateral from such location  without the prior written consent of the
         Lender.  All the




         Borrower's books and records regarding  Collateral are and will be kept
         and maintained at the Borrower's  Notice Address or at BTRL's principal
         office  at 3 Taft  Court,  Rockville,  Maryland  20850  (the  "Maryland
         Office") or at NACL's  principal  office at 75 North Mountain Road, New
         Britian,  Connecticut  06053 (the "Connecticut  Office"),  wherever the
         same  are  currently  located  and  shall  not be  removed  from  those
         locations without the Lender's prior written consent.

                  3.2.12  Powers of Attorney.  The Borrower  hereby  irrevocably
         constitutes  and appoints the Lender as the Borrower's  true and lawful
         attorney,  with full  power of  substitution  (in each case at the sole
         risk,  cost and  expense  of the  Borrower  but for the  benefit of the
         Lender) to do the following:

                           3.2.12.1  at any  time or  times  (whether  or not an
                  Event of Default has occurred), to file and record without the
                  Borrower's signature,  or sign the Borrower's name to and file
                  and record,  financing  statements  and any other  instruments
                  (including without limitation  applications to name the Lender
                  as lienholder on any motor  vehicle or other  Certificates  of
                  Title),  and to take such other actions as the Lender may deem
                  necessary in order to,  perfect or maintain the  perfection or
                  priority  of or  disclose  or protect  the  Lender's  security
                  interests in the Collateral or any portion thereof; to receive
                  and open the  Borrower's  mail,  remove  therefrom and hold or
                  apply any  Collateral  and  dispose  of such mail or turn over
                  such mail (other than such  Collateral) to the Borrower or any
                  trustee  in  bankruptcy,  receiver,  assignee  for  benefit of
                  creditors  or other legal  representatives  to whom the Lender
                  determines  to be the  appropriate  Person  to turn  over such
                  mail;  to  endorse  the name of the  Borrower  in favor of the
                  Lender upon any and all checks,  drafts,  notes, money orders,
                  acceptances and other items, Instruments and forms of payment,
                  and to sign and  endorse  the  name of the  Borrower  on,  and
                  receive as secured party,  any of the Collateral;  to sign the
                  Borrower's name to any invoices, schedules, freight or express
                  receipts,  bills of lading, and other Documents or writings of
                  a similar or different nature, relating to the Collateral;  to
                  sign the name of the Borrower on any schedules and assignments
                  of  Accounts,   and  on  notices  of   assignment,   financing
                  statements   and  other   public   records   relating  to  the
                  Collateral,  and  on any  notice  to  the  Borrower's  Account
                  Debtors for verification of the Receivables Collateral; and to
                  receive  and  apply  any  proceeds  of any  Collateral  and to
                  otherwise  exercise  any rights or remedies  available  to the
                  Lender hereunder or under any of the Financing  Instruments or
                  otherwise  under  agreement or  applicable  law, to the extent
                  exercisable  or  available  to the Lender prior to an Event of
                  Default; and

                           3.2.12.2  at any  time or  times  after  an  Event of
                  Default has  occurred  and is  continuing,  in addition to the
                  actions described in subsection  3.2.12.1 above, to prosecute,
                  defend,  compromise  or  release  any action  relating  to the
                  Collateral;  to notify the post office  authorities  to change
                  the address for delivery of the Borrower's  mail to an address
                  designated by the Lender,  and to sign change of address forms
                  therefor;  to sign the  Borrower's  name in proofs of claim in
                  bankruptcies of Account  Debtors,  notices of lien,  claims of
                  mechanics'  liens,  or  assignments  or releases of mechanics'
                  liens  securing the Accounts;  to take any such actions as may
                  be  necessary  to obtain  payment  of any  letter of credit of
                  which the Borrower is a beneficiary;  to repair,  manufacture,
                  assemble,  complete,  package, deliver, alter or supply goods,
                  if any,  necessary to fulfill in whole or in part the purchase
                  order of any  customer  of the  Borrower;  to take any and all
                  other actions (including, without limitation, the right to sue
                  in the name of the  Borrower or the Lender to collect upon any
                  and all Collateral and to settle, adjust or compromise any and
                  all claims  with  respect to  Collateral  including  insurance
                  claims) as the Lender  shall deem  necessary  or  expedient to
                  convert the Collateral  into cash;  and to otherwise  exercise
                  any rights or remedies to the Lender hereunder or under any of
                  the Financing  Instruments,  or otherwise  under  agreement or
                  applicable law.


                  3.2.13  Ratification  and   Indemnification   Under  Power  of
         Attorney.  In connection  with all powers of attorney set forth in this
         Agreement or in the other Financing Instruments,  the Lender shall have
         full power to  exercise  such  powers as fully and  effectually  as the
         Borrower  might or could do; and the  Borrower  agrees  that the Lender
         shall not be obligated to exercise any of the powers authorized herein,
         and shall be free to exercise or refrain  from  exercising  any of such
         powers at any time or times in its  absolute  discretion,  and,  if the
         Lender  elects  to  exercise  any  of  such  powers,  it  shall  not be
         accountable  for more  than it  actually  receives  as a result of such
         exercise of power,  and shall not be responsible to the Borrower except
         for the  Lender's  actual bad faith or gross  negligence;  and that all
         powers conferred upon the Lender by this Agreement,  being coupled with
         an interest,  shall be irrevocable  until such time as all  Obligations
         have been paid or performed and the Lender's agreement to make advances
         has terminated.

                  3.2.14  Motor  Vehicle  Certificates  of Title.  The  Borrower
         hereby  represents and warrants  that,  with the exception of Equipment
         which has been  financed in compliance  with Section  4.3.1 hereof,  it
         will  promptly  deliver to the Lender upon request the originals of all
         Certificates  of Title within its  possession or control  pertaining to
         any Equipment owned by it for which Certificates of Title are currently
         issued,  together with a duly completed and executed Application to Add
         Lienholder for each such  Certificate;  and the Borrower  covenants and
         agrees that it will  promptly  deliver to the Lender  upon  request all
         Certificates of Title relating to any Equipment  hereafter  acquired by
         it,  together  with a duly  completed and executed  Application  to Add
         Lienholder  therewith (in form and content satisfactory for filing with
         the appropriate office), and that the Borrower shall not seek to obtain
         any  Certificate  of Title for any Equipment  currently  lacking such a
         Certificate,  and it shall not  attempt  to  recertify  or obtain a new
         Certificate for any Equipment  currently  evidenced by a Certificate of
         Title  (whether  in the  Commonwealth  of  Massachusetts  or any  other
         jurisdiction)  without  first  notifying  the  Lender,  and only if the
         original  of such  Certificate  of Title  properly  names the Lender as
         first lienholder thereon (subject only to any Permitted  Encumbrances),
         in each case duly  perfecting the Lender's  security  interest  granted
         under this Agreement.

                  3.2.15 Audit Fees.  The  Borrower  shall pay to the Lender the
         Lender's  usual audit fees (as determined by the Lender for accounts of
         the type and size of the Borrower)  per audit  conducted by the Lender,
         from time to time, of the Collateral  located outside of Massachusetts,
         plus any  reasonable  out-of-pocket  expenses of the Lender  associated
         therewith.

                  3.2.16 Borrowing Base Determinations. The calculations used to
         determine  the  Borrowing  Base are  intended  solely for  purposes  of
         determining the aggregate amount of Loans which the Lender is presently
         willing to make to the Borrower.  The Borrower and the Lender expressly
         agree  that  such  calculations  are  not  intended  to and  shall  not
         constitute for any purposes:

                           3.2.16.1 a determination  by the Lender of the actual
                  present or future value of any Collateral;

                           3.2.16.2   any   limitation   with   respect  to  the
                  description of Collateral;

                           3.2.16.3 any determination by the Lender with respect
                  to the  creditworthiness  of Account Debtors or any assumption
                  by the Lender of any risk concerning such creditworthiness; or

                           3.2.16.4 any  limitation,  reduction or diminution of
                  the Obligations or the security  therefor,  all as provided in
                  this Agreement and the other Financing Instruments.

         3.3 Inventory Collateral.  With respect to all Inventory Collateral, so
long as no Event  of  Default  has  occurred,  the  Borrower  may sell  items of
Inventory Collateral:

                  3.3.1  Pricing  and Cash  Sales.  for cash in amounts not less
         than the Borrower's  published,  usual or customary  prices,  less only
         usual and customary discounts for volume sales or prompt payment; or

                  3.3.2  Credit  Terms and  Accounts.  on credit terms usual and
         customary in the business  conducted by the  Borrower,  at prices which
         conform  to the  terms of  subsection  3.3.1,  above,  and  under  such
         circumstances as give rise to Accounts subject to this Agreement.

Any  Inventory  Collateral  which will be acquired with proceeds of the Loans is
described on the Master Exhibit.

         3.4    Equipment Collateral.  With respect to all Equipment Collateral:

                  3.4.1 Business Use;  Purchase Money  Acquisitions.  all of the
         Equipment  Collateral  is and  will  be  used  by the  Borrower  in the
         ordinary  course  of  its  business   operations,   and  the  Equipment
         Collateral  which is  being  acquired  with  proceeds  of the  Loans is
         specifically described on the Master Exhibit; and

                  3.4.2 Fixtures.  if any part of the Equipment Collateral is or
         will be a Fixture (as defined in the UCC), the same shall be affixed to
         the real property at the Notice  Address of the Borrower or to the real
         property at the  Maryland  Office or at the  Connecticut  Office and to
         such additional locations as are specifically identified and designated
         in the Master  Exhibit;  and,  with respect to all items of  Collateral
         which are or become  Fixtures  prior to the  perfection  of, or in such
         circumstances  as the  interests of any other Person may have  priority
         over, the security interest granted to the Lender under this Agreement,
         the Borrower will, on demand of the Lender,  furnish to the Lender such
         waivers  or  disclaimers  of  any  and  all  interests  in  and  to the
         Collateral which could claim or have priority over the interests of the
         Lender, in each case in such form and upon such terms as the Lender may
         request.

                                    SECTION 4

                    REPRESENTATIONS, COVENANTS AND WARRANTIES

         In addition to such other representations,  covenants and warranties as
are  contained  herein,  or elsewhere in the  Financing  Instruments  or as have
otherwise been made to the Lender, the Borrower hereby represents, covenants and
warrants that:

         4.1  General Representations, Covenants and Warranties.

                  4.1.1  Business;   Supplemental   Information   Regarding  the
         Borrower.  BBI is  engaged in the  business  of  assaying,  processing,
         manufacturing,  selling,  and distributing human blood-based  products;
         BTRL is engaged in the business of biomedical and biotechnical contract
         research  and  services;  NACL is engaged in the  business of providing
         clinical  reference  laboratory  services;  BBI's  principal  place  of
         business and chief  executive  office and mailing address is located at
         the Notice Address set forth at the beginning of this Agreement; BTRL's
         principal  place of business and mailing  address is the address of the
         Maryland  Office and NACL's  principal  place of  business  and mailing
         address is the address of the Connecticut Office. The Borrower does not
         and will not conduct any  business  under any trade name or trade style
         other  than the  Borrower's  legal  name or as set forth in the  Master
         Exhibit.  Set forth in the Master Exhibit attached hereto are the names
         and  addresses of the  respective  officers and members of the Board of
         Directors  of each  Borrower,  the  name  and  title  of  each  officer
         authorized to execute the Financial  Instruments  and  thereafter  deal
         with the Lender on behalf of the  Borrower,  and  locations  of all the
         Borrower's  other  places  of  business  or  at  which  the  Borrower's
         properties may be kept or located,  which information is true, accurate
         and  complete;  the Borrower  agrees to furnish the Lender with written
         notice



         within  ten  (10)  days  of any  changes  in such  information,  or any
         additional  information  necessary  to insure that said Master  Exhibit
         remains true,  accurate and complete.  Nothing in this subsection 4.1.1
         shall be construed  to permit any action which is otherwise  restricted
         or prohibited pursuant to the terms of this Agreement.

                  4.1.2 Due Organization and Existence;  Authorization.  Each of
         BBI, BTRL and NACL (a) is duly organized,  validly existing and in good
         standing under the laws of the Commonwealth of  Massachusetts,  (b) has
         adequate corporate power and authority to own its properties and assets
         and to carry on its business activities as and where now conducted, (c)
         is  qualified  to do business as a foreign  corporation  and is in good
         standing in each jurisdiction  wherein such qualification is necessary,
         and where the  failure  to so qualify  would  have a  material  adverse
         effect on the  business or property  of the  Borrower,  and (d) has the
         corporate  power and  authority  to  execute  and  deliver  such of the
         Financing  Instruments  as have been executed by it, and to perform the
         Financing Instruments in accordance with the terms thereof.

                  4.1.3 Articles of Organization;  Stock;  Accurate Records. The
         Articles of  Organization  and all  amendments  thereto of each of BBI,
         BTRL and NACL have been duly filed and are in proper order. All capital
         stock  issued  by BBI,  BTRL  and  NACL and  currently  outstanding  is
         properly  issued,  and all books and  records  of BBI,  BTRL and NACL ,
         including  but not  limited to, its minute  book,  by-laws and books of
         account, are accurate and up-to-date and will be so maintained.

                  4.1.4 Binding Documents;  Violation of Other Agreements.  Each
         of BBI, BTRL and NACL has taken all steps required by applicable law to
         make this Agreement, and each of such Financing Instruments, its legal,
         valid and binding obligation  enforceable in accordance with its terms,
         and neither the execution,  delivery nor  performance of this Agreement
         or any of the  Financing  Instruments  is in  violation of any law, the
         Articles of Organization,  Bylaws or other organizational  documents of
         it, or of any other  agreement or  instrument to which it is a party or
         by  which  it or any of its  assets  is or may be  bound,  and does not
         constitute  a  default  under  any of the  foregoing,  or result in the
         creation or imposition  of a Lien upon any of its  properties or assets
         other than that in favor of the Lender.

                  4.1.5  Title To  Assets;  Security  Interests  and  Mortgages;
         Leases; Royalties; etc. The Borrower has title (and good, clear, record
         and  marketable  title  in the  case of real  property)  to all  assets
         reflected  in the  financial  statements  hereinafter  referred  to and
         delivered to the Lender,  and to all assets  acquired since the date of
         said  financial   statements  (other  than  those  assets  subsequently
         disposed  of in the  ordinary  course  of  business),  free of any Lien
         except  in  favor  of  the  Lender   and   except  for  the   Permitted
         Encumbrances.

