Filed by: Quest
                                                        Diagnostics Incorporated

                       This communication is filed pursuant to Rules 165 and 425
                       promulgated under the Securities Act of 1933, as amended.

                                        Subject Company:      Unilab Corporation
                                        Commission File No.:  00-11839


FORWARD-LOOKING STATEMENTS:
This communication contains certain forward-looking statements. These
forward-looking statements, which may include, but are not limited to,
statements concerning the financial condition, results of operations and
businesses of Quest Diagnostics and Unilab and the benefits expected to result
from the contemplated transaction, are based on management's current
expectations and estimates and involve risks and uncertainties that could cause
actual results or outcomes to differ materially from those contemplated by the
forward-looking statements.

Factors that could cause or contribute to such differences may include, but are
not limited to, the risk that the conditions relating to the required minimum
tender of Unilab shares or regulatory clearance might not be satisfied in a
timely manner or at all, risks relating to the integration of the technologies
and businesses of Quest Diagnostics and Unilab, unanticipated expenditures,
changing relationships with customers, suppliers and strategic partners,
conditions of the economy and other factors described in the most recent reports
on Form 10-Q, most recent reports on Form 10-K, and other periodic reports filed
by Quest Diagnostics and Unilab with the Securities and Exchange Commission.

ADDITIONAL INFORMATION:
On May 15, 2002, Quest Diagnostics filed a Registration Statement on Form S-4,
as amended, and a Schedule TO, as amended, and Unilab filed a
Solicitation/Recommendation Statement on Schedule 14D-9, as amended, with the
Securities and Exchange Commission in connection with the transaction. A
Prospectus, which is part of the Registration Statement on Form S-4, the
Solicitation/Recommendation Statement on Schedule 14D-9, and related exchange
offer materials, including a letter of election and transmittal, have been
mailed to stockholders of Unilab. In addition, Quest Diagnostics has previously
filed a Statement on Schedule 13D, as amended, relating to its agreement with
Kelso Investment Associates VI, L.P. and KEP VI, LLC. Investors and stockholders
of Unilab are urged to read all of these documents carefully. These documents
contain important information about the transaction and should be read before
any decision is made with respect to the exchange offer. Investors and
stockholders are able to obtain free copies of these documents through the
website maintained by the Securities and Exchange Commission at www.sec.gov.
Free copies of these documents may also be obtained from Quest Diagnostics by
directing a request to Quest Diagnostics Incorporated at One Malcolm Avenue,
Teterboro, New Jersey, 07608, or from Unilab by directing a request to Unilab
Corporation at 18448 Oxnard Street, Tarzana, California, 91356.





In addition to the Registration Statement on Form S-4, Schedule TO, Prospectus,
Solicitation/Recommendation Statement on Schedule 14D-9 and related exchange
offer materials, both Quest Diagnostics and Unilab file annual, quarterly and
special reports, proxy statements and other information with the Securities and
Exchange Commission. You may read and copy any reports, Statements or other
information filed by Quest Diagnostics or Unilab at the SEC public reference
room at 450 Fifth Street, N.W., Washington, D.C., 20549, or at any of the
Securities and Exchange Commission's other public reference rooms in New York,
New York and Chicago, Illinois. Please call the Securities and Exchange
Commission at 800-SEC-0330 for further information on the public reference
rooms. Quest Diagnostics' and Unilab's filings with the Securities and Exchange
Commission are also available to the public from commercial document-retrieval
services and at the website maintained by the Securities and Exchange Commission
at www.sec.gov.

                                      # # #


                  Quest Diagnostics Incorporated
                  One Malcolm Avenue
                  Teterboro, New Jersey 07608

[LOGO]                                          News From Quest Diagnostics
                                                ---------------------------

Contacts:

Quest Diagnostics
Laure Park (Investors): 201-393-5030
Gary Samuels (Media): 201-393-5700

Unilab
Brian Urban: 818-758-6611


                                                     FOR IMMEDIATE RELEASE
                                                     ---------------------


          QUEST DIAGNOSTICS EXTENDS EXCHANGE OFFER FOR SHARES OF UNILAB

              QUEST DIAGNOSTICS AND UNILAB TO DISTRIBUTE MATERIALS
                       REGARDING CHANGES TO EXCHANGE OFFER

TETERBORO, N.J. and TARZANA, Calif. -- (PRNewswire-First-Call)--January 17, 2002
- -- Quest Diagnostics Incorporated (NYSE:DGX) and Unilab Corporation (Nasdaq:
ULAB) announced today that Quest Diagnostics and Unilab plan to file with the
Securities and Exchange Commission and disseminate to Unilab's stockholders on
January 21, 2003 the supplementary disclosure materials describing the amended
terms of the exchange offer made by Quest Diagnostics for all of Unilab's
outstanding shares. Because Quest Diagnostics' exchange offer is required by
federal securities laws to remain open for at least 10 business days following
dissemination of such materials, Quest Diagnostics will extend its offer
accordingly. If, as expected, the materials are filed on January 21, 2003, then
the offer, when extended, would expire at 12:00 midnight on February 3, 2003,
unless further extended. As




previously disclosed, the termination date of the merger agreement was extended
to January 31, 2003; however, unless terminated, the merger agreement remains in
effect.

