Document:

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                                   Exhibit 4.5

           Registration Rights Agreement among Boston Biomedica, Inc.,
               DP Securities, Inc., Wharton Capital Partners, Ltd.,
                    and GCA Strategic Investment Fund Limited

                          REGISTRATION RIGHTS AGREEMENT

         REGISTRATION RIGHTS AGREEMENT (this "Agreement"), dated as of August
25, 2000, between Boston Biomedica, Inc., a Massachusetts corporation (the
"Company"), and GCA Strategic Investment Fund Limited (the "Fund"), Wharton
Capital Partners, Ltd. (Wharton") and DP Securities, Inc. ("DP").

         1.       INTRODUCTION.

                  1.1 SECURITIES PURCHASE AGREEMENT. The Company and the Fund
have today executed that certain Securities Purchase Agreement (the "Securities
Purchase Agreement"), pursuant to which the Company has agreed, among other
things, to issue up to an aggregate of Two Million Two Hundred Fifty Thousand
Dollars ($2,250,000.00) (U.S.) principal amount of 3% Senior Subordinated
Convertible Debentures of the Company (the "Debentures") to the Fund or its
successors, assigns or transferees (collectively, the "holders"). The Debentures
are convertible into an indeterminable number of shares (the "Debenture
Conversion Shares") of the Company's common stock par value, $0.01 per share
(the "Common Stock") pursuant to the terms of the Debentures. In addition,
pursuant to the terms of the Securities Purchase Agreement and the transactions
contemplated thereby, the Company has agreed to issue to the Fund common stock
purchase warrants exercisable for up to an aggregate of 80,000 shares of the
Company's Common Stock and common stock purchase warrants exercisable for up to
an aggregate of 10,000 shares of Common Stock to each of DP and Wharton
(collectively the "Warrant Shares"). The number of Debenture Conversion Shares
and Warrant Shares is subject to adjustment upon the occurrence of stock splits,
recapitalizations and similar events occurring after the date hereof.

                  1.2 DEFINITION OF SECURITIES. The Debenture Conversion Shares
and the Warrant Shares are herein referred to as the "Securities."

                  1.3 NATIONAL MARKET REPRESENTATION. The Company represents and
warrants that the Company's Common Stock is currently eligible for trading on
the Nasdaq National Market under the symbol "BBII." Certain capitalized terms
used in this Agreement are defined in Section 3 hereof; references to sections
shall be to sections of this Agreement.

         2.       REGISTRATION UNDER SECURITIES ACT, ETC.

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                  2.1      MANDATORY REGISTRATION.

                           (a) REGISTRATION OF REGISTRABLE SECURITIES. The
Company shall prepare and file on or before the 30th day following the date
hereof (the "Filing Date") a registration statement (the "Registration
Statement") covering the resale of the Registrable Securities. The Company shall
use its best efforts to cause the Registration Statement to be declared
effective by the Commission on the earlier of (i) 90 days following the date
hereof, (ii) ten (10) days following the receipt of a "No Review" or similar
letter from the Commission or (iii) the first business day following the day the
Commission determines the Registration Statement eligible to be declared
effective (the "Required Effectiveness Date"). Nothing contained herein shall be
deemed to limit the number of Registrable Securities to be registered by the
Company hereunder. As a result, should the Registration Statement not relate to
the maximum number of Registrable Securities acquired by (or potentially
acquirable by) the holders thereof upon conversion of the Debentures, or
exercise of the Common Stock Purchase Warrants described in Section 1 above, the
Company shall be required to promptly file a separate registration statement
(utilizing Rule 462 promulgated under the Securities Act, where applicable)
relating to such Registrable Securities which then remain unregistered. The
provisions of this Agreement shall relate to any such Registration Statement and
any such separate registration statement as if it were an amendment to the
Registration Statement.

                           (b) REGISTRATION STATEMENT FORM. Registrations under
this Section 2.1 shall be on Form S-3 or such other appropriate successor
registration form of the Commission as shall permit the disposition of such
Registrable Securities in accordance with the intended method or methods of
disposition specified by the Fund; provided, however, such intended method of
deposition shall not include an underwritten offering of the Registrable
Securities.

                           (c) EXPENSES. The Company will pay all Registration
Expenses in connection with any registration required by this Section 2.1.

                           (d) EFFECTIVE REGISTRATION STATEMENT. A registration
pursuant to this Section 2.1 shall not be deemed to have been effected (i)
unless a registration statement with respect thereto has become effective within
the time period specified herein, provided that a registration which does not
become effective after the Company filed a registration statement with respect
thereto solely by reason of the refusal to proceed of any holder of Registrable
Securities (other than a refusal to proceed based upon the advice of counsel in
the form of a letter signed by such counsel and provided to the Company relating
to a disclosure matter unrelated to such holder) shall be deemed to have been
effected by the Company unless the holders of the Registrable Securities shall
have elected to pay all Registration Expenses in connection with such
registration, (ii) if, after it has become effective, such registration becomes
subject to any stop order, injunction or other order or extraordinary
requirement of the Commission or other governmental agency or court for any
reason or (iii) if, after it has become effective, such registration ceases to
be effective for more than an aggregate of twenty (20) days.

                           (e) PLAN OF DISTRIBUTION. The Company hereby agrees
that the Registration Statement shall include a plan of distribution section
reasonably acceptable to the Fund; provided, however, such plan of distribution
section shall be modified by the Company so as to not provide for the
disposition of the Registrable Securities on the basis of an underwritten
offering.

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                  2.2      INCIDENTAL REGISTRATION.

                           (a) RIGHT TO INCLUDE REGISTRABLE SECURITIES. If at
any time after the date hereof but before the third anniversary of the date
hereof, the Company proposes to register any of its securities under the
Securities Act (other than by a registration in connection with an acquisition
in a manner which would not permit registration of Registrable Securities for
sale to the public, on Form S-8, or any successor form thereto, on Form S-4, or
any successor form thereto and other than pursuant to Section 2.1), on an
underwritten basis (either best-efforts or firm-commitment), then, the Company
will each such time give prompt written notice to all holders of Registrable
Securities of its intention to do so and of such holders' rights under this
Section 2.2. Upon the written request of any such holder made within twenty (20)
days after the receipt of any such notice (which request shall specify the
Registrable Securities intended to be disposed of by such holder and the
intended method of disposition thereof), the Company will, subject to the terms
of this Agreement, use its commercially reasonable best efforts to effect the
registration under the Securities Act of the Registrable Securities, to the
extent requisite to permit the disposition (in accordance with the intended
methods thereof as aforesaid) of such Registrable Securities so to be
registered, by inclusion of such Registrable Securities in the registration
statement which covers the securities which the Company proposes to register,
provided that if, at any time after written notice of its intention to register
any securities and prior to the effective date of the registration statement
filed in connection with such registration, the Company shall determine for any
reason either not to register or to delay registration of such securities, the
Company may, at its election, give written notice of such determination to each
holder and, thereupon, (i) in the case of a determination not to register, shall
be relieved of this obligation to register any Registrable Securities in
connection with such registration (but not from its obligation to pay the
Registration Expenses in connection therewith), and (ii) in the case of a
determination to delay registering, shall be permitted to delay registering any
Registrable Securities, for the same period as the delay in registering such
other securities. No registration effected under this Section 2.2 shall relieve
the Company of its obligation to effect any registration under Section 2.1, nor
shall any such registration hereunder be deemed to have been effected pursuant
to Section 2.1. The Company will pay all Registration Expenses in connection
with each registration of Registrable Securities requested pursuant to this
Section 2.2. The right provided the holders of the Registrable Securities
pursuant to this Section shall be exercisable at their sole discretion.

                           (b) PRIORITY IN INCIDENTAL REGISTRATIONS. If the
managing underwriter of the underwritten offering contemplated by this Section
2.2 shall inform the Company and holders of the Registrable Securities
requesting such registration by letter of its belief that the number of
securities requested to be included in such registration exceeds the number
which can be sold in such offering, then the Company will include in such
registration, to the extent of the number which the Company is so advised can be
sold in such offering, (i) first securities proposed by the Company to be sold
for its own account, and (ii) second Registrable Securities and securities of
other selling security holders requested to be included in such registration pro
rata on the basis of the number of shares of such securities so proposed to be
sold and so requested to be included; provided, however, the holders of
Registrable Securities shall have priority to all shares sought to be included
by officers and directors of the Company as well as holders of ten percent (10%)
or more of the Company's Common Stock.