                  4.1.6 Investments.  The Borrower has no investment,  in equity
         or debt, in any Person other than  obligations  of the United States or
         Deposit Accounts.

                  4.1.7 Litigation;  Outstanding Orders.  Except as disclosed on
         the  Master  Exhibit  attached  hereto,  there are no  actions,  suits,
         proceedings  or  investigations  pending  or, to the  knowledge  of the
         Borrower, any of its agents, servants or employees,  threatened against
         the Borrower or any of its  properties  in any court,  before any other
         tribunal  or  any  federal,  state,  municipal  or  other  governmental
         authority.  The Borrower is not in default with respect to any order of
         any court, or other tribunal or governmental authority.  The execution,
         delivery and  performance  of this  Agreement and each of the Financing
         Instruments  by the Borrower will not constitute a default of any order
         of any court, or any other tribunal or governmental authority.




                  4.1.8  Financial  Statements   Delivered.   The  Borrower  has
         furnished   to  the  Lender   its   financial   statements,   including
         consolidated  balance  sheet and statement of profit and loss as at and
         for the  fiscal  years  ended  December,  1993 and 1994,  as audited by
         Coopers & Lybrand,  LLP. Said financial  statements  fairly present the
         financial  position of the  Borrower  as at the dates  thereof and said
         statement  of  profit  and loss  fairly  presents  the  results  of the
         operations  of the  Borrower  for the fiscal  years  indicated,  all in
         conformity with GAAP consistently applied.

                  4.1.9 Current  Stockholders.  Set forth on the Master  Exhibit
         annexed  hereto and made a part hereof are the names and  addresses  of
         each shareholder of the Borrower holding 5% or more of any class of the
         outstanding  capital stock of the Borrower having ordinary voting power
         and the number of fully paid and non-assessable shares held by each.

                  4.1.10 Other  Liabilities;  Tax Returns;  No Adverse  Changes.
         Except as may be set forth in the Master Exhibit  annexed  hereto,  (a)
         the  Borrower  has  no  knowledge  of  any  contingent  obligations  or
         liabilities  of the Borrower for taxes or long-term  commitments  which
         are not shown in the  balance  sheets  included in said  statements  or
         noted  therein;  (b) the Borrower has filed all required tax returns or
         extensions  therefor  and has paid all  applicable  federal,  state and
         local taxes shown to be due (other  than taxes which may  hereafter  be
         paid  without  penalty)  and  the  Borrower  has  no  knowledge  of any
         deficiency or additional  assessment in connection  therewith for which
         no provision has been made on its books; (c) there has been no material
         adverse change in the business,  properties or condition  (financial or
         otherwise) of the Borrower since the date of the most recent  financial
         statement   referred   to  above  and  (d)  the   Borrower's   Taxpayer
         Identification  Numbers are  04-2652826  (BBI),  04-3152484  (BTRL) and
         04-3196246  (NACL). The Borrower's federal income tax returns have been
         prepared and filed for its fiscal year(s) stated in the Master Exhibit.

                  4.1.11 No Agency Between the Borrower and the Lender.  Nothing
         herein  contained  shall be construed to constitute the Borrower as the
         Lender's agent for any purpose whatsoever,  and the Lender shall not be
         responsible or liable for any shortage,  discrepancy,  damage,  loss or
         destruction  of any  part of any  Collateral  wherever  the same may be
         located and  regardless of the cause thereof other than as a direct and
         proximate  result  of the  Lender's  actual  bad  faith  or  negligence
         provided  however that a standard of "gross  negligence"  shall be used
         with respect to the Lender's  engagement  of third parties with respect
         to the  foregoing.  The Lender does not,  by anything  herein or in any
         assignment or otherwise, assume any of the Borrower's obligations under
         any contract or agreement  assigned to the Lender, and the Lender shall
         not be  responsible  in any way for the  performance by the Borrower of
         any of the terms and conditions thereof.

                  4.1.12  Regulation  U. The Borrower  does not own, nor has any
         present  intention of  acquiring,  any "margin  security" as defined in
         Regulation  U (12  C.F.R.  Part 221) of the Board of  Governors  of the
         Federal Reserve System (herein called a "margin security"). None of the
         proceeds  of the Loans will be used,  directly or  indirectly,  for the
         purpose  of  purchasing  or  carrying  any margin  security  or for the
         purpose of reducing or retiring any  indebtedness  which was originally
         incurred  to  purchase  or carry a  margin  security  or for any  other
         purpose which might  constitute  this  transaction  a "purpose  credit"
         within the meaning of said Regulation U.

                  4.1.13  ERISA.  The  Borrower  has not  incurred  any material
         accumulated  funding  deficiency  within the  meaning  of the  Employee
         Retirement  Income  Security Act of 1974,  as amended,  or incurred any
         material   liability  to  the  Pension  Benefit  Guaranty   Corporation
         established  under such Act (or any successor  thereto under such Act),
         nor does the  Borrower  foresee  that it will  incur any such  material
         accumulated  funding deficiency or material liability in the future, in
         connection with any employee  benefit plan established or maintained by
         the Borrower.  The making of the Loans will not involve any  prohibited




         transaction  within  the  meaning  of the  Employee  Retirement  Income
         Security Act of 1974 or Section 4975 of the Internal  Revenue  Code, as
         amended.  There are no facts known to the Borrower which create,  or in
         the future may (so far as the  Borrower can now  foresee)  create,  any
         withdrawal or other liability of the Borrower under the  Multi-employer
         Pension Plan Amendment Act of 1980.

                  4.1.14 Necessary Permits and Licenses.  The Borrower possesses
         all franchises, rights, certificates,  variances, licenses, permits and
         other  authorizations,  consents and approvals from all administrative,
         regulatory or governmental bodies and all patents, trademarks,  service
         marks,  trade names,  copyrights,  licenses and other  rights,  in each
         case,  free from  burdensome  restrictions,  that are  necessary in any
         material  respect for the ownership,  maintenance  and operation of its
         business,  properties and assets,  and the Borrower is not in violation
         of any thereof in any material respect.

                  4.1.15 Governmental Approvals Not Required. Neither the nature
         of the  Borrower nor its  business or  property,  nor any  relationship
         between  or among  the  Borrower  and any  other  Person  is such as to
         require any consent, authorization, waiver, approval or other action by
         or any notice to or filing with any court or administrative, regulatory
         or  governmental  body,  including,   without  limitation,   government
         agencies,  offices and  instrumentalities  with which the  Borrower has
         contracts,  in  connection  with  the  execution  and  delivery  by the
         Borrower of this  Agreement or the other  Financing  Instruments or the
         fulfillment of or compliance by the Borrower  with, or the  enforcement
         by the Lender of, the terms and provisions hereof or thereof.

                  4.1.16  Adequate  Financing.  The  Borrower  has no  reason to
         believe  that the  proceeds  of the  Loans,  together  with such  other
         sources of funds as are now directly and  immediately  available to the
         Borrower,  will not be adequate to finance its business  operations for
         the terms of the Amended and Restated Term Loan, the $200,000 Term Loan
         and the $350,000 Term Loan.

                  4.1.17 No Event of Default. As of the date hereof,  there does
         not exist any Event of Default or any event  which,  but for the giving
         of notice or the lapse of time or both,  would  constitute  an Event of
         Default under this Agreement, any of the Financing Instruments or under
         the provisions of any instrument  evidencing  any  indebtedness  of the
         Borrower to any other Person.

                  4.1.18  Compliance  with Leases.  The Borrower enjoys peaceful
         and undisturbed  possession as lessee under all leases necessary in any
         material respect for the operation of its business or of its properties
         and  assets,   none  of  which  contains  any  provisions  which  might
         materially  affect or impair  the  operation  of its  business  or such
         properties and assets. All such leases are valid and subsisting and are
         in full force and effect.

                  4.1.19   President   and  Chief   Executive   Officer;   Major
         Stockholder.  RichardET.  Schumacher  shall  continue  to  perform  the
         traditional  functions of President and chief executive  officer of the
         Borrower and shall  continue to exercise the  traditional  authority of
         such officer. In addition,  Richard T. Schumacher shall continue to own
         and exercise  complete control over not less than  twenty-five  percent
         (25%) of the outstanding  capital stock of BBI;  provided  however that
         such  limitation  shall not apply in the event that BBI offers stock in
         BBI  pursuant to an initial  public  offering or private  placement  to
         investors. In addition,  while any Obligations remain outstanding,  BBI
         shall  continue  to own one  hundred  percent  (100%) of the issued and
         outstanding capital stock of BTRL and NACL.

                  4.1.20 Compliance with Certain Environmental Laws. Neither the
         Borrower, nor any Person for whose conduct the Borrower is responsible,
         owns, occupies or operates,  or has ever owned,  occupied or operated a
         site or vessel on which has been stored any hazardous  material or oil,
         without   compliance  with  all  statutes,   regulations,   ordinances,
         directives,  and orders of every  federal,  state,  municipal and other




         governmental  authority  which  has  or  claims  jurisdiction  relative
         thereto  (the  terms  "site",   "vessel",   and  "hazardous  material",
         respectively,  as used herein include the definitions of those terms in
         Massachusetts  General Laws,  Ch. 2lE);  neither the Borrower,  nor any
         Person for whose conduct the Borrower is responsible, has ever disposed
         of,  transported,  or  arranged  for  the  transport  of any  hazardous
         material or oil without compliance with all such statutes, regulations,
         ordinances,  directives,  and orders; and neither the Borrower, nor any
         Person for whose  conduct the  Borrower is  responsible,  has ever been
         legally  responsible  for any  release  or  threat  of  release  of any
         hazardous  material or oil;  received  notification of any potential or
         known  release or threat of release of any  hazardous  material  or oil
         from any site or vessel owned, occupied or operated by the Borrower, or
         any Person for whose  conduct the  Borrower is  responsible,  or of the
         incurrence  of any expense or loss in connection  with the  assessment,
         containment,  or  removal  of any  release  or threat of release of any
         hazardous material or oil from any such site or vessel.

                  4.1.21  Recent  Changes  of  Name  or  Structure.   Except  as
         reflected in the Master  Exhibit with respect to the corporate  name of
         NACL, the Borrower has not within the preceding four (4) months changed
         its name,  identity or corporate structure and has not previously had a
         principal place of business or chief  executive  office located outside
         the Commonwealth of  Massachusetts;  and no Collateral has been brought
         into this  Commonwealth  within the past four (4)  months  subject to a
         security  interest  in favor of a third party  perfected  in any manner
         under  the law of the  jurisdiction  from  which  said  Collateral  was
         removed.

                  4.1.22 Payment of Wages. The Borrower  represents and warrants
         that all currently  owed wages to employees  have been paid, and agrees
         and covenants that all wages to employees will be paid as and when due.

                  4.2  Certain Affirmative Covenants.

                  4.2.1  Payment  of  Obligations.  The  Borrower  will duly and
         punctually pay or cause to be paid, and perform or observe, or cause to
         be performed or  observed,  as the case may be, all of the  Obligations
         and will pay and perform or observe, or cause to be paid,  performed or
         observed all other duties or liabilities of any kind of the Borrower to
         the  Lender,  under or as  provided in the  Financing  Instruments,  or
         otherwise by agreement or applicable law.

                  4.2.2  Books and  Records.  The  Borrower  will  maintain  its
         financial  books and records in an accurate,  up-to-date,  complete and
         standardized fashion in accordance with GAAP consistently  applied, and
         in  accordance  with  any  state  or  federal  regulatory  requirements
         applicable to the Borrower's business or activities.

                  4.2.3  Inspection.  The Borrower will, at all reasonable times
         during regular business hours, and upon reasonable advance notice, make
         available in its offices,  and shall allow the Lender,  at the Lender's
         expense,  access  to,  all of the  Borrower's  books  and  records  for
         inspection,  audit,  examination  and  copying  by the  Lender  and the
         Lender's  representatives,  and the Borrower  will,  at all  reasonable
         times,  permit  entry by the Lender upon the  Borrower's  premises  for
         purpose of inspection of its  properties by the Lender and the Lender's
         representatives and agents, including but not limited to the Collateral
         or any portion thereof.

                  4.2.4 Commercial Purposes.  All advances under the Loans shall
         be used exclusively for the Borrower's business purposes and operations
         and shall not in any respect be used for personal,  family or household
         purposes.




                  4.2.5  Notice  of  Adverse   Matters.   The   Borrower   will,
         immediately  upon  learning  thereof,  report  to  Lender  all  matters
         materially  adversely  affecting the  Borrower's  business or financial
         condition or properties,  including,  without limitation, any damage or
         destruction  of  any  material  amount  of  the  Borrower's  properties
         (whether or not  constituting  Collateral)  by fire or other  casualty,
         whether or not insured against.

                  4.2.6 Principal  Lending  Business.  The Borrower will use the
         Lender as its sole  lender of  account  and  depository  for BBI's main
         operating  accounts;  provided  however that BTRL and NACL may maintain
         checking  accounts  at banks  other  than the Lender  for  purposes  of
         handling their accounts payable and payroll.

                  4.2.7  Maintenance  of Corporate  Existence;  Compliance  with
         Laws.  The Borrower  will maintain and keep in full force its corporate
         existence and good standing and comply with all laws,  regulations  and
         orders  of the  United  States  and of any state or  states,  and other
         political subdivision thereof, and of any other governmental  authority
         which may have  jurisdiction  over the  Borrower or its  properties  or
         businesses.

                  4.2.8  Payment of Taxes and Filing of  Returns.  The  Borrower
         will pay when due all taxes,  including without limitation all real and
         personal  property  taxes,  assessments  and charges and all franchise,
         income,  unemployment,  old age benefit,  withholding,  sales and other
         taxes  assessed  against  it or any of its  properties,  and  otherwise
         payable  by it, at such  times and in such  manner as is  necessary  to
         prevent any penalty from accruing or any Lien or charge from  attaching
         to its  properties.  The Borrower  shall  prepare and file when due all
         federal,  state and local  tax,  informational  and other  governmental
         returns, reports,  extensions, and filings, as may be applicable to the
         Borrower.  The  provisions  of  this  subsection,  however,  shall  not
         preclude the Borrower from  contesting in good faith and by expeditious
         process any such tax,  and the Borrower  shall not be in default  under
         this subsection by reason of the existence of a Lien for taxes not then
         due, all provided that: (a) an adequate  reserve therefor is maintained
         on the books of the  Borrower;  (b) the  Lender  has been  notified  in
         writing by the Borrower of such contest; (c) the enforcement of any and
         all Liens for  non-payment of such taxes is effectively  stayed and the
         Lender is satisfied, in its judgment, that such contest or dispute does
         not  materially  affect the  existence,  perfection  or priority of the
         Lender's security interest in any of the Collateral;  (d) the Lender is
         reasonably  satisfied that the Borrower has  reasonable  basis for such
         contest or dispute; and (e) the Borrower shall immediately pay the full
         amount of such charges and claims in the event the  Borrower's  contest
         or dispute is unsuccessful.

