EXHIBIT 99.1


CORPORATE PRESS RELEASE

                                     [LOGO]

Dennis R. Shaughnessy
Marcia Gookin
Investor Relations
978-658-6000 Ext. 1329
www.criver.com

           CHARLES RIVER TO ACQUIRE PATHOLOGY ASSOCIATES INTERNATIONAL

WILMINGTON, MA.; DECEMBER 21, 2000: Charles River Laboratories International,
Inc. (NYSE:CRL), through its wholly-owned subsidiary Charles River Laboratories,
Inc., today announced the signing of a definitive agreement to acquire Pathology
Associates International Corporation from Science Applications International
Corporation (SAIC), for $37 million. PAI, headquartered in Frederick, Maryland
and a wholly-owned subsidiary of SAIC since 1995, is the world's leading
contract toxicologic pathology company, with estimated 2000 revenues of $33
million. The acquisition is expected to be neutral to Charles River's earnings
in 2001, and accretive thereafter.

PAI is a strong strategic fit with Charles River's rapidly growing biomedical
products and services segment. The two companies share a customer base, and
utilize complementary technologies to provide a broad range of pre-clinical
outsourcing services. Pathology services are a critical component of drug
discovery and development of human therapeutics, and the market for outsourced
contract pathology services is strong and growing. Large pharmaceutical
companies, established biotech companies, emerging biotech and genomics
companies, and government institutions such as the NIH, are all customers for
these technology-based research support services. Pathology analysis and
evaluation in animal research models such as mice allows a researcher to
determine the safety and efficacy of potential new drug candidates, medical
devices, and other biomedical products and services. There is also an emerging
market for pathology services to support genomics research initiatives, where
there has been a proliferation of genetically altered or "transgenic" mice being
used to identify innovative therapeutic targets and improve accuracy of lead
drug selection. This opportunity complements Charles River's rapidly growing
transgenic services business.

PAI is the leader in the market for contract pathology services in animal
research models, both in terms of market share and scientific expertise. Charles
River plans to accelerate the growth of PAI by using its extensive global
infrastructure and longstanding customer relationships to extend PAI's presence
into new markets, territories and applications. PAI has a long history of strong
and consistent profitability, with excellent opportunities for enhanced returns
through the efficient use of new technology and laboratory management systems.
Charles River's Chairman and CEO, James C. Foster, commented:

"We're very excited about the potential of PAI as a Charles River company. PAI
has world class science, a very talented, deep and committed professional team,
and great potential for expansion and growth. We intend to help the PAI team
achieve and exceed its growth objectives by providing additional strength in
both domestic and international marketing and selling, while adding our support
in a number of other areas where we can clearly add value to our shared customer
base. We see many synergies on the revenue side that will enable PAI to further
increase its share of the contract pathology market, while also offering us the
opportunity to provide to our customers a more complete solution to their
pre-clinical outsourcing needs. PAI is a particularly strong complement to our
drug discovery and development support activities, as well as our contract site
management effort, where revenue growth over the past year has been
exceptionally strong. We're particularly enthusiastic about the opportunities in
the transgenic services area, where the requirements for our services among the
research community continues to grow dynamically. "

Added Mr. Foster: "We think of the acquisition of PAI as another step in our
historically successful acquisition program, where we have carefully added new
capabilities to our core business that leverage our existing customer
relationships, reputation, technologies and global infrastructure. We see
additional opportunities through internal development, technology partnerships,
and with additional targeted acquisitions, that will allow us to continue to
build our pre-clinical products and services franchise consistent with our
commitments to our biomedical research customers as well as to our new
investors. It's a very exciting time to be supporting drug discovery and
development activities around the world."

