Document:

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                                                                     EXHIBIT 4.9

                                  $175,000,000

                 CHARLES RIVER LABORATORIES INTERNATIONAL, INC.

                  3 1/2% SENIOR CONVERTIBLE Debentures DUE 2022

                          REGISTRATION RIGHTS AGREEMENT

                                                                January 24, 2002

Credit Suisse First Boston Corporation
Lehman Brothers Inc.
J.P. Morgan Securities Inc.
SG Cowen Securities Corporation
U.S. Bancorp Piper Jaffray Inc.
Thomas Weisel Partners LLC
Investec PMG Capital Corp.
Jeffries & Company, Inc.
c/o Credit Suisse First Boston Corporation
    Eleven Madison Avenue
    New York, New York 10010-3629

Dear Ladies and Gentlemen:

     Charles River Laboratories International, Inc., a Delaware corporation (the
"Company"), proposes to issue and sell to Credit Suisse First Boston
Corporation, Lehman Brothers Inc., J.P. Morgan Securities Inc., SG Cowen
Securities Corporation, U.S. Bancorp Piper Jaffray Inc., Thomas Weisel Partners
LLC, Investec PMG Capital Corp., and Jeffries & Company, Inc. (collectively, the
"Initial Purchasers"), upon the terms set forth in a purchase agreement of even
date herewith (the "Purchase Agreement"), $175,000,000 aggregate principal
amount (plus up to an additional $25,000,000 aggregate principal amount) of its
3 1/2% Senior Convertible Debentures due 2022 (the "Initial Securities"). The
Initial Securities will be convertible into shares of common stock, par value
$0.01 per share, of the Company (the "Common Stock") at the conversion price set
forth in the Offering Circular, dated January 17, 2002 (the "Offering
Circular"). The Initial Securities will be issued pursuant to an Indenture,
dated as of January 24, 2002 (the "Indenture"), by and between the Company and
State Street Bank and Trust Company, as trustee (the "Trustee"). As an
inducement to the Initial Purchasers to enter into the Purchase Agreement, the
Company agrees with the Initial Purchasers, for the benefit of (i) the Initial
Purchasers and (ii) the holders of the Initial Securities and the Common Stock
issuable upon conversion of the Initial Securities (collectively, the
"Securities") (each of the foregoing, a "Holder" and, collectively, the
"Holders") from time to time until the earliest to occur of (i) the second
anniversary of the effective date of the Shelf Registration Statement (as
defined below) (or for such longer period if extended pursuant to Section 2(h)
below), (ii) such time as such Securities have been sold pursuant to a Shelf
Registration Statement and (iii) the expiration of the holding period applicable
to such Securities held by persons that are not affiliates of the Company under
Rule 144(k) of the Securities Act of 1933, as amended (the "Securities Act"), or
any successor rule thereof, as follows:

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     1. Shelf Registration. (a) The Company shall, at its cost, prepare and, as
promptly as practicable (but in no event more than 90 days after so required or
requested pursuant to this Section 1) file with the Securities and Exchange
Commission (the "Commission") and thereafter use its reasonable efforts to cause
to be declared effective as soon as practicable a registration statement on Form
S-3 (the "Shelf Registration Statement" relating to the offer and sale of the
Transfer Restricted Securities (as defined in Section 5 hereof) by the Holders
thereof from time to time in accordance with the methods of distribution set
forth in the Shelf Registration Statement (which methods will not include an
underwritten offering without the prior written agreement of the Company) and
Rule 415 under the Securities Act (hereinafter, the "Shelf Registration");
provided, however, that no Holder (other than an Initial Purchaser) shall be
entitled to have the Securities held by it covered by such Shelf Registration
Statement unless such Holder agrees in writing to be bound by all the provisions
of this Agreement applicable to such Holder.

     (b) The Company shall use its reasonable efforts to keep the Shelf
Registration Statement continuously effective in order to permit the prospectus
included therein (the "Prospectus") to be lawfully delivered by the Holders of
the relevant Securities, for a period of two years (or for such longer period if
extended pursuant to Section 2(h) below) from the date of its effectiveness or
such shorter period that will terminate (i) when all the Securities covered by
the Shelf Registration Statement have been sold pursuant thereto or (ii) upon
the expiration of the holding period applicable to such Securities held by
persons that are not affiliates of the Company under Rule 144(k) under the
Securities Act, or any successor rule thereof (in any such case, such period
being called the "Shelf Registration Period"). The Company shall be deemed not
to have used its reasonable efforts to keep the Shelf Registration Statement
effective during the requisite period if it voluntarily takes any action that
would result in Holders of Securities covered thereby not being able to offer
and sell such Securities during that period, unless such action is (i) required
by applicable law or (ii) taken by the Company in good faith and contemplated by
Section 2(b)(v) or (vi) below, and the Company thereafter complies with the
requirements of Section 2(h).

     (c) Notwithstanding any other provisions of this Agreement to the contrary,
the Company shall cause the Shelf Registration Statement and the Prospectus and
any amendment or supplement thereto, as of the effective date of the Shelf
Registration Statement, amendment or supplement, (i) to comply in all material
respects with the applicable requirements of the Securities Act and the rules
and regulations of the Commission and (ii) not to contain any untrue statement
of a material fact or omit to state a material fact required to be stated
therein or necessary in order to make the statements therein, in the light of
the circumstances under which they were made, not misleading.

     (d) Each Holder of Transfer Restricted Securities agrees, by its
acquisition of Transfer Restricted Securities, that if such Holder wishes to
sell Transfer Restricted Securities pursuant to a Shelf Registration Statement
and related Prospectus, it will do so only in accordance with this Section 1(d)
and Section 2(h). Each Holder of Transfer Restricted Securities wishing to sell
Transfer Restricted Securities pursuant to a Shelf Registration Statement and
related Prospectus agrees to deliver a written notice, substantially in the form
of Annex A to the Offering Circular (a "Notice and Questionnaire") to the
Company at least five

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(5) Business Days prior to any intended distribution of Transfer Restricted
Securities under the Shelf Registration Statement.

     2. Registration Procedures. In connection with the Shelf Registration
contemplated by Section 1 hereof, the following provisions shall apply:

     (a) The Company shall (i) furnish to each Initial Purchaser, prior to the
filing thereof with the Commission, a copy of the Shelf Registration Statement
and each amendment thereof and each supplement (other than any supplement solely
listing the names of additional Holders), if any, to the prospectus included
therein and, in the event that an Initial Purchaser (with respect to any portion
of an unsold allotment from the original offering) is participating in the Shelf
Registration Statement, shall use its best efforts to reflect in each such
document, when so filed with the Commission, such comments as such Initial
Purchaser reasonably may propose; (ii) include in the Shelf Registration
Statement at the time it is first declared effective, the name of each Holder
that provided a written notice to the Company on or prior to the date five (5)
Business Days prior to such time of effectiveness containing substantially the
information called for by the Notice and Questionnaire; and (iii) from and after
the date the Shelf Registration Statement is initially declared effective, as
promptly as practicable after the date a Notice and Questionnaire is delivered,
if required by applicable law, file with the Commission a post-effective
amendment to the Shelf Registration Statement or prepare and, if required by
applicable law, file a supplement to the related Prospectus or a supplement or
amendment to any document incorporated therein by reference or file any other
document required under the Securities Act so that the Holder delivering such
Notice and Questionnaire is named as a selling securityholder in the Shelf
Registration Statement and the related Prospectus in such a manner as to permit
such Holder to deliver such Prospectus to purchasers of the Transfer Restricted
Securities in accordance with applicable law and, if the Company shall file a
post-effective amendment to the Shelf Registration Statement, use reasonable
efforts to cause such post-effective amendment to be declared effective under
the Securities Act as promptly as is practicable; provided, that if such Notice
and Questionnaire is delivered during a Deferral Period (as defined below), the
Company shall so inform the Holder delivering such Notice and Questionnaire and
shall take the actions set forth above upon expiration of the Deferral Period in
accordance with Section 2(b).

     (b) The Company shall give written notice to the Initial Purchasers and the
Holders of the Transfer Restricted Securities (which notice pursuant to clauses
(ii)-(vi) hereof shall be accompanied by an instruction to suspend the use of
the Prospectus until the requisite changes have been made) (a "Deferral
Notice"):

          (i) when the Shelf Registration Statement or any amendment (other than
     an amendment solely listing the names of any additional Holders) thereto
     has been filed with the Commission and when the Shelf Registration
     Statement or any post-effective amendment thereto has become effective;

          (ii) of any request by the Commission for amendments or supplements to
     the Shelf Registration Statement or the prospectus included therein or for
     additional information;

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

          (iv) of the receipt by the Company or its legal counsel of any
     notification with respect to the suspension of the qualification of the
     Securities for sale in any jurisdiction or the initiation or threatening of
     any proceeding for such purpose;

          (v) of the happening of any event (other than any event covered by
     (vi) below) that requires the Company to make changes in the Shelf
     Registration Statement or the Prospectus in order that the Shelf
     Registration Statement or the Prospectus does not contain an untrue
     statement of a material fact nor omit to state a material fact required to
     be stated therein or necessary to make the statements therein (in the case
     of the Prospectus, in light of the circumstances under which they were
     made) not misleading; and

          (vi) the occurrence of any corporate development or the existence of
     any pending corporate development with respect to the Company that, in the
     good faith discretion of the Company, makes it appropriate to suspend the
     availability of the Shelf Registration Statement and the related
     Prospectus.