                  4.2.9 Maintenance of Properties.  The Borrower will safeguard,
         protect and preserve the Collateral for the benefit of the Lender, will
         keep the Collateral  free from any adverse lien,  security  interest or
         encumbrance  taking  priority over the security  interest of the Lender
         (other than Permitted  Encumbrances),  will keep all tangible  property
         constituting  part of the  Collateral in good working order and repair,
         will preserve all beneficial  contract rights,  will take  commercially
         reasonable steps to collect all Accounts, and will not waste or destroy
         the  Collateral  or any part thereof;  and the Borrower will  otherwise
         preserve,  maintain and protect its rights and keep its  properties and
         assets in good  repair,  working  order and  condition,  and capable of
         identification,  and make (or cause to be made) all  needful and proper
         repairs or renewals, replacements,  additions and improvements thereto,
         and shall use its assets only in the ordinary course of business.

                  4.2.10 Collection Costs;  Legal Fees; etc. The Borrower agrees
         to pay, and to reimburse the Lender, on demand, for all fees, costs and
         expenses (including, without limitation, attorneys' reasonable fees and
         expenses)  incurred  or paid  by the  Lender  in  connection  with  the
         preparation,   negotiation,   interpretation   or   amendment  of  this
         Agreement,  and of any or all of the Financing Instruments,  and of any




         other instrument, agreement or document executed and delivered pursuant
         thereto  or in  connection  therewith,  and for any and all such  fees,
         costs and  expenses  incurred  in  connection  with  collection  of the
         Obligations  or the  enforcement  of the  Lender's  rights and remedies
         under this  Agreement or any of the Financing  Instruments or otherwise
         against the Borrower, or in the administration, supervision, protection
         of  or  realization  on  any  Collateral   held  as  security  for  any
         Obligation,  or in the  defense of any action  against  the Lender with
         respect  to  the  Lender's   rights  or  remedies  in  respect  of  any
         Obligation; and all of the foregoing fees, costs, and expenses shall be
         part of the  Obligations  secured  by  this  Agreement,  and the  other
         Financing Instruments.

                  4.2.11 Insurance.  The Borrower will maintain insurance at all
         times with financially sound and reputable  companies as are reasonably
         satisfactory  to the Lender,  in such amounts and against such risks as
         are customarily  insured  against by businesses  operating in a similar
         line of business in a similar area, and consistent  with sound business
         practice,  in no event less than the greater of (a) the amount required
         to avoid coinsurance or (b) the total aggregate  outstanding  principal
         indebtedness  owing by the  Borrower to the Lender,  including  without
         limitation   casualty  insurance  covering  the  Collateral  and  other
         property of the Borrower against the hazards of fire, flood,  sprinkler
         leakage,  burglary,  theft,  pilferage,  loss in transit, those hazards
         covered by extended coverage,  and such other hazards as the Lender may
         require,  all such  insurance to be in such form,  for such periods and
         with such  companies as shall be  reasonably  acceptable to the Lender.
         All premiums  thereon shall be paid by the Borrower and if the Borrower
         fails to do so, the Lender may at its option (but  without  obligation)
         procure such  insurance and charge the cost to the  Borrower's  Line of
         Credit account; provided,  however, that any such payment by the Lender
         shall not constitute  satisfaction of the Borrower's  obligations  with
         respect to payment hereunder, or a waiver by the Lender of any Event of
         Default  with  respect  to  such  non-payment.   Without  limiting  the
         generality of the foregoing, all such insurance policies shall provide,
         in form and  substance  satisfactory  to the Lender,  that (i) any loss
         thereunder  shall be payable to the Lender as loss payee  (first to the
         Lender and then to the Borrower,  as their interests may appear),  (ii)
         any such  payment to the Lender shall be made by an  instrument  to the
         Lender alone and not to the  Borrower  and Lender  jointly and (iii) no
         cancellation or modification of such policy shall be effective  without
         at least thirty (30) days prior  written  notice to the Lender.  If any
         insurance losses are paid by check,  draft or other instrument  payable
         to the  Borrower  and the Lender  jointly,  the Lender may  endorse the
         Borrower's name thereon and do such other things as the Lender may deem
         advisable to reduce the same to cash. All loss  recoveries  received by
         the Lender upon any such insurance  shall be applied to the Obligations
         in such  order as the  Lender  in its sole  discretion  may  determine,
         unless otherwise  expressly  consented to in writing by the Lender. Any
         surplus  shall be paid by the Lender to the  Borrower or applied as may
         be otherwise  required by law.  Certificates  of insurance of, and true
         and  complete  copies of, and upon request the  originals  of, all such
         casualty insurance policies and endorsements thereto shall be delivered
         to the Lender  contemporaneously  with the execution of this Agreement.
         Annually  thereafter,  the Borrower shall deliver  certificates of such
         insurance coverages to the Lender, along with satisfactory  evidence of
         general liability,  products liability, workmens compensation and other
         insurance coverage,  in form and substance  satisfactory to the Lender.
         The Borrower shall advise the Lender of each claim made by the Borrower
         under any policy of  insurance  which  covers the  Collateral  and will
         permit the Lender,  to the exclusion of the  Borrower,  at the Lender's
         option in each instance,  to conduct the adjustment of each such claim.
         The Borrower hereby  appoints the Lender as the Borrower's  attorney to
         obtain,  adjust,  settle,  and cancel any  insurance  described in this
         section  and to  endorse  in favor of the Lender any and all drafts and
         other  instruments  with  respect  to  such  insurance.  The  foregoing
         appointment  being  coupled with an interest is  irrevocable  until the
         within  Agreement is terminated by a written  instrument  executed by a
         duly authorized  officer of the Lender.  The Lender shall not be liable
         on  account  of any  exercise  pursuant  to said  power  except for any
         exercise in actual wilful bad faith.  The Lender may apply any proceeds
         of such insurance  against the Obligations at any time,  whether or not
         such have  matured,  in such  order of  application  as the  Lender may
         determine.

                  4.2.12 Further  Agreements;  Compliance With Other Agreements;
         Payment of Other Obligations;  Tax Returns; Notice of Litigation and of
         Events of Default.

                  The Borrower will:

                           4.2.12.1  from time to time  execute  and  deliver or
                  cause to be executed and delivered,  and furnish to the Lender
                  such other agreements,  documents,  instruments or statements,
                  and do or cause to be done such  other  acts as the Lender may
                  reasonably  request,  to  effect,  confirm  and  secure to the
                  Lender all rights and  advantages  intended by this  Agreement
                  and the Financing Instruments;

                           4.2.12.2  comply with all leases,  and with all other
                  agreements to which the Borrower is a party if a default under
                  any such  agreement  could  materially  adversely  affect  the
                  Collateral;

                           4.2.12.3   generally   pay  all   other   debts   and
                  liabilities as they become due (except for liabilities,  other
                  than the Obligations,  being contested in good faith for which
                  adequate provision has been made on the books of the Borrower,
                  provided  that all  enforcement  proceedings  are  effectively
                  stayed  pending such contest) and not permit the  acceleration
                  of any indebtedness owed by the Borrower to any Person; and

                           4.2.12.4 give written notice to the Lender within ten
                  (10) days of the occurrence thereof of any litigation filed by
                  or against the Borrower  which claims in connection  therewith
                  exceed,  either  individually  or when  aggregated  with other
                  existing litigation filed by or against the Borrower,  the sum
                  of Twenty-Five Thousand Dollars ($25,000),  and the occurrence
                  or  existence  of  any  Event  of  Default  hereunder,  or the
                  existence of any  situation  or state of facts  which,  either
                  with  notice or lapse of time,  or both  would  constitute  an
                  Event of Default  hereunder,  and the action the  Borrower has
                  taken or proposes to take with respect  thereto,  all provided
                  that the receipt of such notice shall not limit or impair,  in
                  any way the Lender's rights hereunder.

                  4.2.13  Certain Environmental Matters.  The Borrower shall:

                           4.2.13.1  not store  (except in  compliance  with all
                  laws,  ordinances,  and regulations  pertaining  thereto),  or
                  dispose of any hazardous material or oil on any site or vessel
                  owned,  occupied, or operated by the Borrower or by any Person
                  for whose conduct the Borrower is responsible;

                           4.2.13.2 neither directly nor indirectly transport or
                  arrange for the  transport  of any  hazardous  material or oil
                  except in compliance with all laws, ordinances and regulations
                  pertaining thereto;

                           4.2.13.3 provide the Lender with written notice:  (a)
                  upon the  Borrower's  obtaining  knowledge of any potential or
                  known  release,  or threat of  release,  in  violation  of any
                  federal,   state  or  local  law,   ordinance  or   regulation
                  pertaining  thereto,  of any  hazardous  material or oil at or
                  from any site or vessel  owned,  occupied  or  operated by the
                  Borrower,  or by any Person for whose  conduct the Borrower is
                  responsible  or whose  liability may result in any lien on any
                  Collateral;  (b) upon the Borrower's  receipt of any notice to
                  such  effect  from any  federal,  state or other  governmental
                  authority;  or (c) upon the Borrower's  obtaining knowledge of
                  any  incurrence  of any  expense or loss by such  governmental
                  authority in connection  with the  assessment,  containment or
                  removal of any hazardous  material or oil for which expense or
                  loss the  Borrower  may be liable or for which  expense a Lien
                  may be imposed on any Collateral.

                  4.2.14 Changes in Master Exhibit.  The Borrower shall promptly
         notify  the Lender in writing  of any  changes in or  additions  to the
         information set forth in the Master Exhibit.

                  4.2.15 Governmental Approvals. To the extent that the Borrower
         has entered into, or enters into in the future, any contract subject to
         the provisions of the Assignment of Claims Act of 1940, as amended,  31
         U.S.C.  3727 (the "Assignment of Claims Act"),  the Borrower  covenants
         and agrees to  promptly  execute  and  deliver  to Lender a  Collateral
         Assignment  for  each  such  contract  in the  form  of the  Collateral
         Assignment annexed hereto as Exhibit 4.2.15(A) and to complete, execute
         and send by  certified  mail  return  receipt  requested  a  Notice  of
         Assignment of Contract (the "Notice") in the form of the Notice annexed
         hereto as  Exhibit  4.2.15(B)  to (a) the  Contracting  Officer  or the
         agency head; (b) surety on any bond applicable to the contract; and (c)
         the  Disbursing  officer  designated  in the contract to make  payment.
         Furthermore,  the Borrower agrees to seek  acknowledgement of each such
         Notice from the addressees thereof as provided in the form of Notice in
         Exhibit  4.2.15(B)  and to transmit the same to the Lender upon receipt
         thereof.

                  4.2.16  Key  Man  Life  Insurance.  So  long  as  any  of  the
         Obligations  remain  outstanding,  the Borrower agrees to maintain life
         insurance  on the life of Richard  T.  Schumacher  providing  for a net
         payment  in cash upon the death of said  Richard  T.  Schumacher  in an
         amount  of not less  than Two  Million  Dollars  ($2,000,000),  and the
         Borrower shall pledge or collaterally assign such policy or policies to
         the  Lender  and,  at all times,  maintain  such  pledge or  collateral
         assignment. Such insurance coverage shall include a disability rider in
         the full amount of such coverage.

                  4.3  General Negative Covenants.

                  4.3.1 Other Debt.  The Borrower will not issue any evidence of
         indebtedness   or  create,   or  incur,   assume,   guarantee,   become
         contingently  liable for or suffer to exist, any indebtedness in excess
         of  One  Hundred  Fifty  Thousand   Dollars   ($150,000)   (other  than
         indebtedness  to the Lender),  without the prior written consent of the
         Lender  which  consent  will not be  unreasonably  withheld or delayed;
         provided,  however,  that the Borrower may incur  liabilities which are
         incurred or arise in the  ordinary  course of the  Borrower's  business
         (other  than  liabilities  incurred  or arising  with  respect to money
         borrowed  or for the  purchase  or lease of assets)  without  the prior
         written  consent of the Lender.  The  Borrower  shall not enter into or
         participate  in any  agreement,  arrangement  or  transaction  with any
         Person without the prior written  consent of the Lender,  if the effect
         of such agreement,  arrangement or transaction has, or could reasonably
         be  expected  in the future to have,  the effect of (i)  rendering  the
         Borrower either  primarily or contingently  liable for any indebtedness
         or other  obligation of any Person (ii)  transferring  any asset of the
         Borrower  to or  for  the  benefit  of  any  Person  (except  as may be
         otherwise expressly  permitted by this Agreement);  or (iii) subjecting
         any of the  Collateral  to any lien in favor of any third party  (other
         than Permitted Encumbrances), including but not limited to any creditor
         or obligee of any Person.  Notwithstanding the foregoing,  the Borrower
         shall be permitted to grant purchase  money security  interests for the
         purchase of assets otherwise permitted hereunder.

                  4.3.2  Payment of  Dividends.  The  Borrower  will not pay any
         dividends either in cash or kind on any class of its stock nor make any
         distribution  on  account  of their  stock,  nor  redeem,  purchase  or
         otherwise  acquire  directly or indirectly any of their stock,  without
         prior  written  notice to and written  consent of the Lender  except in
         compliance  with this  subparagraph  4.3.2.  During any period that the
         Borrower is a  "Subchapter  S"  corporation  pursuant  to the IRC,  the
         Borrower may pay dividends to its shareholders in the amounts necessary
         to permit such  shareholders  to pay the  portion of their  federal and
         state  income  taxes which is directly  related to the  Borrower's  net
         income attributable to such shareholders.




                  4.3.3 Loans By the  Borrower.  The Borrower  will not make any
         loan or advances  to any Person,  including,  without  limitation,  its
         officers and employees.