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                  2.3 REGISTRATION PROCEDURES. If and whenever the Company is
required to effect the registration of any Registrable Securities under the
Securities Act as provided in Section 2.1 and, as applicable, 2.2, the Company
shall, as expeditiously as possible:

                           (a) prepare and file with the Commission the
Registration Statement or amendments thereto, to effect such registration
(including such audited financial statements as may be required by the
Securities Act or the rules and regulations promulgated thereunder) and
thereafter use its commercially reasonable best efforts to cause such
registration statement to be declared effective by the Commission, as soon as
practicable, but in any event no later than the Required Effectiveness Date
(with respect to a registration pursuant to Section 2.1); provided, however,
that before filing such registration statement or any amendments thereto, the
Company will furnish to the counsel selected by the holders of Registrable
Securities which are to be included in such registration, copies of all such
documents proposed to be filed;

                           (b) with respect to any registration statement
pursuant to Section 2.1, prepare and file with the Commission such amendments
and supplements to such registration statement and the prospectus used in
connection therewith as may be necessary to keep such registration statement
effective and to comply with the provisions of the Securities Act with respect
to the disposition of all Registrable Securities covered by such registration
statement until the earlier to occur of five (5) years after the date of this
Agreement (subject to the right of the Company to suspend the effectiveness
thereof for not more than 10 consecutive days or an aggregate of 30 days in such
five (5) years period) or such time as all of the securities which are the
subject of such registration statement cease to be Registrable Securities (such
period, in each case, the "Registration Maintenance Period");

                           (c) furnish to each seller of Registrable Securities
covered by such registration statement such number of conformed copies of such
registration statement and of each such amendment and supplement thereto (in
each case including all exhibits), such number of copies of the prospectus
contained in such registration statement (including each preliminary prospectus
and any summary prospectus) and any other prospectus filed under Rule 424 under
the Securities Act, in conformity with the requirements of the Securities Act,
and such other documents, as such seller and underwriter, if any, may reasonably
request in order to facilitate the public sale or other disposition of the
Registrable Securities owned by such seller;

                           (d) use its commercially reasonable best efforts to
register or qualify all Registrable Securities and other securities covered by
such registration statement under such other securities laws or blue sky laws as
any seller thereof shall reasonably request, to keep such registrations or
qualifications in effect for so long as such registration statement remains in
effect, and take any other action which may be reasonably necessary to enable
such seller to consummate the disposition in such jurisdictions of the
securities owned by such seller, except that the Company shall not for any such
purpose be required to qualify generally to do business as a foreign corporation
in any jurisdiction wherein it would not but for the requirements of this
subdivision (d) be obligated to be so qualified or to consent to general service
of process in any such jurisdiction;

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                           (e) use its commercially reasonable best efforts to
cause all Registrable Securities covered by such registration statement to be
registered with or approved by such other governmental agencies or authorities
as may be necessary to enable the seller or sellers thereof to consummate the
disposition of such Registrable Securities;

                           (f) furnish to each seller of Registrable Securities
a signed counterpart, addressed to such seller, and the underwriters, if any,
of:

                               (1) an opinion of counsel for the Company, dated
the effective date of such registration statement (or, if such registration
includes an underwritten public offering, an opinion dated the date of the
closing under the underwriting agreement), reasonably satisfactory in form and
substance to such seller including that the prospectus and any prospectus
supplement forming a part of the Registration Statement does not contain an
untrue statement of a material fact or omits a material fact required to be
stated therein or necessary in order to make the statements therein, in light of
the circumstances under which they were made, not misleading, and

                               (2) if such registration includes an underwritten
public offering, a "comfort letter" dated the date of the closing and required
to be delivered to the underwriter under the underwriting agreement, signed by
the independent public accountants who have certified the Company's financial
statements;

                            (g) notify the Sellers' Representative and its
counsel promptly and confirm such advice in writing promptly after the Company
has knowledge thereof:

                               (1) when the Registration Statement, the
prospectus or any prospectus supplement related thereto or post-effective
amendment to the Registration Statement has been filed, and, with respect to the
Registration Statement or any post-effective amendment thereto, when the same
has become effective;

                               (2) of any request by the Commission for
amendments or supplements to the Registration Statement or the prospectus or for
additional information;

                               (3) of the issuance by the Commission of any stop
order suspending the effectiveness of the Registration Statement or the
initiation of any proceedings by any Person for that purpose; and

                               (4) of the receipt by the Company of any
notification with respect to the suspension of the qualification of any
Registrable Securities for sale under the securities or blue sky laws of any
jurisdiction or the initiation or threat of any proceeding for such purpose;

                            (h) notify each seller of Registrable Securities
covered by such registration statement, at any time when a prospectus relating
thereto is required to be delivered under the Securities Act, upon discovery
that, or upon the happening of any event as a result of which, the prospectus
included in such registration statement, as then in effect, includes an untrue
statement of a material fact or omits to state any material facts required to be
stated therein or

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necessary to make the statements therein not misleading in the light of the
circumstances then existing, and at the request of any such seller promptly
prepare and furnish to such seller a reasonable number of copies of a supplement
to or an amendment of such prospectus as may be necessary so that, as thereafter
delivered to the purchasers of such securities, such prospectus shall not
include an untrue statement of a material fact or omit to state a material fact
required to be stated therein or necessary to make the statements therein not
misleading in the light of the circumstances then existing;

                            (i) use its commercially reasonable best efforts to
obtain the withdrawal of any order suspending the effectiveness of the
Registration Statement at the earliest possible moment;

                            (j) otherwise use its commercially reasonable best
efforts to comply with all applicable rules and regulations of the Commission,
and make available to its security holders, as soon as reasonably practicable,
an earnings statement covering the period of at least twelve months, but not
more than eighteen months, beginning with the first full calendar month after
the effective date of such registration statement, which earnings statement
shall satisfy the provisions of Section 11(a) of the Securities Act and Rule 158
thereunder;

                            (k) use its commercially reasonable best efforts to
list all Registrable Securities covered by such registration statement on any
securities exchange on which any of the Registrable Securities are then listed.

         The Company may require each seller of Registrable Securities as to
which any registration is being effected to furnish the Company such information
regarding such seller and the distribution of such securities as the Company may
from time to time reasonably request in writing.

         The Company will not file any registration statement pursuant to
Section 2.1, or amendment thereto or any prospectus or any supplement thereto
(including such documents incorporated by reference and proposed to be filed
after the initial filing of the Registration Statement) to which the Sellers'
Representative shall reasonably object, provided that the Company may file such
documents in a form required by law or upon the advice of its counsel.

         The Company represents and warrants to each holder of Registrable
Securities that it has obtained all necessary waivers, consents and
authorizations necessary to execute this Agreement and consummate the
transactions contemplated hereby other than such waivers, consents and/or
authorizations specifically contemplated by the Securities Purchase Agreement.

         The Fund agrees that, upon receipt of any notice from the Company of
the occurrence of any event of the kind described in subdivision (h) of this
Section 2.3, the Fund will forthwith discontinue the Fund's disposition of
Registrable Securities pursuant to the Registration Statement relating to such
Registrable Securities until such Fund's receipt of the copies of the
supplemented or amended prospectus contemplated by subdivision (h) of this
Section 2.3 and, if so directed by the Company, will deliver to the Company (at
the Company's expense) all copies, other than permanent file copies,

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then in the Fund's possession of the prospectus relating to such Registrable
Securities current at the time of receipt of such notice.

                  2.4      UNDERWRITTEN OFFERINGS.

                           (a) INCIDENTAL UNDERWRITTEN OFFERINGS. If the Company
at any time proposes to register any of its securities under the Securities Act
as contemplated by Section 2.2 and such securities are to be distributed by or
through one or more underwriters, the Company will, if requested by any holder
of Registrable Securities as provided in Section 2.2 and subject to the
provisions of Section 2.2(a), use its commercially reasonable best efforts to
arrange for such underwriters to include all the Registrable Securities to be
offered and sold by such holder among the securities to be distributed by such
underwriters.

                           (b) HOLDBACK AGREEMENTS. Subject to such other
reasonable requirements as may be imposed by the underwriter as a condition of
inclusion of holder's Registrable Securities in the registration statement, each
holder agrees by acquisition of Registrable Securities, if so required by the
managing underwriter, not to sell, make any short sale of, loan, grant any
option for the purchase of, effect any public sale or distribution of or
otherwise dispose of, except as part of such underwritten registration, any
equity securities of the Company, during such reasonable period of time
requested by the underwriter; provided however, such period shall not exceed the
150 day period commencing 30 days prior to the commencement of such underwritten
offering and ending 120 days following the completion of such underwritten
offering.

                           (c) PARTICIPATION IN UNDERWRITTEN OFFERINGS. No
holder of Registrable Securities may participate in any underwritten offering
under Section 2.2 unless such holder of Registrable Securities (i) agrees to
sell such Person's securities on the basis provided in any underwriting
arrangements approved, subject to the terms and conditions hereof, approved by
the Company and (ii) completes and executes all questionnaires, indemnities,
underwriting agreements and other documents (other than powers of attorney)
required under the terms of such underwriting arrangements. Notwithstanding the
foregoing, no underwriting agreement (or other agreement in connection with such
offering) shall require any holder of Registrable Securities to make any
representations or warranties to or agreements with the Company or the
underwriters other than representations and warranties contained in a writing
furnished by such holder expressly for use in the related registration statement
or representations, warranties or agreements regarding such holder, such
holder's Registrable Securities and such holder's intended method of
distribution and any other representation required by law.