     (c) The Company shall make every reasonable effort to obtain the withdrawal
at the earliest possible time, of any order suspending the effectiveness of the
Shelf Registration Statement.

     (d) The Company shall furnish to each Holder of Securities included within
the coverage of the Shelf Registration, without charge, at least one copy of the
Shelf Registration Statement and any post-effective amendment thereto, including
financial statements and schedules, and, if the Holder so requests in writing,
all exhibits thereto (including those, if any, incorporated by reference).

     (e) The Company shall, during the Shelf Registration Period, deliver to
each Holder of Securities included within the coverage of the Shelf
Registration, without charge, as many copies of the Prospectus (including each
preliminary prospectus) included in the Shelf Registration Statement and any
amendment or supplement thereto as such person may reasonably request. The
Company consents, subject to the provisions of this Agreement, to the use of the
Prospectus or any amendment or supplement thereto by each of the selling Holders
of the Securities in connection with the offering and sale of the Securities
covered by the Prospectus, or any amendment or supplement thereto, included in
the Shelf Registration Statement.

     (f) Prior to any public offering of the Securities pursuant to the Shelf
Registration Statement, the Company shall register or qualify or cooperate with
the Holders of the Securities included therein and their respective counsel in
connection with the registration or qualification of the Securities for offer
and sale under the securities or "blue sky" laws of such states of the United
States as any Holder of the Securities reasonably requests in writing and do any
and all other acts or things necessary or advisable to enable the offer and sale
in such jurisdictions of the Securities covered by such Registration Statement;
provided, however, that the Company shall

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not be required to (i) qualify generally to do business in any jurisdiction
where it is not then so qualified or (ii) take any action which would subject it
to general service of process or to taxation in any jurisdiction where it is not
then so subject.

     (g) The Company shall cooperate with the Holders of the Securities to
facilitate the timely preparation and delivery of certificates representing the
Securities to be sold pursuant to any Registration Statement free of any
restrictive legends and in such denominations and registered in such names as
the Holders may request a reasonable period of time prior to sales of the
Securities pursuant to the Shelf Registration Statement.

     (h) Upon the occurrence of any event contemplated by paragraphs (ii)
through (vi) of Section 2(b) above during the period for which the Company is
required to maintain an effective Shelf Registration Statement, the Company
shall use all reasonable efforts to ensure that the use of the Prospectus may be
resumed, including, without limitation, preparing and filing a post-effective
amendment to the Shelf Registration Statement or an amendment or supplement to
the Prospectus and any other required document so that, as thereafter delivered
to Holders or purchasers of the Securities, the Prospectus will not contain an
untrue statement of a material fact or omit to state any material fact required
to be stated therein or necessary to make the statements therein, in the light
of the circumstances under which they were made, not misleading (x) in the case
of clauses (ii) through (iv) of Section 2(b) above, as promptly as practicable,
(y) in the case of clause (v) of Section 2(b) above, as soon as, in the
reasonable judgment of the Company, public disclosure of such material event
would not be prejudicial to or contrary to the interests of the Company and (z)
in the case of clause (vi) of Section 2(b) above, as soon as, in the good faith
discretion of the Company, such suspension is no longer appropriate. The period
during which the availability of the Registration Statement and any Prospectus
is suspended (the "Deferral Period") shall not exceed 45 days in any three-month
period or 120 days in any twelve-month period. To the extent the suspension of
any Registration Statement or Prospectus exceeds either the 45-day or 120-day
limitations in the preceding sentence, the Company shall pay Liquidated Damages
to the Holders otherwise entitled to such payments hereunder. If the Company
notifies the Initial Purchasers and the Holders in accordance with paragraphs
(ii) through (vi) of Section 2(b) above to suspend the use of the Prospectus
until the requisite changes to the Prospectus have been made, then the Initial
Purchasers and the Holders shall suspend use of such prospectus, and the period
of effectiveness of the Shelf Registration Statement provided for in
Section 1(b) above shall be extended by the number of days from and including
the date of the giving of such notice to and including the date when the Initial
Purchasers and the Holders shall have received such amended or supplemented
prospectus pursuant to this Section 2(h).

     (i) Not later than the effective date of the Shelf Registration Statement,
the Company will provide CUSIP numbers for the Initial Securities and the Common
Stock registered under the Shelf Registration Statement, and provide the Trustee
with printed certificates for the Initial Securities, in a form eligible for
deposit with The Depository Trust Company.

     (j) The Company will comply with all rules and regulations of the
Commission to the extent and so long as they are applicable to the Shelf
Registration and will make generally available to its security holders (or
otherwise provide in accordance with Section 11(a) of the Securities Act) an
earnings statement satisfying the provisions of Section 11(a) of the Securities
Act, no later than 45 days after the end of a 12-month period (or 90 days, if
such period is a

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fiscal year) beginning with the first month of the Company's first fiscal
quarter commencing after the effective date of the Shelf Registration Statement,
which statement shall cover such 12-month period.

     (k) The Company shall cause the Indenture to be qualified under the Trust
Indenture Act of 1939, as amended, (the "Trust Indenture Act") not later than
the effective date of the Shelf Registration Statement and containing such
changes, if any, as shall be necessary for such qualification. In the event that
such qualification would require the appointment of a new trustee under the
Indenture, the Company shall appoint a new trustee thereunder pursuant to the
applicable provisions of the Indenture.

     (l) The Company may require each Holder of Securities to be sold pursuant
to the Shelf Registration Statement to furnish to the Company such information
regarding the Holder and the distribution of the Securities as the Company may
from time to time reasonably require for inclusion in the Shelf Registration
Statement, and the Company may exclude from such registration the Securities of
any Holder that fails to furnish such information within a reasonable time after
receiving such request.

     (m) The Company shall enter into such customary agreements and take all
such other actions, if any, as Holders of a majority of the Securities shall
reasonably request in order to facilitate the disposition of the Securities
pursuant to the Shelf Registration.

     (n) The Company will use its best efforts if the Initial Securities have
been rated prior to the initial sale of such Initial Securities, confirm such
ratings will apply to the Securities covered by a Registration Statement.

     (o) The Company shall use its reasonable efforts to take all other steps
necessary to effect the registration of the Securities covered by a Registration
Statement contemplated hereby.

     3. Registration Expenses. (a) All expenses incident to the Company's
performance of and compliance with this Agreement will be borne by the Company,
regardless of whether a Registration Statement is ever filed or becomes
effective, including without limitation;

          (i) all registration and filing fees and expenses;

          (ii) all fees and expenses of compliance with federal securities and
     state "blue sky" or securities laws;

          (iii) all expenses of printing (including printing certificates for
     the Securities to be issued and printing of Prospectuses), messenger and
     delivery services and telephone;

          (iv) all fees and disbursements of counsel for the Company;

          (v) all application and filing fees in connection with listing the
     Securities on a national securities exchange or automated quotation system
     pursuant to the requirements hereof; and

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          (vi) all fees and disbursements of independent certified public
     accountants of the Company (including the expenses of any special audit
     letter required by or incident to such performance).

The Company will bear its internal expenses (including, without limitation, all
salaries and expenses of its officers and employees performing legal or
accounting duties), the expenses of any annual audit and the fees and expenses
of any person, including special experts, retained by the Company.

     (b) In connection with the Shelf Registration Statement required by this
Agreement, the Company will reimburse the Initial Purchasers and the Holders of
Securities covered by the Shelf Registration Statement, for the reasonable fees
and disbursements of not more than one counsel (which shall not exceed $20,000
in the aggregate), designated by the Holders of a majority in principal amount
of the Securities covered by the Shelf Registration Statement (provided that
Holders of Common Stock issued upon the conversion of the Initial Securities
shall be deemed to be Holders of the aggregate principal amount of Initial
Securities from which such Common Stock was converted) to act as counsel for the
Holders in connection therewith.