                  4.3.4  Investments.  The Borrower will not invest in equity or
         debt of any Person  other  than  obligations  of the  United  States or
         Deposit Accounts.

                  4.3.5 Mergers, etc. The Borrower will not merge or consolidate
         or be merged or  consolidated  with or into any other  Person,  or be a
         party to any  reorganization,  change in legal  structure  or any sale,
         lease, transfer or other disposition of all or substantially all of its
         assets.

                  4.3.6 Sales of Assets.  The Borrower will not sell,  lease, or
         dispose  of any of its  assets  except  for sales of  Inventory  in the
         ordinary and usual course of its business,  and for Equipment no longer
         needed  in the  operation  of its  business,  so long  as the  Borrower
         receives  therefor a sum  substantially  equal to such Equipment's fair
         value and such sum is  immediately  paid to Lender to be applied to the
         Loan.

                  4.3.7 No Liens; Permitted Encumbrances.  The Borrower will not
         grant or assume or suffer to exist any Lien with  respect to any of its
         assets  or  property,  tangible  or  intangible,  whether  now owned or
         hereafter acquired,  except for Liens granted to the Lender pursuant to
         this  Agreement,  and  except  for  the  following  (collectively,  the
         "Permitted  Encumbrances"):  (a)  liens  in  respect  of  taxes,  fees,
         assessments and other governmental  charges not yet due and payable, or
         with respect to which the validity thereof is currently being contested
         in good  faith  by  appropriate  proceedings  in  accordance  with  the
         provisions of this Agreement;  (b) landlord's  liens in respect of rent
         not in  default  or Liens in  respect  of  pledges  or  deposits  under
         worker's compensation,  unemployment insurance, social security laws or
         similar  legislation  or in  connection  with appeal and similar  bonds
         incidental to litigation,  mechanics', laborers', and materialmen's and
         similar liens,  if the  obligations  secured by such liens are not then
         delinquent,  and liens securing statutory obligations incidental to the
         conduct of the business of the Borrower  which do not in the  aggregate
         materially  detract  from the value of the  property of the Borrower or
         materially  impair the use thereof in the operation of their respective
         businesses;  (c) judgment  liens which shall not have been in existence
         for a period  longer than thirty (30) days after the  creation  thereof
         (provided no foreclosure or execution action shall have been commenced)
         or if a stay of execution  shall have been obtained for a period longer
         than  thirty  days  after  the  expiration  of such stay  (provided  no
         foreclosure  or  execution  action  shall have yet been  commenced)  or
         judgment  liens for which the  Borrower has obtained a bond in favor of
         the  judgment  holder in the full  amount of the lien and which bond is
         otherwise satisfactory to Lender; (d) the security interests, mortgages
         or Liens, if any,  described in the Master Exhibit annexed hereto;  and
         (e) Liens otherwise permitted pursuant to Section 4.3.1 hereof.

                  4.3.8 Continuance of Business. The Borrower will not engage in
         any business other than the businesses in which it is currently engaged
         or a business reasonably allied thereto, and the Borrower will continue
         to conduct and operate its business actively and in good faith.

                                    SECTION 5

                        FINANCIAL AND REPORTING COVENANTS

         5.1 Reporting Covenants. The Borrower agrees to provide the Lender with
the reports, statements,  certificates and information set forth in this Section
5, all of which are referred to as the "Reporting Requirements".

                  5.1.1  Quarterly  Financial  Statements.   The  Borrower  will
         furnish to the Lender,  within  forty-five (45) days after the close of
         each   calendar   quarter  of  its  fiscal   year,   consolidated   and
         consolidating   (except





         the last in each fiscal year) financial statements, including a balance
         sheet,  and a statement  of profit and loss  reflecting  the  financial
         condition  of the Borrower at the end of such period and the results of
         its operations for such period and for the period from the beginning of
         the current fiscal year to the end of such period,  in comparative form
         with figures for the corresponding  periods of the previous fiscal year
         accompanied by a certificate by the Borrower's chief financial  officer
         or  President  to the  effect  that such  financial  statements  fairly
         present such  financial  condition  and results of operations as of the
         end of and during such period,  in  accordance  with GAAP  consistently
         applied, subject only to year-end adjustments and audit.

                  5.1.2 Annual Financial  Statements.  The Borrower will furnish
         the  Lender,  within one hundred  twenty  (120) days after the close of
         each fiscal year,  consolidated and consolidating financial statements,
         including a balance sheet,  statement of profit and loss, statements of
         cash  flow,  and  a  statement  of  changes  in  shareholders   equity,
         reflecting  the financial  condition of the Borrower at the end of such
         fiscal year and the results of its  operations  during such fiscal year
         (in each  case  setting  forth in  comparative  form the  corresponding
         figures for the  preceding  year)  audited and  reported  upon (in form
         generally  recognized as "unqualified")  by Coopers & Lybrand,  LLP, or
         such other independent certified public accountant  satisfactory to the
         Lender,  prepared in accordance with GAAP, applied  consistently in the
         preparation  thereof  and with  prior  periods,  and  accompanied  by a
         certificate by the Borrower's chief financial officer or president that
         such financial  statements fairly present such financial  condition and
         results of operations as of the end of and during such period; together
         with, upon request of the Lender,  an opinion of such certified  public
         accountant  that to its  knowledge  there has  occurred  no event which
         constitutes,  or which  with the  lapse of time or  giving of notice or
         both  would  constitute  an  Event of  Default  hereunder,  or,  if the
         contrary  appears to be true,  a statement of such Event of Default and
         the nature thereof.

                  5.1.3  Monthly and Weekly  Reports.  The  Borrower  shall also
         furnish to the Lender monthly, within fifteen (15) days of the last day
         of each month hereafter:

                           5.1.3.1 an accounts receivable agings and collections
                  report in  sufficient  detail to allow  Lender to determine if
                  the Borrower is in compliance with the Borrowing Base;

                           5.1.3.2  a  Borrowing   Certificate   detailing   the
                  Eligible  Accounts and Eligible  Inventory  then  available to
                  support the Line of Credit in accordance  with this Agreement;
                  and

                           5.1.3.3   an   Inventory   breakdown   report,   with
                  certificates  of the Borrower's  President or chief  financial
                  officer as to the values of the Borrower's Inventory,  each in
                  form  satisfactory  to  Lender,   together  with  evidence  of
                  shipments or deliveries and such other  information  regarding
                  Inventory as Lender may request.

         The Borrower  shall also furnish to the Lender  weekly,  within two (2)
         business  days of the end of each week,  copies of its weekly sales and
         cash journals.

                  All of such reports,  to the extent governed by GAAP, shall be
         prepared  in  accordance  with  GAAP,   applied   consistently  in  the
         preparation thereof and with prior periods.

                  5.1.4 Officer's Certificates.  The Borrower will, upon request
         of the Lender but in any event  within  thirty  (30) days of the end of
         each calendar quarter,  deliver to the Lender an officer's  certificate
         signed by its President or chief financial officer certifying that: (a)
         the signer has reviewed the relevant terms of the Financing Instruments
         and is familiar  with the  operations  and  financial  condition of the
         Borrower;  (b) there is in existence  no Event of Default  described in
         any of the Financing Instruments and no event which, with the giving of
         notice or lapse of time, or both,  would result in the occurrence of an




         Event of Default; or (c) if there is a continuing Event of Default or a
         continuing condition which, with the giving of notice or lapse of time,
         or both,  would result in the  occurrence  of an Event of Default,  the
         nature and period thereof and the action which has been taken, is being
         taken or is proposed to be taken with respect thereto, provided that no
         such notice,  action or proposed  action shall affect  Lender's  rights
         hereunder with respect to any Event of Default.

                  5.1.5 Other  Information.  In addition to the  foregoing,  the
         Borrower will furnish the Lender from time to time with such  financial
         information and statements as the Lender may reasonably  request,  and,
         upon request of the Lender, with copies of all financial statements and
         financial  reports  that the Borrower  sends or makes  available to its
         members of its Board of  Directors  or to any  governmental  authority,
         together with copies of all  management  letters of substance and other
         reports of  substance  submitted  to the  Borrower  by its  independent
         accountants in connection  with any annual or interim audit;  and, upon
         request of the  Lender,  the  Borrower  will  authorize  and direct all
         accountants and auditors to exhibit and deliver copies of any financial
         statements, trial balances or other accounting records of any sort, and
         to disclose to the Lender any information  they may have concerning the
         Borrower's financial or business condition.

         5.2  Financial Covenants.

         The Borrower shall maintain and observe all of the following  financial
standards,  in each case,  determined  and  classified in  accordance  with GAAP
applied on a consistent  basis at the applicable  dates or during the applicable
time periods indicated in the following table:




====================================================================================================================
                                       APPLICABLE DATE OR TIME                    APPLICABLE RATIOS
        FINANCIAL STANDARDS                     PERIOD                        OR MONETARY REQUIREMENTS
- --------------------------------------------------------------------------------------------------------------------
                                                                                        
5.2.1:  Consolidated Debt Service     Quarterly, at the end of    At least 1.25:1 (rounded to nearest hundredth)
Ratio                                 each quarter                on an average four- quarter rolling basis
- --------------------------------------------------------------------------------------------------------------------
5.2.2:  Consolidated Total Debt:      Quarterly                   Not to exceed 3.0:1 (in each case rounded to the
Tangible Net Worth Ratio                                          nearest hundredth)
- --------------------------------------------------------------------------------------------------------------------
5.2.3:  Fixed Asset Expenditures      Annually                    For 1995, the Borrower will not make
                                                                  Expenditures (as hereinafter defined) for the
                                                                  purchase of fixed assets from the proceeds of
                                                                  any debt financing (including the Line of Credit
                                                                  or the other Loans) in excess of an aggregate of
                                                                  $600,000; provided however that the Borrower may
                                                                  $150,000 for such Expenditures.  Thereafter, the
                                                                  Borrower will not make Expenditures for the
                                                                  purchase of fixed assets from the proceeds of
                                                                  the Line of Credit in any fiscal year in excess
                                                                  of an aggregate of $150,000 per year, without
                                                                  the prior written consent of the Lender, which
                                                                  consent will not be unreasonably withheld or
                                                                  delayed; provided however that this covenant
                                                                  shall not reduce the level of indebtedness of
                                                                  $150,000 which is permitted to be incurred by
                                                                  the Borrower pursuant to subsection 4.3.1
                                                                  hereof.  This covenant shall be reviewed
                                                                  annually by the Lender and any change therein
                                                                  shall be determined by the Lender by notice to
                                                                  the Borrower.
=====================================================================================================================





                  3.3.6  As used in this Agreement:

                  (a) "Total Debt" means the aggregate of all liabilities of the
         Borrower for money borrowed, incurred from any source and in any manner
         whatsoever,  all in accordance  with GAAP,  including all  subordinated
         debt, plus the  capitalization of all obligations on leases of real and
         personal property;

                  (b) "Tangible Net Worth" means the aggregate  tangible  assets
         of the  Borrower  after  excluding  the book  value  of all  Intangible
         Assets,  minus  the  amount of  aggregate  liabilities,  including  all
         deferred  income  taxes,  and  "Intangible  Assets"  shall  include all
         goodwill,   organizational  expense,  licenses,  patents,   trademarks,
         tradenames,  copyrights, capitalized research and development expenses,
         deferred  charges,  and all other  intangible  assets as  determined in
         accordance with GAAP consistently applied);

                  (c) "Consolidated Debt Service Ratio" means Adjusted Operating
         Cash Flow (as described on Exhibit 5.2.1  attached  hereto)  divided by
         Total Debt Service (as described on Exhibit 5.2.1 attached hereto).

                  (d) "Expenditures" shall refer to entire purchase price of any
         fixed asset in the event of purchase, and the aggregate rental over the
         entire rental  period in the case of a lease.  The  acquisition  of any
         fixed asset under a lease shall be deemed a purchase of a fixed asset.

                  3.3.6 Computation  According to GAAP. All of the terms used in
         the  foregoing  financial  covenants,  except to the  extent  otherwise
         specifically  defined  herein,  and all  computations  made  under  the
         foregoing covenants, shall in all respects be governed by and performed
         in accordance with GAAP consistently applied.

                                    SECTION 6

                                EVENTS OF DEFAULT

         Notwithstanding  any  provision  to  the  contrary  in  any  instrument
evidencing  any  Obligation,  the occurrence of any one or more of the following
shall constitute and mean an "Event of Default" under this Agreement:

         6.1 Any statement,  report,  certificate,  representation  or warranty,
made or furnished by the Borrower in, or in  connection  with the  execution and
delivery of this Agreement or any of the Financing Instruments, or in compliance
with the  provisions of this Agreement or any of the Financing  Instruments,  or
otherwise furnished to the Lender at any time, shall prove to have been false or
erroneous  when  made in any  material  respect,  or  omits  or fails to state a
material fact  necessary in order to make the  statements  contained  therein or
herein not misleading;



         6.2 The  Borrower  shall  fail  to make  payment  of the  principal  or
interest on the Loans when and as due;

         6.3 The  Borrower  shall fail to make  payment of any other  Obligation
within fifteen (15) days of the date when and as due;

         6.4 The Borrower shall fail to perform, observe, comply with or satisfy
any covenant,  agreement or condition  contained in this  Agreement  (other than
payment of any  Obligation)  not cured within thirty (30) days of the earlier of
(i)  notice by the  Lender  to the  Borrower  or (ii)  actual  knowledge  by the
Borrower of the occurrence thereof, plus such additional time as may be required
to cure such default  because of delays beyond the Borrower's  control,  if such
default is  susceptible  of being  cured and if the  Borrower  is acting in good
faith and is making diligent  efforts to cure such default;  provided,  however,
that such cure  period  shall not exceed the  aggregate  of ninety (90) days and
shall  not  apply  to:  (a) any  transfer  or  voluntary  encumbrance  of assets
(including  Collateral);  (b) any failure with respect to any requirement of the
Borrower  to give  notice to the Lender as provided  herein;  (c) the  Reporting
Requirements;  or (d) any event which is otherwise an Event of Default  pursuant
to any other  subsections  of this  Section  6; and such cure  period  shall run
concurrently  with, and not in addition to, any and all applicable grace or cure
periods contained in any of the other Financing Instruments;

