For Immediate Release

                                                       Contact:
                                                       MEDIA
                                                       Kathleen O'Neil
                                                       (847) 938-3895

                                                       FINANCIAL COMMUNITY
                                                       Larry Peepo
                                                       (847) 935-6722

ABBOTT LABORATORIES COMMENCES TENDER OFFER FOR ALL OUTSTANDING SHARES
OF VYSIS, INC.


     - ABBOTT AND VYSIS MOVE FORWARD AFTER LAST WEEK'S DEFINITIVE AGREEMENT -

     ABBOTT PARK, Ill., October 31, 2001 - Abbott Laboratories (NYSE:ABT) today
announced the commencement of its cash tender offer for all outstanding shares
of common stock of Vysis, Inc. (Nasdaq:VYSI) for $30.50 per share. The tender
offer is being made pursuant to an Offer to Purchase, dated October 31, 2001,
and in connection with the Agreement and Plan of Merger, dated as of October 24,
2001, by and among Abbott, Rainbow Acquisition Corp., a wholly owned subsidiary
of Abbott, and Vysis, which Abbott and Vysis announced on October 24, 2001.

     The tender offer is scheduled to expire at 12:00 midnight, New York City
time, on Thursday, November 29, 2001, unless the tender offer is extended. The
consummation of the tender offer is subject to receipt of at least 51 percent of
the Vysis shares (on a fully-diluted basis), expiration or termination of the
waiting period under the Hart-Scott-Rodino Antitrust Improvements Act and other
conditions specified in the offer documents. Following completion of the tender
offer and, if required, receipt of stockholder approval, Abbott intends to
consummate a merger in which remaining Vysis stockholders will receive the same
cash price per share as paid in the tender offer.


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ABBOTT LABORATORIES COMMENCES TENDER OFFER FOR ALL OUTSTANDING SHARES
OF VYSIS, INC.
PAGE 2


     As part of the transaction with Vysis, Abbott has entered into an agreement
with Amoco Technology Company (ATC), an indirect subsidiary of BP America Inc.
and owner of approximately 65 percent of the outstanding shares of Vysis,
pursuant to which ATC has agreed to tender and not withdraw all of its Vysis
shares in the tender offer.

     The Depositary for the tender offer is EquiServe Trust Company, N.A., 150
Royall Street, Canton, MA 02021.

     The Dealer Manager for the tender offer is Goldman, Sachs & Co., 85 Broad
Street, New York, NY 10004.

     The Information Agent for the tender offer is Georgeson Shareholder
Communications Inc., 17 State Street, 10th Floor, New York, NY 10004.

     Abbott Laboratories is a global, diversified health care company devoted to
the discovery, development, manufacture and marketing of pharmaceuticals,
nutritionals, and medical products, including devices and diagnostics. The
company employs approximately 70,000 people and markets its products in more
than 130 countries. In 2000, the company's sales and net earnings were $13.7
billion and $2.8 billion, respectively, with diluted earnings per share of
$1.78. Abbott's news releases and other information are available on the
company's Web site at www.abbott.com.



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ABBOTT LABORATORIES COMMENCES TENDER OFFER FOR ALL OUTSTANDING SHARES
OF VYSIS, INC.
PAGE 3


     Vysis is a genomic disease management company that develops, commercializes
and markets DNA-based clinical products providing information critical to the
evaluation and management of cancer, prenatal disorders and other genetic
diseases. The company has direct sales operations in the United States and
Europe; a marketing partnership in Japan with Fujisawa Pharmaceutical Co.; and a
worldwide distribution network. Vysis' news releases and other information are
available on the company's Web site at www.vysis.com.

ADDITIONAL INFORMATION

     This announcement is neither an offer to purchase nor a solicitation of an
offer to sell securities of Vysis. The tender offer is being made pursuant to a
tender offer statement and related materials. Vysis stockholders are advised to
read the tender offer statement and related materials, which will be filed by
Abbott with the U.S. Securities and Exchange Commission (SEC). The tender offer
statement (including an offer to purchase, letter of transmittal and related
tender offer documents) and the solicitation/ recommendation statement to be
filed by Vysis with the SEC will contain important information which should be
read carefully before any decision is made with respect to the offer. These
documents will be available at no charge at the SEC's Web site at www.sec.gov.

     The tender offer statement and related materials may be obtained for free
by directing a request by mail to Georgeson Shareholder Communications Inc., 17
State Street, 10th Floor, New York, NY 10004, or by calling toll-free (800)
223-2064, and may also be obtained from Abbott by directing a request by mail to
Abbott Laboratories, 100 Abbott Park Road, Abbott Park, IL 60064-6048, Attn:
Investor Relations, Telephone: (847) 938-5632.

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