     4. Indemnification. (a) The Company agrees to indemnify and hold harmless
each Holder and each person, if any, who controls such Holder within the meaning
of the Securities Act or the Exchange Act (each Holder, and such controlling
persons are referred to collectively as the "Indemnified Parties") from and
against any losses, claims, damages or liabilities, joint or several, or any
actions in respect thereof (including, but not limited to, any losses, claims,
damages, liabilities or actions relating to purchases and sales of the
Securities) to which each Indemnified Party may become subject under the
Securities Act, the Exchange Act or otherwise, insofar as such losses, claims,
damages, liabilities or actions arise out of or are based upon any untrue
statement or alleged untrue statement of a material fact contained in the Shelf
Registration Statement or prospectus including any document incorporated by
reference therein, or in any amendment or supplement thereto or in any
preliminary prospectus relating to the Shelf Registration, or arise out of, or
are based upon, the 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 shall reimburse, as incurred, the Indemnified Parties for
any legal or other expenses reasonably incurred by them in connection with
investigating or defending any such loss, claim, damage, liability or action in
respect thereof; provided, however, that (i) the Company shall not be liable in
any such case to the extent that such loss, claim, damage or liability arises
out of or is based upon (x) any untrue statement or alleged untrue statement or
omission or alleged omission made in the Shelf Registration Statement or
prospectus or in any amendment or supplement thereto or in any preliminary
prospectus relating to the Shelf Registration in reliance upon and in conformity
with written information pertaining to such Holder and furnished to the Company
by or on behalf of such Holder specifically for inclusion therein or (y) an
offer or sale of Transfer Restricted Securities occurring during a Deferral
Period, if the Holder received a Deferral Notice prior to mailing or
distributing any preliminary prospectus or prospectus during the Deferral
Period, and (ii) with respect to any untrue statement or omission or alleged
untrue statement or omission made in any preliminary prospectus relating to the
Shelf Registration Statement, the indemnity agreement contained in this
subsection (a) shall not inure to the benefit of any Holder from whom the person
asserting any such losses, claims, damages or liabilities purchased the
Securities concerned, to the extent that a prospectus

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relating to such Securities was required to be delivered by such Holder under
the Securities Act in connection with such purchase and any such loss, claim,
damage or liability of such Holder results from the fact that there was not sent
or given to such person, at or prior to the written confirmation of the sale of
such Securities to such person, a copy of the final prospectus if the Company
had previously furnished copies thereof to such Holder; provided further,
however, that this indemnity agreement will be in addition to any liability
which the Company may otherwise have to such Indemnified Party. The Company
shall also indemnify underwriters, their officers and directors and each person
who controls such underwriters within the meaning of the Securities Act or the
Exchange Act to the same extent as provided above with respect to the
indemnification of the Holders of the Securities if requested by such Holders.

     (b) Each Holder, severally and not jointly, will indemnify and hold
harmless the Company, its officers and directors and each person, if any, who
controls the Company within the meaning of the Securities Act or the Exchange
Act from and against any losses, claims, damages or liabilities or any actions
in respect thereof, to which the Company or any such controlling person may
become subject under the Securities Act, the Exchange Act or otherwise, insofar
as such losses, claims, damages, liabilities or actions arise out of or are
based upon any untrue statement or alleged untrue statement of a material fact
contained in the Shelf Registration Statement or prospectus or in any amendment
or supplement thereto or in any preliminary prospectus relating to the Shelf
Registration, or arise out of or are based upon the omission or alleged omission
to state therein a material fact necessary to make the statements therein not
misleading, but in each case only to the extent that the untrue statement or
omission or alleged untrue statement or omission was made in reliance upon and
in conformity with written information pertaining to such Holder and furnished
to the Company by or on behalf of such Holder specifically for inclusion
therein; and, subject to the limitation set forth immediately preceding this
clause, shall reimburse, as incurred, the Company for any legal or other
expenses reasonably incurred by the Company or any such controlling person in
connection with investigating or defending any loss, claim, damage, liability or
action in respect thereof. This indemnity agreement will be in addition to any
liability which such Holder may otherwise have to the Company or any of its
controlling persons.

     (c) Promptly after receipt by an indemnified party under this Section 4 of
notice of the commencement of any action or proceeding (including a governmental
investigation), such indemnified party will, if a claim in respect thereof is to
be made against the indemnifying party under this Section 4, notify the
indemnifying party of the commencement thereof; but the omission so to notify
the indemnifying party will not, in any event, relieve the indemnifying party
from any obligations to any indemnified party other than the indemnification
obligation provided in paragraph (a) or (b) above. In case any such action is
brought against any indemnified party, and it notifies the indemnifying party of
the commencement thereof, the indemnifying party will be entitled to participate
therein and, to the extent that it may wish, jointly with any other indemnifying
party similarly notified, to assume the defense thereof, with counsel reasonably
satisfactory to such indemnified party (who shall not, except with the consent
of the indemnified party, be counsel to the indemnifying party), and after
notice from the indemnifying party to such indemnified party of its election so
to assume the defense thereof the indemnifying party will not be liable to such
indemnified party under this Section 4 for any legal or other expenses, other
than reasonable costs of investigation, subsequently incurred by such
indemnified party in connection with the defense thereof. It is understood that
the indemnifying

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party shall not, in respect of the legal expenses of any indemnified party in
connection with any proceeding or related proceedings in the same jurisdiction,
be liable for (a) the fees and expenses of more than one separate firm (in
addition to any local counsel) for the Initial Purchasers, Holders of Transfer
Restricted Securities, and all persons, if any, who control the Initial
Purchasers or Holders of Transfer Restricted Securities within the meaning of
the Securities Act or the Exchange Act, (b) the fees and expenses of more than
one separate firm (in addition to any local counsel) for the Company, its
directors and each person, if any, who controls the Company within the meaning
of either such Section, and that all such fees and expenses shall be reimbursed
as they are incurred. In the case of any such separate firm for the Initial
Purchasers, Holders of Transfer Restricted Securities, and control persons of
the Initial Purchasers and Holders of Transfer Restricted Securities, such firm
shall be designated in writing by the Initial Purchasers. In the case of any
such separate firm for the Company, and such directors, officers and control
persons of the Company, such firm shall be designated in writing by the Company.
No indemnifying party shall, without the prior written consent of the
indemnified party, effect any settlement of any pending or threatened action in
respect of which any indemnified party is or could have been a party and
indemnity could have been sought hereunder by such indemnified party unless such
settlement (i) includes an unconditional release of such indemnified party from
all liability on any claims that are the subject matter of such action, and (ii)
does not include a statement as to or an admission of fault, culpability or a
failure to act by or on behalf of any indemnified party.

     (d) If the indemnification provided for in this Section 4 is unavailable or
insufficient to hold harmless an indemnified party under subsections (a) or (b)
above, then each indemnifying party shall contribute to the amount paid or
payable by such indemnified party as a result of the losses, claims, damages or
liabilities (or actions in respect thereof) referred to in subsection (a) or (b)
above in such proportion as is appropriate to reflect the relative fault of the
indemnifying party or parties on the one hand and the indemnified party on the
other in connection with the statements or omissions that resulted in such
losses, claims, damages or liabilities (or actions in respect thereof) as well
as any other relevant equitable considerations. The relative fault of the
parties shall be determined by reference to, among other things, whether the
untrue or alleged untrue statement of a material fact or the omission or alleged
omission to state a material fact relates to information supplied by the Company
on the one hand or such Holder or such other indemnified party, as the case may
be, on the other, and the parties' relative intent, knowledge, access to
information and opportunity to correct or prevent such statement or omission.
The amount paid by an indemnified party as a result of the losses, claims,
damages or liabilities referred to in the first sentence of this subsection (d)
shall be deemed to include any legal or other expenses reasonably incurred by
such indemnified party in connection with investigating or defending any action
or claim which is the subject of this subsection (d). Notwithstanding any other
provision of this Section 4(d), the Holders shall not be required to contribute
any amount in excess of the amount by which the net proceeds received by such
Holders from the sale of the Securities pursuant to the Shelf Registration
Statement exceeds the amount of damages which such Holders have otherwise been
required to pay by reason of such untrue or alleged untrue statement or omission
or alleged 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. For purposes of this paragraph (d), each person, if any, who
controls such indemnified party within the meaning of the Securities Act or the
Exchange Act shall have the same rights to

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contribution as such indemnified party and each person, if any, who controls the
Company within the meaning of the Securities Act or the Exchange Act shall have
the same rights to contribution as the Company.

     (e) The agreements contained in this Section 4 shall survive the sale of
the Securities pursuant to the Shelf Registration Statement and shall remain in
full force and effect, regardless of any termination or cancellation of this
Agreement or any investigation made by or on behalf of any indemnified party.

     5. Liquidated Damages Under Certain Circumstances. (a) Liquidated damages
("Liquidated Damages") with respect to the Transfer Restricted Securities shall
be assessed as follows if any of the following events occur (each such event in
clauses (i) through (iii) below being herein called a "Registration Default"):

          (i) the Shelf Registration Statement has not been filed with the
     Commission by the 90th day after the first date of original issuance of the
     Initial Securities;

          (ii) the Shelf Registration Statement has not been declared effective
     by the Commission by the 180th day after the first date of original issue
     of the Initial Securities; or

          (iii) the Shelf Registration Statement is declared effective by the
     Commission but (A) the Shelf Registration Statement thereafter ceases to be
     effective or (B) the Shelf Registration Statement or the Prospectus ceases
     to be usable in connection with resales of Transfer Restricted Securities
     (as defined below) during the periods specified herein for periods in
     excess of those permitted in Section 2(h) because either (1) any event
     occurs as a result of which the Prospectus forming part of such Shelf
     Registration Statement would include any untrue statement of a material
     fact or omit to state any material fact necessary to make the statements
     therein in the light of the circumstances under which they were made not
     misleading or (2) it shall be necessary to amend such Shelf Registration
     Statement or supplement the related prospectus, to comply with the
     Securities Act or the Exchange Act or the respective rules thereunder.

Each of the foregoing will constitute a Registration Default whatever the reason
for any such event and whether it is voluntary or involuntary or is beyond the
control of the Company or pursuant to operation of law or as a result of any
action or inaction by the Commission.