                  2.5 PREPARATION; REASONABLE INVESTIGATION. In connection with
the preparation and filing of each registration statement under the Securities
Act pursuant to this Agreement, the Company will give Sellers' Representative
and counsel and accountants for Sellers' Representative, the opportunity to
participate in the preparation of such registration statement, each prospectus
included therein or filed with the Commission, and each amendment thereof or
supplement thereto, and will give each of them such access to its books and
records and such opportunities to discuss the business of the Company with its
officers and the independent public accountants who have certified its financial
statements as shall be necessary, in the reasonable opinion of such holders' and
such

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underwriters' respective counsel, to conduct a reasonable investigation within
the meaning of the Securities Act.

                  2.6 REGISTRATION DEFAULT FEE. If the Registration Statement
contemplated in Section 2.1 is (x) not declared effective by the Required
Effectiveness Date or (y) such effectiveness is not maintained for the
Registration Maintenance Period, then the Company shall pay to the Fund the
Default Fee specified in Section 10.4 of the Securities Purchase Agreement.

                  2.7      INDEMNIFICATION.

                           (a) INDEMNIFICATION BY THE COMPANY. In the event of
any registration of any securities of the Company under the Securities Act, the
Company will, and hereby does agree to indemnify and hold harmless the holder of
any Registrable Securities covered by such registration statement, its directors
and officers, each other Person who participates as an underwriter in the
offering or sale of such securities and each other Person, if any, who controls
such holder or any such underwriter within the meaning of the Securities Act
against any losses, claims, damages or liabilities, joint or several, to which
such holder or any such director or officer or underwriter or controlling person
may become subject under the Securities Act or otherwise, insofar as such
losses, claims, damages or liabilities (or actions or proceedings, whether
commenced or threatened, in respect thereof) arise out of or are based upon any
untrue statement or alleged untrue statement of any material fact contained in
any registration statement under which such securities were registered under the
Securities Act, any preliminary prospectus, final prospectus or summary
prospectus contained therein, or any amendment or supplement thereto, or any
omission or alleged omission to state therein a material fact required to be
stated therein or necessary to make the statements therein not misleading, and
the Company will reimburse such holder and each such director, officer,
underwriter and controlling person for any legal or any other expenses
reasonably incurred by them in connection with investigating or defending any
such loss, claim, liability, action or proceeding, provided that the Company
shall not be liable in any such case to the extent that any such loss, claim,
damage, liability, (or action or proceeding in respect thereof) or expense
arises out of or is based upon an untrue statement or alleged untrue statement
or omission or alleged omission made in such registration statement, any such
preliminary prospectus, final prospectus, summary prospectus, amendment or
supplement in reliance upon and in conformity with written information furnished
to the Company by such holder or underwriter stating that it is for use in the
preparation thereof and, provided further that the Company shall not be liable
to any Person who participates as an underwriter in the offering or sale of
Registrable Securities or to any other Person, if any, who controls such
underwriter within the meaning of the Securities Act, in any such case to the
extent that any such loss, claim, damage, liability (or action or proceeding in
respect thereof) or expense arises out of such Person's failure to send or give
a copy of the final prospectus, as the same may be then supplemented or amended,
within the time required by the Securities Act to the Person asserting the
existence of an untrue statement or alleged untrue statement or omission or
alleged omission at or prior to the written confirmation of the sale of
Registrable Securities to such Person if such statement or omission was
corrected in such final prospectus or an amendment or supplement thereto. Such
indemnity shall remain in full force and effect regardless of any investigation
made by or on behalf of such holder or any such director, officer, underwriter
or controlling person and shall survive the transfer of such securities by such
holder.

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                           (b) INDEMNIFICATION BY THE HOLDERS. The Company may
require, as a condition to including any Registrable Securities in any
registration statement filed pursuant to this Agreement, that the Company shall
have received an undertaking satisfactory to it from the prospective seller of
such Registrable Securities, to indemnify and hold harmless (in the same manner
and to the same extent as set forth in subdivision (a) of this Section 2.7) the
Company, each director of the Company, each officer of the Company and each
other Person, if any, who controls the Company within the meaning of the
Securities Act, with respect to any statement or alleged statement in or
omission or alleged omission from such registration statement, any preliminary
prospectus, final prospectus or summary prospectus contained therein, or any
amendment or supplement thereto, if such statement or alleged statement or
omission or alleged omission was made in reliance upon and in conformity with
written information furnished to the Company through an instrument duly executed
by such seller specifically stating that it is for use in the preparation of
such registration statement, preliminary prospectus, final prospectus, summary
prospectus, amendment or supplement. Any such indemnity shall remain in full
force and effect, regardless of any investigation made by or on behalf of the
Company or any such director, officer or controlling person and shall survive
the transfer of such securities by such seller.

                           (c) NOTICES OF CLAIMS, ETC. Promptly after receipt by
an indemnified party of notice of the commencement of any action or proceeding
involving a claim referred to in the preceding subdivisions of this Section 2.7,
such indemnified party will, if a claim in respect thereof is to be made against
an indemnifying party, give written notice to the latter of the commencement of
such action, provided that the failure of any indemnified party to give notice
as provided herein shall not relieve the indemnifying party of its obligations
under the preceding subdivisions of this Section 2.7, except to the extent that
the indemnifying party is actually prejudiced by such failure to give notice. In
case any such action is brought against an indemnified party, unless in the
opinion of the indemnified party's counsel a conflict of interest between such
indemnified and indemnifying parties may exist in respect of such claim, the
indemnifying party shall be entitled to participate in and to assume the defense
thereof, jointly with any other indemnifying party similarly notified, to the
extent that the indemnifying party may wish, with counsel reasonably
satisfactory to such indemnified party, and after notice from the indemnifying
party to such indemnified party of its election so to assume the defense
thereof, the indemnifying party shall not be liable to such indemnified party
for any legal or other expenses subsequently incurred by the latter in
connection with the defense thereof other than reasonable costs of
investigation. No indemnifying party shall, without the consent of the
indemnified party, consent to entry of any judgment or enter into any settlement
of any such action which does not include as an unconditional term thereof the
giving by the claimant or plaintiff to such indemnified party of a release from
all liability, or a covenant not to sue, in respect to such claim or litigation.
No indemnified party shall consent to entry of any judgment or enter into any
settlement of any such action the defense of which has been assumed by an
indemnifying party without the consent of such indemnifying party.

                           (d) OTHER INDEMNIFICATION. Indemnification similar to
that specified in the preceding subdivisions of this Section 2.7 (with
appropriate modifications) shall be given by the Company and each seller of
Registrable Securities (but only if and to the extent required pursuant

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to the terms of Section 2.7(b)) with respect to any required registration or
other qualification of securities under any Federal or state law or regulation
of any governmental authority, other than the Securities Act.

                           (e) INDEMNIFICATION PAYMENTS. The indemnification
required by this Section 2.7 shall be made by periodic payments of the amount
thereof during the course of the investigation or defense, as and when bills are
received or expense, loss, damage or liability is incurred.

                           (f) CONTRIBUTION. If the indemnification provided for
in the preceding subdivision of this Section 2.7 is unavailable to an
indemnified party in respect of any expense, loss, claim, damage or liability
referred to therein, then each indemnifying party, in lieu of indemnifying such
indemnified party, shall contribute to the amount paid or payable by such
indemnified party as a result of such expense, loss, claim, damage or liability
(i) in such proportion as is appropriate to reflect the relative benefits
received by the Company on the one hand and the holder or underwriter, as the
case may be, on the other from the distribution of the Registrable Securities or
(ii) if the allocation provided by clause (i) above is not permitted by
applicable law, in such proportion as is appropriate to reflect not only the
relative benefits referred to in clause (i) above but also the relative fault of
the Company on the one hand and of the holder or underwriter, as the case may
be, on the other in connection with the statements or omissions which resulted
in such expense, loss, damage or liability, as well as any other relevant
equitable considerations. The relative benefits received by the Company on the
one hand and the holder or underwriter, as the case may be, on the other in
connection with the distribution of the Registrable Securities shall be deemed
to be in the same proportion as the total net proceeds received by the Company
from the initial sale of the Registrable Securities by the Company to the
purchasers bear to the gain, if any, realized by all selling holders
participating in such offering or the underwriting discounts and commissions
received by the underwriter, as the case may be. The relative fault of the
Company on the one hand and of the holder or underwriter, as the case may be, on
the other shall be determined by reference to, among other things, whether the
untrue or alleged untrue statement of a material fact or omission to state a
material fact relates to information supplied by the Company, by the holder or
by the underwriter and the parties' relative intent, knowledge, access to
information supplied by the Company, by the holder or by the underwriter and the
parties' relative intent, knowledge, access to information and opportunity to
correct or prevent such statement or omission, provided that the foregoing
contribution agreement shall not inure to the benefit of any indemnified party
if indemnification would be unavailable to such indemnified party by reason of
the provisions contained in the first sentence of subdivision (a) of this
Section 2.7, and in no event shall the obligation of any indemnifying party to
contribute under this subdivision (f) exceed the amount that such indemnifying
party would have been obligated to pay by way of indemnification if the
indemnification provided for under subdivision (b) of this Section 2.7 had been
available under the circumstances.