         6.5 The Borrower shall default in payment of (a) any obligations  under
the lease between BBI and C.W.B. Realty Trust concerning the premises from which
the Borrower operates its business;  or (b) any obligation under any lease which
default  could  materially  adversely  affect  the  Collateral  or the  business
operations of the Borrower;  or (c) any obligation or  indebtedness to any other
Person at any time  outstanding,  continued for a period sufficient to cause the
acceleration of the maturity of such obligation or indebtedness  (whether or not
such obligation or indebtedness is actually  accelerated) and such  acceleration
could materially  adversely affect the Collateral or the business  operations of
the Borrower;

         6.6 Failure,  generally,  of the Borrower to pay its debts when due and
such failure could  materially  adversely  affect the Collateral or the business
operations of the Borrower; or the taking of possession,  custody or control of,
or the attachment by judicial process of, or issuance of an injunction  against,
or creation of any other Lien (other than in favor of the Lender) upon, any part
of the  Borrower's  assets by any Person,  which action is not dissolved  within
thirty (30) days;

         6.7  The Borrower:

                  6.7.1 files a voluntary  petition  in  bankruptcy  (which term
         includes any action under Title 11 of the United  States Code  entitled
         "Bankruptcy" and commonly referred to as the "Bankruptcy Code"); or

                  6.7.2  is adjudicated a bankrupt or insolvent; or

                  6.7.3 files any petition or answers  seeking or acquiescing in
         any    reorganization,    arrangement,    composition,    readjustment,
         liquidation,  dissolution  or similar  relief for itself  under any law
         relating to bankruptcy, insolvency or other relief for debtors; or

                  6.7.4 seeks or consents to or acquiesces in the appointment of
         any trustee, receiver, master or liquidator (or other similar official)
         of itself or of all or any substantial part of its property; or

                  6.7.5  makes  any  general   assignment  for  the  benefit  of
         creditors; or

                  6.7.6  admits in writing to its general  inability  to pay its
         debts as they become due;






         6.8  Commencement of any bankruptcy,  insolvency,  or other  creditor's
relief proceedings against, or entry by a court of competent jurisdiction of any
order,  judgment or decree  approving  a petition  filed  against the  Borrower,
seeking any reorganization, arrangement, composition, readjustment, liquidation,
dissolution  or similar  relief under any present or future federal or state law
or regulation relating to bankruptcy,  insolvency,  or other relief for debtors,
which proceeding, order, judgment or decree remains unvacated or unstated for an
aggregate  of thirty  (30) days,  whether or not  consecutive,  from the date of
entry thereof;

         6.9 A material  portion of the  Borrower's  assets  shall be damaged by
fire or other  casualty,  the  restoration or  replacement  cost of which damage
exceeds,  in the aggregate,  the amount of insurance  proceeds readily available
(less  applicable  deductibles  and plus capital in an amount which, in Lender's
sole  discretion (a) is available for such purposes and (b)  expenditure of such
capital  for such  purposes is  appropriate  under the  circumstances)  for such
restoration or replacement;

         6.10 The issuance or existence of any judgment or judgments against the
Borrower by any court of competent jurisdiction, or other governmental authority
of competent jurisdiction, aggregating in excess of One Hundred Thousand Dollars
($100,000)  in any fiscal year,  and not covered by  insurance,  not paid within
thirty (30) days of the date thereof;

         6.11 The loss,  suspension or revocation  of any  governmental  license
required  or  necessary  in  connection  with the  operation  of the  Borrower's
business;

         6.12  The  termination  or  revocation  of any  guaranty  given  by any
Guarantor to guarantee payment of any of the Obligations;

         6.13 Service of any process upon the Lender  seeking to attach by means
of trustee process any funds of the Borrower or of any Affiliate on deposit with
Lender, which attachment or process is not dissolved within thirty (30) days; or

         6.14 The  occurrence  of any  change  in the  Borrower's  condition  or
affairs  (financial or  otherwise)  that,  in the Lender's  reasonable  opinion,
impairs the Lender's  security or  materially  increases the Lender's risk under
this Agreement or the Financing  Instruments,  or the occurrence of any event or
circumstance  with respect to the Borrower such that the Lender reasonably deems
itself insecure.

                                    SECTION 7

                                    REMEDIES

         7.1 General  Remedies.  In addition to and without in any way  limiting
any other rights and remedies available to the Lender under this Agreement prior
to an Event of Default, or any other rights and remedies available to the Lender
(whether  prior to or after an Event  of  Default)  under  any of the  Financing
Instruments or under applicable law or in equity,  upon and at any time or times
after the occurrence of any Event of Default hereunder:

                  7.1.1 the Lender may  declare  and cause all or any portion of
         the Obligations to be immediately due and payable;

                  7.1.2  the  Lender  may  decline  to honor  the  credit of the
         Borrower or may refuse to make further advances to the Borrower;





                  7.1.3 The Lender may collect the  Receivables  Collateral with
         or without taking possession of the Collateral;

                  7.1.4 the Lender shall be entitled to immediate  possession of
         the  Collateral  or any portion or portions  thereof and may enter upon
         the Borrower's  premises to take  possession  thereof;  may require the
         Borrower to assemble the Collateral and make it available to the Lender
         at a  place  to  be  designated  by  the  Lender  which  is  reasonably
         convenient to both parties;  and/or may require the Borrower to deliver
         all books,  records  and  accounts  relating to the  Collateral  to the
         Lender;

                  7.1.5 the Lender may enter upon,  occupy, and use any premises
         owned or occupied by the  Borrower,  and may exclude the Borrower  from
         such  premises  or portion  thereof  as may have been so entered  upon,
         occupied,  or used by the Lender.  The Lender  shall not be required to
         remove any of the  Collateral  from any such premises upon the Lender's
         taking possession  thereof,  and may render any Collateral  unusable to
         the  Borrower.  In no event shall the Lender be liable to the  Borrower
         for use or  occupancy  by the Lender of any  premises  pursuant to this
         Agreement   except  for  claims  arising  out  of  the  Lender's  gross
         negligence,  willful  misconduct or bad faith, nor for any charge (such
         as wages  for the  Borrower's  employees  and  utilities)  incurred  in
         connection  with the  Lender's  exercise  of the  Lender's  rights  and
         remedies;

                  7.1.6 the Lender may take such steps as it deems  necessary to
         protect the Lender's interest in and to preserve the Collateral and the
         Borrower  agrees to  cooperate  fully with all of  Lender's  efforts to
         preserve,  and will take such  actions  as the Lender  shall  direct to
         preserve, the Collateral;

                  7.1.7 the  Lender  shall have the  rights  and  remedies  of a
         secured party under the UCC and other  applicable  laws, the choice and
         manner of exercise of any right or remedy  being in the  Lender's  sole
         discretion;  and  pursuant  thereto the Lender  shall have the right to
         foreclose  the  security  interest  granted  in any  Collateral  by any
         available  judicial procedure and to take possession of and sell any or
         all of the Collateral with or without judicial process;  the Lender may
         lease  or  otherwise  dispose  of  the  Collateral,  or  may  sell  the
         Collateral, or any part thereof, at public or private sale, at any time
         or place, in one or more sales, at such price or prices,  and upon such
         terms,  either for cash,  credit or future delivery,  as the Lender may
         elect,  and,  except  as to  that  part  of  the  Collateral  which  is
         perishable or threatens to decline steadily in value, or is of the type
         customarily  sold on a  recognized  market,  the Lender  shall give the
         Borrower reasonable notification of such sale or sales, it being agreed
         that in all events written notice mailed to the Borrower at least seven
         (7) days prior to such sale or sales is reasonable notification, and it
         is hereby  further  agreed  that at any public sale the Lender may (but
         shall have no  obligation  to) bid for and become the  purchaser of any
         Collateral;  the Borrower  hereby waives any and all rights it may have
         to  judicial  hearing  in  advance  of  the  enforcement  of any of the
         Lender's rights hereunder,  indicting  without  limitation the Lender's
         right to take immediate  possession of the  Collateral;  and the Lender
         may do any of the  foregoing or otherwise  deal with the  Collateral in
         its then  condition or following  such  preparation as the Lender deems
         advisable, with or without taking possession thereof;

                  7.1.8  the  Lender  shall  have  the  right  to  apply  to the
         Obligations  any deposits or other sums at any time  credited by or due
         from the Lender to the Borrower; and

                  7.1.9  the  Lender  may  treat  any or  all  of the  Financing
         Instruments  as  being in  default  and may  exercise  any  rights  and
         remedies thereunder as it shall deem appropriate.

         7.2 License.  The Borrower  hereby grants to the Lender a  nonexclusive
irrevocable license to use, apply, and affix any trademark, trade name, logo, or
the like in which the Borrower or any  Affiliate  now or  hereafter  has rights,
such license being granted in connection  with the completion of the manufacture
of Inventory or sale or other disposition of Inventory by Lender in the exercise
of its rights and remedies hereunder.






         7.3 No Duty of  Preservation;  Joint  Property.  The  Lender may at all
times  proceed  directly  against  the  Borrower  to enforce  the payment of the
Borrower's  Obligations  to the  Lender,  and shall not be  required to take any
action of any kind to preserve, collect upon or protect the rights of the Lender
in any Collateral obtained pursuant to the Financing  Instruments.  In the event
any Collateral,  or any Deposit  Account,  is held in joint or common names, the
Lender may deal with such Collateral,  or any Deposit Account,  for all purposes
hereunder, and under any or all of the Financing Instruments, as if belonging to
any one, and no more than one, of such joint or common owners.

         7.4 Cumulative Remedies. The enumeration of rights and remedies herein,
and in each of the Financing Instruments, shall be cumulative and not exclusive,
and shall be in addition  to, and shall not  exclusive  of, any other  rights or
remedies the Lender may have,  whether under the UCC or other applicable law, or
in equity,  or otherwise.  The Lender shall,  in its  discretion,  determine its
choice of rights and  remedies  and the order in which they shall be  exercised,
and whether or not, and which,  Collateral  is to be proceeded  against,  and in
which order. The exercise of any right or remedy shall not preclude the exercise
of others.

                                    SECTION 8

                               WAIVER; TERMINATION

         8.1  Waiver  By  the  Borrower.  The  Borrower  hereby  waives  demand,
presentment, protest and notice thereof with respect to any and all instruments,
notice of acceptance  hereof,  notice of Loan or advances made, credit extended,
Collateral received or delivered, or any other action taking in reliance herein,
and all other  notices  and demands of any kind  except as  expressly  set forth
herein.






         8.2 Lender's Option To Waive. The Lender may at its sole discretion, at
any time and from time to time,  waive  any of the  requirements  or  provisions
hereof,  or contained  within any of the Financing  Instruments,  or any default
hereunder  or under any of the  Financing  Instruments,  but only by an  express
written waiver signed by an authorized  officer of the Lender; no act other than
an express written  waiver,  nor any failure to act or delay by the Lender shall
constitute a waiver of any requirement or provision of, or any default under, or
any of the  Lender's  rights or remedies  under,  this  Agreement  or any of the
Financing  Instruments.  No  single  or  partial  waiver  by the  Lender  of any
provision of this Agreement or any of the Financing  Instruments,  or any breach
or  default  thereunder,  or of any right or remedy  which the  Lender may have,
shall  operate as a waiver of any other  provision,  breach,  default,  right or
remedy, nor of the same one on any future occasion.

                                    SECTION 9

                                  MISCELLANEOUS

         9.1 Deposits As  Collateral;  Set-Off.  Any and all  deposits,  Deposit
Accounts, and other sums at any time credited by or due to the Borrower from the
Lender or any of its  banking or lending  affiliates  or any lender  acting as a
participant under any loan arrangement between the Lender and the Borrower,  and
any cash, certificates of deposit, securities,  instruments, documents, policies
and certificates of insurance, goods, Accounts, choses in action, Chattel Paper,
and other  property  of the  Borrower  in the  possession  or control  of, or in
transit to or from, the Lender, or any of its banking or lending affiliates,  or
any lender acting as a participant under any loan arrangement between the Lender
and the Borrower,  or any third party acting on the Lender's behalf,  regardless
of the reason the  Lender,  or such other  party,  receives or is to receive the
same  (whether in pledge,  or for  safekeeping,  or as agent for  collection  or
transmission   or   otherwise)   and   regardless  of  whether  the  Lender  has
conditionally  released the same, shall at all times constitute security for any
and all  Obligations,  and may be applied or set off against such Obligations at
any time,  whether or not other  collateral  is available to the Lender.  Lender
shall have the  unrestricted  right from time to time to apply (or to change the
application  already  made of) proceeds of  Collateral  to any  Obligations,  as
Lender in its discretion may determine.

         9.2 Transfer of Collateral to Bank.  Upon the occurrence of an Event of
Default,  the Lender may at any time thereafter transfer any securities or other
property  constituting  Collateral  into its own name or that of its nominee and
receive  the income  thereon and hold the same as security  for  Obligations  or
apply it to  principal  or interest due on  Obligations.  Insofar as  Collateral
shall  consist of  Accounts,  contract  rights,  other  claims and rights to the
payment of money,  insurance  policies,  instruments,  chattel  paper,  chose in
action or the like, the Lender may, without notice to or demand on the Borrower,
demand,  collect,  receipt  for,  settle,  compromise,  adjust,  use,  sue  for,
foreclosure or realize upon  Collateral as the Lender may determine,  whether or
not Obligations or Collateral are then due, and for the purpose of realizing the
Lender's rights  therein,  the Lender may receive and open mail addressed to the
Borrower  and  endorse  and/or  remove  notes,  checks,  drafts,  money  orders,
documents  of title or other  evidences  of payment,  shipment or storage or any
form of  Collateral or items which relate  directly to any of the  Collateral on
behalf of and in the name of the  Borrower.  All  contents of mail opened by the
Lender,  except for removal of Collateral  therefrom,  shall be forwarded to the
Borrower and the Lender  shall not  disclose  the contents  thereof to any other
party,  except Bank's  attorneys,  agents and  independent  contractors  who are
directly involved with the Lender's  relationship with the Borrower,  unless any
such contents relate directly to Collateral.  The powers conferred on the Lender
by this  subsection  are solely to protect the  interest of the Lender and shall
not impose any duties on the Lender to exercise any powers.

         9.3 No Duty To Preserve or Collect. The Lender shall have no duty as to
the collection or protection of the  Collateral  beyond the safe custody of such
of the  Collateral  as may come into  possession of the Lender and shall have no
duty as to the  preservation of rights against prior parties or any other rights
pertaining  thereto.  The Lender's rights and remedies may be exercised  without
resort or regard to any other source of satisfaction of the Obligations.




