<PAGE>

                                 UNITED STATES
                       SECURITIES AND EXCHANGE COMMISSION
                             Washington, D.C. 20549

                                   FORM 10-Q

(Mark One)
    [X]  QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES
         EXCHANGE ACT OF 1934
    For the quarterly period ended March 30, 1997
                                      OR
    [ ]  TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES
         EXCHANGE ACT OF 1934
    For the transition period from ____________ to ____________

    Commission File Number: 0-12798

                                  CHIRON CORPORATION
--------------------------------------------------------------------------------
                (Exact name of registrant as specified in its charter)

    Delaware                                     94-2754624
--------------------------------------------------------------------------------
(State or other jurisdiction of                  (I.R.S. Employer
incorporation or organization)                   Identification No.)

4560 Horton Street, Emeryville, California       94608
--------------------------------------------------------------------------------
(Address of principal executive offices)         (Zip code)

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

                                    Not Applicable
--------------------------------------------------------------------------------
                       (Former name, former address and former
                      fiscal year, if changed since last report)

Indicate by check mark whether the registrant (1) has filed all reports required
to be filed by Section 13 or 15(d) of the Securities Exchange Act of 1934 during
the preceding 12 months (or for such shorter period that the registrant was
required to file such reports), and (2) has been subject to such filing
requirements for the past 90 days.
                               Yes  /X/   No
                                   -----     -----

Indicate the number of shares outstanding of each of the issuer's classes of
common stock, as of the latest practicable date.

          Class                              Outstanding at April 30, 1997
          -----                              -----------------------------
Common Stock, $0.01 par value                         172,897,928

<PAGE>

                                  CHIRON CORPORATION
                                  TABLE OF CONTENTS
--------------------------------------------------------------------------------

                                                                        PAGE NO.
                                                                        --------
PART I.  FINANCIAL INFORMATION

    ITEM 1.  FINANCIAL STATEMENTS

         Consolidated Balance Sheets as of
         March 31, 1997 and December 31, 1996. . . . . . . . . . . . . . .    3

         Consolidated Statements of Operations for the
         three months ended March 31, 1997 and 1996. . . . . . . . . . . .    4

         Consolidated Statements of Cash Flows for the
         three months ended March 31, 1997 and 1996  . . . . . . . . . . .    5

         Notes to Consolidated Financial Statements. . . . . . . . . . . .    6

    ITEM 2.  MANAGEMENT'S DISCUSSION AND ANALYSIS OF
             FINANCIAL CONDITION AND RESULTS OF OPERATIONS . . . . . . . .    8


PART II. OTHER INFORMATION

    ITEM 1.  LEGAL PROCEEDINGS . . . . . . . . . . . . . . . . . . . . . .   16

    ITEM 6.  EXHIBITS AND REPORTS ON FORM 8-K. . . . . . . . . . . . . . .   16


SIGNATURES     . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .   31


                                          2
<PAGE>

                                  CHIRON CORPORATION
                             CONSOLIDATED BALANCE SHEETS
                                    (IN THOUSANDS)
--------------------------------------------------------------------------------
<TABLE>
<CAPTION>
                                                                     March 31,    December 31,
                                                                       1997            1996
                                                                    -----------   -------------
                                                                    (Unaudited)

<S>                                                                 <C>            <C>
                        ASSETS
Current assets:
  Cash and cash equivalents                                         $    99,335    $    68,114
  Short-term investments in marketable debt securities                   27,944         38,694
                                                                    -----------    -----------
        Total cash and short-term investments                           127,279        106,808
  Accounts receivable                                                   327,306        351,971
  Inventories                                                           181,286        180,534
  Other current assets                                                   63,448         57,455
                                                                    -----------    -----------
        Total current assets                                            699,319        696,768
Noncurrent investments in marketable debt securities                     14,001         22,027
Property, plant, equipment and leasehold improvements, at cost:
    Land and buildings                                                  231,760        231,998
    Laboratory, production and office equipment                         385,934        381,421
    Leasehold improvements                                              116,092        114,282
    Construction in progress                                             75,895         69,120
                                                                    -----------    -----------
                                                                        809,681        796,821
    Less accumulated depreciation and amortization                     (227,795)      (213,217)
                                                                    -----------    -----------
     Net property, plant, equipment and leasehold improvements          581,886        583,604
Purchased technology, net                                                63,165         65,592
Other intangible assets, net                                             73,182         76,669
Investments in equity securities and affiliated companies               183,592        184,328
Other assets                                                             63,270         59,682
                                                                    -----------    -----------
                                                                    $ 1,678,415    $ 1,688,670
                                                                    -----------    -----------
                                                                    -----------    -----------
        LIABILITIES AND STOCKHOLDERS' EQUITY
Current liabilities:
  Accounts payable                                                  $    81,768    $    96,157
  Accrued compensation and related expenses                              44,506         56,695
  Short-term borrowings                                                 143,090        137,467
  Current portion of unearned revenue                                    33,542         19,638
  Taxes payable                                                          36,530         33,407
  Other current liabilities                                             128,137        129,805
                                                                    -----------    -----------
    Total current liabilities                                           467,573        473,169
Long-term debt                                                          391,688        419,589
Other noncurrent liabilities                                             29,420         31,057
                                                                    -----------    -----------
    Total liabilities                                                   888,681        923,815
                                                                    -----------    -----------
Commitments and contingencies
Stockholders' equity:
  Common stock                                                            1,724          1,707
  Additional paid-in capital                                          1,789,914      1,774,406
  Accumulated deficit                                                (1,017,218)    (1,032,554)
  Cumulative foreign currency translation adjustment                    (18,288)        (6,318)
  Unrealized gain from investments                                       34,562         28,574
  Notes receivable from stock sales                                        (960)          (960)
                                                                    -----------    -----------
    Total stockholders' equity                                          789,734        764,855
                                                                    -----------    -----------
                                                                    $ 1,678,415    $ 1,688,670
                                                                    -----------    -----------
                                                                    -----------    -----------
</TABLE>
              THE ACCOMPANYING NOTES TO CONSOLIDATED FINANCIAL STATEMENTS
                       ARE AN INTEGRAL PART OF THIS STATEMENT.

                                          3

<PAGE>

                                  CHIRON CORPORATION
                        CONSOLIDATED STATEMENTS OF OPERATIONS
                                     (UNAUDITED)
                        (IN THOUSANDS, EXCEPT PER SHARE DATA)
--------------------------------------------------------------------------------
<TABLE>
<CAPTION>
                                                                     Three Months Ended
                                                                   -----------------------
                                                                   March 31,      March 31,
                                                                     1997           1996
<S>                                                                <C>             <C>
                                                                  --------       --------
Revenues:
  Product sales, net                                              $251,129       $239,822
  Equity in earnings of unconsolidated joint businesses             25,214         23,608
  Collaborative agreement revenues                                  26,848         31,414
  Other revenues                                                    27,092         10,907
                                                                  --------       --------
    Total revenues                                                 330,283        305,751
                                                                  --------       --------

Expenses:
  Cost of sales                                                    108,332        101,979
  Research and development                                          91,705         84,048
  Selling, general and administrative                               96,606         92,330
  Other operating expenses                                           3,279          3,107
                                                                  --------       --------
    Total expenses                                                 299,922        281,464
                                                                  --------       --------

Income from operations                                              30,361         24,287

Interest expense                                                    (8,486)        (7,013)
Other income, net                                                      353          1,195
                                                                  --------       --------

Income before income taxes                                          22,228         18,469

Provision for income taxes                                           6,892          5,725
                                                                  --------       --------

Net income                                                        $ 15,336       $ 12,744
                                                                  --------       --------
                                                                  --------       --------

Net income per share                                              $   0.09       $   0.07
                                                                  --------       --------
                                                                  --------       --------

Weighted average number of shares
   used in computing per share amounts                             176,610        178,485
                                                                  --------       --------
                                                                  --------       --------

</TABLE>
 
             THE ACCOMPANYING NOTES TO CONSOLIDATED FINANCIAL STATEMENTS
                       ARE AN INTEGRAL PART OF THIS STATEMENT.


                                          4

<PAGE>

                                  CHIRON CORPORATION
                        CONSOLIDATED STATEMENTS OF CASH FLOWS
                                     (UNAUDITED)
                                    (IN THOUSANDS)
--------------------------------------------------------------------------------
<TABLE>
<CAPTION>
                                                                          Three Months Ended
                                                                       -----------------------
                                                                       March 31,      March 31,
                                                                         1997           1996
                                                                       --------       --------
<S>                                                                  <C>             <C>
Cash flows from operating activities:
  Net income                                                           $ 15,336       $ 12,744
  Adjustments to reconcile net income
    to net cash provided by operating activities:
      Depreciation and amortization                                      22,149         27,666
      Other, net                                                          5,582          5,548
      Changes, excluding effects of acquisitions, to:
        Accounts receivable                                              11,789        (12,571)
        Inventories                                                     (18,521)       (10,814)
        Other current assets                                             (2,727)        (6,556)
        Accounts payable and accrued expenses                           (22,106)       (21,035)
        Taxes payable                                                     3,210          3,893
        Other current liabilities                                           420          5,436
        Current portion of unearned revenue                              14,392           (746)
        Other noncurrent liabilities                                       (206)         1,784
                                                                       --------       --------
           Net cash provided by operating activities                     29,318          5,349
Cash flows from investing activities:
  Purchases of investments in marketable debt securities                 (9,418)       (44,517)
  Proceeds from sale and maturity of investments in
    marketable debt securities                                           28,178         59,317
  Capital expenditures                                                  (15,499)       (31,841)
  (Increase) decrease in other assets                                     4,603         (1,156)
                                                                       --------       --------
           Net cash provided by (used in) investing activities            7,864        (18,197)
Cash flows from financing activities:
  Net borrowings under line of credit arrangements                           --          5,600
  Proceeds from issuance of short-term debt                               8,271             --
  Repayment of notes payable and capital leases                         (29,698)        (3,849)
  Proceeds from issuance of common stock                                 15,466         21,588
                                                                       --------       --------
           Net cash provided by (used in) financing activities           (5,961)        23,339
                                                                       --------       --------
           Net increase in cash and cash equivalents                     31,221         10,491
Cash and cash equivalents at beginning of the period                     68,114         74,318
                                                                       --------       --------
Cash and cash equivalents at end of the period                         $ 99,335       $ 84,809
                                                                       --------       --------
                                                                       --------       --------

</TABLE>
 
             THE ACCOMPANYING NOTES TO CONSOLIDATED FINANCIAL STATEMENTS
                       ARE AN INTEGRAL PART OF THIS STATEMENT.