         The Company and the holders of Registrable Securities agree that it
would not be just and equitable if contribution pursuant to this subdivision (f)
were determined by pro rata allocation (even if the holders and any underwriters
were treated as one entity for such purpose) or by any other method of
allocation that does not take account of the equitable considerations referred
to in the

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immediately preceding paragraph. The amount paid or payable by an indemnified
party as a result of the losses, claims, damages and liabilities referred to in
the immediately preceding paragraph shall be deemed to include, subject to the
limitations set forth in the preceding sentence and subdivision (c) of this
Section 2.7, any legal or other expenses reasonably incurred by such indemnified
party in connection with investigating or defending any such action or claim.

         Notwithstanding the provisions of this subdivision (f), no holder of
Registrable Securities or underwriter shall be required to contribute any amount
in excess of the amount by which (i) in the case of any such holder, the net
proceeds received by such holder from the sale of Registrable Securities or (ii)
in the case of an underwriter, the total price at which the Registrable
Securities purchased by it and distributed to the public were offered to the
public exceeds, in any such case, the amount of any damages that such holder or
underwriter has otherwise been required to pay by reason of such untrue or
allege untrue statement or omission. No Person guilty of fraudulent
misrepresentation (within the meaning of Section 11(f) of the Securities Act)
shall be entitled to contribution from any person who was not guilty of such
fraudulent misrepresentation.

         3. DEFINITIONS. As used herein, unless the context otherwise requires,
the following terms have the following respective meanings:

            "AGREEMENT": As defined in Section 1.

            "COMMISSION": The Securities and Exchange Commission or any other
Federal agency at the time administering the Securities Act.

            "COMMON STOCK": As defined in Section 1.

            "COMPANY": As defined in the introductory paragraph of this
Agreement.

            "DEBENTURE CONVERSION SHARES": As defined in Section 1.

            "DEBENTURES": As defined in Section 1, such term to include any
securities issued in substitution of or in addition to such Debentures.

            "EXCHANGE ACT": The Securities Exchange Act of 1934, as amended, and
the rules and regulations of the Commission promulgated thereunder.

            "PERSON": A corporation, association, partnership, limited liability
company, trust, organization, business, individual, governmental or political
subdivision thereof or a governmental agency.

            "REGISTRABLE SECURITIES": The Securities and any securities issued
or issuable with respect to such Securities by way of stock dividend or stock
split or in connection with a combination of shares, recapitalization, merger,
consolidation or other reorganization or otherwise. Once issued such securities
shall cease to be Registrable Securities when (a) a registration statement with
respect to the sale of such securities shall have become effective under the
Securities Act and

                                       11
<PAGE>

such securities shall have been disposed of in accordance with such registration
statement, (b) they shall have been distributed to the public pursuant to Rule
144 (or any successor provision) under the Securities Act, (c) they shall have
been otherwise transferred, new certificates for them not bearing a legend
restricting further transfer shall have been delivered by the Company and
subsequent disposition of them shall not require registration or qualification
of them under the Securities Act or any similar state law then in force, (d)
they shall have ceased to be outstanding, (e) on the expiration of the
applicable Registration Maintenance Period or (f) any and all legends
restricting transfer thereof have been removed in accordance with the provisions
of Rule 144(k) (or any successor provision) under the Securities Act.

            "REGISTRATION EXPENSES": All expenses incident to the Company's
performance of or compliance with this Agreement, including, without limitation,
all registration, filing and NASD fees, all stock exchange and OTC Bulletin
Board or other NASD or stock exchange listing fees, all fees and expenses of
complying with securities or blue sky laws, all word processing, duplicating and
printing expenses, messenger and delivery expenses, the fees and disbursements
of counsel for the Company and of its independent public accountants, including
the expenses of any special audits or "cold comfort" letters required by or
incident to such performance and compliance, the reasonable fees and
disbursements of not more than one law firm (not to exceed $20,000) retained by
the holder or holders of more than 50% of the Registrable Securities, premiums
and other costs of policies of insurance of the Company against liabilities
arising out of the public offering of the Registrable Securities being
registered and any fees and disbursements of underwriters customarily paid by
issuers or sellers of securities, but excluding underwriting discounts and
commissions and transfer taxes, if any, provided that, in any case where
Registration Expenses are not to be borne by the Company, such expenses shall
not include salaries of Company personnel or general overhead expenses of the
Company, auditing fees, premiums or other expenses relating to liability
insurance required by underwriters of the Company or other expenses for the
preparation of financial statements or other data normally prepared by the
Company in the ordinary course of its business or which the Company would have
incurred in any event.

            "REGISTRATION MAINTENANCE PERIOD": As defined in Section 2.3.

            "REQUIRED EFFECTIVENESS DATE": As defined in Section 2.1.

            "SECURITIES": As defined in Section 1.2.

            "SECURITIES ACT": The Securities Act of 1933, as amended, and the
rules and regulations of the Commission promulgated thereunder.

            "SECURITIES PURCHASE AGREEMENT": As defined in Section 1.

            "SELLERS' REPRESENTATIVE": Global Capital Advisors Ltd. or such
Person designated by Global Capital Advisors Ltd. as of the time of disposition
of the last of the Debentures held by the Fund (or subsequent Sellers'
Representative).

            "WARRANT SHARES": As defined in Section 1.

                                       12
<PAGE>

         4. RULE 144. The Company shall timely file the reports required to be
filed by it under the Securities Act and the Exchange Act (including but not
limited to the reports under Sections 13 and 15(d) of the Exchange Act referred
to in subparagraph (c) of Rule 144 adopted by the Commission under the
Securities Act) and the rules and regulations adopted by the Commission
thereunder (or, if the Company is not required to file such reports, will, upon
the request of any holder of Registrable Securities, make publicly available
other information) and will take such further action as any holder of
Registrable Securities may reasonably request, all to the extent reasonably
required from time to time to enable such holder to sell Registrable Securities
without registration under the Securities Act within the limitation of the
exemptions provided by (a) Rule 144 under the Securities Act, as such Rule may
be amended from time to time, or (b) any similar rule or regulation hereafter
adopted by the Commission. Upon the request of any holder of Registrable
Securities, the Company will deliver to such holder a written statement as to
whether it has complied with the requirements of this Section 4.

         5. AMENDMENTS AND WAIVERS. This Agreement may be amended and the
Company may take any action herein prohibited, or omit to perform any act herein
required to be performed by it, only if the Company shall have obtained the
written consent to such amendment, action or omission to act, of the holder or
holders of the sum of 51% or more of the shares of (i) Registrable Securities
issued at such time, plus (ii) Registrable Securities issuable upon exercise or
conversion of the Securities then constituting derivative securities (if such
Securities were not fully exchanged or converted in full as of the date such
consent if sought). Each holder of any Registrable Securities at the time or
thereafter outstanding shall be bound by any consent authorized by this Section
5, whether or not such Registrable Securities shall have been marked to indicate
such consent.

         6. NOMINEES FOR BENEFICIAL OWNERS. In the event that any Registrable
Securities are held by a nominee for the beneficial owner thereof, the
beneficial owner thereof may, at its election, be treated as the holder of such
Registrable Securities for purposes of any request or other action by any holder
or holders of Registrable Securities pursuant to this Agreement or any
determination of any number of percentage of shares of Registrable Securities
held by an holder or holders of Registrable Securities contemplated by this
Agreement. If the beneficial owner of any Registrable Securities so elects, the
Company may require assurances reasonably satisfactory to it of such owner's
beneficial ownership of such Registrable Securities.

         7. NOTICES. Except as otherwise provided in this Agreement, all
notices, requests and other communications to any Person provided for hereunder
shall be in writing and shall be given to such Person (a) in the case of a party
hereto other than the Company, addressed to such party in the manner set forth
in the Securities Purchase Agreement or at such other address as such party
shall have furnished to the Company in writing, or (b) in the case of any other
holder of Registrable Securities, at the address that such holder shall have
furnished to the Company in writing, or, until any such other holder so
furnishes to the Company an address, then to and at the address of the last
holder of such Registrable Securities who has furnished an address to the
Company, or (c) in the case of the Company, at the address set forth on the
signature page hereto, to the attention of its President, or at such other
address, or to the attention of such other officer, as the Company shall have
furnished to each holder of Registrable Securities at the time outstanding. Each
such notice, request

                                       13
<PAGE>

or other communication shall be effective (i) if given by mail, four (4) days
after such communication is deposited in the United States mails with first
class postage prepaid, addressed as aforesaid or (ii) if given by any other
means (including, without limitation, by fax or air courier), when delivered at
the address specified above, provided that any such notice, request or
communication shall not be effective until received.