         9.4   Survival  of   Covenants;   Binding   Effect.   All   agreements,
representations,   covenants  and  warranties  made  by  the  Borrower  in  this
Agreement,  the Financing  Instruments,  or in any certificate or other document
delivered to the Lender in connection  herewith shall survive the termination of
this  Agreement and survive the execution  and delivery of this  Agreement,  and
shall remain in full force and effect until all  Obligations  to the Lender have
been paid in full and  satisfied,  and the  security  interest,  lien and rights
granted to the Lender in any  Collateral  and its rights and remedies  hereunder
and under the  Financing  instruments  shall  continue  in full force and effect
notwithstanding  the fact that the  Borrower's  Line of Credit loan  account may
from time to time be in a zero or credit  position,  until all Obligations  have
been satisfied. All the terms and provisions of this Agreement and the Financing
Instruments shall be binding upon and inure to and be enforceable by and against
the parties hereto and their respective successors and assigns.

         9.5      Termination of Agreement.

                  9.5.1  This  Agreement  shall  terminate  upon the  final  and
         irrevocable payment in full by the Borrower of the Obligations, or upon
         acceleration  of  the  Obligations   pursuant  to  the  terms  of  this
         Agreement.

                  9.5.2 The  termination of this Agreement  shall not affect any
         rights of the  Borrower or the Lender  arising  prior to the  effective
         date of such termination, as the case may be, and the provisions hereof
         shall continue to be fully  operative  until all  transactions  entered
         into,  rights created or Obligations  incurred prior to such occurrence
         or  termination  shall  have  been  fully  disposed  of,  concluded  or
         liquidated.   Upon  termination  of  this  Agreement,  all  Obligations
         (including,  without  limitation,  the Loans)  shall be due and payable
         without  notice or demand.  The  security  interests,  liens and rights
         granted to the Lender  hereunder  and under any  instrument or document
         delivered  pursuant hereto or in connection  herewith shall continue in
         full  force  and  effect,   notwithstanding  the  termination  of  this
         Agreement  or the fact that the  Borrower's  Accounts  may from time to
         time be temporarily in a credit position,  until all of the Obligations
         have   been   paid  in  full   after  the   termination   hereof.   All
         representations,   warranties,   covenants,   waivers  and   agreements
         contained herein shall survive the termination  hereof unless otherwise
         provided.

         Notwithstanding  the foregoing,  if after receipt of any payment of all
         or any part of the Obligations,  the Lender is for any reason compelled
         to surrender  such payment to any person or entity because such payment
         is  determined  to be void or voidable as a  preference,  impermissible
         setoff,  a  diversion  of trust  funds or for any  other  reason,  this
         Agreement shall continue in full force and the Borrower shall be liable
         to, and shall indemnify and hold the Lender harmless for, the amount of
         such payment  surrendered  until the Lender shall have been finally and
         irrevocably  paid in full.  The  provisions of the  foregoing  sentence
         shall be and remain effective notwithstanding any contrary action which
         may have been taken by the Lender in reliance  upon such  payment,  and
         any such  contrary  action so taken shall be without  prejudice  to the
         Lender's  rights under this  Agreement and shall be deemed to have been
         conditioned upon such payment having become final and irrevocable.

         9.6 Conflict of Terms.  In the event of any  conflict or  contradiction
between or among any provision or provisions of this Agreement and any provision
or provisions of any of the other Financing Instruments,  the provisions of this
Agreement shall govern.

         9.7 Prior Discussions;  Amendments in Writing; Counterparts;  Filing As
Financing  Statement.   This  Agreement  and  all  other  Financing  Instruments
incorporate  all  discussions  and  negotiations  between the  Borrower  and the
Lender,  either express or implied,  concerning the matters  included herein and
therein,  any  custom  or  usage  to  the  contrary  notwithstanding.   No  such
discussions  or  negotiations  shall  limit,  modify,  or  otherwise  affect the





provisions  of the  Financing  Instruments.  This  Agreement  may be  amended or
modified only in writing  signed by the parties  hereto,  and in the case of the
Lender  signed by a duly  authorized  officer  thereof.  This  Agreement  may be
executed  in two or  more  counterparts,  each  of  which  shall  constitute  an
original,  but such  counterparts  together  shall  constitute  one and the same
instrument. A carbon, photographic or other reproduction of this Agreement or of
any financing statement executed to perfect the security interest created herein
may be filed as a  financing  statement  under  the UCC (or  under  the  Uniform
Commercial Code in effect in any jurisdiction outside Massachusetts).

         9.8 General  Indemnification.  The  Borrower  shall,  and does  hereby,
further  indemnify and save the Lender  harmless  from any and all  liabilities,
damages, costs, losses and expenses (including,  without limitation, court costs
and  attorney's  reasonable  fees and  expenses)  that the Lender may sustain or
incur by reason  of,  relating  to or  arising  out of the  preparation  of this
Agreement,  the  defending or  protecting  of any  Collateral or the priority of
Lender's interest therein, or in collecting or enforcing the Obligations,  or in
enforcing any of Lender's  rights or remedies,  or in the prosecution or defense
of any action or proceeding  concerning  any matter  growing out of or connected
with this Agreement, any of the Financing Instruments,  the Obligations,  or the
Collateral,  or on account of the Lender's  relationship with the Borrower (each
of which may be  defended,  compromised,  settled or pursued by the Lender  with
counsel of  Lender's  selection,  at expense  of the  Borrower)  except for such
claims which have been  determined by a court of competent  jurisdiction to have
arisen  out  of  the  Lender's  gross   negligence  or  bad  faith.  The  within
indemnification  shall survive  termination  of this  Agreement.  The Borrower's
obligations under this subsection  constitute part of the Obligations secured by
the  security  interest  created by this  Agreement  and by the other  Financing
Instruments.

         9.9  Destruction  of Documents;  Jurisdiction.  This  Agreement and all
other   Financing   Instruments,   may  be  reproduced  by  the  Lender  by  any
photographic,  photostatic,  microfilm,  or similar process,  and the Lender may
destroy  the  original  from  which any  document  was so  reproduced.  Any such
reproduction  shall be  admissible  in  evidence as the  original  itself in any
judicial  or  administrative  proceeding  (whether  or not  the  original  is in
existence and whether or not such reproduction was made in the regular course of
business).  The Borrower  acknowledges  receipt of a true,  correct and complete
copy or counterpart of this Agreement.





         9.10 Notices.

                  9.10.1 All notices or demands  hereunder to the parties hereto
         shall be made in writing and shall be deemed to have been  sufficiently
         given for all purposes one business day after being sent by  recognized
         overnight  delivery service for next day delivery service,  on the same
         business day if delivered by hand and three  business  days after being
         sent by United States mail,  certified mail return  receipt  requested,
         first class,  postage  prepaid,  and  addressed to the parties at their
         respective  Notice  Addresses  set  forth  above,   together  with  the
         following additions: (a) for the Lender, "Attention: Commercial Banking
         Group" and (b) for the  Borrower,  "Attention:  Richard T.  Schumacher,
         President".  Either  of the  parties  may  change  its  Notice  Address
         hereunder  by  giving  notice  of such  change  to the  other  party in
         accordance with the provisions of this subsection.

                  9.10.2  Notwithstanding  any provision herein to the contrary,
         the  Borrower  agrees that the failure or delay by the Lender in giving
         any  notice  or  statement  hereunder,  or any  inaccuracy  therein  or
         incompleteness  thereof,  shall  not in any way  alter  or  affect  the
         absolute  and  unconditional  obligation  of the  Borrower  to pay  and
         perform in full the  Obligations,  but any action taken or not taken by
         the Borrower as a direct result of such lack or delay of notice,  or of
         the Borrower's good faith reliance upon a material  inaccuracy  therein
         or the material  incompleteness  thereof, as the case may be, shall not
         in of itself, and to the extent thereof, constitute an Event of Default
         hereunder,  so long as the Borrower does not otherwise  have or receive
         notice or  knowledge  of the  material  contents or  substance  of such
         notice, or of the inaccuracy or incompleteness thereof, as the case may
         be, and the Borrower acts at all times in good faith.

         9.11 Application of Proceeds.  The proceeds of any collection,  sale or
disposition  of the  Collateral,  or of any other payments  received  hereunder,
shall be applied  toward the  Obligations in such order and manner as the Lender
determines in its sole discretion,  any statute (the application of which may be
waived  or  modified   by   agreement),   customs  or  usage  to  the   contrary
notwithstanding.  The  Borrower  shall  remain  liable  to the  Lender  for  any
deficiency remaining following such application.

         9.12  Continuance  of  Defaults.  As  used  herein,  and  in any of the
Financing Instruments, upon any and each occurrence of an Event of Default, such
Event of Default  shall be deemed to  continue  until  cured by the  Borrower in
accordance  with this Agreement (and the applicable  provisions of the Financing
Instruments,  as the case may be), and until such time as the Borrower  requests
and receives from the Lender the Lender's written acknowledgment that such Event
of  Default  (as  specified  in the  request)  has been  cured  and is no longer
continuing,  which acknowledgment the Lender shall not unreasonably  withhold or
delay.

         9.13  Severability.  If any  provision of this  Agreement or any of the
Financing  Instruments,  or any portion of such  provision,  or the  application
thereof to any person or  circumstance,  shall to any extent be held  invalid or
unenforceable,  the remainder of this Agreement and the Financing Instruments or
the remainder of such provision and the application  thereof to other persons or
circumstances (other than those as to which it is held invalid or unenforceable)
shall not be affected  thereby,  and each term and  provision  hereof and of the
Financing  Instruments  shall  be  valid  and  enforced  to the  fullest  extent
permitted by law. To the extent  permitted by law, the parties  hereto waive any
provision of law which renders any such provision prohibited or unenforceable in
any respect.

         9.14  Headings.  Headings  appearing in this Agreement are intended for
convenience only and do not constitute and shall not be interpreted to be a part
of this Agreement.

         9.15 Governing Law; Sealed  Instrument.  This Agreement is executed and
delivered in The  Commonwealth of  Massachusetts,  and for all purposes shall be
construed in  accordance  with and governed by the laws of The  Commonwealth  of
Massachusetts,  and shall  take  effect  as a sealed  instrument.  The  Borrower
submits



itself to the  jurisdiction of the Courts of The  Commonwealth of  Massachusetts
for all purposes with respect to this Agreement and the Borrower's  relationship
with the Lender.

         9.16 Force Majeure.  The Lender shall not be responsible  for delays or
failures in  performance  hereunder  resulting  from causes  beyond its control,
including without  limitation,  acts of God, strikes,  lockouts,  riots, acts of
war,  governmental   regulations,   fire,  communication  line  failures,  power
failures, earthquakes or other disasters.

         9.17  Interpretation  of  Agreement.   Should  any  provision  of  this
Agreement  or  the  other  Financing   Instruments  require   interpretation  or
construction,  it is agreed by the parties hereto that the court, administrative
body, or other entity  interpreting  or construing  this  Agreement or the other
Financing  Instruments shall not apply a presumption that the provisions thereof
shall be more  strictly  construed  against  one  party by reason of the rule of
construction  that a document is to be construed more strictly against the party
who itself or through its agents  prepared  the same,  it being  agreed that the
parties and/or their respective  attorneys and agents have fully participated in
the  preparation  of all  provisions of this  Agreement and the other  Financing
Instruments.




         EXECUTED  as an  instrument  under  seal as of the day and  year  first
stated above.

                                         Borrower:

Signed in the presence of:               BOSTON BIOMEDICA, INC.


______________________________           By:_________________________________
Witness                                  Kevin W. Quinlan, Treasurer, hereunto
                                         duly authorized


                                         BTRL CONTRACTS AND SERVICES, INC.


                                         By:_________________________________
                                                Kevin W. Quinlan, Treasurer,
                                                hereunto duly authorized


                                         BBI-NORTH AMERICAN CLINICAL
                                         LABORATORIES, INC.


                                         By:_________________________________
                                                Kevin W. Quinlan, Treasurer,
                                                hereunto duly authorized

                                         Lender:

                                         THE FIRST NATIONAL BANK OF BOSTON


                                         By:_________________________________
                                                Roger F. Allard
Vice President/Director






                                  EXHIBIT 1.4.1


              Appraisal conducted by Frank Ronne & Associates dated
                  August 9, 1994 of BBI, BTRL and NACL Eligible
                                Equipment is held
                              in the Lender's files









                                   EXHIBIT 1.8

                       TO SECOND AMENDED AND RESTATED LOAN
                             AND SECURITY AGREEMENT


1)    Contract Number:     263-MQ-519321-1

      Issued By:           National Cancer Institute, NIH

      Contracting
      Officer:             Ms. Patricia Haun

      Description:         LN2 Freezer Maintenance Contract (#108)

      Disbursing
      Officer:             Chief, Contracts Section, FAAB, Division of
                           Financial Mgmt. Bldg. 31, Rm. B1B05A,
                           9000 Rockville Pike, Bethesda, MD 20892

      Sureties:            N/A



2)    Contract Number:     NO1-CP-33060

      Issued By:           Cancer Etiology Contracts Section, NCI, NIH

      Contracting
      Officer:             Nancy E. Coleman

      Description:         Repository for Cancer Study (#115)

      Disbursing
      Officer:             Chief, Contracts Section, FAAB, Division of
                           Financial Mgmt. Bldg. 31, Rm. B1B05A,
                           9000 Rockville Pike, Bethesda, MD 20892

      Sureties:            N/A



3)    Contract Number:     2-R44-AI29224

      Issued By:           National Institute of Allergy &
                           Infectious Diseases, NIH

      Contracting
      Officer:             Todd Ball, Grants Mgmt. Officer, GMB, DEA-NIAID

      Description:         Lyme PCR (#117)

      Disbursing
      

      Officer:             Ms. Jessilynn Elliott, Division of Payment
                           Management, P.O. Box
                           6021, Rockville, MD 20852

      Sureties:            N/A



4)    Grant Number:        5-RO1-AI-33066 (NIH, NIAID)
      Subcontract No.:     5-50257

      Issued By:           University of North Carolina

      Contracting
      Officer:             Ms. Carol Alderson, NIAID Contract Specialist

      Description:         Plant Anti-HIV Drug Testing (#112)

      Disbursing
      Officer:             Mary Fedash, Chief, Contracts Section, FAAB, Div. of
                           Financial Mgmt. Bldg. Rm. B1B05A,
                           9000 Rockville Pike, Bethesda, MD 20892