     Liquidated Damages shall accrue on the Transfer Restricted Securities (in
addition to the interest set forth in the title of the Initial Securities) from
and including the date on which any such Registration Default shall occur to but
excluding the date on which all such Registration Defaults have been cured, at
(x) in respect of any Initial Securities, a rate of 0.50% per annum of the
principal amount thereof plus accrued interest thereon to the Damages Payment
Date (as defined below), and (y) in respect of any shares of Common Stock issued
upon conversion of each $1,000 principal amount of Initial Securities, a rate of
0.50% per annum of the principal amount of such Initial Securities so converted,
plus accrued interest thereon to the Damages Payment Date, divided by the
Conversion Price (as defined in the Indenture), in each case determined as of
the Business Day immediately preceding the next Damages Payment Date; provided,
that any Liquidated Damages accrued with respect to any Initial Security or
portion

                                       10
<Page>

thereof called for redemption on a redemption date or converted into shares of
Common Stock on a conversion date prior to the Damages Payment Date, shall, in
any such event, be paid instead to the Holder who submitted such Security or
portion thereof for redemption or conversion on the applicable redemption date
or conversion date, as the case may be, on such date (or promptly following the
conversion date in the case of conversion). Notwithstanding the foregoing, no
Liquidated Damages shall accrue as to any Transfer Restricted Security from and
after the earlier of (x) the date such security is no longer a Transfer
Restricted Security and (y) expiration of the Shelf Registration Period, nor
shall Liquidated Damages accrue during a Deferral Period, unless the Deferral
Period exceeds either the 45-day or 120-day limitations set forth in Section
2(h) hereof. The rate of accrual of the Liquidated Damages with respect to any
period shall not exceed the rate provided for in this paragraph notwithstanding
the occurrence of multiple concurrent Registration Defaults until all
Registration Defaults have been cured.

     (b) Any amounts of Liquidated Damages due pursuant to Section 5(a) will be
payable in cash on the regular interest payment dates with respect to the
Initial Securities (each a "Damages Payment Date") to record Holders of then
outstanding Securities that are Transfer Restricted Securities. The amount of
Liquidated Damages will be determined on the basis of a 360-day year comprised
of twelve 30-day months and the actual number of days on which Liquidated
Damages accrued during such period.

     (c) "Transfer Restricted Securities" means each Security until the earliest
of (i) the date on which such Security has been effectively registered under the
Securities Act and disposed of in accordance with the Shelf Registration
Statement, (ii) the date on which such Security is distributed to the public
pursuant to Rule 144 under the Securities Act or (iii) the date on which such
Security would be saleable pursuant to Rule 144(k) under the Securities Act were
it not held by an affiliate of the Company.

     6. Rules 144 and 144A. During the Shelf Registration Period, the Company
shall use its best efforts to file the reports required to be filed by it under
the Securities Act and the Exchange Act in a timely manner and, if at any time
the Company is not required to file such reports, it will, upon the request of
any Holder, make publicly available other information so long as necessary to
permit sales of their securities pursuant to Rules 144 and 144A. The Company
covenants that it will take such further action as any Holder may reasonably
request, all to the extent required from time to time to enable such Holder to
sell Transfer Restricted Securities without registration under the Securities
Act within the limitation of the exemptions provided by Rules 144 and 144A
(including the requirements of Rule 144A(d)(4)). The Company will provide a copy
of this Agreement to prospective purchasers of Securities identified to the
Company by the Initial Purchasers upon request. Upon the request of any Holder,
the Company shall deliver to such Holder a written statement as to whether it
has complied with such requirements. Notwithstanding the foregoing, nothing in
this Section 6 shall be deemed to require the Company to register any of its
securities pursuant to the Exchange Act.

     7. Underwritten Registrations. If any of the Transfer Restricted Securities
covered by the Shelf Registration are to be sold in an underwritten offering
effected with the prior written agreement of the Company (as described in
Section 1(a) hereof), the investment banker or investment bankers and manager or
managers that will administer the offering ("Managing Underwriters") will be
selected by the holders of a majority in aggregate principal amount of such
Transfer Restricted Securities to be included in such offering; provided that
holders of

                                       11
<Page>

Common Stock issued upon conversion of the Initial Securities shall not be
deemed holders of Common Stock, but shall be deemed to be holders of the
aggregate principal amount of Initial Securities from which such Common Stock
was converted.

     No person may participate in any underwritten registration hereunder unless
such person (i) agrees to sell such person's Transfer Restricted Securities on
the basis reasonably provided in any underwriting arrangements approved by the
persons entitled hereunder to approve such arrangements and (ii) completes and
executes all questionnaires, powers of attorney, indemnities, underwriting
agreements and other documents reasonably required under the terms of such
underwriting arrangements.

     8. Holder's Obligations. Each Holder agrees, by acquisition of the Transfer
Restricted Securities, that no Holder of Transfer Restricted Securities shall be
entitled to sell any of such Transfer Restricted Securities pursuant to a
Registration Statement or to receive a Prospectus relating thereto, unless such
Holder has furnished the Company with a Notice and Questionnaire as required
pursuant to Section 1(d) hereof (including the information required to be
included in such Notice and Questionnaire) and the information set forth in the
next sentence. Each Holder agrees promptly to furnish to the Company all
information required to be disclosed in order to make the information previously
furnished to the Company by such Holder not misleading and any other information
regarding such Holder and the distribution of such Transfer Restricted
Securities as may be required to be disclosed in the Registration Statement
under applicable law or pursuant to Commission comments or as the Company may
reasonably request. Each Holder further agrees to notify the Company, within ten
business days of request, of the amount of Transfer Restricted Securities sold
by such Holder pursuant to the Registration Statement and, in the absence of a
response, the Company may assume that all of the Holder's Transfer Restricted
Securities were so sold; provided, that, such request by the Company shall
clearly state that if the Holder fails to provide a response, the Company shall
assume that the Holder's Transfer Restricted Securities have been sold.

     9. Miscellaneous.

     (a) Remedies. The Company acknowledges and agrees that any failure by the
Company to comply with its obligations under Section 1 hereof may result in
material irreparable injury to the Initial Purchasers or the Holders for which
there is no adequate remedy at law, that it will not be possible to measure
damages for such injuries precisely and that, in the event of any such failure,
the Initial Purchasers or any Holder may obtain such relief as may be required
to specifically enforce the Company's obligations under Sections 1 hereof. The
Company further agrees, to the extent permitted by applicable law, to waive the
defense in any action for specific performance that a remedy at law would be
adequate. The parties agree that the sole monetary damages payable for a
violation of the terms of this Agreement with respect to which liquidated
damages are expressly provided shall be the Liquidated Damages.

     (b) No Inconsistent Agreements. The Company will not on or after the date
of this Agreement enter into any agreement with respect to its securities that
is inconsistent with the rights granted to the Holders in this Agreement or
otherwise conflicts with the provisions hereof. The rights granted to the
Holders hereunder do not in any way conflict with and are not inconsistent with
the rights granted to the holders of the Company's securities under any
agreement in effect on the date hereof.

                                       12
<Page>

     (c) Amendments and Waivers. The provisions of this Agreement may not be
amended, modified or supplemented, and waivers or consents to departures from
the provisions hereof may not be given, except by the Company and the written
consent of the holders of a majority in principal amount of the Securities
affected by such amendment, modification, supplement, waiver or consents
(provided that holders of Common Stock issued upon conversion of Initial
Securities shall not be deemed holders of Common Stock, but shall be deemed to
be holders of the aggregate principal amount of Initial Securities from which
such Common Stock was converted). Without the consent of the Holder of each
Initial Security, however, no modification may change the provisions relating to
the payment of Liquidated Damages.

     (d) Notices. All notices and other communications provided for or permitted
hereunder shall be made in writing by hand delivery, first-class mail, facsimile
transmission, or air courier which guarantees overnight delivery:

          (1) if to a Holder of the Securities, at the most current address
     given by such Holder to the Company.

          (2) if to the Initial Purchasers;

              Credit Suisse First Boston Corporation
              Eleven Madison Avenue
              New York, NY 10010-3629
              Fax No.:  (212) 325-8278
              Attention:  Transactions Advisory Group

     with a copy to:

              Latham & Watkins
              885 Third Avenue, Ste. 1000
              New York, NY  10022
              Fax No.: (212) 751-4864
              Attention: Peter M. Labonski

          (3) if to the Company, at its address as follows:

              Charles River Laboratories International, Inc.
              251 Ballardville Street
              Wilmington, MA  01887
              Fax No.: (978) 658-7132
              Attention: Dennis Shaughnessy

     with a copy to:

              Davis Polk & Wardwell
              450 Lexington Avenue
              New York, NY  10017
              Fax No.: (212) 450-4800
              Attention: Richard Truesdell

                                       13
<Page>

     All such notices and communications shall be deemed to have been duly
given: at the time delivered by hand, if personally delivered; three business
days after being deposited in the mail, postage prepaid, if mailed; when receipt
is acknowledged by recipient's facsimile machine operator, if sent by facsimile
transmission; and on the day delivered, if sent by overnight air courier
guaranteeing next day delivery.