         8. ASSIGNMENT. This Agreement shall be binding upon and inure to the
benefit of and be enforceable by the parties hereto. In addition, and whether or
not any express assignment shall have been made, the provisions of this
Agreement which are for the benefit of the parties hereto other than the Company
shall also be for the benefit of and enforceable by any subsequent holder of any
Registrable Securities. Each of the holders of the Registrable Securities
agrees, by accepting any portion of the Registrable Securities after the date
hereof, to the provisions of this Agreement including, without limitation,
appointment of the Sellers' Representative to act on behalf of such holder
pursuant to the terms hereof which such actions shall be made in the good faith
discretion of the Sellers' Representative and be binding on all persons for all
purposes.

         9. DESCRIPTIVE HEADINGS. The descriptive headings of the several
sections and paragraphs of this Agreement are inserted for reference only and
shall not limit or otherwise affect the meaning hereof.

         10. GOVERNING LAW. THIS AGREEMENT SHALL BE CONSTRUED AND ENFORCED IN
ACCORDANCE WITH, AND THE RIGHTS OF THE PARTIES SHALL BE GOVERNED BY, THE LAWS OF
THE STATE OF MASSACHUSETTS WITHOUT REFERENCE TO THE PRINCIPLES OF CONFLICTS OF
LAWS.

         11. COUNTERPARTS. This Agreement may be executed by facsimile and may
be signed simultaneously in any number of counterparts, each of which shall be
deemed an original, but all such counterparts shall together constitute one and
the same instrument.

         12. ENTIRE AGREEMENT. This Agreement embodies the entire agreement and
understanding between the Company and each other party hereto relating to the
subject matter hereof and supercedes all prior agreements and understandings
relating to such subject matter.

         13. SEVERABILITY. If any provision of this Agreement, or the
application of such provisions to any Person or circumstance, shall be held
invalid, the remainder of this Agreement, or the application of such provision
to Persons or circumstances other than those to which it is held invalid, shall
not be affected thereby.

                            [SIGNATURE PAGE FOLLOWS]

                                       14
<PAGE>

         IN WITNESS WHEREOF, the parties have caused this Agreement to be
executed and delivered by their respective officers thereunto duly authorized as
of the date first above written.

                             BOSTON BIOMEDICA, INC.

                               By: /s/ Kevin W. Quinlan
                                   --------------------------------------------
                               Name: Kevin W. Quinlan
                               Title: President
                               Address: Boston Biomedica, Inc.
                                        375 West Street
                                        Bridgewater, MA 02379

                                        Fax:  (508) 580-1110
                                        Tel.: (508) 580-1900

                             GCA STRATEGIC INVESTMENT FUND LIMITED

                               By:      /s/ Lewis N. Lester
                                        ---------------------------------------
                               Name:    Lewis N. Lester
                               Title:   Director
                               Address: c/o Prime Management Limited
                                        Mechanics Building
                                        12 Church Street
                                        Hamilton HM II, Bermuda
                                        Fax:  441-295-3926
                                        Tel.: 441-295-0329

                             WHARTON CAPITAL PARTNERS, LTD.

                             By: /s/ Barry Minsky
                                -----------------------------------------------
                             Name:   Barry Minsky
                                  ---------------------------------------------
                             Title:  Chief Executive Officer
                                   --------------------------------------------
                             Address: 545 Madison Ave., New York City, NY 10022
                                     ------------------------------------------

                                     Fax:  (212) 888-7054
                                         --------------------------------------
                                     Tel.: (212) 765-6777
                                          -------------------------------------

                             DP SECURITIES, INC.

                             By: /s/ Brian M. Overstreet
                                -----------------------------------------------
                             Name:   Brian M. Overstreet
                                  ---------------------------------------------
                             Title:  Vice President
                                   --------------------------------------------
                             Address: 3655 Nobel Drive, Suite 540
                                      San Diego, CA 92122
                                     ------------------------------------------
                                     Fax:  (858) 623-1601
                                         --------------------------------------
                                     Tel.: (858) 623-1600
                                          -------------------------------------<PAGE>

                                   Exhibit 4.6

         Senior Subordinated Convertible Debenture to Richard P. Kiphart

THE SECURITIES REPRESENTED HEREBY HAVE NOT BEEN REGISTERED UNDER THE UNITED
STATES SECURITIES ACT OF 1933, AS AMENDED (THE "SECURITIES ACT"). THE HOLDER
HEREOF, BY PURCHASING SUCH SECURITIES AGREES FOR THE BENEFIT OF THE COMPANY THAT
SUCH SECURITIES MAY BE OFFERED, SOLD OR OTHERWISE TRANSFERRED ONLY (A) TO THE
COMPANY, (B) PURSUANT TO AN EXEMPTION FROM REGISTRATION UNDER THE SECURITIES
ACT, OR (C) IF REGISTERED UNDER THE SECURITIES ACT AND ANY APPLICABLE STATE
SECURITIES LAWS. IN ADDITION, A SECURITIES PURCHASE AGREEMENT, DATED AS OF THE
DATE HEREOF, A COPY OF WHICH MAY BE OBTAINED FROM THE COMPANY AT ITS PRINCIPAL
EXECUTIVE OFFICE, CONTAINS CERTAIN ADDITIONAL AGREEMENTS AMONG THE PARTIES,
INCLUDING, WITHOUT LIMITATION, PROVISIONS WHICH (A) LIMIT THE CONVERSION RIGHTS
OF THE HOLDER, (B) SPECIFY VOLUNTARY AND MANDATORY REPAYMENT, PREPAYMENT AND
REDEMPTION RIGHTS AND OBLIGATIONS AND (C) SPECIFY EVENTS OF DEFAULT FOLLOWING
WHICH THE REMAINING BALANCE DUE AND OWING HEREUNDER MAY BE ACCELERATED.

No.  2                                                               $780,000.00

                  3% SENIOR SUBORDINATED CONVERTIBLE DEBENTURE
                                       of

         Boston Biomedica, Inc., a Massachusetts corporation (together with its
successors, the "Company"), for value received hereby promises to pay to:

                               RICHARD P. KIPHART

(The "Holder") and registered assigns, the principal sum of $780,000.00 or, if
less, the principal amount of this Senior Subordinated Convertible Debenture
(this "Convertible Debenture") then outstanding, on the Maturity Date by wire
transfer of immediately available funds to the Holder in such coin or currency
of the United States of America as at the time of payment shall be legal tender
for the payment of public and private debts, and to pay interest which shall
accrue beginning the date hereof, quarterly in arrears, on (i) the last day of
March, June, September and December of each year until the Maturity Date,
commencing September 30, 2000 (unless such day is not a Business Day, in which
event on the next succeeding Business Day) (each an "Interest Payment Date"),
(ii) the Maturity Date, (iii) each Conversion Date, as hereafter defined, and
(iv) the date the principal

<PAGE>

amount of the Convertible Debentures shall be declared to be or shall
automatically become due and payable, on the principal sum hereof outstanding in
like coin or currency, at the rates per annum set forth below, from the most
recent Interest Payment Date to which interest has been paid on this Convertible
Debenture, or if no interest has been paid on this Convertible Debenture, from
the date of this Convertible Debenture until payment in full of the principal
sum hereof has been made. The Maturity Date is August 25, 2003.

         The interest rate shall be three percent (3%) per annum (the "Interest
Rate") or, if less, the maximum rate permitted by applicable law. Past due
amounts (including interest, to the extent permitted by law) will also accrue
interest at the Interest Rate plus 2% per annum or, if less, the maximum rate
permitted by applicable law, and will be payable on demand ("Default Interest").
Interest on this Convertible Debenture will be calculated on the basis of a
360-day year of twelve 30 day months. All payments of principal and interest
hereunder shall be made for the benefit of the Holder pursuant to the terms of
the Agreement (hereafter defined). At the option of the Company, interest may be
paid in cash or in shares of Common Stock. If the Company determines to pay
interest in shares of Common Stock, it shall be required to notify the Holder of
such election on the Closing Date. On each Conversion Date, interest shall be
paid in shares of Common Stock on the portion of the principal balance of the
Convertible Debenture then being converted. The number of shares of Common Stock
issued as interest shall be determined by dividing the dollar amount of interest
due on the applicable Interest Payment Date by the Conversion Price then in
effect.

         This Convertible Debenture is a duly authorized issuance of Convertible
Debentures of the Company referred to in that certain Securities Purchase
Agreement dated as of the date hereof between the Company and the Purchaser
named therein (the "Agreement"). The Agreement contains certain additional
agreements among the parties with respect to the terms of this Convertible
Debenture, including, without limitation, provisions which (A) limit the
conversion rights of the Holder, (B) specify voluntary and mandatory repayment,
prepayment and redemption rights and obligations and (C) specify Events of
Default following which the remaining balance due and owing hereunder may be
accelerated. All such provisions are an integral part of this Convertible
Debenture and are incorporated herein by reference. This Convertible Debenture
is transferable and assignable to one or more Persons, in accordance with the
limitations set forth in the Agreement.