      Sureties:            N/A



5)    Contract Number:     N01-HD-33183

      Issued By:           NICHD, NIH

      Contracting
      Officer:             Harvey Shifrin

      Description:         Repository for PAMA Studies (116)

      Disbursing
      Officer:             Chief, Contracts Section, FAAB, Division of
                           Financial Mgmt. Bldg. 31, Rm. B1B05A,
                           9000 Rockville Pike, Bethesda, MD 20892

      Sureties:            N/A



6)    Contract Number:     1 R43 HL54370

      Issued By:           National Heart, Lung & Blood Institute, NIH

      Contracting Officer: Jane R. Davis, Section Grants Mgmt. Officer, GOB








      Description:         Multiplex PCR (#120)

      Disbursing
      Officer:             Ms. Mary S. Reid, Division of Financial
                           Management, NIH
                           Building 31, Room B1B11, Bethesda, MD 20892

      Sureties:            N/A



7)    Contract Number:     N01-HD-5-3232

      Issued By:           NICHD, NIH

      Contracting Officer: Ms. Mya Hlaing

      Description:         Repository for MFMU Studies (122)

      Disbursing
      Officer:             Chief, Contracts Section, FAAB, Division of
                           Financial Mgmt. Bldg. 31, Rm. B1B05A,
                           9000 Rockville Pike, Bethesda, MD 20892

      Sureties:            N/A



8)    Contract Number:     263-00045134-03-BPA/G

      Issued By:           NIH, PHS, DHHS

      Contracting Officer: Bill Ainsworth
      Description:         NIH BPA

      Disbursing
      Officer:             Accounts Payable Section, DFM, Bldg. 31,
                           Rm. B1B39

      Sureties:            N/A

9)    Contract Number:     FDA 001273-00-95-00 00

      Issued By:           FDA, Supply Contracts Section, HFA-513

      Contracting
      Officer:             Donald W. Broome

      Description:         FDA BPA







      Disbursing
      Officer:             DHHS/FDS/Commercial Accts., 5600 Fishers    Lane,
                           HFA-122, Rockville, MD 20857

      Sureties:            N/A



10)   Contract Number:     DAMD17-94-A-4011 (BPA)

      Issued By:           U.S. Army Medical Research Acquisition Activity

      Contracting
      Officer:             Herman F. Willis, Jr.

      Description:         Army BPA

      Disbursing
      Officer:             Finance & Accounting Office, Bldg. 810,
                           Fort Detrick, MD 21702-5000

      Sureties:            N/A






11)   Contract Number:     N01-AI-42902 (MAA)

      Issued By:           National Institute of Allergy and Infectious Disease,
NIH

      Contracting
      Officer:             Toni A. Kuhn

      Description:         NIAID Master Agreement

      Disbursing
      Officer:             Chief, Contracts Section, FAAB, Division of
                           Financial Mgmt. Bldg. 31, Rm. B1B05A,
                           9000 Rockville Pike, Bethesda, MD 20892

      Sureties:            N/A






                                  EXHIBIT 3.2.1

                               LOCK BOX AGREEMENT


      This Lock Box  Agreement  (the  "Agreement"),  dated as of this ___ day of
________ , 199_ , by and between  ______________  , a Massachusetts  corporation
("________"), and THE FIRST NATIONAL BANK OF BOSTON (the "Lender").  Capitalized
terms used without  definition  shall have the  meanings  given them in the Loan
Agreement (as hereinafter defined).

      WHEREAS,  the Lender has entered into a Second  Amended and Restated  Loan
and Security Agreement with Boston Biomedica, Inc., BTRL Contracts and Services,
Inc.  and  BBI - North  American  Clinical  Laboratories,  Inc.  (together,  the
"Borrower") dated as of August 2, 1995 (the "Loan Agreement")  pursuant to which
the  Borrower has granted the Lender a security  interest  in,  inter alia,  its
present and future Eligible Accounts and proceeds thereof; and

      WHEREAS,  the Loan Agreement provides that all collections and proceeds of
such  Eligible  Accounts  shall be remitted in kind to the Lender in  accordance
with the provisions of this Agreement and the Loan Agreement.

      NOW,  THEREFORE,  in  consideration  of the  premises  and other  good and
valuable  consideration,  the  receipt  and  sufficiency  of  which  are  hereby
acknowledged, the parties hereto hereby agree as follows:

      1. Post  Office  Box.  The Lender has rented a Post  Office Box (the "Lock
Box") at the post  office  located  at , in the name of for the  benefit  of the
Lender under  United  States Post Office Box No. . hereby  authorizes  Lender to
date and deliver the executed  Notice to Postmaster to the Post Office  attached
hereto as Exhibit A. __________ hereby  represents,  warrants and covenants that
all customers of have been instructed to mail their  remittances to the Lock Box
in accordance with the terms of the Loan  Agreement.  In the event that receives
any such remittances, shall promptly deliver such remittances to the Lender.

      2.  Access to Contents of Lock Box.  The Lender  will have  exclusive  and
unrestricted  access  to the Lock  Box and  will  have  complete  and  exclusive
authority  to receive,  pick up and open all regular,  registered,  certified or
insured mail  addressed  to at the Lock Box.  Such mail will be picked up by the
Lender at the same time as its own mail is collected throughout the working day.

      3. Remittance  Collection.  The Lender will open all mail addressed to the
Lock Box and will remove and inspect the  enclosures.  All checks,  money orders
and  other  forms or  orders  for the  payment  of money  and  other  collection
remittances  (hereinafter   collectively  referred  to  as  "checks")  shall  be
processed by the Lender as follows:

               (a) Missing Date.  All undated checks will be dated by the Lender
      as of the date of receipt and processed as hereafter provided.

               (b)  Postdated.  Checks  postdated  two days from date of receipt
      will be processed on the date of receipt.  Checks  postdated three days or
      more from the date of receipt  will be processed on the date of receipt in
      the absence of notice of a specific  agreement  between  ________  and the
      Lender in which case the Lender will consult with ___________ .

               (c) Stale Date. Checks dated six months or more prior to the date
      of collection will be deposited on the date of receipt.








               (d) Differing Amounts.  Where written and numeric amounts differ,
      a check will be  processed  by the Lender in  accordance  with the written
      amount.

               (e)  Signature  Missing.  Checks  which do not bear the  drawer's
      signature  will be deposited  and  processed by affixing a notice  thereto
      requesting that the drawee Lender contact the drawer thereof for authority
      to pay thereunder.

               (f)  Alterations and  Restrictions.  The Lender will consult with
      __________   regarding   checks  with   alterations   and  checks  bearing
      restrictive  notations  such as those  marked  "Payment in Full",  and the
      Lender will either deposit such checks or return them to the maker.

               (g) Foreign  Currency.  Checks drawn in foreign  currency will be
      processed  in  accordance  with the  Lender's  normal  procedure  for such
      checks.

      4.  Processing  of  Acceptable  Checks.  All  checks,   except  those  not
acceptable for deposit under the terms of this Agreement,  shall be deposited on
the day of  receipt  by the  Lender to  Account  _______________  , and shall be
endorsed as follows:

      CREDIT TO THE ACCOUNT OF THE WITHIN NAMED PAYEE.  PAYMENT ACCEPTED WITHOUT
      PREJUDICE. ABSENCE OF ENDORSEMENT GUARANTEED. WORCESTER COUNTY INSTITUTION
      FOR SAVINGS.

      __________________ agrees to indemnify the Lender from and against any and
all  losses,   costs  and  expenses  incurred  by  it  which  result  from  such
endorsement.

      All  remittances,   advices,  envelopes  and  written  matter  (except  as
expressly  provided herein) received in the Lock Box shall be sent by the Lender
to  ____________ . On each day on which there is a deposit to said account,  the
Lender shall send by telecopier to a detailed analysis of the check amount,  the
check  number and the invoices  being paid,  and the Lender shall mail a monthly
statement of account to ______________.

      5. Returned  Checks.  Checks  deposited in said account which are returned
unpaid because of insufficient  or uncollected  funds will be redeposited by the
Lender only once. If redeposit is not warranted because payment has been stopped
on the  check or  because  the  account  on which  the  check was drawn has been
closed,  or if a check is  returned a second  time,  the Lender will charge said
account and send a debit advice with the item to ____.

      6.  Remittances  Received by _______.  will forward to the Lock Box on the
day received any remittances which are sent directly to ____.

      7. Record  Maintenance.  All deposited checks will be microfilmed on front
and back by the  Lender and  retained  for seven  years by the  Lender  prior to
destruction thereof.

      8.  Lender  Charges.  All  charges  of the Lender  for  services  rendered
pursuant to this Agreement shall be debited to ______'s account.

      9.  Force  Majeure.  The  Lender  shall not be  responsible  for delays or
failures in  performance  hereunder  resulting  from causes  beyond its control,
including without  limitation,  acts of God, strikes,  lockouts,  riots, acts of
war,  governmental   regulations,   fire,  communication  line  failures,  power
failures, earthquakes or other disasters.

      10. Term.  This  Agreement  shall  continue in full force and effect until
termination by the Lender in accordance with the Loan Agreement or prior written
notice to _____.








      11. Modification.  This Agreement may be modified only by a writing signed
by all of the parties hereto.

      12.  Addresses.  All  notices,  including  phone  notices,  daily  deposit
advices,  monthly  statements  of  account  and  copies  of all  checks  and the
documents  which are to be given or sent hereunder  shall be sent as provided in
the Loan Agreement and, where applicable, given at the following phone numbers:


      If to the Lender: The First National Bank of Boston
                                  ATTN: Roger F. Allard, Vice President/Director
                                        (508) 770-7125

      If to the Borrower:        ________________________________
                                  ATTN: Kevin J. Quinlan, Chief
                                        Financial Officer
                                        (508) 580-1900

      13.  Jurisdiction.  This  Agreement  shall be  governed by the laws of the
Commonwealth of Massachusetts.

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

                                       THE FIRST NATIONAL BANK OF BOSTON



                                       By:
                                          ---------------------------           
                                          Roger F. Allard
                                          Vice President/Director





                                       By:
                                          -----------------------------
                                          Kevin W. Quinlan, Treasurer








                                    EXHIBIT A



                                  ____________




                                   DATE __________, 199



Postmaster
Worcester, Massachusetts


Dear Sir/Madam:

        We request and  authorize  that you rent to The First  National  Bank of
Boston  ("FNBB") a post office box in our name and to grant  representatives  of
FNBB  unrestricted  access to the post  office  box for the  removal of any mail
placed therein.




                                                    ______________


                                                    By:____________________
                                                    Name:  Kevin W. Quinlan
                                                    Title: Treasurer











                               EXHIBIT 4.2.15 (A)


                         [FORM OF COLLATERAL ASSIGNMENT]



         This Collateral  Assignment (the  "Assignment") is made this ___ day of
_______, 19___ by _____________________________________________, a Massachusetts
corporation      having     a     principal     place     of     business     at
_________________________________          (the          "Assignor")          to
____________________________,  a Massachusetts  bank having a principal place of
business at _____________________________________________ (the "Assignee").

         This  Assignment  is  executed  and  delivered  by the  Assignor to the
Assignee     pursuant     to    and    in     furtherance     of    a    certain
_____________________________________  executed and delivered by the Assignor to
the Assignee dated _____________________ (the "Loan Agreement").

         FOR VALUE  RECEIVED,  and other good and  valuable  consideration,  the
receipt and  sufficiency  of which are hereby  acknowledged,  the Assignor  does
hereby  transfer,  assign,  convey,  set over and deliver to the Assignee all of
Assignor's rights, title and interests in and to all moneys due or to become due
under the contracts listed on Schedule A attached hereto and incorporated herein
by reference  and entered into by and between the Assignor and the United States
of  America  and  amendments  thereof  and  supplements  thereto  heretofore  or
hereafter made (the "Contracts").

         This  Assignment  shall be deemed to  include,  and the  Assignor  does
hereby  assign to the  Assignee  all moneys due or to become due to the Assignor
from the UNITED STATES OF AMERICA,  under any letter of intent, letter of award,
acceptance of bid or proposal, other contract, order,  authorization to commence
performance,  communication or instruction  received by the Assignor relative to
or in anticipation  of said  Contracts,  including said Contracts in their final
definitive form and any amendments thereof and supplements thereto, all of which
shall be included in the term "Contracts" as herein used. Assignor warrants that
the  property  purported  to be  assigned  hereby  is  assignable  by it to  the
Assignee,  that it has full  right to make this  Assignment  and that it has not
made any prior assignment of the Contracts or of any moneys due or to become due
thereunder.  Assignor will execute and deliver such further  instruments  and do
such  further  acts as the  Assignee  may  request or as shall be  necessary  or
desirable  for the  further  assurance  of the  Assignee of the moneys due or to
become due from the UNITED STATES OF AMERICA under the  Contracts,  will deliver
and transfer to the Assignee  upon request all books,  correspondence  and other
papers  appropriate  to verify or  substantiate  such moneys,  and will give the
Assignee all  reasonable  assistance in collecting  such.  Assignor will hold in
trust  for the  Assignee  all  such  moneys  hereafter  received  by it and will
forthwith  transmit  the  same in  specie  (after  first  making  any  necessary
endorsements) to the Assignee.

         This  Assignment is executed in accordance  with the  provisions of the
Assignment of Claims Act of 1940 as amended.

         The Assignee is authorized  and shall be entitled to do in its name, or
in the name of the Assignor,  all things with  reference to the moneys due under
the  Contracts  or any of them  and  hereby  assigned  under  the  terms of this
instrument,  that the  Assignor  might have done but for this  Assignment.  Such
include, without limitation, the following:

         1.   To  receive,  collect (by suit or  otherwise)  and receipt for the
              payment of all moneys due or  hereafter to become due under any of
              the Contracts;

         2.   To  endorse  in the name of the  Assignor  any  checks  or  drafts
              payable to the  Assignor  which shall be  collected or received on
              account  of or in  payment  of  any  moneys  due  or  which  shall
              hereafter become due under the terms of any of the Contracts;








         3.   To settle,  adjust and  compromise  all present and future  claims
              arising  out of any of the moneys due or  hereafter  to become due
              under the terms of the Contracts or any of them, without liability
              except for its own wilful malfeasance in connection therewith.