Unilab and Quest Diagnostics entered into a definitive merger agreement in
April, 2002, pursuant to which Quest Diagnostics has offered to acquire all of
the outstanding shares of Unilab. The parties amended the terms of the merger
agreement on January 4, 2003. The amendment, among other things, reduced the
per-share consideration available to Unilab stockholders in the offer. As
previously announced, the parties have been engaged in ongoing settlement
discussions with the Federal Trade Commission regarding the concerns expressed
by the FTC about the proposed transaction.

About Unilab
Unilab Corporation is the largest provider of clinical laboratory testing
services in California through its primary testing facilities in Los Angeles,
San Jose and Sacramento and over 400 patient service centers and rapid response
laboratories located throughout the state. Additional information is available
on the Company's website at: www.unilab.com.

FORWARD-LOOKING STATEMENTS:
This communication contains certain forward-looking statements under the Private
Securities Litigation Reform Act of 1995. These forward-looking statements,
which may include, but are not limited to, statements concerning the financial
condition, results of operations and business of Unilab, are based on
management's current expectations and estimates and involve risks and
uncertainties that could cause actual results or outcomes to differ materially
from those contemplated by the forward-looking statements. Certain of these
risks and uncertainties are described in Unilab's most recent reports on Form
10-Q, most recent reports on Form 10-K and other periodic reports filed by
Unilab with the Securities and Exchange Commission.

About Quest Diagnostics
Quest Diagnostics Incorporated is the nation's leading provider of diagnostic
testing, information and services, providing insights that enable physicians,
hospitals, managed care organizations and other healthcare professionals to make
decisions to improve health. The company offers the broadest access to
diagnostic laboratory services through its national network of laboratories and
patient service centers. Quest Diagnostics is the leading provider of esoteric
testing, including gene-based medical testing, and empowers healthcare
organizations and clinicians with state-of-the-art connectivity solutions that
improve practice management. Additional company information can be found on the
Internet at: www.questdiagnostics.com.

FORWARD-LOOKING STATEMENTS:
This communication contains certain forward-looking statements under the Private
Securities Litigation Reform Act of 1995. These forward-looking statements,
which may include, but are not limited to, statements concerning the financial
condition, results of operations and business of Unilab, are based on
management's current expectations and estimates and involve risks and
uncertainties that could cause actual results or outcomes to differ materially
from those contemplated by the forward-looking statements. Certain of these
risks and uncertainties are described in Unilab's most recent reports on Form
10-Q, most recent reports on Form 10-K and other periodic reports filed by
Unilab with the Securities and Exchange Commission.

ADDITIONAL INFORMATION:

On May 15, 2002, Quest Diagnostics filed a Registration Statement on Form S-4,
as amended, and a Schedule TO, as amended, and Unilab filed a Solicitation/
Recommendation Statement on Schedule 14D-9, as amended, with the Securities and
Exchange Commission in connection with the transaction. A Prospectus, which is
part of the Registration Statement on Form S-4, the Solicitation/Recommendation
Statement on Schedule 14D-9, and related exchange offer




materials, including a letter of election and transmittal, has been mailed to
stockholders of Unilab. In addition, Quest Diagnostics has previously filed a
Statement on Schedule 13D, as amended, relating to its agreement with Kelso
Investment Associates VI, L.P. and KEP VI, LLC. Investors and stockholders of
Unilab are urged to read all of these documents carefully. These documents
contain important information about the transaction and should be read before
any decision is made with respect to the exchange offer. Investors and
stockholders are able to obtain free copies of these documents through the
website maintained by the Securities and Exchange Commission at www.sec.gov.
Free copies of these documents may also be obtained from Quest Diagnostics by
directing a request to Quest Diagnostics Incorporated at One Malcolm Avenue,
Teterboro, New Jersey, 07608, or from Unilab by directing a request to Unilab
Corporation at 18448 Oxnard Street, Tarzana, California, 91356.

In addition to the Registration Statement on Form S-4, Schedule TO, Prospectus,
Solicitation/Recommendation Statement on Schedule 14D-9 and related exchange
offer materials, both Quest Diagnostics and Unilab file annual, quarterly and
special reports, proxy statements and other information with the Securities and
Exchange Commission. You may read and copy any reports, Statements or other
information filed by Quest Diagnostics or Unilab at the SEC public reference
room at 450 Fifth Street, N.W., Washington, D.C., 20549, or at any of the
Securities and Exchange Commission's other public reference rooms in New York,
New York and Chicago, Illinois. Please call the Securities and Exchange
Commission at 800-SEC-0330 for further information on the public reference
rooms. Quest Diagnostics' and Unilab's filings with the Securities and Exchange
Commission are also available to the public from commercial document-retrieval
services and at the website maintained by the Securities and Exchange Commission
at www.sec.gov.

                                      # # #