                                          5

<PAGE>

                                  CHIRON CORPORATION
                      NOTES TO CONSOLIDATED FINANCIAL STATEMENTS

                                    MARCH 31, 1997
--------------------------------------------------------------------------------

1.  SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES

    BASIS OF PRESENTATION

         The information at March 31, 1997, and for the three months ended
    March 31, 1997 and 1996, is unaudited, but includes all normal recurring
    adjustments which the management of Chiron Corporation (the "Company" or
    "Chiron") believes to be necessary for fair presentation of the periods
    presented.  The consolidated balance sheet amounts at December 31, 1996
    have been derived from audited financial statements.  Interim results are
    not necessarily indicative of results for a full year.  This information
    should be read in conjunction with Chiron's audited consolidated financial
    statements for the year ended December 29, 1996, which are included in the
    Annual Report on Form 10-K filed by the Company with the Securities and
    Exchange Commission.

         Certain previously reported amounts have been reclassified to conform
    with the current period presentation.

    FISCAL YEAR

         The fiscal year of the Company is a 52 or 53-week year ending on the
    Sunday nearest the last day in December of each year.  As a result, the
    first quarters of 1997 and 1996 represent the thirteen-week periods ended
    March 30, 1997 and March 31, 1996, respectively.  For presentation
    purposes, dates used in the consolidated financial statements and notes
    refer to the calendar month end.

    INVENTORIES

         Pharmaceutical inventories are stated at the lower of cost or market
    using the average cost method or, in the case of vaccine products, using
    the last-in, first-out ("LIFO") method. Diagnostic and ophthalmic products
    are valued at cost, using the first-in, first-out ("FIFO") method which is
    less than market value.  Inventories consist of the following:

                                  MARCH 31,      DECEMBER 31,
                                    1997             1996
                                  --------       ------------
                                        (IN THOUSANDS)
         Finished goods           $ 91,558        $ 94,875
         Work in process            49,306          45,874
         Raw materials              40,422          39,785
                                  --------        --------
                                  $181,286        $180,534
                                  --------        --------
                                  --------        --------

    INCOME TAXES

         Income tax expense for the quarters ended March 31, 1997 and March 31,
    1996 is based on an estimated annual effective income tax rate.


                                          6

<PAGE>

    PER SHARE DATA

         Per share data is based on the weighted average number of common and
    dilutive common equivalent shares outstanding.  Common equivalent shares
    result from the assumed exercise of outstanding stock options and warrants
    that have a dilutive effect when applying the treasury stock method.
    Shares assumed to be issued upon conversion of the Company's convertible
    debentures are not included for any of the periods presented since their
    inclusion would be anti-dilutive.  Fully diluted per share data has not
    been presented, as the amounts would not differ materially from primary per
    share data.

    NEW ACCOUNTING STANDARD

         In February 1997, the Financial Accounting Standards Board issued
    Statement of Financial Accounting Standards No. 128, "Earnings per Share"
    ("SFAS 128"), which will be effective for financial statements for periods
    ending after December 15, 1997, including interim periods, and establishes
    standards for computing and presenting earnings per share.  Earlier
    application is not permitted.  In its consolidated financial statements for
    the year ending December 31, 1997, the Company will make the required
    disclosures of basic and diluted earnings per share and provide a
    reconciliation of the numerator and denominator of its basic and diluted
    earnings per share computations.  All prior period earnings per share data
    will be restated by the Company upon adoption of SFAS 128. The application 
    of SFAS 128 for the three months ended March 31, 1997 and 1996 would not 
    have a material effect on the Company's per share data presented for those 
    periods.

2.  CONTINGENCIES

         The Company is party to various claims, investigations and legal
    proceedings arising out of the normal course of its business.  These
    claims, investigations and legal proceedings relate to intellectual
    property rights, contractual rights and obligations, employment matters,
    shareholder derivative claims, claims of product liability, and other
    issues.  While there can be no assurance that an adverse determination of
    any such matters could not have a material adverse impact in any future
    period, management does not believe, based upon information known to it,
    that the final resolution of these matters will have a material adverse
    effect upon the Company's consolidated financial position and annual
    results of operations and cash flows.

3.  LONG-TERM DEBT

         In January 1997, the Company entered into an agreement to purchase for
    $29.8 million a manufacturing facility and related buildings that had been
    previously leased under a long-term capital lease obligation.  As a result,
    the Company eliminated the related obligation which totaled $29.4 million.


                                          7

<PAGE>

                       MANAGEMENT'S DISCUSSION AND ANALYSIS OF
                    FINANCIAL CONDITION AND RESULTS OF OPERATIONS
--------------------------------------------------------------------------------

OVERVIEW

    THE DISCUSSION BELOW CONTAINS FORWARD-LOOKING STATEMENTS THAT INVOLVE RISKS
AND UNCERTAINTIES RELATING TO THE FUTURE FINANCIAL PERFORMANCE OF CHIRON
CORPORATION (THE "COMPANY" OR "CHIRON"), AND ACTUAL EVENTS OR RESULTS MAY DIFFER
MATERIALLY.  IN EVALUATING SUCH STATEMENTS, STOCKHOLDERS AND INVESTORS SHOULD
SPECIFICALLY CONSIDER THE VARIOUS FACTORS IDENTIFIED UNDER THE CAPTION "FACTORS
THAT MAY AFFECT FUTURE OPERATING RESULTS" WHICH COULD CAUSE ACTUAL RESULTS TO
DIFFER MATERIALLY FROM THOSE INDICATED BY SUCH FORWARD-LOOKING STATEMENTS. THE
COMPANY UNDERTAKES NO OBLIGATION TO PUBLICLY RELEASE THE RESULTS OF ANY
REVISIONS TO THESE FORWARD-LOOKING STATEMENTS WHICH MAY BE MADE TO REFLECT
EVENTS OR CIRCUMSTANCES AFTER THE DATE HEREOF OR TO REFLECT THE OCCURRENCES OF
UNANTICIPATED EVENTS.

    THE DISCUSSION BELOW SHOULD BE READ IN CONJUNCTION WITH PART I, ITEM 1,
"FINANCIAL STATEMENTS," OF THIS QUARTERLY REPORT ON FORM 10-Q AND PART II, ITEMS
7 AND 8, "MANAGEMENT'S DISCUSSION AND ANALYSIS OF FINANCIAL CONDITION AND
RESULTS OF OPERATIONS" AND "FINANCIAL STATEMENTS AND SUPPLEMENTARY DATA,"
RESPECTIVELY, OF THE COMPANY'S ANNUAL REPORT ON FORM 10-K FOR THE YEAR ENDED
DECEMBER 29, 1996.

    Chiron is a diversified, science-driven, market-directed healthcare company
that applies biotechnology and other techniques of modern biology and chemistry
to develop, produce and sell products intended to improve the quality of life by
diagnosing, preventing and treating human disease.  Chiron participates in four
human healthcare markets: (i) diagnostics, including blood screening tests,
automated immunodiagnostic systems, critical blood analyte systems and new
quantitative probe tests; (ii) therapeutics, with an emphasis on oncology,
serious infectious diseases and critical care diseases; (iii) adult and
pediatric vaccines; and (iv) ophthalmic surgical products, including instruments
and devices used for the surgical correction of vision and intraocular implants
to deliver drugs to the eye.  Chiron also develops or acquires new technologies,
employing these technologies to discover new products for the Company or for its
partners.

RESULTS OF OPERATIONS

REVENUES

    The Company's revenues are derived from a variety of sources, including
product sales, joint business arrangements, collaborative agreements and product
royalty agreements.  Product sales, Chiron's largest revenue category, consists
of the following product lines for each of the three-month periods ended March
31:

                               1997      1996
                             --------  --------
                               (IN THOUSANDS)
    Diagnostic products      $149,022  $135,911
    Ophthalmic products        50,338    44,941
    Vaccine products           18,519    20,834
    Betaseron-TM- sales        13,788    20,892
    Oncology products          18,676    16,155
    Other products                786     1,089
                             --------  --------
                             $251,129  $239,822
                             --------  --------
                             --------  --------


                                          8

<PAGE>

    As Chiron continues to increase the sales of certain products that are
seasonal and expand its presence in international markets, particularly European
markets, seasonal fluctuations in product sales and the related gross profit
amounts have become more significant. For this reason, revenues and gross profit
amounts from certain product lines are generally higher in the first half and
fourth quarter of the year.  As a result, Chiron's results in any one quarter
are not necessarily indicative of results to be expected for a full year.

    Diagnostic product sales include direct sales and sales-type leases of 
fully-automated, random-access immunodiagnostic testing systems (ACS:180-TM-, 
automated chemiluminescence system) and reagents for these systems, as well 
as sales of critical blood analyte systems (CBA-TM-), clinical chemistry 
products, manual immunodiagnostic systems and branched DNA ("bDNA") probe 
kits for human immunodeficiency virus ("HIV").  Sales of diagnostic products 
increased during the first quarter of 1997 as compared to the first quarter 
of 1996, primarily due to increased sales of bDNA probe kits, critical blood 
analyte systems in foreign markets and immunodiagnostic products.  The growth 
in immunodiagnostic product sales resulted from increased sales volume of 
reagents resulting from the compounding effect of increased ACS:180-TM- 
system placements.  The overall increase in diagnostic product sales was 
partially offset by reduced sales of manual immunodiagnostic systems and 
unfavorable foreign currency exchange rates, primarily in Japan, Germany and 
France, which when compared to rates in effect for the first quarter of 1996, 
reduced the increase by $6.7 million.