         This Convertible Debenture shall rank senior to any indebtedness of the
Company except (a) the Company's outstanding credit facility with Fleet Bank and
any successor thereof, including increases to such credit facility; (b) the
Company's mortgage loan with Commerce Bank; and (c) any future sale and lease
back transaction in connection with the Company's headquarters building in West
Bridgewater, MA, to which it shall be junior in ranking. This Convertible
Debenture shall rank on a pari passu basis with the Company's outstanding 3%
convertible debentures.

         The Company shall keep a register (the "Register") in which shall be
entered the names and addresses of the registered holder of this Convertible
Debenture and particulars of this Convertible

                                       2

<PAGE>

Debenture held by such holder and of all transfers of this Convertible
Debenture. References to the Holder or "Holders" shall mean the Person listed
in the Register as registered holder of such Convertible Debentures. The
ownership of this Convertible Debenture shall be proven by the Register.

         1.       CERTAIN TERMS DEFINED. All terms defined in the Agreement and
not otherwise defined herein shall have for purposes hereof the meanings
provided for in the Agreement.

         2.       COMPANY COVENANTS. The Company covenants and agrees to observe
and perform each of its covenants, obligations and undertakings contained in the
Agreement, which obligations and undertakings are expressly assumed herein by
the Company and made for the benefit of the holder hereof.

         3.       PAYMENT OF PRINCIPAL. The Company shall repay the remaining
unpaid balance of this Convertible Debenture on the Maturity Date. The Company
may, and shall be obligated to, prepay all or a portion of this Convertible
Debenture on the terms specified in the Agreement.

         4.       CONVERSION.

         4.1      CONVERSION OF CONVERTIBLE DEBENTURE. Subject to Section 5
         hereof, the Holder shall have the right, at its option, at any time
         from and after the 90th day following the date of issuance of this
         Convertible Debenture, to convert the principal amount of this
         Convertible Debenture, or any portion of such principal amount, into
         that number of fully paid and nonassessable shares of Common Stock (as
         such shares shall then be constituted) determined pursuant to this
         Section 4.1. The number of shares of Common Stock to be issued upon
         each conversion of this Convertible Debenture shall be determined by
         dividing the Conversion Amount (as defined below) by the Conversion
         Price in effect on the date (the "Conversion Date") a Notice of
         Conversion is delivered to the Company, as applicable, by the Holder by
         facsimile dispatched prior to 5:00 p.m., E.S.T. Prior to sending the
         facsimile Notice of Conversion to the Company, the Holder shall notify
         the Company of such conversion by telephone to one of the following
         individuals on the following order of priority: (1) Richard T.
         Schumacher, (2) Kevin Quinlan and (3) Kathi Benjamin (or to each of the
         individual's voicemail if none of the individuals is available) as set
         forth in Section 4.4 hereto. The Company may change the individuals to
         whom such telephone notice shall be directed by notifying the Holder of
         any such change. The term "Conversion Amount" means, with respect to
         any conversion of this Convertible Debenture, the sum of (1) the
         principal amount of this Convertible Debenture to be converted in such
         conversion plus (2) accrued and unpaid interest, if any, on such
         principal amount at the interest rates provided in this Convertible
         Debenture to the Conversion Date plus (3) Default Interest, if any, on
         the interest referred to in the immediately preceding clause (2) plus
         (4) at the Holder's option, any amounts owed to the Holder pursuant to
         Section 4.3 hereof, Section 10.1 of the Agreement or Section 10.4 of
         the Agreement.

                                       3

<PAGE>

         4.2      CONVERSION PRICE. At the option of the Holder, any portion or
         all of the outstanding principal amount of this Convertible Debenture
         shall be converted into a number of shares of Common Stock at the
         conversion price (the "Conversion Price") equal to the lesser of (i)
         110% of the volume weighted average sales price of the Common Stock, as
         reported by Bloomberg L.P. on the day immediately preceding the Closing
         Date (the "Fixed Conversion Price") and (ii) 90% of the average of the
         five (5) lowest volume weighted average sales prices of the Common
         Stock as reported by Bloomberg L.P. during the 25 Trading Days
         immediately preceding but not including the date of the related Notice
         of Conversion (the "Formula Conversion Price").

         4.3      AUTHORIZED SHARES.

                  (1) Consistent with Section 7.11 of the Agreement, the Company
         (i) shall promptly irrevocably instruct the Company's transfer agent to
         issue certificates for the Common Stock issuable upon conversion of
         this Convertible Debenture and (ii) agrees that its issuance of this
         Convertible Debenture shall constitute full authority to its officers
         and agents who are charged with the duty of executing stock
         certificates to execute and issue the necessary certificates for shares
         of Common Stock in accordance with the terms and conditions of this
         Convertible Debenture.

                  (2) If at any time a Holder of this Convertible Debenture
         submits a Notice of Conversion (x) the Company does not have sufficient
         authorized but unissued shares of Common Stock available to effect such
         conversion in full in accordance with the provisions of this Article 4
         or (y) the Company is prohibited by the applicable rules of the OTC
         Bulletin Board or the National Market on which the shares of Common
         Stock are listed and traded at that time to effect such conversion in
         full as provided in subsection (3) below, without stockholder approval
         (each, a "Conversion Default"), the Company shall issue to the Holder
         all of the shares of Common Stock which are then available to effect
         such conversion. The portion of this Convertible Debenture which the
         Holder included in its Conversion Notice and which exceeds the amount
         which is then convertible into available shares of Common Stock (the
         "Excess Amount") shall, notwithstanding anything to the contrary
         contained herein, not be convertible into Common Stock in accordance
         with the terms hereof until (and at the Holder's option at any time
         after) the date additional shares of Common Stock are authorized by the
         Company, or its stockholders, as applicable, at which time the
         Conversion Price in respect thereof shall be the lower of (i) the
         Conversion Price on the Conversion Default Date (as defined below) and
         (ii) the Conversion Price on the Conversion Date thereafter elected by
         the Holder in respect thereof. The Company shall pay to the Holder
         payments ("Conversion Default Payments") for a Conversion Default in
         the amount of (N/365) x .24 x the Excess Amount on the Conversion Date
         in respect of the Conversion Default (the "Conversion Default Date"),
         where N = the number of days from the Conversion Default Date to the
         date (the "Authorization Date") that the Company, or its stockholders,

                                       4

<PAGE>

         as applicable, authorizes a sufficient number of shares of Common
         Stock to effect conversion of the full outstanding principal balance
         of this Convertible Debenture or until the Company redeems the
         Excess Amount in accordance with the terms of this Convertible
         Debenture. The Company shall use its best efforts to authorize, or
         cause its stockholders to authorize within 40 days of the occurrence
         of a Conversion Default, as applicable, a sufficient number of
         shares of Common Stock as soon as practicable following the earlier
         of (i) such time that the Holder notifies the Company or that the
         Company otherwise becomes aware that there are or likely will be
         insufficient shares to allow full conversion thereof and (ii) a
         Conversion Default. The Company shall send notice to the Holder of
         the authorization of additional shares of Common Stock, the
         Authorization Date and the amount of Holder's accrued Conversion
         Default Payments. The accrued Conversion Default Payments for each
         calendar month shall be paid in cash or shares of Common Stock (at
         such time as there are sufficient authorized shares of Common Stock)
         at the Holder's option, as follows:

                           (a) In the event the Holder elects to take such
                  payment in cash, cash payment shall be made to Holder by the
                  fifth Business Day of the month following the month in which
                  it has accrued; and

                           (b) In the event the Holder elects to take such
                  payment in Common Stock, the Holder may convert such payment
                  amount into Common Stock at the Conversion Price (as in effect
                  at the time of payment) at any time after the fifth Business
                  Day of the month following the month in which it has accrued
                  (at such time as there are sufficient authorized shares of
                  Common Stock) in accordance with the terms of this Article 4.

                  (3) The Holder's election pursuant to this Section 4.3 shall
         be made in writing to the Company at any time prior to 5:00 p.m.,
         E.S.T., on the third Business Day of the month following the month in
         which Conversion Default payments have accrued. If no election is made,
         the Holder shall be deemed to have elected to receive cash. Nothing
         herein shall limit the Holders right to pursue actual damages (to the
         extent in excess of the Conversion Default Payments) due to the
         Company's failure to maintain a sufficient number of authorized shares
         of Common Stock.