     (e) Third Party Beneficiaries. The Holders shall be third party
beneficiaries to the agreements made hereunder between the Company, on the one
hand, and the Initial Purchasers, on the other hand, and shall have the right to
enforce such agreements directly to the extent they may deem such enforcement
necessary or advisable to protect their rights or the rights of Holders
hereunder.

     (f) Successors and Assigns. This Agreement shall be binding upon the
Company and its successors and assigns.

     (g) Counterparts. This Agreement may be executed in any number of
counterparts and by the parties hereto in separate counterparts, each of which
when so executed shall be deemed to be an original and all of which taken
together shall constitute one and the same agreement.

     (h) Headings. The headings in this Agreement are for convenience of
reference only and shall not limit or otherwise affect the meaning hereof.

     (i) Governing Law. THIS AGREEMENT SHALL BE GOVERNED BY, AND CONSTRUED IN
ACCORDANCE WITH, THE LAWS OF THE STATE OF NEW YORK WITHOUT REGARD TO PRINCIPLES
OF CONFLICTS OF LAWS.

     By the execution and delivery of this Agreement, the Company submits to the
nonexclusive jurisdiction of any federal or state court in the State of New
York.

     (j) Severability. If any one or more of the provisions contained herein, or
the application thereof in any circumstance, is held invalid, illegal or
unenforceable, the validity, legality and enforceability of any such provision
in every other respect and of the remaining provisions contained herein shall
not be affected or impaired thereby.

     (k) Securities Held by the Company. Whenever the consent or approval of
Holders of a specified percentage of principal amount of Securities is required
hereunder, Securities held by the Company or its affiliates (other than
subsequent Holders of Securities if such subsequent Holders are deemed to be
affiliates solely by reason of their holdings of such Securities) shall not be
counted in determining whether such consent or approval was given by the Holders
of such required percentage.

                                       14
<Page>

     If the foregoing is in accordance with your understanding of our agreement,
please sign and return to the Company a counterpart hereof, whereupon this
instrument, along with all counterparts, will become a binding agreement among
the several Initial Purchasers and the Company in accordance with its terms.

                                  Very truly yours,

                                  CHARLES RIVER LABORATORIES INTERNATIONAL, INC.

                                  By: /s/  Dennis R. Shaughnessy
                                     -------------------------------------------
                                     Name:  Dennis R. Shaughnessy
                                     Title: Vice President, Corporate
                                            Development, General Counsel and
                                            Secretary

The foregoing Registration Rights Agreement is hereby confirmed and accepted as
of the date first above written.

CREDIT SUISSE FIRST BOSTON CORPORATION
LEHMAN BROTHERS INC.
J.P. MORGAN SECURITIES INC.
SG COWEN SECURITIES CORPORATION
U.S. BANCORP PIPER JAFFRAY INC.
THOMAS WEISEL PARTNERS LLC
INVESTEC PMG CAPITAL CORP.
JEFFRIES & COMPANY, INC.

By: CREDIT SUISSE FIRST BOSTON CORPORATION

By: /s/  Edward M. Brown
    ---------------------------------------
    Name:  Edward M. Brown
    Title: Managing Director<Page>

                                                                      ANNEX I

            AMENDMENT NO. 2 TO AMENDED AND RESTATED CREDIT AGREEMENT
                                       AND
                     AMENDMENT NO. 1 TO AMENDED AND RESTATED
                      HOLDCO GUARANTY AND PLEDGE AGREEMENT

               THIS AMENDMENT NO. 2 TO AMENDED AND RESTATED CREDIT

AGREEMENT AND AMENDMENT NO. 1 TO AMENDED AND RESTATED HOLDCO GUARANTY AND PLEDGE
AGREEMENT (this "AMENDMENT"), dated as of January 11, 2002, among Charles River
Laboratories, Inc., a Delaware corporation (the "BORROWER"), Charles River
Laboratories International, Inc. (f/k/a Charles River Laboratories Holdings,
Inc.), a Delaware corporation ("HOLDCO"), Credit Suisse First Boston, as lead
arranger, as sole book runner and as syndication agent (in such capacity, the
"SYNDICATION AGENT ") for the Lenders (as defined below), and Fleet National
Bank, as administrative agent (the "ADMINISTRATIVE AGENT") for the Lenders.

                               W I T N E S S E T H:

      WHEREAS, the Borrower, certain financial institutions (together with their
respective successors and assigns, the "LENDERS"), the Syndication Agent and the
Administrative Agent are parties to the Amended and Restated Credit Agreement,
dated as of February 2, 2001 (as heretofore modified and supplemented and in
effect from time to time, the "EXISTING CREDIT AGREEMENT" and as further amended
hereby, the "CREDIT AGREEMENT");

      WHEREAS, Holdco and the Administrative Agent are parties to the Amended
and Restated Holdco Guaranty and Pledge Agreement, dated as of February 6, 2001
(as heretofore modified and supplemented and in effect from time to time, the
"EXISTING HOLDCO GUARANTY" and as further amended hereby, the "HOLDCO
GUARANTY");

      WHEREAS, Holdco desires, among other things, to (a) issue up to
$200,000,000 in aggregate principal amount of its convertible senior unsecured
debentures that, subject to certain conditions set forth therein, may be
converted to common stock of Holdco and (b) make a cash contribution and/or an
intercompany loan of all of the net cash proceeds from such issuance to the
Borrower;

      WHEREAS, the Borrower desires, among other things, to use the proceeds of
such cash contribution and intercompany loan to (a) redeem and/or defease and
redeem all of its outstanding Senior Subordinated Notes and (b) use any amount
remaining following such redemption and/or defeasance and redemption for general
corporate purposes; and

      WHEREAS, the Borrower and Holdco desire, and the Lenders are willing, on
the terms and subject to the conditions hereinafter set forth, to amend the
Existing Credit Agreement and the Holdco Guaranty as set forth herein to permit
them to do so;

<Page>

      NOW, THEREFORE, the parties hereto hereby agree as follows:

                                    PART I DEFINITIONS

      SUBPART 1.1 CERTAIN DEFINITIONS. Unless otherwise defined herein or the
context otherwise requires, terms used in this Amendment, including its preamble
and recitals, have the following meanings (such meanings to be equally
applicable to the singular and plural forms thereof):

      "ADMINISTRATIVE AGENT" is defined in the PREAMBLE.

      "AMENDMENT" is defined in the PREAMBLE.

      "AMENDMENT EFFECTIVE DATE" is defined in SUBPART 4.1.

      "BORROWER" is defined in the PREAMBLE.

      "CREDIT AGREEMENT" is defined in FIRST RECITAL.

      "EXISTING CREDIT AGREEMENT" is defined in the FIRST RECITAL.

      "EXISTING HOLDCO GUARANTY" is defined in the SECOND RECITAL.

      "HOLDCO" is defined in the PREAMBLE.

      "HOLDCO GUARANTY" is defined in the SECOND RECITAL.

      "LENDERS" is defined in the FIRST RECITAL.

      "SYNDICATION AGENT" is defined in the PREAMBLE.

      SUBPART 1.2 OTHER DEFINITIONS. Unless otherwise defined herein or the
context otherwise requires, terms used in this Amendment, including its preamble
and recitals, have the meanings set forth in the Existing Credit Agreement. Each
reference to "hereof", "hereunder", "herein" and "hereby" and each other similar
reference and each reference to "this Agreement" and each other similar
reference contained in the Existing Credit Agreement shall from and after the
Amendment Effective Date refer to the Credit Agreement.

                                     PART II

                     AMENDMENTS TO EXISTING CREDIT AGREEMENT

      Effective on (and subject to the occurrence of) the Amendment Effective
Date, the Existing Credit Agreement is hereby amended in accordance with this
Part II. Except to the extent amended by this Amendment, the Existing Credit
Agreement is and shall continue to be in full force and effect and is hereby
ratified and confirmed in all respects.

      SUBPART 2.1 AMENDMENTS TO ARTICLE I. Article I of the Existing Credit
Agreement is amended as set forth in this Subpart 2.1.

                                        2
<Page>

      (a) Section 1.1 of such Article is hereby amended by inserting the
following definitions in such Section in the appropriate alphabetical order:

           "AMENDMENT NO. 2" means Amendment No. 2 to Amended and Restated
      Credit Agreement and Amendment No. 1 to Amended and Restated Holdco
      Guaranty and Pledge Agreement, dated as of January 11, 2002, among the
      Borrower, Holdco and the Agents, which amendment was consented to by the
      Lenders constituting the Required Lenders.

           "CONVERTIBLE SENIOR UNSECURED DEBENTURES" is defined in Section
      5.9(b)(i) of the Holdco Guaranty and Pledge Agreement.

           "CONVERTIBLE SENIOR UNSECURED DEBENTURES CASH CONTRIBUTION" is
      defined in Section 5.9(b)(i) of the Holdco Guaranty and Pledge Agreement.

           "CONVERTIBLE SENIOR UNSECURED DEBT" means the Indebtedness evidenced
      by the Convertible Senior Unsecured Debentures, if any.