    Sales of ophthalmic products increased for the first quarter of 1997 as 
compared to the first quarter of 1996 primarily due to increased sales of 
excimer lasers, refractive surgical instruments and the Vitrasert-TM- Implant 
product (Cytovene-TM-; Roche Laboratories).  The Vitrasert-TM- Implant was 
approved by the U.S. Food and Drug Administration ("FDA") in March 1996. 
Vitrasert-TM- Implant revenues for the first quarter of 1997 were $3.2 
million as compared to $1.0 million in the first quarter of 1996.  The 
overall increase in ophthalmic product sales was partially offset by lower 
sales of certain cataract surgery products and unfavorable changes in foreign 
currency exchange rates between years.

    Vaccine product sales consist primarily of sales of pediatric and flu
vaccines primarily in Italy and to certain international health services by
Chiron S.p.A.  Sales of Chiron S.p.A.'s flu vaccine are seasonal, with strong
sales generally occurring during the flu season in the fourth quarter of the
year.  The decrease in Chiron S.p.A.'s vaccine product sales in the first
quarter of 1997 as compared to the first quarter of 1996 is primarily due to
lower sales of acellular pertussis vaccines and unfavorable changes in foreign
currency exchange rates between years.  Vaccine product sales in the first
quarter of 1996 reflect a higher sales volume of acellular pertussis vaccines
sales resulting from their introduction in late 1995.

    Under the terms of a development and supply agreement with Schering AG,
Germany ("Schering"), and its U.S. affiliate, Berlex Laboratories, Inc.
("Berlex"), Chiron manufactures Betaseron-TM- (interferon beta-1b) for Berlex.
Under the terms of the agreement, Chiron earns an initial partial payment for
Betaseron-TM- upon shipment to Berlex and a subsequent secondary payment for
Betaseron-TM- upon Berlex's net sales of the product to patients. The decrease
in Betaseron-TM- product sales during the first three months of 1997 over the
comparable period in 1996 is due to a decrease in commercial vials shipped to
Berlex and a decrease in secondary revenues.

    Future levels of Chiron's Betaseron-TM- shipments will depend upon the rate
at which new patients are enrolled from existing and future markets, the extent
to which patients, once enrolled, remain compliant with the prescribed treatment
regimen and continue to regularly receive Betaseron-TM-, and the impact of
competing products, including other beta interferon products that were approved
for sale in the U.S. during 1996.  In addition, based upon the level of
inventories carried by Berlex, the timing of future shipments to Berlex and the
related revenue may vary.


                                          9

<PAGE>

    Sales of oncology products, principally Proleukin-TM- (aldesleukin,
interleukin-2), increased during the first quarter of 1997 over the comparable
period in 1996, primarily due to a 17 percent increase in Proleukin-TM-
quantities sold.  Proleukin-TM- revenues increased in both the domestic and
European markets, but particularly in the U.S.

    The Company markets many of its commercial products internationally.  As a
result, product revenues in almost all product lines are affected by fluctuating
foreign currency exchange rates.  Foreign product sales were approximately
$141.4 million and $133.6 million for the quarters ended March 31, 1997 and
1996,  respectively.  International sales of diagnostic and ophthalmic products
accounted for the majority of the increase in foreign product sales between
periods.  For the quarter ended March 31, 1997, approximately 56 percent of
Chiron's product sales were denominated in foreign currencies. Product sales
would have been $10.0 million higher during the first quarter of 1997 if
currency exchange rates remained the same as in 1996.  Changing currency
exchange rates have had, and will continue to have, an impact on Chiron's
results.  The Company's other revenues, discussed below, are largely denominated
in U.S. dollars but are impacted by the Company's joint partners' and
collaborators' non-U.S. operations.

    Equity in earnings of unconsolidated joint businesses consists 
substantially of Chiron's one-half interest in the pretax operating earnings 
of its joint diagnostics business with Ortho Diagnostic Systems, Inc. 
("Ortho"), a Johnson & Johnson ("J&J") company. The joint business sells 
tests used to screen blood for the potential presence of hepatitis C virus 
("HCV") and HIV. The joint business also holds the immunodiagnostic rights to 
Chiron's hepatitis and retrovirus technology and receives royalties from 
several companies, including Abbott Laboratories and Pasteur Sanofi 
Diagnostics, for their sales of certain tests. Chiron and Ortho are each 
developing new instrument systems expected to contain broad menus of 
immunodiagnostic tests to serve the clinical diagnostic segment of the 
market. A recently concluded arbitration confirmed that Chiron is required to 
obtain Ortho's agreement in order to market hepatitis and retrovirus tests 
that are being developed for use on Chiron Diagnostics' new systems. Although 
it cannot assure the ultimate resolution of on-going negotiations with Ortho, 
Chiron believes that both companies ultimately will market these tests for 
use on their respective new instrument systems.

    During the first quarter of 1997, Chiron's share of the pretax operating 
earnings of the joint business, which is recorded by Chiron on a one-month 
lag based upon estimates supplied by Ortho and are subject to a final annual 
accounting during the first quarter of the subsequent year, increased to 
$25.1 million from $22.5 million for the comparable quarter of 1996. The 
increase was primarily due to increased sales of HCV and HIV tests and 
increased royalties, partially offset by a reduction in the revenue derived 
from the final annual accounting. In the first quarter of 1997, Chiron 
recognized joint business revenue of $0.8 million from the final accounting 
for 1996, as compared to $3.8 million recognized in the first quarter of 1996 
from the final accounting for 1995.

    Also included in equity in earnings of unconsolidated joint businesses is
Chiron's 49 percent share of the after-tax operating results of a joint venture
with Behringwerke AG of Germany, which was acquired in July 1996.  Results from
the joint venture are recorded by Chiron on a one-month lag.  Chiron's share of
earnings was $0.1 million, which includes amortization of intangibles and
Chiron's share of a $2.0 million up-front license fee that was expensed.  The
low earnings are also due in part to the seasonal nature of the business.

    Equity in earnings of unconsolidated joint businesses for the first quarter
of 1996 also includes $1.2 million related to Chiron's 50 percent interest in a
generic cancer chemotherapeutics business with Ben Venue Laboratories, Inc.
("Ben Venue").  Chiron sold its interest in this business to Ben Venue in May
1996.

    Collaborative agreement revenues consist of fees received for research
services as they are performed, fees received for completed research or
technology, fees received upon attainment of benchmarks specified in the related
research agreements, and proceeds from sales of biological materials to research
partners for clinical and preclinical testing.  Collaborative agreement revenues
for the first quarter of 1997 decreased to $26.8 million from $31.4 million in
the first quarter of 1996.  In the first


                                          10

<PAGE>

quarter of 1996, Chiron recognized revenues of $7.5 million pursuant to the
terms of a technology transfer and development agreement with Japan Tobacco Inc.
("JT"), whereby the pharmaceutical division of JT acquired a non-exclusive,
perpetual license to apply certain of Chiron's combinatorial chemistry
technologies in JT's research and product development programs.  Under this
agreement, Chiron will earn another $7.5 million during the third quarter of
1997.

    Also included in collaborative agreement revenues are amounts from Novartis
AG ("Novartis"), the successor to Ciba-Geigy Ltd. ("Ciba"). Pursuant to the
terms of a research funding agreement, Novartis agreed in 1995 to provide $250
million (which may be increased to $300 million subject to certain conditions)
over five years in support of research at Chiron.  As a result, Chiron
recognized revenues of $15.8 million and $16.0 million under this agreement
during the first quarters of 1997 and 1996, respectively.  Through March 31,
1997, Chiron has cumulatively recognized revenues of $114.8 million pursuant to
this agreement.  Chiron anticipates continued utilization of the research
funding provided by Novartis.

    Additionally, during the first quarter of 1997, Chiron recognized $3.8
million of collaborative agreement revenues pursuant to the November 1996
agreement with Novartis, which was primarily executed in conjunction with a
consent and agreement that resolved the Federal Trade Commission's review of the
merger between Ciba and Sandoz Ltd. which created Novartis.  In partial
consideration for Chiron agreeing to grant royalty-bearing licenses for certain
patent rights on the herpes simplex virus thymidine kinase gene in the field of
gene therapy, Novartis agreed to pay Chiron up to $60.0 million over the next
five years, $15.0 million of which relates to 1997 and was received in January
1997.

    Other revenues consist principally of product royalties and sales fees 
earned by the Company for sales and marketing services for 
Aredia-TM-(pamidronate disodium for injection) that were rendered on behalf 
of Novartis. Other revenues increased in the first quarter of 1997 as 
compared to the first quarter of 1996, primarily due to increased sales fees 
resulting from increased sales of Aredia-TM- in the U.S.  These sales fees 
increased to $12.8 million during the first quarter of 1997 from $3.6 million 
during the comparable period in 1996.  Additionally, other revenues increased 
due to increased royalties related to hepatitis B and insulin and royalty 
revenues resulting from Schering's European sales of Betaferon-TM- which 
started during the second quarter of 1996.  Chiron's contract with Novartis 
for exclusive promotion of Aredia-TM- in the U.S. expired in March 1997.  
Under a new agreement, the details of which will be finalized in 1997, Chiron 
and Novartis will co-promote Aredia-TM- for two additional years after a 
six-month transitional period.  The sales fee income resulting from the new 
agreement is not expected to be as high as current levels of income under the 
prior agreement.