                  (4) In no event shall the Company issue more than the Maximum
         Number of Shares upon conversion of this Convertible Debenture, unless
         the Company shall have obtained approval by the stockholders of the
         Company ("Stockholder Approval") or a waiver of such requirement by the
         OTC Bulletin Board or the National Market on which the shares of Common
         Stock are listed and traded at that time. Once the Maximum Number of
         Shares has been issued (the date of which is hereinafter referred to as
         the "Maximum Conversion Date"), unless the Company shall have obtained
         Stockholder Approval or a waiver of such requirement by the OTC
         Bulletin Board or the National Market on which the shares of Common
         Stock are listed and traded at that time within 40 days of the Maximum
         Conversion

                                       5

<PAGE>

         Date, the Company shall pay to the Holder within five (5) Business Days
         of the Maximum Conversion Date (or, if the Company is, in good faith,
         using its best efforts to obtain Stockholder Approval, then the earlier
         of (x) 40 days following the Maximum Conversion Date, and (y) such date
         that it becomes reasonably apparent that Stockholder Approval will not
         be obtained within such 40 days period), the Redemption Price for the
         Excess Amount plus accrued and unpaid Default Interest, if any.

                  (5) The Maximum Number of Shares shall be subject to
         adjustment from time to time for stock splits, stock dividends,
         combinations, capital reorganizations and similar events relating to
         the Common Stock occurring after the date hereof as contemplated by
         Article 11 of the Agreement. With respect to each Holder of Convertible
         Debentures, the Maximum Number of Shares shall refer to such Holder's
         pro rata share thereof based upon the aggregate principal balance of
         the Convertible Debentures then outstanding. In the event that the
         Company obtains Stockholder Approval, approval of the OTC Bulletin
         Board or the National Market on which the shares of Common Stock are
         listed and traded at that time, or otherwise is able to increase the
         number of shares to be issued above the Maximum Number of Shares (such
         increased number being the "New Maximum Number of Shares"), the
         references to Maximum Number of Shares above shall be deemed to be,
         instead, references to the New Maximum Number of Shares.

         4.4      METHOD OF CONVERSION.

                  (1) Prior to sending the Notice of Conversion via facsimile as
         set forth in Section 4.1 hereof, the Holder shall give notice to
         Richard T. Schumacher by telephone (and if Mr. Schumacher is not
         available to be reached by telephone, either Kevin Quinlan or Kathi
         Benjamin by telephone, or such other person designated by the Company
         after the Closing Date) that the Holder intends to submit a Notice of
         Conversion on such date. Notwithstanding anything to the contrary set
         forth herein, upon conversion of this Convertible Debenture in
         accordance with the terms hereof, the Holder shall not be required to
         physically surrender this Convertible Debenture to the Company unless
         the entire unpaid principal amount of this Convertible Debenture is so
         converted. Rather, the Holder shall send to the Company, and the
         Company shall send to the Holder, via overnight delivery service (a)
         the originally signed and executed Notice of Conversion and (b) an
         originally signed and executed ANNEX A to this Convertible Debenture
         indicating the amounts to be converted and the new principal balance of
         this Convertible Debenture taking into account the Notice of
         Conversion. The Company shall keep as part of its records the
         originally executed ledger and the Holder shall maintain a copy
         thereof. Upon execution of the conversion contemplated by the Notice of
         Conversion, the Company and the Holder shall deliver to one another an
         executed copy of ANNEX A. It is specifically contemplated that the
         Company shall act as the calculation agent for conversions and
         repayments. In the event there is a dispute as to the number of shares
         of Common Stock the Holder is entitled to receive upon a conversion of
         this Convertible Debenture (or the amount of cash to be

                                       6

<PAGE>

         received upon repayment or redemption of this Convertible Debenture),
         the amount of any payments due upon an Event of Default under this
         Convertible Debenture or the calculation of any of the foregoing, the
         Holder and the Company agree that (i) the Company shall issue to the
         Holder the undisputed number of shares of Common Stock (or pay any
         undisputed cash amounts with respect to a redemption or default
         payments) and (ii) each party will use its best efforts to resolve such
         dispute within one business day following the receipt of a Notice of
         Conversion (or Notice of Redemption, as applicable). If such dispute
         cannot be resolved within the one-day period, the Company and the
         Holder shall submit the dispute to an independent accountant mutually
         agreed upon by the Company and the Holder to make a determination as to
         the amounts due to the Holder. Any such determination shall be final
         and binding on the Company and the Holder. The Company shall issue
         shares of Common Stock or pay any cash amounts owed to the Holder as a
         result of the resolution of the dispute within two business days
         following the receipt of the independent accountant's determination.
         The Holder and any assignee, by acceptance of this Convertible
         Debenture, acknowledge and agree that, by reason of the provisions of
         this paragraph, following a conversion of a portion of this Convertible
         Debenture, the principal amount represented by this Convertible
         Debenture will be the amount indicated on the ledger evidenced by ANNEX
         A attached hereto (which may be less than the amount stated on the face
         hereof).

                  (2) The Company shall not be required to pay any tax which may
         be payable in respect of any transfer involved in the issuance and
         delivery of shares of Common Stock or other securities or property on
         conversion of this Convertible Debenture in a name other than that of
         the Holder (or in street name), and the Company shall not be required
         to issue or deliver any such shares or other securities or property
         unless and until the person or persons (other than the Holder or the
         custodian in whose street name such shares are to be held for the
         Holder's account) requesting the issuance thereof shall have paid to
         the Company the amount of any such tax or shall have established to the
         satisfaction of the Company that such tax has been paid.

                  (3) Subject to Section 5 hereof, upon receipt by the Company
         of a Notice of Conversion, the Holder shall be deemed to be the holder
         of record of the Common Stock issuable upon such conversion, the
         outstanding principal amount and the amount of accrued and unpaid
         interest on this Convertible Debenture shall be deemed reduced to
         reflect such conversion, and, unless the Company defaults on its
         obligations under this Article 4, all rights with respect to the
         portion of this Convertible Debenture being so converted shall
         forthwith terminate except the right to receive the Common Stock or
         other securities, cash or other assets, as herein provided, on such
         conversion. Subject to Section 5 hereof, if the Holder shall have given
         a Notice of Conversion as provided herein, the Company's obligation to
         issue and deliver the certificates for shares of Common Stock shall be
         absolute and unconditional, irrespective of the absence of any action
         by the Holder to enforce the same, any waiver or consent with respect
         to any provisions thereof, the recovery of any judgment against any
         person or any action by the Holder to enforce the same, any failure or

                                       7

<PAGE>

         delay in the enforcement of any other obligation of the Company to the
         Holder of record, or any setoff, counterclaim, recoupment, limitation
         or termination, other than a breach by the Holder of any obligation to
         the Company, and subject to Section 4.4(1) irrespective of any other
         circumstance which might otherwise limit such obligation of the Company
         to the Holder in connection with such conversion. The date of receipt
         (including receipt via telecopy) of such Notice of Conversion shall be
         the Conversion Date so long as it is received and the telephone notice
         thereof in accordance with Section 4.4(1) is made before 5:00 p.m.,
         E.S.T., on such date.

                  (4) Notwithstanding the foregoing, if a Holder has not
         received certificates for all shares of Common Stock prior to the
         expiration of the Deadline with respect to a conversion of any portion
         of this Convertible Debenture for any reason, then (unless the Holder
         otherwise elects to retain its status as a holder of Common Stock by so
         notifying the Company), the Holder shall regain the rights of a Holder
         of this Convertible Debenture with respect to such unconverted portions
         of this Convertible Debenture and the Company shall, as soon as
         practicable, return such unconverted Convertible Debenture to the
         holder or, if the Convertible Debenture has not been surrendered,
         adjust its records to reflect that such portion of this Convertible
         Debenture not been converted. In all cases, the Holder shall retain all
         of its rights and remedies (including, without limitation, (i) the
         right to receive Conversion Default Payments to the extent required
         thereby for such Conversion Default and any subsequent Conversion
         Default and (ii) the right to have the Conversion Price with respect to
         subsequent conversions determined in accordance with Section 4.3 for
         the Company's failure to convert this Convertible Debenture.)

                  (5) In lieu of delivering physical certificates representing
         the Common Stock issuable upon conversion, provided the Company's
         transfer agent is participating in the Depository Trust Company ("DTC")
         Fast Automated Securities Transfer program, upon request of the Holder
         and its compliance with the provisions contained in Section 4.1 and in
         this Section 4.4, the Company shall use its best efforts to cause its
         transfer agent to electronically transmit the Common Stock issuable
         upon conversion to the Holder by crediting the account of Holder's
         prime broker (as designated by Holder from time to time) with DTC
         through its Deposit Withdrawal Agent Commission System.