           "CONVERTIBLE SENIOR UNSECURED DEBT DOCUMENTS" means the Convertible
      Senior Unsecured Debentures and all other instruments, agreements or other
      documents evidencing or governing any Convertible Senior Unsecured Debt or
      pursuant to which any Convertible Senior Unsecured Debt has been issued.

           "DESIGNATED ACCOUNT" means a securities account (as defined in
      Section 8-501 of the UCC) maintained by a securities intermediary (as
      defined in Section 8-102(a)(14) of the UCC) satisfactory to Holdco and the
      Agents pursuant to the Designated Account Agreement.

           "DESIGNATED ACCOUNT AGREEMENT " means an account control agreement
      in form and substance satisfactory to the Agents, among Holdco, as debtor,
      the Administrative Agent, as secured party, and a securities intermediary
      (as defined in Section 8-102(a)(14) of the UCC) satisfactory to Holdco and
      the Agents, which agreement shall provide for, among other things, that
      (a) the Administrative Agent will have control (as defined in Section
      8-106 of the UCC) over the Designated Account and the financial assets (as
      defined in Section 8-102(a)(9) of the UCC) credited thereto, (b) Holdco
      may only issue entitlement orders (as defined in Section 8-102(a)(8) of
      the UCC) to such securities intermediary that direct such securities
      intermediary to transfer or redeem and transfer any such financial asset
      to (i) pay the Convertible Senior Unsecured Debentures or (ii) the
      Borrower and (c) such securities intermediary shall agree (i) not to
      comply with any such entitlement order from Holdco following notice by the
      Administrative Agent to Holdco that an Event of Default has occurred, (ii)
      to follow any entitlement order issued to such securities intermediary by
      the Administrative Agent following the giving of such notice by the
      Administrative Agent, (iii) waive its right of set-off against the
      Designated Account and the assets therein and (iv) to treat all cash and
      all other property in the Designated Account as financial assets (as
      defined in Section 8-102(a)(9)(iii) of the UCC).

           "HOLDCO INTERCOMPANY LOAN" is defined in CLAUSE (L) of SECTION 7.2.2.

                                       3
<Page>

           "HOLDCO INTERCOMPANY NOTE" is defined in clause (l) of Section 7.2.2.

           "SENIOR SUBORDINATED INDENTURE" means the Indenture, dated as of
      September 29, 1999, among the Borrower, the guarantors parties thereto and
      State Street Bank and Trust Company, as trustee.

      (b) The definition of "Debt" contained in Section 1.1 of such Article is
hereby amended to insert the words "Holdco and" immediately following the words
"the outstanding principal amount of all Indebtedness of" and immediately
preceding the words "the Borrower and its Restricted Subsidiaries" in such
definition.

      (c) Clause (vi) of the definition of "Excluded Equity Proceeds" contained
in Section 1.1 of such Article is hereby amended and restated in its entirety to
read as follows: "(vi) the issuance by Holdco of (A) any of its common stock to
repay or prepay or effect the conversion of (1) the PAIC Subordinated
Convertible Note in accordance with the proviso to CLAUSE (b) of SECTION 7.2.6
or (2) the Convertible Senior Unsecured Debentures in accordance with the terms
thereof and (B) $16,500,000 of its common stock in connection with the Primedica
Related Issuance,".

      (d) Clause (b)(iii) of the definition of "Fixed Charge Coverage Ratio"
contained in Section 1.1 of such Article is hereby amended by deleting the
clause reference "(c)(iii)(y) of SECTION 7.2.6" contained in such definition and
inserting the clause reference "(c)(iii)(y)(II) of SECTION 7.2.6" in lieu
thereof.

      (e) The last sentence of the definition of "Indebtedness" contained in
Section 1.1 of such Article is hereby amended by:

           (i) inserting the clause lettering "(x)" immediately following the
      words "the Indebtedness of any Person shall" and immediately preceding the
      words "include the Indebtedness of any partnership or joint venturer" in
      such sentence; and

           (ii) inserting the words "and (y) exclude the Senior Subordinated
      Debt and any Contingent Liabilities in respect thereof so long as,
      following the defeasance of the Senior Subordinated Debt pursuant to
      clause (y) of the proviso to SECTION 7.2.6(b), Sections 4.07, 4.08, 4.09,
      4.11, 4.12, 4.14, 4.15, 4.16 and 4.17 of the Senior Subordinated Indenture
      are not binding upon the Borrower or any of its Restricted Subsidiaries"
      immediately following the words "such Person is liable for such
      Indebtedness)" and immediately preceding the period (".") at the end of
      such sentence.

      (f) The definition of "Interest Expense" contained in Section 1.1 of such
Article is hereby amended by inserting a new sentence at the end of such
definition, which new sentence shall read in its entirety as follows:

      "Notwithstanding anything to the contrary herein, Interest Expense shall
      include interest expense of Holdco in respect of the Convertible Senior
      Unsecured Debentures but shall exclude interest expense of the Borrower in
      respect of the Holdco Intercompany Loan.

                                       4
<Page>

      (g) Clause (a) of the definition of "Leverage Ratio" contained in Section
1.1 of such Article is hereby amended and restated in its entirety to read as
follows:

            "(a) total Debt less the sum of (i) cash and Cash Equivalent
      Investments of the Borrower and its Restricted Subsidiaries on a
      consolidated basis outstanding at such time and (ii) cash and Cash
      Equivalent Investments of Holdco that are held in the Designated
      Account;".

      (h) The definition of "Loan Document" contained in Section 1.1 of such
Article is hereby amended to insert the words "the Designated Account
Agreement," immediately following the words "each Pledge Agreement," and
immediately preceding the words "the Subsidiary Guaranty" in such definition.

      (i) The definition of "Material Documents" contained in Section 1.1 of
such Article is hereby amended by inserting the words ", the Convertible Senior
Unsecured Debt Documents" immediately following the words "the Primedica
Purchase Agreement " and immediately preceding the words "and the Senior
Subordinated Debt Documents" in such definition.

      (j) Section 1.4 of such Article is hereby amended by inserting a new
clauses (c) and (d) at the end of such Section, which new clauses (c) and (d)
shall read in their entirety as follows:

           "(c) Notwithstanding anything to the contrary herein, cash and
      securities of the Borrower and its Restricted Subsidiaries that are
      deposited into an irrevocable trust in connection with the defeasance of
      the Senior Subordinated Notes in accordance with CLAUSE (y)(bb) of the
      proviso to CLAUSE (b) of SECTION 7.2.6 shall not constitute assets of the
      Borrower or such Restricted Subsidiary following the making of such
      deposit.

           (d) Notwithstanding anything to the contrary herein, in determining
      `the cash portion of Interest Expense (net of interest income)' for
      purposes of clause (b)(i) of the definition of the term `Excess Cash
      Flow', clause (b)(i) of the definition of the term `Fixed Charge Coverage
      Ratio' and clause (b)(i) of the definition of the term `Interest Coverage
      Ratio', interest income shall include interest income earned by Holdco.".

      SUBPART 2.2 AMENDMENTS TO ARTICLE VII. Section 7.2. of the Existing Credit
Agreement is hereby amended as set forth in this Subpart 2.2.

      (a) Section 7.2.2 of the Existing Credit Agreement is hereby amended by:

           (i) inserting the words "until the date that such Indebtedness is
      defeased in accordance with CLAUSE (y)(bb) of the proviso to CLAUSE (b) of
      SECTION 7.2.6" immediately following the words "and subordinated
      guarantees thereof" and immediately preceding the semicolon (";") at the
      end of clause (e) of such Section;

           (ii) deleting the word "and" following the semicolon (";") at the end
      of clause (j) of such Section;

           (iii) deleting the period at the end of clause (k) of such Section
      and inserting the text "; and" in lieu thereof: and

                                       5
<Page>

           (iv) inserting a new clause (1) to such Section immediately following
      clause (k) thereof, which new clause (l) shall read in its entirety as
      follows:

                "(1) unsecured Indebtedness of the Borrower owing to Holdco
            and consisting of one or more intercompany loans (collectively, the
            `HOLDCO INTERCOMPANY LOAN') made by Holdco to the Borrower with the
            net cash proceeds of the issuance of the Convertible Senior
            Unsecured Debt or pursuant to the proviso to Section 7.2.6(b)(i)(B)
            or Section 5.3 of the Holdco Guaranty and Pledge Agreement, which
            intercompany loans shall (A) not mature prior to the sixth
            anniversary of the issuance thereof and (B) be evidenced by a single
            promissory note (the `HOLDCO INTERCOMPANY NOTE') in form and
            substance reasonably satisfactory to the Agents which shall be duly
            executed and delivered to (and indorsed to the order of) the
            Administrative Agent in pledge pursuant to the Holdco Guaranty and
            Pledge Agreement;".