COSTS AND EXPENSES

    Cost of sales increased consistently with the increase in product sales
between years.  The gross profit margin was 57 percent for the first quarter of
1997 and 1996.  Improvements in gross profit margins, resulting from increased
sales of immunodiagnostic reagents and bDNA kits, were offset by certain charges
related to vaccine products and an adverse sales mix occasioned from sales of
lower margin critical blood analyte systems to foreign distributors.  Gross
profit margin percentages may fluctuate significantly in future periods as the
Company's product mix continues to evolve and as the costs of new facilities are
included in cost of goods sold.

    Research and development expenses increased from $84.0 million in the first
quarter of 1996 to $91.7 million in 1997.  Chiron's research and development
expenses fluctuate from period to period depending upon the extent of clinical
trial-related activities, including the manufacturing of material; the number of
products under development and their progress; and the acquisition of companies
and new technology and licensing rights.  The overall increase in research and
development expenses was due to


                                          11

<PAGE>

the continued development of bDNA probes; the ACS:Centaur-TM-, a more powerful
immunoassay system designed to markedly increase laboratory productivity and
provide a platform for unique analytes that will help clinicians manage disease
progression; Regranex-TM-, a wound healing agent; as well as additional amounts
related to research involving hepatitis and other vaccines.  Additionally,
during the first quarter of 1997, Chiron made a $1.5 million payment to Novartis
resulting from the February 1997 filing of a new drug application with the FDA
for Myotrophin-TM- (rhIGF-1 or mecasermin [recombinant DNA origin]) Injection.
On May 8, 1997, an FDA advisory committee found that there was not substantial
evidence that Myotrophin-TM- Injection is effective in the treatment of
amyotrophic lateral sclerosis (ALS or Lou Gehrig's disease).  Chiron and its
collaborative partner, Cephalon, Inc., will be reviewing with the FDA the
advisory committee's recommendation.

    During 1995 and 1996, Chiron, together with J&J, co-funded the development
and introduction of a home HIV testing service business, Direct Access
Diagnostics.  Chiron recently elected not to exercise its option, which expires
in May 1997, to participate in this venture with J&J.

    Selling, general and administrative ("SG&A") expenses as a percentage of
product sales was 38 percent for the first quarter of 1997 and 1996. Selling and
marketing expenses continue to represent the largest portion of total SG&A
expenses, as Chiron devoted significant resources to support sales volumes in
its existing product lines as well as new products, such as Chiron's new bDNA
probes and Rapidpoint-TM- 400, a critical care system designed specifically for
critical care settings in hospitals.  The Rapidpoint-TM- 400 was introduced in
Europe during the first quarter of 1997, with release worldwide planned for
later this year.

    Interest expense increased between the first quarters of 1997 and 1996 as a
result of increased debt borrowings.

    Other income, net, consists primarily of investment income on the Company's
cash and investment balances and other non-operating gains and losses. Other
income, net, decreased between the first quarters of 1997 and 1996, primarily as
a result of reduced investment income arising from lower balances in the
Company's investment portfolio and exchange rate losses.

    The provision for income taxes in 1997 and 1996 is based on an estimated
annual effective income tax rate.  The 1997 rate is less than the U.S. Federal
statutory rate, primarily due to the utilization of foreign and U.S. net 
operating losses.

LIQUIDITY AND CAPITAL RESOURCES

    Chiron's capital requirements are generally funded from debt borrowings 
and sales of equity.  In addition to these sources of capital, future capital 
requirements may be financed through a combination of debt, utilization of 
research funding and debt guarantees provided by Novartis, possible 
off-balance-sheet financing, cash generated from operations and the use of 
existing cash and investment balances.  Chiron's cash and investments, which 
totaled $141.3 million at March 31, 1997, are invested in a diversified 
portfolio of investment grade financial instruments, including money market 
instruments, corporate notes and bonds, government or government agency 
securities, and other debt securities.  By policy, the amount of credit 
exposure to any one institution is limited.  These investments are generally 
not collateralized and primarily mature within three years.  Investments with 
maturities in excess of one year are presented on the balance sheet as 
noncurrent investments.

    Chiron attempts to reduce its exposure to fluctuations in foreign currency
exchange rates by entering into forward currency contracts ("forwards") and
options.  The Company is


                                          12

<PAGE>

primarily exposed to fluctuations in currencies in western European countries
and Japan.  Forwards are used to hedge balance sheet exposure resulting from
completed transactions denominated in a foreign currency, and options are used
to hedge certain anticipated transactions.  Forward contracts are settled
quarterly, and option contracts expire quarterly through December 1997.  As of
March 31, 1997, the Company held forward and option contracts totaling $76.6
million and $88.0 million, respectively.

    In future periods, Chiron expects to incur substantial capital spending.
Chiron's liquidity may be further impacted in future periods by its decision to
fund its share of expenses in certain of its joint ventures and collaboration
arrangements.  Over the next several years, Chiron anticipates funding
collaborations with a number of its research partners, and may make additional
equity investments in  collaborative partners.

    During the three months ended March 31, 1997, cash and investments in 
marketable debt securities increased by $12.4 million. The increase was 
primarily due to $29.3 million of cash generated by operations, $15.5 million 
of proceeds related to the issuance of common stock under the Company's stock 
option and employee stock purchase plans and $8.3 million of incremental 
short-term debt borrowings.  These increases were offset by $15.5 million of 
capital expenditures and the repayment of a long-term capital lease 
obligation totaling $29.4 million. In January 1997, Chiron purchased a 
manufacturing facility and related buildings in Emeryville, California that 
had been previously leased under the long-term capital lease obligation.

    During the three months ended March 31, 1996, cash and investments in
marketable debt securities decreased by $4.9 million.  The decrease was
primarily due to $31.8 million of capital expenditures, offset by $5.3 million
of cash generated by operations, $21.6 million of proceeds related to the
issuance of common stock under the Company's stock option and employee stock
purchase plans and $1.8 million of net debt borrowings.

    Chiron believes that its cash and investments, funds provided by operations
and capital market transactions will be sufficient to meet its cash requirements
during the upcoming twelve months and through the foreseeable future.

    NEW ACCOUNTING STANDARD

    In February 1997, the Financial Accounting Standards Board issued 
Statement of Financial Accounting Standards No. 128, "Earnings per Share" 
("SFAS 128"), which will be effective for financial statements for periods 
ending after December 15, 1997, including interim periods, and establishes 
standards for computing and presenting earnings per share.  Earlier 
application is not permitted.  In its consolidated financial statements for 
the year ending December 31, 1997, Chiron will make the required disclosures 
of basic and diluted earnings per share and provide a reconciliation of the 
numerator and denominator of its basic and diluted earnings per share 
computations.  All prior period earnings per share data will be restated by 
the Company upon adoption of SFAS 128. The application of SFAS 128 for the 
three months ended March 31, 1997 and 1996 would not have a material effect 
on the Company's per share data presented for those periods.

FACTORS THAT MAY AFFECT FUTURE OPERATING RESULTS

    Chiron wishes to caution stockholders and investors that the following
important factors, among others, in some cases have affected, and in the future
could affect, Chiron's actual results and could cause Chiron's actual
consolidated results for the second quarter of 1997, and beyond, to differ
materially from those expressed in any forward-looking statements made by, or on
behalf of, Chiron.  The statements under this caption are intended to serve as
cautionary statements within the meaning of the Private Securities Litigation
Reform Act of 1995.  The following information is not intended to limit


                                          13

<PAGE>

in any way the characterization of other statements or information under other
captions as cautionary statements for such purpose:

    -    Delays, difficulties or failure in obtaining regulatory approval
         (including approval of its systems, procedures and facilities for
         production) for the Company's products.  These may include, for
         example, approval of the Company's Italian manufacturing facilities
         and processes as satisfying regulatory requirements for production of
         the Company's diphtheria, tetanus and genetically engineered acellular
         pertussis and adjuvanted flu vaccines, approval for Myotrophin-TM- for
         which additional clinical trials may be required by the FDA, and
         approval for Quantiplex-TM- for HIV and follow-on bDNA probe products,
         for which the FDA may require substantial additional process and
         systems validation.

    -    Inability to maintain or initiate third party arrangements which
         generate revenues, in the form of license fees, research and
         development support, royalties, sales fees and other payments, in
         return for rights in technology or products under development or
         promotional or other services provided by the Company.

    -    The issuance and use of patents and proprietary technology by Chiron
         and its competitors, including the possible negative effect on the
         Company's ability to develop, manufacture and sell its products if it
         is unable to obtain licenses to patents which may be required for such
         products.

    -    Failure of corporate partners to commercialize successfully the
         Company's products or to retain and expand the markets served by the
         commercial collaborations; conflicts of interest, priorities and
         commercial strategies which may arise between the Company and such
         corporate partners, including conflicts as to the strategy for
         realizing value arising from evolving opportunities.

    -    Delay, difficulty or inability on acceptable terms to resolve        
         conflicts with partners, including resolution with Ortho of Chiron's 
         ability to market hepatitis and retrovirus immunodiagnostic tests    
         that are under development for use on its ACS: Centaur-TM-           
         instrument system.

    -    Delays or difficulties in developing and acquiring technology and
         technical and managerial personnel to manufacture and/or deliver the
         Company's products in commercial quantities at reasonable costs and in
         compliance with applicable quality assurance and environmental
         regulations and governmental permitting requirements.

    -    Possible changes in laws, regulations and guidelines of regulatory
         agencies, which may affect the development and sales of certain of the
         Company's products including, for example, off-label sales of
         pharmaceuticals and research use only sales of diagnostic tests and
         systems.

    -    The ability and willingness of customers to substitute competitive
         products for the Company's products once other products for similar
         indications are approved for marketing.

    -    Difficulties in obtaining key raw materials and supplies of acceptable
         quality used in the manufacture of the Company's products.

    -    Increased costs of development, regulatory approval, manufacture,
         sales, and marketing associated with the introduction of novel
         products and fluctuation of such costs between periods.

    -    Difficulties in launching or marketing the Company's products, many of
         which are novel products based on biotechnology, and unpredictability
         of customer acceptance of such products.