Dr. Gary Knutsen, the founder of PAI, added: "We're absolutely delighted to be
joining the Charles River family. We think this new relationship presents us
with a wealth of opportunities to continue and indeed accelerate our growth as a
company. We think Charles River is the ideal partner for PAI, as the strategic
and organizational fit is truly exceptional. We both enjoy longstanding
reputations as the scientific, quality and market leaders in our fields. And we
were each founded and continued to be built upon a commitment to providing
innovative tools, technologies and services to the biomedical research
community. We think combining PAI's unique scientific capabilities and Charles
River's worldwide presence and infrastructure is an very exciting proposition,
and one we expect will allow us to further increase our contribution to our
customers' drug discovery and development successes."

Charles River and SAIC expect the stock purchase transaction, which is subject
to customary closing conditions, to be completed in early January. (The
Hart-Scott-Rodino 30-day waiting period is scheduled to expire tomorrow.) The
purchase price of $37 million includes $25 million in cash (a portion of which
is expected to be financed with bank credit) and a $12 million convertible note.
The five-year term note will carry a 2% interest rate, and be convertible under
certain conditions into shares of CRL at $23.38 per share. After the
transaction, PAI will make up to $3 million in retention and incentive payments
to a broad group of employees, over a three-year period. PAI has no outstanding
debt.

PAI has nearly two decades of experience and more than 400 employees, including
over 40 pathologists and doctoral level professionals. The Company is organized
into three divisions, including a core pathology business, a government contract
site management operation and an FDA regulatory consulting group.

The Company is the industry leader in providing pathology-based technologies
needed to support FDA filings (such as INDs and NDAs). Services include
neuropathology, medical device pathology, bone/joint pathology, immunopathology,
molecular pathology, ultrastructural pathology,





automated morphometrics, cell kinetics, aquatic pathology, reproductive
toxicology and teratology, and archive/repository services. The government
contract site management operation provides outsourced on-site and off-site
laboratory support services to biomedical research agencies such as the National
Institutes of Health, typically under long-term contracts. This group's
expertise is in the efficient management of both small and large colonies of
animal research models under rigorous quality assurance standards. The small but
rapidly growing regulatory consulting group supports both small and large
biopharmaceutical companies through the FDA regulated processes associated with
efficacy and safety assessment in animal models. The staff is comprised of
former FDA and pharmaceutical industry professionals experienced in both the
science and strategy of the product development process for new medicines and
devices.

Charles River Laboratories, based in Wilmington, Massachusetts, is a leading
provider of critical research tools and integrated support services that enable
innovative and efficient drug discovery and development. The Company is the
global leader in providing the animal research models required in research and
development for new drugs, devices and therapies. The Company also offers a
broad and growing portfolio of biomedical products and services that enable
customers to reduce cost, increase speed, and enhance productivity and
effectiveness in drug discovery and development. Charles River's customer base
spans over 50 countries, and includes all of the major pharmaceutical and
biotechnology companies, as well as many leading hospitals and academic
institutions. The Company operates 53 facilities in 15 countries worldwide.

                                      # # #

This document may contain "forward looking statements." Such statements involve
a number of risks and uncertainties that could cause actual results to differ
materially from those stated or implied by the forward looking statements,
including the failure to satisfy the conditions necessary for the closing of the
transaction, the failure to recognize expected synergies and revenue growth,
contaminations, industry trends, new displacement technologies, outsourcing
trends, USDA and FDA regulation, changes in law, acquisition integration risks,
special interests groups, continued availability of products and supplies,
personnel and control, and others that are described in the Risk Factors
contained in Company's Registration Statement of Form S-1, as filed on June 23,
2000, and as may be updated from time to time in the Company's periodic SEC
filings. The Company disclaims an intent or obligation to update forward looking
statements, and otherwise claims the "safe harbor" protections for forward
looking statements afforded under The Private Securities Litigation Reform Act
of 1995.

Charles River Laboratories International, Inc. is listed on the New York Stock
Exchange under the symbol CRL. The Company's listing application contains
additional information, available to the public on request, upon which the NYSE
relied in authorized the listing.