                  [REMAINDER OF PAGE INTENTIONALLY LEFT BLANK]








         IN WITNESS  WHEREOF,  the  Assignor  has caused this  instrument  to be
executed  and  delivered  in its  name  and on its  behalf  by an  officer  duly
authorized, as an instrument under seal, as of the date first written above.

ATTEST:                             ASSIGNOR:

                                    _____________________________


________________________   By: ______________________________
Clerk/Assistant Clerk
                            Its: ____________________

                            [AFFIX CORPORATE SEAL OR
                            ATTACH CERTIFIED COPY OF
                         BOARD OF DIRECTORS' RESOLUTION
                        AUTHORIZING EXECUTION BY SIGNOR]



                          COMMONWEALTH OF MASSACHUSETTS

___________________, ss.                             Date:  __________________

         Then personally appeared the above named  ________________________  who
being  by  me  duly   sworn,   said   that  he  is  the   _________________   of
_______________________  the corporation  described above and which executed the
foregoing  instrument,  and  that  he is  duly  authorized  to so  execute  said
instrument as aforesaid, before me.

                                            ----------------------------
                                            Notary Public
                                            My Commission Expires:








                                   SCHEDULE A

TO COLLATERAL ASSIGNMENT BETWEEN ___________________________ AND 
______________________________________________



1)    Contract Number:

      Issued By:

      Contracting
      Officer:

      Disbursing
      Officer:



2)    Contract Number:

      Issued By:

      Contracting
      Officer:

      Disbursing
      Officer:













                               EXHIBIT 4.2.15 (B)

                    [FORM OF NOTICE OF COLLATERAL ASSIGNMENT]




Certified Mail                                            Date: _________, 199__
Return Receipt Requested
Receipt No. __________________



________________________                               ________________________
________________________                               ________________________
________________________                               ________________________
                       
ATTN: ____________                                     ATTN:___________________
(CONTRACTING OFFICER OR
DISBURSING OFFICER OR DESIGNATED
AGENCY HEAD IN THE CONTRACT
TO MAKE PAYMENT)


      Re:      NOTICE OF ASSIGNMENT OF CONTRACTS as more particularly  described
               on  Schedule A attached  hereto  (hereinafter  referred to as the
               "Contracts")  made  by  _________________________________________
               with  BTRL   Contracts  and  Services,   Inc.,  a   Massachusetts
               corporation  with a  principal  place  of  business  at 375  West
               Street,  West  Bridgewater,  MA  02379  (hereinafter  called  the
               "Corporation")

Dear Sir/Madam:

      Please  take  notice  that  all of the  Corporation's  rights,  title  and
interest  in and to all monies  due or to become  due under the  above-described
Contracts,  including all amendments thereof and supplements thereto,  have been
assigned to The First  National Bank of Boston having a principal  office at 100
Front Street,  Worcester,  MA 01608 (hereinafter  called "FNBB") pursuant to the
provisions of the Assignment of Claims Act of 1940, as amended,  31 U.S.C. 3727,
41 U.S.C. 15 (the "Act").

      A true copy of the instrument of assignment executed by the Corporation as
Contractor on / / is attached to this notice.

      Pursuant to the Act, we advise you that:

      1.       FNBB is a Massachusetts bank;

      2.       The assignment covers all amounts payable to the Corporation 
under the Contracts which have not already been paid;

      3.       The assignment has been made to FNBB and no part thereof has been
made to any other parties; and

      4.       No further assignment has been made.









      The copy of the  Contracts we have reviewed does not indicate any sureties
with respect to the Contracts. We would appreciate your confirming this fact or,
if such is not the case,  please supply us with appropriate  names and addresses
of all  sureties  with  respect to the  Contracts,  so that they can be notified
under the Act.

      The Contracts  also indicate that payment will be made by the  "disbursing
officer" as defined under the Act unless you advise us further below.

      All payments due or to become due on the Contracts  should be made payable
to: FNBB,  and should be mailed to: 100 Front Street,  Worcester,  MA 01615-0073
Attention: Commercial Banking Group.

      Please return to the  undersigned the three enclosed copies of this Notice
with the  appropriate  notations  (showing  the date  and hour of  receipt,  and
confirming the above information concerning sureties and disbursing officer) and
duly signed by the  addressee or person  acknowledging  receipt on behalf of the
addressee,  to: First National Bank of Boston, 100 Front Street,  Worcester,  MA
01608, Attention: Commercial Banking Group.









      If you have any  questions or problems,  please  contact the  undersigned.
Thank you for your cooperation.

                                           Very truly yours,

                                           FIRST NATIONAL BANK OF BOSTON

                                           By: _______________________________
                                              (Signature of Signing Officer)

                                           Its: _______________________________
                                               (Title of Signing Officer)

                                                100 Front Street
                                                Worcester, MA 01615-0073
                                                Address of Assignee


                                 ACKNOWLEDGMENT

      The addressee  designated above hereby  acknowledges  receipt of the above
Notice of Assignment of Contracts and of a copy of the  instrument of assignment
attached hereto at _______, __m. on ________________, 19___.

                                                ----------------------------
                                                Title: ________________________
 
                                                ON BEHALF OF:

                                                ----------------------------









                                  EXHIBIT 5.2.1




A.    OPERATING CASH FLOW ("OCF")

      Add:     1.          Earnings before interest and taxes (EBIT)
               2.          Depreciation and Amortization
               3.          Non-cash related and other
      Less:    4.          Cash taxes
               5.          Capital Expenditures (CAPEX)                         
               6.          OCF                                                  

B.    ADJUSTMENTS TO OCF ("Adjusted OCF")

      Add:     7.          Net Equity Raised (1)
               8.          Financed Capex (2)                                   
               9.          Adjusted OCF                                         

C.    TOTAL DEBT SERVICE ("TDS")

               1.          Interest Expense
               2.          Current Maturities of Long Term Debt (CMLTD)         
               3.          TDS                                                  


Adjusted OCF/TDS = Debt Service Ratio




      Note:
      (1)    Net equity raised is less any equity used to finance acquisitions.
      (2)    Financed Capex is bank/lease debt used to offset capital purchases.








 
                                                                       EXECUTION


                 FIRST AMENDMENT TO SECOND AMENDED AND RESTATED
                           LOAN AND SECURITY AGREEMENT

      This First  Amendment  to Second  Amended and  Restated  Loan and Security
Agreement  (this  "Agreement")  is dated as of December ___, 1995, and is by and
among BOSTON  BIOMEDICA,  INC.,  ("BBI"),  BTRL  CONTRACTS  AND  SERVICES,  INC.
("BTRL") and BBI - NORTH AMERICAN CLINICAL LABORATORIES, INC., formerly known as
NORTH AMERICAN LABORATORY GROUP, INC. ("NACL"), each of which is a Massachusetts
corporation  validly  created,  legally  existing and in good standing under the
laws of the  Commonwealth  of  Massachusetts  and each of which has its  "Notice
Address" at 375 West Street,  West Bridgewater,  Massachusetts  02379 (BBI, BTRL
and NACL, together with their successors and assigns, are collectively  referred
to herein as the "Borrower")  and THE FIRST NATIONAL BANK OF BOSTON,  a national
banking   association   having  an  office  and  "Notice  Address"  at  Bank  of
Boston-Worcester   Tower,   P.O.  Box  15073,   100  Front  Street,   Worcester,
Massachusetts   01608-1438  (together  with  its  successors  and  assigns,  the
"Lender").

      WHEREAS,  the  Borrower  and the  Lender are  parties to a certain  Second
Amended and Restated Loan and Security Agreement (the "Loan Agreement") dated as
of August 2, 1995 (the Loan  Agreement,  together  with any other  documents and
instruments  executed  and  delivered  in  connection  therewith or securing the
payment and performance obligations of the Borrower thereunder shall be referred
to collectively as the "BBI Commercial Financing Documents"); and

      WHEREAS, the Borrower has requested that the Lender extend to the Borrower
and the Lender has  agreed to so extend a loan (the "Real  Estate  Loan") in the
original amount of $750,000 to finance BBI's  acquisition of two parcels of real
property with the improvements thereon known as and numbered 375 West Street and
80 Manley Street, West Bridgewater,  Plymouth County, Massachusetts (referred to
together as the "Property"); and

      WHEREAS, the Real Estate Loan is to be evidenced by a Term Promissory Note
given by the Borrower to the Lender in the original principal amount of the Real
Estate Loan and a Real Estate Loan Agreement, which is, in turn, secured in part
by two certain  Mortgage,  Financing  Statement  and  Security  Agreements,  two
certain  Assignments  of  Rents  and  Leases  and  two  certain  Assignments  of
Agreements,  Permits  and  Rights,  each with  respect to the  Property,  and an
Environmental  Indemnification  (the foregoing documents referred to together as
the "Real Estate Loan Documents"); and

      WHEREAS,  the Lender is willing to extend the Real  Estate  Loan to or for
the benefit of the Borrower in accordance with the terms of the Real Estate Loan
Documents  only if the  Borrower  agrees to amend the Loan  Agreement to provide
that (i) the payment and performance  obligations of the Borrower under the Real
Estate  Loan  Documents  are  "Obligations"  under  the  Loan  Agreement,  which
Obligations are secured, in part, by the BBI Commercial  Financing Documents and
in part by the Real Estate Loan Documents,  and (ii) the occurrence of any Event
of Default,  as defined in the Real Estate Loan Documents,  shall  constitute an
Event of Default under the Loan Agreement and the other BBI Commercial Financing
Documents;









      NOW,  THEREFORE,  in order to induce the Lender to extend the Real  Estate
Loan and to grant  certain  other  financial  accommodations,  all to or for the
benefit of the Borrower,  and in  consideration  thereof and in consideration of
the mutual covenants herein contained, the parties hereby agree as follows:

      1. Definitions. Terms not otherwise specifically defined in this Agreement
shall have the respective meanings given to them in the Loan Agreement or in the
Real Estate Loan Documents.

      2. Amendments to the Loan Agreement.  The Loan Agreement is hereby amended
as follows:

               A.  Section  2.1  Amounts  and Types of Loans;  Notes  Evidencing
        Loans.  The word "and" at the end of subsection 2.1.3 is hereby deleted.
        The period at the end of subsection  2.1.4 is hereby deleted and "; and"
        substituted therefor.  The following subsection 2.1.5 is hereby added at
        the end of Section 2.1:

                       2.1.5 a term  loan in the  original  principal  amount of
                Seven Hundred Fifty Thousand  Dollars  ($750,000) (the "$750,000
                Real  Estate  Term  Loan"),  evidenced  by the  Borrower's  Term
                Promissory  Note (the  "$750,000  Term Note") dated December 11,
                1995 in the face amount of the full principal thereof.

        and the  sentence  in  parentheses  at the end of Section  2.1 is hereby
        deleted and the following substituted therefor:

                (The Line of Credit Note,  the Amended and  Restated  Term Note,
                the $200,000 Term Note,  the $350,000 Term Note and the $750,000
                Term Note may each be referred  to as a "Note" and  collectively
                as the "Notes".

               B.  Section  2.5 Use of  Proceeds.  The word  "and" at the end of
        subsection 2.5.3 is hereby deleted.  The period at the end of subsection
        2.5.4 is hereby deleted and ";and" substituted  therefor.  The following
        subsection 2.5.5 is hereby added at the end of Section 2.5:

                       2.5.5 with respect to the $750,000 Real Estate Term Loan,
                advances up to the full amount of the $750,000  Real Estate Term
                Loan shall be made to acquire two parcels of real  estate,  with
                the buildings and other improvements thereon,  known as 375 West
                Street and 80 Manley  Street,  West  Bridgewater,  Massachusetts
                (together, the "Property") as more particularly described in the
                Mortgages.

               C. Section 3.1 Granting  Clause;  Desription of  Collateral.  The
        word "and" at the end of subsection 3.1.10 is hereby deleted. The period
        at the end of subsection 3.1.11 is hereby deleted and ";and" substituted
        therefor.  The following subsection 3.1.12 is hereby added at the end of
        Section 3.1:

                       3.1.12  The "Mortgaged Estate" as defined in the 
                Mortgages.




                                      -2-




               D.  Section  6.4.  The phrase "or any  Financing  Instrument"  is
        hereby  added after the word  "Agreement"  in the second line of Section
        6.4.

      2.  Ratification  and  Confirmation  of  Representations,   Covenants  and
Warranties.  In order to induce  the Lender to enter  into this  Agreement,  the
Borrower  hereby  ratifies  and  confirms  all  representations,  covenants  and
warranties contained in the Loan Agreement and all other Financing  Instruments,
and the  Borrower  hereby  restates  all  such  representations,  covenants  and
warranties as of the date of this Agreement.

      3. Incorporation of Agreement into the Loan Agreement. Except as expressly
amended hereby,  the Loan Agreement shall continue in full force and effect, and
all  references  to the  Loan  Agreement  in any  of the  Financing  Instruments
hereafter shall mean the Loan Agreement as amended by this Agreement.

      4. Counterpart Execution.  To facilitate execution,  this Agreement may be
executed in as many counterparts as may be convenient or required.  It shall not
be necessary  that the  signature and  acknowledgment  of, or on behalf of, each
party, or that the signature and  acknowledgment of all persons required to bind
any party,  appear on each  counterpart.  All  counterparts  shall  collectively
constitute  a single  instrument.  It shall not be  necessary in making proof of
this  Agreement  to  produce  or  account  for more  than a  single  counterpart
containing the respective  signatures  and  acknowledgment  of, or on behalf of,
each of the parties hereto.




                                      -3-






   EXECUTED AS A SEALED INSTRUMENT as of the day and year first stated above.

                                                     BOSTON BIOMEDICA, INC.



__________________________ By:_______________________________
Witness as to Borrower                            Richard T. Schumacher
                                                  President
                                                  Hereunto duly authorized


                                               BTRL CONTRACTS AND SERVICES,
                                                          INC.


                                               By:__________________________
                                                  Richard T. Schumacher
                                                  President
                                                  Hereunto duly authorized

                                               BBI - NORTH AMERICAN CLINICAL
                                               LABORATORIES, INC.


                                               By:__________________________
                                                  Richard T. Schumacher
                                                  President
                                                  Hereunto duly authorized

                                               
                                               THE FIRST NATIONAL BANK OF BOSTON



                                               By:_________________________     
Witness as to Lender                              Roger F. Allard
                                                  Vice President/Director
                                                  Hereunto duly authorized




PABOS:SCS:201888_2




                                      -4-