    -    Decline in the Betaseron-TM- customer base in the U.S.; the extent to
         which patients, once enrolled, remain compliant with the prescribed
         treatment regimen and continue to regularly receive Betaseron-TM-; the
         impact of competing products, including other beta interferon
         products; pricing, promotional and marketing decisions by the
         Company's partner, Schering.


                                          14

<PAGE>

    -    Changes in the product mix of the Chiron-Ortho joint business, whereby
         the proportion of higher margin HCV tests sold relative to other lower
         margin products decreases; continued margin erosion of HCV tests.

    -    Continued increases in research and development spending in order to
         develop new products and increase market share.

    -    Continued or increased pressure to reduce selling prices of the
         Company's products.

    -    Underutilization of the Company's existing or new manufacturing
         facilities or of any facility expansions, resulting in production
         inefficiencies and higher costs; start-up costs and inefficiencies and
         delays and increased depreciation costs in connection with the start
         of production in new plants and expansions.

    -    The cost of acquiring in-process technology, either by license,
         collaboration or purchase of another entity.

    -    Changes in the Company's plans involving the utilization of its
         long-lived assets, which include manufacturing facilities such as the
         Company's idle fill and finishing facility in Puerto Rico, in response
         to changes in the projected level of demand for the Company's
         products, product pricing, success of clinical trials, timing of
         regulatory approval, introduction of competing products and other
         market conditions.

    -    Increased financing costs resulting from the expanded use of debt for
         operating and acquisition-related activities.

    -    Amount and rate of growth in Chiron's selling, general and
         administrative expenses; and the impact of unusual or infrequent
         charges resulting from Chiron's ongoing evaluation of its business
         strategies and organizational structures, including the continued
         costs of integration of newly acquired businesses.

    -    The acquisition of fixed assets and other assets, including
         inventories and receivables; and the making or incurring of any
         expenditures and expenses, including, among others, depreciation and
         research and development expenses; any revaluation of assets,
         including, among others, the Company's investments in the equity
         securities of other companies with whom it collaborates, or related
         expenses, and the amount of, and any changes to, tax rates.

    -    The ability or inability of Chiron to obtain, or hedge against,
         foreign currency, foreign exchange rates and fluctuations in those
         rates.

    -    The costs and other effects of legal and administrative cases and
         proceedings (whether civil, such as product-related or environmental,
         or criminal); settlements and investigations; developments or
         assertions by or against Chiron relating to intellectual property
         rights and licenses.

    -    Seasonal fluctuations in product sales and resulting gross margin
         amounts.


                                          15

<PAGE>

ITEM 1.  LEGAL PROCEEDINGS.

              The Company is party to certain lawsuits, which are described in
         Part I, Item 3, "Legal Proceedings," on page 10 of the Company's
         Annual Report on Form 10-K for the year ended December 29, 1996. No
         material developments in the area of legal proceedings have occurred
         since such Form 10-K was filed.


ITEM 6.  EXHIBITS AND REPORTS ON FORM 8-K.

    (a)  EXHIBITS.

         Exhibit
         Number                        Exhibit
         -------                       -------
         2.01      Agreement and Plan of Merger, made as of February 6, 1987,
                   incorporated by reference to Exhibit 2.01 of the
                   Registrant's Form 10-Q report for the period ended September
                   30, 1994.

         3.01      Restated Certificate of Incorporation of the Registrant, as
                   filed with the Office of the Secretary of State of Delaware
                   on August 17, 1987, incorporated by reference to Exhibit
                   3.01 of the Registrant's Form 10-K report for fiscal year
                   1996.

         3.02      Certificate of Amendment of Restated Certificate
                   of Incorporation of the Registrant, as filed with
                   the Office of the Secretary of State of Delaware
                   on December 12, 1991, incorporated by reference to
                   Exhibit 3.02 of the Registrant's Form 10-K report
                   for fiscal year 1996.

         3.03      Bylaws of the Registrant, as amended, incorporated by
                   reference to Exhibit 3.03 of the Registrant's Form 10-K
                   report for fiscal year 1994.

         3.04      Certificate of Amendment of Restated Certificate
                   of Incorporation of the Registrant, as filed with
                   the Office of the Secretary of State of Delaware
                   on May 22, 1996, incorporated by reference to
                   Exhibit 3.04 of the Registrant's Form 10-Q report
                   for the period ended June 30, 1996.

         4.01      Indenture, dated as of May 21, 1987, between Cetus
                   Corporation and Bankers Trust Company, Trustee,
                   incorporated by reference to Exhibit 4.01 of the
                   Registrant's Form 10-Q report for the period ended
                   September 30, 1994.

         4.02      First Supplemental Indenture, dated as of December
                   12, 1991, by and among Registrant, Cetus
                   Corporation, and Bankers Trust Company,
                   incorporated by reference to Exhibit 4.02 of the
                   Registrant's Form 10-K report for fiscal year
                   1992.


                                          16

<PAGE>

         4.03      Second Supplemental Indenture, dated as of March
                   25, 1996, by and among the Registrant, Cetus
                   Oncology Corporation (formerly Cetus Corporation),
                   and Bankers Trust Company, incorporated by
                   reference to Exhibit 4.03 of the Registrant's Form
                   10-Q report for the period ended June 30, 1996.

         4.04      Indenture, dated as of November 15, 1993, between
                   Registrant and The First National Bank of Boston,
                   as Trustee, incorporated by reference to Exhibit
                   4.03 of the Registrant's Form 10-K report for
                   fiscal year 1993.

         4.05      $1,000,000 County of Lorain, Ohio Variable Rate
                   Industrial Revenue Bonds dated as of July 1, 1984,
                   due July 1, 2014, incorporated by reference to
                   Exhibit 4.06 of the Registrant's Form 10-Q report
                   for the period ended April 2, 1995. The Registrant
                   agrees to furnish to the Commission upon request a
                   copy of such agreement which it has elected not to
                   file under the provisions of Regulation
                   601(b)(4)(iii).

         4.06      $1,000,000 Walpole Industrial Development
                   Authority 6.75% Industrial Revenue Bonds dated as
                   of July 1, 1979, due July 1, 2004, incorporated by
                   reference to Exhibit 4.07 of the Registrant's Form
                   10-Q report for the period ended April 2, 1995.
                   The Registrant agrees to furnish to the Commission
                   upon request a copy of such agreement which it has
                   elected not to file under the provisions of
                   Regulation 601(b)(4)(iii).

         10.01     Lease between Registrant and BGR Associates, a
                   California limited partnership, dated May 26,
                   1989, incorporated by reference to Exhibit 10.01
                   of the Registrant's Form 10-Q report for the
                   period ended September 30, 1994.

         10.02     First Amendment to Lease between Registrant and
                   BGR Associates, a California limited partnership,
                   incorporated by reference to Exhibit 10.02 of the
                   Registrant's Form 10-K report for fiscal year
                   1995.

         10.03     Second Amendment to Lease, dated as of May 9,
                   1996, between BGR Associates, a California limited
                   partnership, as lessor and Registrant, as lessee
                   [BGR I Property Building NQ Lease], incorporated
                   by reference to Exhibit 10.03 of the Registrant's
                   Form 10-K report for fiscal year 1996.

         10.04     Third Amendment to Triple Net Lease, dated as of
                   January 31, 1997, between BGR Associates, a
                   California limited partnership, as lessor and
                   Registrant, as lessee [BGR I Property Building NQ
                   Lease], incorporated by reference to Exhibit 10.04
                   of the Registrant's Form 10-K report for fiscal
                   year 1996.


                                          17

<PAGE>

         10.05     Lease between Registrant and BGR Associates II, a
                   California limited partnership, dated May 26,
                   1989, incorporated by reference to Exhibit 10.02
                   of the Registrant's Form 10-Q report for the
                   period ended September 30, 1994.

         10.06     First Amendment to Lease between Registrant and
                   BGR Associates II, a California limited
                   partnership, dated as of March 15, 1995,
                   incorporated by reference to Exhibit 10.04 of the
                   Registrant's Form 10-K report for fiscal year
                   1995.

         10.07     Second Amendment to Lease, dated as of May 9,
                   1996, between BGR Associates II, a California
                   limited partnership, as lessor and Registrant, as
                   lessee, incorporated by reference to Exhibit 10.07
                   of the Registrant's Form 10-K report for fiscal
                   year 1996.

         10.08     Third Amendment to Triple Net Lease, dated as of
                   January 31, 1997, between BGR Associates II, a
                   California limited partnership, as lessor and
                   Registrant, as lessee [BGR II Property Lease],
                   incorporated by reference to Exhibit 10.08 of the
                   Registrant's Form 10-K report for fiscal year
                   1996.

         10.09     Lease made and entered into December 17, 1984
                   between BGR Associates, a California limited
                   partnership, and Cetus Corporation and Amendment
                   to Lease dated December 17, 1984 entered into
                   effective February 1, 1986, incorporated by
                   reference to Exhibit 10.69 of the Registrant's
                   Form 10-Q report for the period ended April 2,
                   1995.

         10.10     Second Amendment to Lease dated as of March 15,
                   1995, between BGR Associates, a California limited
                   partnership, and Registrant, incorporated by
                   reference to Exhibit 10.73 of the Registrant's
                   Form 10-K report for fiscal year 1995.

         10.11     Third Amendment to Lease, dated as of May 9, 1996,
                   between BGR Associates, a California limited
                   partnership, as lessor and Registrant, as lessee
                   [BGR I Property Building R Lease], incorporated by
                   reference to Exhibit 10.11 of the Registrant's
                   Form 10-K report for fiscal year 1996.

         10.12     Fourth Amendment to Triple Net Lease, dated as of January
                   31, 1997, between BGR Associates, a California limited
                   partnership, as lessor and Registrant, as lessee [BGR I
                   Property Building R Lease], incorporated by reference to
                   Exhibit 10.12 of the Registrant's Form 10-K report for
                   fiscal year 1996.