      (b) Clause (b) of Section 7.2.6 is hereby amended and restated in its
entirety to read as follows:

           "(b) the Borrower will not, and will not permit any of its Restricted
      Subsidiaries to, (i) directly or indirectly make any payment or prepayment
      of principal of, or make any payment of interest on, (A) any Senior
      Subordinated Debt or the Indebtedness evidenced by the PAIC Subordinated
      Convertible Note on any day other than the stated, scheduled date for such
      payment or prepayment set forth in the Senior Subordinated Debt Documents
      or the PAIC Subordinated Convertible Note or which would violate the
      subordination provisions of such Senior Subordinated Debt Documents or the
      PAIC Subordinated Convertible Note or (B) the Holdco Intercompany Loan on
      any day other than payments of cash interest on the stated, scheduled date
      for such payment set forth in the Holdco Intercompany Note (PROVIDED,
      HOWEVER, that such payments of interest on the Holdco Intercompany Loan
      may only be made so long as no Default shall have occurred and be
      continuing on the date such payment is to be made and to the extent the
      proceeds of such payment are not concurrently applied by Holdco upon its
      receipt thereof to the payment of cash interest on the Convertible Senior
      Unsecured Debentures, Holdco shall make a cash contribution or an
      intercompany loan that is evidenced by the Holdco Intercompany Note, which
      cash contribution or intercompany loan, shall be in the amount of such
      proceeds not so applied to the payment of cash interest on the Convertible
      Senior Unsecured Debentures to the Borrower on the date such payment is
      made) or (ii) redeem, purchase or defease any Senior Subordinated Debt or
      Indebtedness evidenced by the PAIC Subordinated Convertible Note or the
      Holdco Intercompany Note; PROVIDED, HOWEVER, that all Indebtedness
      (whether consisting of principal or interest) that is evidenced by (x) the
      PAIC Subordinated Convertible Note may (A) be repaid or prepaid in
      accordance with the conversion provisions thereof so long as (1) no cash
      is paid by or on behalf of the Borrower in connection therewith and (2)
      the sole consideration for such repayment or prepayment is common stock of
      Holdco (such repayment or prepayment referred to herein as the `PAIC
      CONVERSION EVENT') or (B) be repaid or prepaid in cash with the proceeds
      of the issuance by Holdco of its Capital Stock so long as no Event of
      Default has occurred and is the n outstanding and (y) all (and not less
      than all) of the Senior Subordinated Notes may be (aa) redeemed and/or
      (bb) defeased and redeemed, in

                                       6
<Page>

      each case, (I) in accordance with the terms and conditions set forth in
      the Senior Subordinated Debt Documents (including in the case of such
      defeasance and redemption, the applicable terms and conditions set forth
      in Section 8.04 of the Senior Subordinated Indenture) and pursuant to
      documentation in form and substance reasonably satisfactory to the Agents
      (which documentation shall be certified by an Authorized Officer of the
      Borrower as being true and complete), (II) with the proceeds of the
      Convertible Senior Unsecured Debentures Cash Contribution and/or the
      Holdco Intercompany Loan (other than the Holdco Intercompany Loans made
      pursuant to the proviso to SECTION 7.2.6(b)(i)(B)) and (III) so long as no
      Event of Default has occurred and is then continuing;".

      (c) Clause (c)(iii)(y) of Section 7.2.6 of the Existing Credit Agreement
is hereby amended by inserting the words "(I) the Convertible Senior Unsecured
Debentures and (II)" immediately following the words "make cash payments of
interest with respect to" and immediately preceding the words "the Senior
Discount Debentures in accordance with the terms thereof" contained in such
clause.

                                    PART III
                     AMENDMENTS TO EXISTING HOLDCO GUARANTY

      Effective on (and subject to the occurrence of) the Amendment Effective
Date, the Existing Holdco Guaranty is hereby amended in accordance with this
Part III. Except to the extent amended by this Amendment, the Existing Holdco
Guaranty is and shall continue to be in full force and effect and is hereby
ratified and confirmed in all respects.

      SUBPART 3.1 AMENDMENTS TO ARTICLE I. Article I of the Holdco Guaranty is
amended as set forth in this Subpart 3.1.

      (a) Section 1.1 of such Article is hereby amended by inserting the
following definition in such Section in the appropriate alphabetical order:

            "PLEDGED NOTE" means the Holdco Intercompany Note or other
      promissory note issued in substitution therefor, as amended, modified or
      supplemented from time to time.

      (b) The definition of "Pledged Property" contained in Section 1.1 of such
Article is hereby amended to insert the words "the Pledged Note," immediately
following the words "all other pledged shares of Capital Stock," and immediately
preceding the words "all other securities" in such definition.

      SUBPART 3.2 AMENDMENTS TO ARTICLE II. Article II of the Existing Holdco
Guaranty is amended as set forth in this Subpart 3.2.

      (a) Section 2.1 of such Article is hereby amended by as follows:

           (i) clauses (c), (d) and (e) of such Section are hereby relettered as
clauses (d), (e) and (g), respectively;

                                       7
<Page>

           (ii) a new clause (c) is hereby inserted in such Section immediately
following clause (b) and immediately preceding such relettered clause (d) of
such Section, which new clause (c) shall read in its entirety as follows:

                 "(c) the Pledged Note;";

           (iii) such relettered clause (e) is hereby amended by (A) inserting
the words "interest," immediately following the words "all Dividends,
Distributions," and immediately preceding the words "and other payments and
rights" in such clause and (B) deleting the word "and" at the end of such
clause; and

           (iv) a new clause (f) is hereby inserted in such Section immediately
following relettered clause (e) and immediately preceding such relettered clause
(g) of such Section, which new clause (f) shall read in its entirety as follows:

                 "(f) the Designated Account, if any, all cash, securities,
      financial assets and other assets therein and all interest, earnings and
      proceeds in respect thereof;".

      (b) Section 2.3 of such Article is hereby amended by

           (i) inserting the words "and the Pledged Note" immediately following
the words "including all Pledged Shares" and immediately preceding the words ",
shall (to the extent" in such Section; and

           (ii) inserting the words "(and, in the case of the Pledged Note,
      endorsed to the order of)" immediately following the words "delivered to
      and held by or on behalf of" and immediately preceding the words "the
      Administrative Agent pursuant hereto" in such Section.

      (c) The last sentence of Section 2.5 of such Article is hereby amended by
ins erting the words "and the Pledged Note" immediately following the words
"representing or evidencing all Pledged Shares" and immediately preceding the
words ", together with all other Collateral" in such Section.

      SUBPART 3.3 AMENDMENTS TO ARTICLE IV. Article IV of the Existing Holdco
Guaranty is amended as set forth in this Subpart 3.3.

      (a) Section 4.1 of such Article is hereby amended by inserting the words
"and the Pledged Note" immediately following the words "(including each pledge
and delivery of Pledged Shares" and immediately preceding the words ") by Holdco
to the Administrative Agent " in such Section.

      (b) Section 4.1.3 of such Article is hereby amended by and restated in its
entirety to read as follows:

            "SECTION 4.1.3. VALID SECURITY INTEREST. The execution and delivery
      of this Agreement, together with (a) in the case of the Collateral (other
      than the Collateral

                                       8
<Page>

      described in CLAUSE (f) of SECTION 2.1), the delivery of such Collateral
      to the Administrative Agent and (b) in the case of the Collateral
      described in CLAUSE (f) of SECTION 2.1, the execution and delivery to the
      Administrative Agent of the Designated Account Agreement by the parties
      thereto, is effective to create a valid, perfected, first-priority
      security interest in such Collateral and all proceeds thereof, securing
      the Secured Obligations, subject only to Liens of the type referred to
      in  clauses (b), (d) and (g) of Section 7.2.3 of the Credit Agreement.
      Possession by the Administrative Agent of the Collateral (other than the
      Collateral described in CLAUSE (f) of SECTION 2.1) and the effectiveness
      of the Designated Account Agreement is the only action necessary to
      perfect or protect such security interest in all of the Collateral,
      subject to Section 9-315 of the U.C.C.

      (c) Section 4.1.4 of such Article is hereby amended by

           (i) inserting the words "THE PLEDGED NOTE AND THE DESIGNATED ACCOUNT"
      immediately following the words "AS TO PLEDGED SHARES" and immediately
      preceding the period (".") in the heading of such Section;

           (ii) inserting the clause lettering "(a)" immediately following the
      heading to such Section and immediately preceding the first sentence of
      such Section; and

           (iii) inserting new clauses (b) and (c) at the end of such Section,
      which new clauses (b) and (c) shall read in their entirety as follows:

                  "(b) The Pledged Note has been duly authorized, executed,
            endorsed, issued and delivered and is the legal, valid and binding
            obligation of the Borrower.

                  (c) The Administrative Agent shall have the right to apply any
            amount in the Designated Account to the payment of any Obligations
            which are due and payable or payable upon demand.".

      SUBPART 3.4 AMENDMENTS TO ARTICLE V. Article V of the Existing Holdco
Guaranty is amended as set forth in this Subpart 3.4.

      (a) Section 5.3 of such Article is hereby amended by inserting (i) the
words "the Pledged Note, all interest, principal and other proceeds with respect
to the Pledged Note," immediately following the words "all Dividends and
Distributions with respect thereto," and immediately preceding the words "and
all other Collateral and other securities" in such Section and (ii) a new
sentence at the end of such Section, which new sentence shall read in its
entirety as follows:

      "Holdco further agrees that it shall not issue any entitlement orders to
      the securities intermediary at which the Designated Account is maintained;
      PROVIDED, HOWEVER, that Holdco may issue an entitlement order to such
      securities intermediary to transfer or redeem and transfer assets in the
      Designated Account to make (a) scheduled payments of cash interest in
      respect of the Convertible Senior Unsecured Debentures in the amount and
      on the date provided for in the Convertible Senior Unsecured Debentures so
      long as no Default has occurred and is then outstanding or would result
      therefrom and (b) cash

                                       9
<Page>

      contributions or an intercompany loan that is evidenced by the Holdco
      Intercompany Note to the Borrower."