         5.       REDEMPTION BY COMPANY.

         5.1      COMPANY'S RIGHT TO REDEEM UPON RECEIPT OF NOTICE OF
         CONVERSION. In addition to the redemption rights set forth in the
         Agreement, upon delivery of a Notice of Conversion by the Holder (the
         "Initial Notice of Conversion"), if the Closing Bid Price of the
         Company's Common Stock on the date of the Notice of Conversion is less
         than 65% of the Closing Bid Price of the Common Stock on the Closing
         Date, the Company may elect to redeem in whole or in part, the
         remaining unpaid principal amount of this Convertible Debenture, for
         cash at a redemption price (the "Redemption Price") equal to (x) the
         number of shares of Common

                                       8

<PAGE>

         Stock into which this Convertible Debenture is then convertible, times
         (y) the average Closing Bid Price of Common Stock for the five (5)
         Trading Days as reported by Bloomberg L.P. immediately prior to the
         date that this Convertible Debenture is called for redemption, plus
         accrued and unpaid interest. The election by the Company to redeem any
         amount of this Convertible Debenture shall be applicable to any
         subsequent amount to be converted as set forth in any Notice of
         Conversion received by the Company in the twenty (20) calendar day
         period following the date of the Initial Notice of Conversion, subject
         to the provisions of Section 5.2 below.

         5.2      MECHANICS OF REDEMPTION. The Company shall provide written
         notice of its election to redeem rather than convert the amounts set
         forth in the Notice of Conversion ("Redemption Notice") via facsimile
         to the Holder within one Business Day of the Confirmed Delivery of the
         Notice of Conversion to the Company, if such Confirmed Delivery is on a
         Business Day or by 5:00 E.S.T. of the next Business Day if such Notice
         of Conversion is not delivered on a Business Day, with a copy by either
         overnight or 2-day courier to the Holder of this Convertible Debenture
         to be redeemed at the address and facsimile number of such Holder
         appearing in the Company's register for the Convertible Debentures. The
         Company shall effect each such redemption within three (3) Business
         Days of giving the Redemption Notice. Such Redemption Notice shall
         indicate whether the Company will redeem all or part of such portion of
         the Convertible Debenture to be redeemed and the applicable Redemption
         Price. The Company shall not be entitled to send any notice of
         redemption and begin the redemption procedure unless it has (i) the
         full amount of the Redemption Price, in cash, available in a demand or
         other immediately available account in a bank or similar financial
         institution or (ii) immediately available credit facilities, in the
         full amount of the Redemption Price, with a bank or similar financial
         institution on the date the Redemption Notice is sent to the Holders of
         this Convertible Debenture. Provided, however, the Company will process
         any Notice of Conversion received prior to the issuance of a Redemption
         Notice; and further provided that, after a Redemption Notice has been
         issued, the Holder may issue a Notice of Conversion which will not be
         honored unless the Company fails to make the redemption payment when
         due. In the event of such failure, the Notice of Conversion will be
         honored as of the date of the Notice of Conversion. Additionally, if
         the Company fails to make full payments of the Redemption Price of this
         Convertible Debenture being redeemed by the third Business Day
         following the Notice of Redemption, then the Company waives its right
         to redeem any of the remaining then outstanding Convertible Debentures
         pursuant to Section 5.1, unless approved in writing by the Holder.

         5.3      PAYMENT OF REDEMPTION PRICE. The Redemption Price shall be
         paid to the Holder of this Convertible Debenture within three (3)
         Business Days of the delivery of the Redemption Notice.

                                        9

<PAGE>

         6.       HOLDER'S RIGHT TO ADVANCE NOTICE OF ELECTION TO REDEEM.

         6.1      HOLDER'S RIGHT TO ELECT TO RECEIVE NOTICE OF CASH REDEMPTION
         BY COMPANY. The Holder of this Convertible Debenture shall have the
         right to require the Company to provide advance notice stating whether
         the Company will elect to redeem all or part of the redeemable portion
         in cash, pursuant to the Company's redemption rights discussed in
         Section 5.1 above.

         6.2      MECHANICS OF HOLDER'S ELECTION NOTICE. Holder shall give
         notice to the Company by facsimile (the "Election Notice"), requiring
         that the Company disclose whether the Company would elect to redeem the
         redeemable portion of this Convertible Debenture (in whole or in part)
         if the Holder were to provide a Notice of Conversion within the next
         four (4) Business Days and sought to convert the Convertible Debenture
         in such principal amount as is specified in the Election Notice.

         6.3      COMPANY'S RESPONSE. Company must respond, disclosing its
         election, within two (2) Business Days of receipt of Holder's Election
         Notice via facsimile. If Company does not respond to Holder within two
         (2) Business Days (by 12:00 noon, if required above) via facsimile,
         Company shall be deemed to have forfeited its right to exercise
         redemption pursuant to Section 5.1 upon its receipt of (but only with
         respect to) that Notice of Conversion.

         7.       HOLDER'S COVENANTS. The Holder of this Convertible Debenture,
by its acceptance thereof, covenants and agrees that the Convertible Debenture
is being acquired as an investment and not with a view to the distribution
thereof in violation of the Securities Act, and that the Convertible Debenture
may not be transferred, sold, assigned, hypothecated or otherwise disposed of,
in whole, or in part, except as provided on the first page hereof and provided
that the Holder shall have furnished to the Company an opinion of counsel, in
form and substance reasonably satisfactory to the Company, to the effect that
such transfer is exempt from the registration requirements of the Securities Act
and any applicable state securities laws.

         8.       MISCELLANEOUS. This Convertible Debenture shall be deemed to
be a contract made under the laws of the State of Massachusetts, and for all
purposes shall be governed by and construed in accordance with the laws of said
State. The parties hereto, including all guarantors or endorsers, hereby waive
presentment, demand, notice, protest and all other demands and notices in
connection with the delivery, acceptance, performance and enforcement of this
Convertible Debenture, except as specifically provided herein, and assent to
extensions of the time of payment, or forbearance or other indulgence without
notice. The Company hereby submits to the exclusive jurisdiction of the United
States District Court for Boston, Massachusetts and of any Massachusetts state
court sitting in Boston, Massachusetts for purposes of all legal proceedings
arising out of or relating to this Convertible Debenture. The Company
irrevocably waives, to the fullest extent permitted by law, any objection which
it may now or hereafter have to the laying of the venue of any such proceeding

                                       10

<PAGE>

brought in such a court and any claim that any such proceeding brought in such a
court has been brought in an inconvenient forum. The Company hereby irrevocably
waives any and all right to trial by jury in any legal proceeding arising out of
or relating to this Convertible Debenture.

         The Holder of this Convertible Debenture by acceptance of this
Convertible Debenture agrees to be bound by the provisions of this Convertible
Debenture which are expressly binding on such Holder.

                            [Signature page follows]

                                       11

<PAGE>

                       SIGNATURE PAGE TO KIPHART DEBENTURE

         IN WITNESS WHEREOF, the Company has caused this instrument to be duly
executed.

         Dated as of August 25, 2000

                                         BOSTON BIOMEDICA, INC.

                                         By: /s/ Kevin W. Quinlan
                                             ----------------------
                                             Name: Kevin W. Quinlan
                                             Title: President

<PAGE>

                                     ANNEX A

                         CONVERSION AND REPAYMENT LEDGER

<TABLE>
<CAPTION>

------- ----------------- ---------------------- ---------------------- ----------------------- ---------------- -----------------
                          INTEREST CONVERTED OR   PRINCIPAL CONVERTED
  DATE  PRINCIPAL BALANCE       PAID                OR PAID              NEW PRINCIPAL BALANCE   ISSUER INITIALS  HOLDER INITIALS
------- ----------------- ---------------------- ---------------------- ----------------------- ---------------- -----------------
<S>     <C>               <C>                    <C>                    <C>                     <C>              <C>

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

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

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

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

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

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

</TABLE>

BOSTON BIOMEDICA, INC.                        HOLDER:

By: ___________________________               By:____________________________

Name:__________________________               Name:__________________________

Title: ________________________               Title:    _____________________

<PAGE>

FULL NAME AND ADDRESS OF SUBSCRIBER FOR REGISTRATION PURPOSES:

NAME:

ADDRESS:

TEL NO:

FAX NO:

CONTACT
NAME:

DELIVERY INSTRUCTIONS (IF DIFFERENT FROM REGISTRATION NAME):

NAME:

ADDRESS:

TEL NO:

FAX NO:

CONTACT
NAME:

SPECIAL INSTRUCTIONS:
                     -----------------------------------------------------------

<PAGE>

                              NOTICE OF CONVERSION

                    (To be Executed by the Registered Holder

                 in order to Convert the Convertible Debenture)

                  The undersigned hereby irrevocably elects to convert $________
of the principal balance of the Convertible Debenture into shares of Common
Stock, $.01 par value per share (the "Common Stock"), of Boston Biomedica, Inc.
(the "Company") according to the conditions hereof, as of the date written
below. No fee will be charged to the Holder for any conversion, except for
transfer taxes, if any. The undersigned, as contemplated by Section 5.1 of the
Securities Purchase Agreement pursuant to which the Convertible Debenture was
issued, hereby states that the representations and warranties of the undersigned
set forth therein are true and correct in all material respects as of the date
hereof.

Conversion calculations:

                                            ------------------------------------
                                            Date of Conversion

                                            ------------------------------------
                                            Applicable Conversion Price

                                            ------------------------------------
                                            Number of Shares

                                            ------------------------------------
                                            Name/Signature

                                            Address:

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

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

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