         10.13     Triple Net Lease dated as of January 20, 1989,
                   between Cetus Corporation and BGR Associates III,
                   a California limited partnership, and Marin County
                   Exchange


                                          18

<PAGE>

                   Corporation, incorporated by reference to Exhibit 10.34 of
                   the Registrant's Form 10-Q report for the period ended
                   September 30, 1994.

         10.14     First Amendment to Triple Net Lease, dated as of
                   September 10, 1996, between BGR Associates III, a
                   California limited partnership, as lessor and
                   Registrant, as lessee, incorporated by reference
                   to Exhibit 10.14 of the Registrant's Form 10-K
                   report for fiscal year 1996.

         10.15     Second Amendment to Triple Net Lease, dated as of
                   January 31, 1997, between BGR Associates III, a
                   California limited partnership, as lessor and
                   Registrant, as lessee [BGR III Lease],
                   incorporated by reference to Exhibit 10.15 of the
                   Registrant's Form 10-K report for fiscal year
                   1996.

         10.16     Assignment of Lessor Claims, dated as of January
                   31, 1997, between BGR Associates III, a California
                   limited partnership, as assignor and Registrant,
                   as assignee, incorporated by reference to Exhibit
                   10.16 of the Registrant's Form 10-K report for
                   fiscal year 1996.

         10.17     Agreement and Plan of Merger dated as of April 23,
                   1995 between Viagene, Inc., a Delaware
                   corporation, and Chiron Corporation, incorporated
                   by reference to Exhibit 10.67 of the Registrant's
                   current report on Form 8-K dated April 24, 1995.

         10.18     Stockholders' Agreement dated as of April 23, 1995
                   among certain stockholders of Viagene, Inc., a
                   Delaware corporation, and Chiron Corporation,
                   incorporated by reference to Exhibit 10.68 of the
                   Registrant's current report on Form 8-K dated
                   April 24, 1995.

         10.19     Stock and Asset Purchase Agreement dated as of
                   March 6, 1995, by and among Johnson & Johnson, a
                   New Jersey corporation, Site Microsurgical
                   Systems, Inc., a Pennsylvania corporation, and
                   Chiron Corporation and Amendment No. 1 to Stock
                   and Asset Purchase Agreement, entered into March
                   31, 1995 by and among Johnson & Johnson, Site
                   Microsurgical Systems, Inc. and Chiron
                   Corporation, incorporated by reference to Exhibit
                   10.05 of the Registrant's Form 10-Q report for the
                   period ended April 2, 1995.

         10.20     Revolving Credit Facility dated as of March 24,
                   1995, between Chiron Corporation and Swiss Bank
                   Corporation, San Francisco Branch ("Swiss Bank
                   Credit Agreement"), incorporated by reference to
                   Exhibit 10.06 of the Registrant's Form 10-Q report
                   for the period ended April 2, 1995.


                                          19

<PAGE>

         10.21     First Amendment to Swiss Bank Credit Agreement
                   dated as of March 20, 1996.

         10.22     Agreement between the Registrant and Ortho
                   Diagnostic Systems, Inc., a New Jersey
                   corporation, dated August 17, 1989, and Amendment
                   to Collaboration Agreement between Ortho
                   Diagnostic Systems, Inc. and Registrant, dated
                   December 22, 1989 (with certain confidential
                   information deleted), incorporated by reference to
                   Exhibit 10.14 of the Registrant's Form 10-Q report
                   for the period ended September 30, 1994.

         10.23     License and Supply Agreement between Ortho
                   Diagnostic Systems, Inc., a New Jersey
                   corporation, the Registrant and Abbott
                   Laboratories, an Illinois corporation, dated
                   August 17, 1989 (with certain confidential
                   information deleted), incorporated by reference to
                   Exhibit 10.15 of the Registrant's Form 10-Q report
                   for the quarter ended June 30, 1994.

         10.24     Chiron 1991 Stock Option Plan, as amended,
                   incorporated by reference to Annex 2 of the
                   Registrant's Proxy Statement dated April 11,
                   1996.*

         10.25     Forms of Option Agreements, Chiron 1991 Stock
                   Option Plan, as amended, incorporated by reference
                   to Exhibit 10.17 of the Registrant's Form 10-K
                   report for fiscal year 1993.*

         10.26     Form of Automatic Share Right Agreement, Chiron
                   1991 Stock Option Plan, as amended, incorporated
                   by reference to Exhibit 10.19 of Registrant's Form
                   10-Q report for the period ended September 29,
                   1996.*

         10.27     Forms of Option Agreements, Cetus Corporation
                   Amended and Restated Common Stock Option Plan.*

         10.28     Forms of Supplemental Letter concerning the
                   assumption of Cetus Corporation options by the
                   Registrant, incorporated by reference to Exhibit
                   10.27 of Registrant's Form 10-K report for fiscal
                   year 1996.*

         10.29     Indemnification Agreement between the Registrant
                   and Dr. William J. Rutter, dated as of February
                   12, 1987 (which form of agreement is used for each
                   member of Registrant's Board of Directors),
                   incorporated by reference to Exhibit 10.21 of the
                   Registrant's Form 10-Q report for the period ended
                   September 30, 1994.


                                          20

<PAGE>

         10.30     Stock Purchase Agreement by and between the
                   Registrant and Johnson & Johnson Development
                   Corporation, a corporation organized and existing
                   under the laws of the State of New Jersey, dated
                   as of October 3, 1986, incorporated by reference
                   to Exhibit 10.22 of the Registrant's Form 10-Q
                   report for the period ended September 30, 1994.

         10.31     Revolving Credit Agreement, dated as of July 12,
                   1996, between Registrant and Bank of America
                   National Trust and Savings Association,
                   incorporated by reference to Exhibit 10.24 of the
                   Registrant's Form 10-Q report for the period ended
                   June 30, 1996.

         10.32     Form of Debenture Purchase Agreement between the
                   Registrant and Ciba-Geigy, Limited, a Swiss
                   corporation, dated June 22, 1990, incorporated by
                   reference to Exhibit 10.25 of the Registrant's
                   Form 10-K report for fiscal year 1994.

         10.33     Chiron Corporation 1.90% Convertible Subordinated
                   Note due 2000, Series B, incorporated by reference
                   to Exhibit 10.25 of the Registrant's Form 10-K
                   report for fiscal year 1993.

         10.34     Investment Agreement dated as of November 20, 1994
                   among Ciba-Geigy Limited, Ciba-Geigy Corporation,
                   Ciba Biotech Partnership, Inc. and Chiron
                   Corporation, incorporated by reference to Exhibit
                   10.54 of the Registrant's current report on Form
                   8-K dated November 20, 1994.

         10.35     Governance Agreement dated as of November 20, 1994
                   among Ciba-Geigy Limited, Ciba-Geigy Corporation
                   and Chiron Corporation, incorporated by reference
                   to Exhibit 10.55 of the Registrant's current
                   report on Form 8-K dated November 20, 1994.

         10.36     Subscription Agreement dated as of November 20,
                   1994 among Ciba-Geigy Limited, Ciba-Geigy
                   Corporation, Ciba Biotech Partnership, Inc. and
                   Chiron Corporation, incorporated by reference to
                   Exhibit 10.56 of the Registrant's current report
                   on Form 8-K dated November 20, 1994.

         10.37     Cooperation and Collaboration Agreement dated as
                   of November 20, 1994, between Ciba-Geigy Limited
                   and Chiron Corporation, incorporated by reference
                   to Exhibit 10.57 of the Registrant's current
                   report on Form 8-K dated November 20, 1994.

         10.38     Registration Rights Agreement dated as of November
                   20, 1994 between Ciba Biotech Partnership, Inc.
                   and Chiron Corporation, incorporated by reference
                   to Exhibit 10.58 of


                                          21

<PAGE>

                   the Registrant's current report on Form 8-K dated November
                   20, 1994.

         10.39     Market Price Option Agreement dated as of November
                   20, 1994 among Ciba-Geigy Limited, Ciba-Geigy
                   Corporation, Ciba Biotech Partnership, Inc. and
                   Chiron Corporation, incorporated by reference to
                   Exhibit 10.59 of the Registrant's current report
                   on Form 8-K dated November 20, 1994.

         10.40     Amendment dated as of January 3, 1995 among
                   Ciba-Geigy Limited, Ciba-Geigy Corporation, Ciba
                   Biotech Partnership, Inc. and Chiron Corporation,
                   incorporated by reference to Exhibit 10.60 of the
                   Registrant's current report on Form 8-K dated
                   January 4, 1995.

         10.41     Supplemental Agreement dated as of January 3, 1995
                   among Ciba-Geigy Limited, Ciba-Geigy Corporation,
                   Ciba Biotech Partnership, Inc. and Chiron
                   Corporation, incorporated by reference to Exhibit
                   10.61 of the Registrant's current report on Form
                   8-K dated January 4, 1995.

         10.42     Amendment with Respect to Employee Stock Option
                   Arrangements dated as of January 3, 1995 among
                   Ciba-Geigy Limited, Ciba-Geigy Corporation, Ciba
                   Biotech Partnership, Inc. and Chiron Corporation,
                   incorporated by reference to Exhibit 10.62 of the
                   Registrant's current report on Form 8-K dated
                   January 4, 1995.*

         10.43     Agreement, dated November 27, 1996, between
                   Ciba-Geigy Limited and the Registrant,
                   incorporated by reference to Exhibit 10.92 of the
                   Registrant's Form 8-K report filed with the
                   Commission on December 17, 1996.

         10.44     Amendment dated March 26, 1997, to Agreement dated
                   November 27, 1996, between Novartis Pharma AG and
                   the Registrant.