      (b) Section 5.6(b) of such Article is hereby amended by deleting the open
   square bracket ("[") and the close square bracket ("]") around the number
   "$5,000,000" in such Section.

      (c) Section 5.9(b)(i) of such Article is hereby amended by inserting the
    words ", unsecured Indebtedness in an aggregate principal amount not
    exceeding $200,000,000, which Indebtedness is evidenced by convertible
    senior unsecured debentures (the `CONVERTIBLE SENIOR UNSECURED DEBENTURES')
    of Holdco (PROVIDED, HOWEVER, that (A) all of the terms and provisions of
    the Convertible Senior Unsecured Debentures and the other Convertible Senior
    Unsecured Debt Documents shall be reasonably satisfactory to the Agents,
    (B) no Default or Event of Default shall have occurred and be then
    outstanding both immediately before and after such issuance, (C) after
    giving effect to such issuance (and the redemption by the Borrower of all or
    any of its Senior Subordinated Notes on the same day of such issuance), the
    Borrower shall be in PRO FORMA compliance with the covenants set forth in
    clauses (b), (c) and (d) of Section 7.2.4 of the Credit Agreement for the
    most recent full Fiscal Quarter immediately preceding the date of the making
    of such issuance (and redemptions) for which the relevant financial
    information has been delivered pursuant to clause (a) or clause (b) of
    Section 7.1.1 of the Credit Agreement, (D) Holdco shall have made (1) a cash
    contribution (the `CONVERTIBLE SENIOR UNSECURED DEBENTURES CASH
    CONTRIBUTION') and/or (2) the Holdco Intercompany Loan to the Borrower using
    all of the net cash proceeds from such issuance to the Borrower upon
    Holdco's receipt of such proceeds (PROVIDED, HOWEVER, that Holdco may
    withhold from the funding of the Convertible Senior Unsecured Debentures
    Cash Contribution and the Holdco Intercompany Loan, (i) a portion of such
    net cash proceeds in an amount not exceeding the amount of cash required to
    make the first scheduled payment of cash interest on the Convertible Senior
    Unsecured Debentures or (ii) any amount of such net cash proceeds so long as
    such net cash proceeds are placed in the Designated Account (PROVIDED
    FURTHER, HOWEVER, that if the Senior Subordinated Notes are or are to be
    redeemed and/or defeased and redeemed at any time, Holdco shall (in the
    case of any amounts held in the Designated Account, to the extent permitted
    under CLAUSE (b) of the proviso to the last sentence of SECTION 5.3) make a
    cash contribution of such withheld cash to the Borrower concurrent with
    such redemption and/or defeasance and redemption in an amount necessary to
    effect such redemption and/or defeasance and redemption and such cash
    contribution shall be deemed to constitute proceeds of the Convertible
    Senior Unsecured Debentures Cash Contribution for purposes of the Credit
    Agreement)) and (E) prior to or concurrent with the issuance of such
    Convertible Senior Unsecured Debentures, an Authorized Officer of Holdco
    shall have provided the Agents with a certificate certifying that (1)
    attached thereto are true and complete copies of the Convertible Senior
    Unsecured Debentures and all other Convertible Senior Unsecured Debt
    Documents, together with such notes and documents, (2) after giving effect
    to such issuance (and all redemptions by the Borrower of its Senior
    Subordinated Notes on the same day of such issuance), the Borrower shall be
    in PRO FORMA compliance with the covenants set forth in clauses (b), (c) and
    (d) of Section 7.2.4 of the Credit Agreement for the most recent full Fiscal
    Quarter immediately preceding the date of the making of such issuance (and
    redemptions) for which the relevant financial information has been delivered
    pursuant to clause (a) or clause (b) of Section 7.1.1 of the Credit
    Agreement, together with calculations in support thereof (in form and detail
    reasonably satisfactory to the Agents) and (3) no Default or Event of
    Default has or will have occurred and be then outstanding both immediately
    before and

                                      10
<Page>

after such is suance)" immediately following the words "unsecured Indebtedness
in respect of the Seller Subordinated Discount Note of Holdco" and immediately
preceding the words "or other Indebtedness consented to by the Required Lenders"
contained at the end of such Section.

      (d) Section 5.9(b)(v) of such Article is hereby amended by deleting the
words "any schedules, exhibits or agreements related thereto, in each case"
contained therein and inserting the words "any Convertible Senior Unsecured
Debenture or any other Convertible Senior Unsecured Debt Document" in lieu
thereof.

      (e) Section 5.9(b)(vi) of such Article is hereby amended by inserting the
words "(b) (so long as such Investment is maintained in the Designated Account)
or" immediately following the words "an Investment of the type referred to in
clause" and immediately preceding the words "(g) of Section 7.2.5 of the Credit
Agreement" in such Section.

                                     PART IV
                           CONDITIONS TO EFFECTIVENESS

      SUBPART 4.1 AMENDMENT EFFECTIVE DATE. This Amendment shall become
effective as of the date (the "AMENDMENT EFFECTIVE DATE") when the Agents shall
have received counterparts of this Amendment, duly executed by the Borrower,
Holdco, the Syndication Agent and the Administrative Agent on behalf of the
Required Lenders who shall have delivered to the Administrative Agent their
written consent to the amendments, as explicitly set forth herein and subject to
the terms hereof.

                                    PART V MISCELLANEOUS

      SUBPART 5.1 EXPENSES. The Borrower hereby agrees to pay and reimburse the
Agents for all of their respective reasonable fees and expenses incurred in
connection with the negotiation, preparation, execution and delivery of this
Amendment and related documents, including all reasonable fees and disbursements
of Mayer, Brown & Platt, counsel to the Agents.

      SUBPART 5.2 BORROWER AND HOLDCO REPRESENTATIONS AND WARRANTIES. The
delivery of an executed counterpart hereof by each of the Borrower and Holdco
shall constitute a representation and warranty by each such Obligor that:

            (a) on the Amendment Effective Date, after giving effect to this
      Amendment, (i) all representations, warranties and other statements set
      forth in Article VI of the Existing Credit Agreement and Article IV of the
      Existing Holdco Guaranty, as then amended by this Amendment, are true and
      correct in all material respects as of such date, except to the extent
      that such representation, warranty or statement expressly relates to an
      earlier date (in which case such representation, warranty or statement
      shall have been true and correct in all material respects on and as of
      such earlier date) and (ii) no Default has occurred and is then
      continuing; and

            (b) this Amendment constitutes the legal, valid and binding
      obligation of each of the Borrower and Holdco enforceable in accordance
      with its terms subject to the effects of bankruptcy, insolvency,
      fraudulent conveyance, reorganization, moratorium and other

                                      11
<Page>

      similar laws relating to or affecting creditors' rights generally, general
      equitable principles (whether considered in a proceeding in equity or at
      law) and an implied covenant of good faith and fair dealing.

      SUBPART 5.3 LOAN DOCUMENT PURSUANT TO CREDIT AGREEMENT. This Amendment is
a Loan Document executed pursuant to the Credit Agreement and shall (unless
otherwise expressly indicated therein) be construed, administered and applied in
accordance with all of the terms and provisions of the Credit Agreement, as
amended hereby.

      SUBPART 5.4 SUCCESSORS AND ASSIGNS. This Amendment shall be binding upon
and inure to the benefit of the parties hereto and their respective successors
and assigns.

      SUBPART 5.5 COUNTERPARTS. This Ame ndment may be executed by the parties
hereto in several counterparts, each of which when executed and delivered shall
be an original and all of which shall constitute together but one and the same
agreement.

      SUBPART 5.6 GOVERNING LAW. THIS AMENDMENT SHALL BE GOVERNED BY, AND
CONSTRUED IN ACCORDANCE WITH, THE INTERNAL LAWS OF THE STATE OF NEW YORK.

                                      12
<Page>

      IN WITNESS WHEREOF, the parties hereto have executed and delivered this
Amendment as of the date first above written.

BORROWER:                             CHARLES RIVER LABORATORIES, INC.

                                       By:___________________________________
                                           Name:
                                           Title:

HOLDCO:                               CHARLES RIVER LABORATORIES
                                        INTERNATIONAL, INC. (f/k/a Charles
                                        River Laboratories Holdings, Inc.)

                                       By:___________________________________
                                           Name:
                                           Title:

AGENTS :                              CREDIT SUISSE FIRST BOSTON, as
                                        Syndication Agent

                                       By:___________________________________
                                           Name:
                                           Title:

                                       By:___________________________________
                                           Name:
                                           Title:

                                      FLEET NATIONAL BANK, as Administrative
                                        Agent

                                       By:___________________________________
                                           Name:
                                           Title:

                                       S-1

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