8-K

                       SECURITIES AND EXCHANGE COMMISSION

                             Washington, D.C. 20549

                                    FORM 8-K

                                 CURRENT REPORT

                       PURSUANT TO SECTION 13 OR 15(D) OF

                       THE SECURITIES EXCHANGE ACT OF 1934

      Date of Report (Date of earliest event reported): September 18, 2000

                               Chiron Corporation
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             (Exact name of registrant as specified in its charter)

  Delaware                   0-12798                   94-2754624
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(State or other            (Commission               (IRS Employer
 jurisdiction of            File Number)           Identification No.)
 incorporation)

       4560 Horton Street, Emeryville, CA              94608
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   (Address of principal executive offices)          (Zip Code)

Registrant's telephone number, including area code (510) 655-8730
                                                  -----------------

                                       N/A
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          (Former name or former address, if changed since last report)





ITEM 2.  ACQUISITION OR DISPOSITION OF ASSETS.

On September 18, 2000, Picard Acquisition Corp. ("Picard"), a Delaware
corporation and a wholly-owned subsidiary of Chiron Corporation ("Chiron" or
"Registrant"), acquired 15,962,011 shares, or approximately 96% of the
outstanding shares, of common stock, par value $0.001 per share (the "Common
Stock"), together with the associated rights to purchase Series A Junior
Preferred Stock, of PathoGenesis Corporation, a Delaware corporation
("PathoGenesis"), through a cash tender offer (the "Tender Offer") at $38.50 per
share. The Tender Offer was effected pursuant to an Agreement and Plan of Merger
(the "Merger Agreement"), dated as of August 13, 2000, among Chiron, Picard and
PathoGenesis.

Following the Tender Offer, on September 21, 2000, Picard merged with and into
PathoGenesis under Section 253 of the General Corporation Law of the State of
Delaware (the "Merger"), and PathoGenesis became a wholly-owned subsidiary of
Registrant, with each remaining outstanding share of PathoGenesis Common Stock
converted into the right to receive $38.50 per share pursuant to the Merger
Agreement.

Chiron acquired all of the outstanding voting securities of PathoGenesis for an
aggregate consideration of approximately $700 million in cash. The purchase
price of $38.50 for each share of PathoGenesis Common Stock was established by
negotiation at the time of the Merger Agreement.

The acquisition consideration was paid by Chiron from its available cash and
cash equivalents and through liquidation of certain of its long-term investments
in marketable debt securities.

Seattle-based PathoGenesis develops and commercializes drugs to treat chronic
infectious diseases - particularly serious lung infections, including those
common in cystic fibrosis, bronchiectasis and ventilator patients. PathoGenesis'
first drug, TOBI-Registered Trademark (tobramycin solution for inhalation), is
approved for the management of cystic fibrosis patients with pseudomonas
aeruginosa lung infections. PathoGenesis' Common Stock, previously traded on the
Nasdaq National Market System under the symbol "PGNS", was deregistered
following the merger.

ITEM 7.  FINANCIAL STATEMENTS AND EXHIBITS.

         (a)      Financial statements of business acquired.

                  Financial statements required by this Item are not included in
                  this initial report on Form 8-K. Such financial statements
                  will be filed by amendment not later than December 2, 2000.


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         (b)      Pro forma financial information.

                  Pro forma financial information required by this Item is not
                  included in this initial report on Form 8-K. Such pro forma
                  financial information will be filed by amendment not later
                  than December 2, 2000.

         (c)      Exhibits.

                  EXHIBIT NUMBER

                  99.1              Press Release issued by Registrant on
                                    September 19, 2000, announcing the
                                    acquisition of approximately 96% of the
                                    outstanding voting securities of
                                    PathoGenesis Corporation pursuant to
                                    completion of a cash tender offer by
                                    Registrant's wholly-owned subsidiary, Picard
                                    Acquisition Corp. on September 18, 2000,
                                    referred to in Item 2 above.(1)

                  99.2              Press release issued by Registrant on
                                    September 22, 2000, announcing the merger of
                                    PathoGenesis into Registrant's wholly-owned
                                    subsidiary, Picard Acquisition Corp.,
                                    pursuant to which PathoGenesis Corporation
                                    became a wholly-owned subsidiary of
                                    Registrant as of September 21, 2000,
                                    referred to Item 2 above.

                  -------
                  (1) Incorporated by reference to Exhibit (a) (16) of
                  Registrant's Schedule TO filed with the Securities and
                  Exchange Commission on September 19, 2000.




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                                   SIGNATURES

         Pursuant to the requirements of the Securities Exchange Act of 1934,
the registrant has duly caused this report to be signed on its behalf by the
undersigned hereunto duly authorized.

                                           CHIRON CORPORATION

Date:    October 2, 2000                   By:   /s/ WILLIAM G. GREEN
                                                 --------------------
                                                     William G. Green
                                                     Senior Vice President,
                                                     General Counsel and
                                                     Secretary




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EX-99.2

                                                               Exhibit 99.2

FOR IMMEDIATE RELEASE

CONTACTS:
Vince Barella                                       Shelley Schneiderman
Manager,                                            Associate Manager,
Corporate Communications &                          Corporate Communications &
Investor Relations                                  Investor Relations
(510) 923-2138                                      (510) 923-6905


                    CHIRON CORPORATION COMPLETES ACQUISITION
                           OF PATHOGENESIS CORPORATION

EMERYVILLE, CA, SEPTEMBER 22, 2000 - Chiron Corporation (Nasdaq: CHIR) announced
today the completion of the acquisition of PathoGenesis Corporation (Nasdaq:
PGNS) by Picard Acquisition Corp., a wholly owned subsidiary of Chiron
Corporation. The merger follows a cash tender offer for all outstanding shares
of PathoGenesis common stock at $38.50 per share, which was completed at
midnight, New York City time, on September 18, 2000. As a result of the merger,
each outstanding share of PathoGenesis not owned by Chiron, its subsidiaries or
PathoGenesis has been automatically converted into the right to receive $38.50
in cash. PathoGenesis shareholders who did not tender their shares into the
tender offer will receive a Notice of Merger and a Letter of Transmittal that
will instruct them as to how to receive the $38.50 per share or, in the
alternative, exercise appraisal rights under Delaware law.

ABOUT CHIRON CORPORATION
Chiron Corporation, headquartered in Emeryville, California, is a leading
biotechnology company that participates in three global healthcare markets:
biopharmaceuticals, vaccines, and blood testing. The company is applying a broad
and integrated scientific approach to the development of innovative products for
preventing and treating cancer, infection and cardiovascular disease. For more
information about Chiron, visit the company's web site at HTTP://WWW.CHIRON.COM.

THIS NEWS RELEASE CONTAINS FORWARD-LOOKING STATEMENTS THAT INVOLVE RISKS AND
UNCERTAINTIES. A FULL DISCUSSION OF CHIRON'S OPERATIONS AND FINANCIAL CONDITION,
INCLUDING FACTORS THAT MAY AFFECT ITS BUSINESS AND FUTURE PROSPECTS, IS
CONTAINED IN DOCUMENTS THE COMPANY FILES WITH THE SEC, SUCH AS FORM 10-Q AND
FORM 10-K. THESE DOCUMENTS IDENTIFY IMPORTANT FACTORS THAT COULD CAUSE THE
COMPANY'S ACTUAL PERFORMANCE TO DIFFER FROM CURRENT EXPECTATIONS, INCLUDING THE
OUTCOME OF CLINICAL TRIALS, REGULATORY REVIEW, MANUFACTURING CAPABILITIES AND
MARKETING.

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