         10.45     Letter Agreement, dated May 6, 1996, as to consent
                   to assignment of contracts to Novartis Limited,
                   among the Registrant, Ciba-Geigy Limited,
                   Ciba-Geigy Corporation and Ciba Biotech
                   Partnership, Inc., incorporated by reference to
                   Exhibit 10.43 of the Registrant's Form 10-K report
                   for fiscal year 1996.

         10.46     Letter Agreement, dated December 19, 1996,
                   regarding compensation paid by the Registrant for
                   director services performed by employees of
                   Ciba-Geigy Limited, incorporated by reference to
                   Exhibit 10.44 of the Registrant's Form 10-K report
                   for fiscal year 1996.*


                                          22

<PAGE>

         10.47     Supplemental Benefits Agreement, dated July 21,
                   1989, between the Registrant and Dr. William
                   J. Rutter, incorporated by reference to Exhibit
                   10.27 of the Registrant's Form 10-Q report for the
                   period ended September 30, 1994.*

         10.48     Lease commencing March 1, 1987, between EuroCetus
                   B.V. and the Municipal Land Company of the City of
                   Amsterdam (Translation), incorporated by reference
                   to Exhibit 10.40 of the Registrant's Form 10-K
                   report for fiscal year 1995.

         10.49     Form of Option Agreement (with Purchase Agreements
                   attached thereto) between Cetus Corporation and
                   each former limited partner of Cetus Healthcare
                   Limited Partnership, a California limited
                   partnership, incorporated by reference to Exhibit
                   10.31 of the Registrant's Form 10-Q report for the
                   period ended September 30, 1994.

         10.50     Form of Option Agreement (with forms of Purchase
                   Agreements attached thereto), dated December 30,
                   1986, between Cetus Corporation and each former
                   limited partner of Cetus Healthcare Limited
                   Partnership II, a California limited partnership,
                   incorporated by reference to Exhibit 10.32 of the
                   Registrant's Form 10-Q report for the period ended
                   September 30, 1994.

         10.51     License Agreement between the Registrant and the
                   Board of Trustees of the Leland Stanford Junior
                   University, dated December 15, 1981, incorporated
                   by reference to Exhibit 10.07 of the Registrant's
                   Form 10-Q report for the period ended September
                   30, 1994.

         10.52     Stock Purchase and Warrant Agreement dated May 9,
                   1989, between Cetus Corporation and Hoffmann-La
                   Roche Inc., incorporated by reference to Exhibit
                   10.36 of the Registrant's Form 10-Q report for the
                   period ended September 30, 1994.

         10.53     Letter Agreement, dated as of December 12, 1991,
                   relating to Stock Purchase and Warrant Agreement
                   between Registrant and Hoffmann-La Roche Inc.,
                   incorporated by reference to Exhibit 10.51 of
                   Registrant's Form 10-K report for fiscal year
                   1996.

         10.54     Letter Agreement dated September 26, 1990 between
                   the Registrant and William G. Green, incorporated
                   by reference to Exhibit 10.41 of the Registrant's
                   Form 10-K report for fiscal year 1992.*

         10.55     Letter Agreement dated December 18, 1991 between
                   Registrant and Jack Schuler, incorporated by
                   reference to Exhibit 10.42 of the Registrant's
                   Form 10-K report for fiscal year 1992.*


                                          23

<PAGE>

         10.56     Lease between Sclavo S.p.A. and Biocine Sclavo
                   S.p.A., dated January 7, 1992, incorporated by
                   reference to Exhibit 10.49 of the Registrant's
                   Form 10-Q report for the period ended April 2,
                   1995.

         10.57     Agreement made as of November 11, 1993 by and
                   between Kodak Clinical Diagnostics Limited, a
                   company registered in England, and Ciba Corning
                   Diagnostics Corp., a Delaware corporation, and
                   Letter dated October 7, 1994 from Kodak Clinical
                   Diagnostics Limited to Ciba Corning Diagnostics
                   Corp., incorporated by reference to Exhibit 10.50
                   of Amendment No. 1 to the Registrant's Form 10-Q
                   report for the period ended April 2, 1995.
                   [Certain information has been omitted from the
                   Agreement pursuant to a request by Registrant for
                   confidential treatment pursuant to Rule 24b-2.]

         10.58     Regulatory Filing, Development and Supply
                   Agreement between the Registrant, Cetus Oncology
                   Corporation, a wholly- owned subsidiary of the
                   Registrant, and Schering AG, a German company,
                   dated as of May 10, 1993 (with certain
                   confidential information deleted), incorporated by
                   reference to Exhibit 10.50 of the Registrant's
                   current report on Form 8-K dated February 9, 1994.

         10.59     Letter Agreement dated December 30, 1993 by and
                   between Registrant and Schering AG, a German
                   company (with certain confidential information
                   deleted), incorporated by reference to Exhibit
                   10.51 of the Registrant's Form 10-K report for
                   fiscal year 1993.

         10.60     Description of Executive Officer Variable
                   Compensation Program, incorporated by reference to
                   Exhibit 10.58 of the Registrant's Form 10-K report
                   for fiscal year 1996.*

         10.61     Chiron Corporation 1995 Executive Officer Variable
                   Cash Compensation Plan, incorporated by reference
                   to Annex 2 of the Registrant's Proxy Statement
                   dated April 18, 1995.*

         10.62     Amended and Restated License Agreement effective
                   April 1, 1996, between Ciba Corning Diagnostics
                   Corp., a Delaware corporation, and Bioanalysis
                   Limited, a corporation organized under the laws of
                   the United Kingdom of Great Britain and Northern
                   Ireland, incorporated by reference to Exhibit
                   10.56 of the Registrant's Form 10-Q report for the
                   period ended September 29, 1996. [Certain
                   confidential information has been omitted from the
                   Agreement and filed separately with the Securities
                   and Exchange Commission pursuant to a request by
                   Registrant for confidential treatment pursuant to
                   Rule 24b-2.]


                                          24

<PAGE>

         10.63     Guaranty, dated as of September 29, 1994, made by
                   Registrant, in favor of Bankers Trust Company, as
                   trustee, incorporated by reference to Exhibit
                   10.52 of the Registrant's Form 10-Q report for the
                   period ended September 30, 1994.

         10.64     Guaranty, dated as of September 29, 1994, made by
                   Cetus Corporation, in favor of The First National
                   Bank of Boston, as trustee, incorporated by
                   reference to Exhibit 10.53 of the Registrant's
                   Form 10-Q report for the period ended
                   September 30, 1994.

         10.65     Letter Agreements dated September 11, 1992, July
                   15, 1994 and September 14, 1994 between the
                   Registrant and Lewis T. Williams, incorporated by
                   reference to Exhibit 10.54 of the Registrant's
                   Form 10-Q report for the period ended
                   September 30, 1994.*

         10.66     Letters dated May 6, 1996 and May 25, 1996 to
                   Magnus Lundberg, incorporated by reference to
                   Exhibit 10.61 of the Registrant's Form 10-Q report
                   for the period ended September 29, 1996.*

         10.67     Letter dated January 8, 1997 to Magnus Lundberg,
                   incorporated by reference to Exhibit 10.65 of the
                   Registrant's Form 10-K report for fiscal year
                   1996.*

         10.68     Research Agreement, dated as of July 15, 1985,
                   between Ciba-Geigy Limited, a Swiss corporation,
                   and Ciba Corning Diagnostics Corp., a Delaware
                   corporation, incorporated by reference to Exhibit
                   10.64 of the Registrant's Form 10-Q report for the
                   period ended April 2, 1995.

         10.69     Licensing Agreement, effective December 18, 1986,
                   by and between Miles Laboratories, Inc., a
                   Delaware corporation, and Ciba Corning Diagnostics
                   Corp., a Delaware corporation, and Letter dated
                   December 18, 1992 from Ciba Corning Diagnostics
                   Corp. to Miles Laboratories, Inc., incorporated by
                   reference to Exhibit 10.65 of Amendment No. 1 to
                   the Registrant's Form 10-Q report for the period
                   ended April 2, 1995.  [Certain information has
                   been omitted from the Agreement pursuant to a
                   request by Registrant for confidential treatment
                   pursuant to Rule 24b-2.]

         10.70     Magnetocluster Binding Assay Technology Agreement,
                   dated as of January 21, 1983, by and between
                   Bioclinical Group, Inc., a Delaware corporation,
                   and Corning Glass Works, a New York corporation,
                   incorporated by reference to Exhibit 10.66 of
                   Amendment No. 1 to the Registrant's Form 10-Q
                   report for the period ended April 2, 1995.
                   [Certain information has been omitted from the
                   Agreement pursuant to


                                          25

<PAGE>

                   a request by Registrant for confidential treatment pursuant
                   to Rule 24b-2.]

         10.71     Turn-back License Agreement, dated as of May 30,
                   1986, by and between Ciba Corning Diagnostics
                   Corp., a Delaware corporation, and Advanced
                   Magnetics, Inc., a Delaware corporation,
                   incorporated by reference to Exhibit 10.67 of the
                   Registrant's Form 10-Q report for the period ended
                   April 2, 1995. [Certain information has been
                   omitted from the Agreement pursuant to a request
                   by Registrant for confidential treatment pursuant
                   to Rule 24b-2.]

         10.72     Settlement Agreement, dated August 30, 1989,
                   between Ciba Corning Diagnostics Corp. and
                   Advanced Magnetics, Inc., incorporated by
                   reference to Exhibit 10.68 of the Registrant's
                   Form 10-Q report for the period ended April 2,
                   1995.  [Certain information has been omitted from
                   the Agreement pursuant to a request by Registrant
                   for confidential treatment pursuant to Rule
                   24b-2.]

         10.73     Agreement, effective as of December 21, 1988, by
                   and between Hoffmann-La Roche Inc., a New Jersey
                   corporation, and Cetus Corporation, incorporated
                   by reference to Exhibit 10.70 of the Registrant's
                   Form 10-Q report for the period ended April 2,
                   1995. [Certain information has been omitted from
                   the Agreement pursuant to a request by Registrant
                   for confidential treatment pursuant to Rule
                   24b-2.]

         10.74     Agreement, effective as of December 21, 1988, by
                   and among F. Hoffmann-La Roche Ltd., a Swiss
                   corporation, Cetus Corporation, and EuroCetus
                   International, B.V., a Netherlands Antilles
                   corporation, incorporated by reference to Exhibit
                   10.71 of the Registrant's Form 10-Q report for the
                   period ended April 2, 1995. [Certain information
                   has been omitted from the Agreement pursuant to a
                   request by Registrant for confidential treatment
                   pursuant to Rule 24b-2.]

         10.75     Agreement, by and between Cetus Oncology
                   Corporation, EuroCetus International, N.V., and F.
                   Hoffmann-La Roche Ltd., incorporated by reference
                   to Exhibit 10.72 of the Registrant's Form 10-Q
                   report for the period ended April 2, 1995.
                   [Certain information has been omitted from the
                   Agreement pursuant to a request by Registrant for
                   confidential treatment pursuant to Rule 24b-2.]

         10.76     Agreement commencing January 1, 1991, between
                   EuroCetus B.V. and the Municipal Development
                   Corporation (Translation), incorporated by
                   reference to Exhibit 10.41 of the Registrant's
                   Form 10-K report for fiscal year 1994.


                                          26

<PAGE>

         10.77     Settlement Agreement on Purified IL-2, made as of
                   April 14, 1995, by and between Cetus Oncology
                   Corporation, dba Chiron Therapeutics, a Delaware
                   corporation, and Takeda Chemical Industries, Ltd.,
                   a Japanese corporation, incorporated by reference
                   to Exhibit 10.74 of the Registrant's Form 10-Q
                   report for the period ended July 2, 1995.
                   [Certain information has been omitted from the
                   Agreement pursuant to a request by Registrant for
                   confidential treatment pursuant to Rule 24b-2.]

         10.78     License Agreement made and entered into December
                   1, 1987, by and between Sloan Kettering Institute
                   for Cancer Research, a not-for-profit New York
                   corporation, and Cetus Corporation, incorporated
                   by reference to Exhibit 10.75 of the Registrant's
                   Form 10-Q report for the period ended July 2,
                   1995.  [Certain information has been omitted from
                   the Agreement pursuant to a request by Registrant
                   for confidential treatment pursuant to Rule
                   24b-2.]

         10.79     Chiron Funding L.L.C. Limited Liability Company
                   Agreement, entered into and effective as of
                   December 28, 1995, among the Registrant, Chiron
                   Biocine Company and Biocine S.p.A. and Ciba-Geigy
                   Corporation, incorporated by reference to Exhibit
                   10.80 of the Registrant's Form 10-K report for
                   fiscal year 1995. [Certain information has been
                   omitted from the Agreement and filed separately
                   with the Securities and Exchange Commission
                   pursuant to a request by Registrant for
                   confidential treatment pursuant to Rule 24b-2.
                   The omitted confidential information has been
                   identified by the following statement:
                   "Confidential Treatment Requested".]

         10.80     Agreement between Ciba-Geigy Limited and the
                   Registrant made November 15, 1995, incorporated by
                   reference to Exhibit 10.81 of the Registrant's
                   Form 10-K report for fiscal year 1995.  [Certain
                   information has been omitted from the Agreement
                   and filed separately with the Securities and
                   Exchange Commission pursuant to a request by
                   Registrant for confidential treatment pursuant to
                   Rule 24b-2.  The omitted confidential information
                   has been identified by the following statement:
                   "Confidential Treatment Requested".]

         10.81     Reimbursement Agreement dated as of March 24,
                   1995, between Ciba-Geigy Limited, a Swiss
                   corporation, and the Registrant, incorporated by
                   reference to Exhibit 10.76 of the Registrant's
                   Form 10-Q report for the period ended July 2,
                   1995.

         10.82     Promissory Note, as amended and restated, dated
                   January 1, 1995 by Ciba Corning Diagnostics Corp.,
                   incorporated by


                                          27

<PAGE>

                   reference to Exhibit 10.83 of the Registrant's Form 10-K
                   report for fiscal year 1995.

         10.83     Commercial lease between Domilyon Corporation and
                   Domilens Laboratories and Amendment No. 1 to
                   Commercial Lease dated May 9, 1994, incorporated
                   by reference to Exhibit 10.84 of the Registrant's
                   Form 10-K report for fiscal year 1995.

         10.84     Agreement between the Registrant and Cephalon,
                   Inc. dated as of January 7, 1994, and Letter
                   Agreements between the Registrant and Cephalon
                   dated January 13, 1995 and May 23, 1995,
                   incorporated by reference to Exhibit 10.85 of the
                   Registrant's Form 10-K report for fiscal year
                   1995.  [Certain information has been omitted from
                   the Agreements and filed separately with the
                   Securities and Exchange Commission pursuant to a
                   request by Registrant for confidential treatment
                   pursuant to Rule 24b-2.  The omitted confidential
                   information has been identified by the following
                   statement: "Confidential Treatment Requested".]

         10.85     Reimbursement Agreement, dated as of June 28,
                   1996, between Ciba-Geigy Limited, a Swiss
                   corporation, and the Registrant, incorporated by
                   reference to Exhibit 10.94 of the Registrant's
                   Form 10-Q report for the period ended June 30,
                   1996.

         10.86     Reimbursement Agreement, dated as of May 20, 1996,
                   between Ciba-Geigy Limited, a Swiss corporation,
                   and the Registrant, incorporated by reference to
                   Exhibit 10.95 of the Registrant's Form 10-Q report
                   for the period ended June 30, 1996.

         10.87     Letter Agreement between the Registrant and Dr.
                   Richard W. Barker, dated May 1, 1996, incorporated
                   by reference to Exhibit 10.88 of the Registrant's
                   Form 10-Q report for the period ended June 30,
                   1996.*

         10.88     Revolving Credit Agreement, dated as of March 23,
                   1996, between the Registrant and Morgan Guaranty
                   Trust Company of New York, incorporated by
                   reference to Exhibit 10.89 of the Registrant's
                   Form 10-Q report for the period ended June 30,
                   1996.

         10.89     Purchase and Assignment Agreement between
                   Behringwerke Aktiengesellschaft, on the one side,
                   and 31.CORSA Verwaltungsgesellschaft mbH and the
                   Registrant, on the other side, dated February 17,
                   1996, Closing Agreement, by and among Behringwerke
                   Aktiengesellschaft, on the one side, and the
                   Registrant and 31.CORSA Verwaltungsgesellschaft
                   mbH, on the other side, dated June 29, 1996 and
                   Letter



                                          28

<PAGE>

                   Agreement dated June 29, 1996 between the Registrant,
                   31.CORSA Verwaltungsgesellschaft mbH and Behringwerke
                   Aktiengesellschaft, incorporated by reference to Exhibit
                   10.86 of the Registrant's Form 10-Q report for the period
                   ended September 29, 1996.  [Certain confidential information
                   has been omitted from the Agreements and filed separately
                   with the Securities and Exchange Commission pursuant to a
                   request by Registrant for confidential treatment pursuant to
                   Rule 24b-2.]

         10.90     Royalty Projects Agreement by and between Ciba
                   Corning Diagnostics Corp., a Delaware corporation,
                   and Ciba-Geigy Limited, a Swiss corporation,
                   incorporated by reference to Exhibit 10.87 of the
                   Registrant's Form 10-Q report for the period ended
                   September 29, 1996.  [Certain confidential
                   information has been omitted from the Agreement
                   and filed separately with the Securities and
                   Exchange Commission pursuant to a request by
                   Registrant for confidential treatment pursuant to
                   Rule 24b-2.]

         10.91     Purchase Agreement between BNP Leasing Corporation
                   and the Registrant, dated June 28, 1996,
                   incorporated by reference to Exhibit 10.90 of the
                   Registrant's Form 10-Q report for the period ended
                   June 30, 1996.

         10.92     Lease Agreement between BNP Leasing Corporation
                   and the Registrant, dated June 28, 1996,
                   incorporated by reference to Exhibit 10.91 of the
                   Registrant's Form 10-Q report for the period ended
                   June 30, 1996.

         10.93     Ground Lease between BNP Leasing Corporation and
                   the Registrant, dated June 28, 1996, incorporated
                   by reference to Exhibit 10.92 of the Registrant's
                   Form 10-Q report for the period ended June 30,
                   1996.

         10.94     Reimbursement Agreement, dated as of July 12,
                   1996, between Ciba-Geigy Limited, a Swiss
                   corporation, and the Registrant, incorporated by
                   reference to Exhibit 10.93 of the Registrant's
                   Form 10-Q report for the period ended June 30,
                   1996.

         10.95     Form of Performance Unit Agreement, Chiron 1991
                   Stock Option Plan, as amended, incorporated by
                   reference to Exhibit 10.94 of the Registrant's
                   Form 10-K report for fiscal year 1996.*

         11        Statement of Computation of Earnings per Share.

         27        Financial Data Schedule.

--------------
    * Management contract, compensatory plan or arrangement.


                                          29

<PAGE>

         (b)  Reports on Form 8-K

    There were no reports on Form 8-K filed during the quarter ended March 30,
    1997.

                                          30

<PAGE>

                                  CHIRON CORPORATION

                                    March 30, 1997


                                      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 thereunto duly authorized.


                                                 CHIRON CORPORATION



DATE: May 14, 1997                     BY:  /s/Edward E. Penhoet
    -------------------------               ------------------------------
                                            Edward E. Penhoet, Ph.D.
                                            President and Chief
                                            Executive Officer



DATE: May 14, 1997                     BY:  /s/Dennis L. Winger
    -------------------------               ------------------------------
                                            Dennis L. Winger
                                            Senior Vice President, Finance
                                            and Administration, Chief Financial
                                            Officer, and Principal Accounting
                                            Officer


                                          31