<TABLE> <S> <C>

<PAGE>
<ARTICLE> 5
<LEGEND>
THIS SCHEDULE CONTAINS SUMMARY FINANCIAL INFORMATION EXTRACTED FROM CHIRON
CORPORATION'S UNAUDITED CONSOLIDATED BALANCE SHEET DATED SEPTEMBER 30, 1997 AND
UNAUDITED CONSOLIDATED STATEMENT OF OPERATIONS FOR THE NINE MONTHS ENDED
SEPTEMBER 30, 1997 AND IS QUALIFIED IN ITS ENTIRETY BY REFERENCE TO SUCH
FINANCIAL STATEMENTS.
</LEGEND>
<MULTIPLIER> 1,000
       
<S>                             <C>
<PERIOD-TYPE>                   9-MOS
<FISCAL-YEAR-END>                          DEC-31-1997<F5>
<PERIOD-START>                             JAN-01-1997
<PERIOD-END>                               SEP-30-1997<F5>
<CASH>                                         103,537
<SECURITIES>                                    74,641<F1>
<RECEIVABLES>                                  324,185
<ALLOWANCES>                                         0
<INVENTORY>                                    185,355
<CURRENT-ASSETS>                               725,711
<PP&E>                                         807,549
<DEPRECIATION>                                 257,059
<TOTAL-ASSETS>                               1,701,762
<CURRENT-LIABILITIES>                          466,424
<BONDS>                                        395,640<F2>
<PREFERRED-MANDATORY>                                0
<PREFERRED>                                          0
<COMMON>                                         1,750
<OTHER-SE>                                     812,667<F3>
<TOTAL-LIABILITY-AND-EQUITY>                 1,701,762
<SALES>                                        609,762
<TOTAL-REVENUES>                               850,887
<CGS>                                          257,344
<TOTAL-COSTS>                                  257,344
<OTHER-EXPENSES>                               314,551<F4>
<LOSS-PROVISION>                                     0
<INTEREST-EXPENSE>                              24,823
<INCOME-PRETAX>                                 34,394
<INCOME-TAX>                                    17,393
<INCOME-CONTINUING>                             17,001
<DISCONTINUED>                                   1,396
<EXTRAORDINARY>                                      0
<CHANGES>                                            0
<NET-INCOME>                                    18,397
<EPS-PRIMARY>                                     0.10<F6>
<EPS-DILUTED>                                     0.10<F6>
<FN>
<F1>CONSISTS OF BOTH SHORT-TERM AND NONCURRENT INVESTMENTS IN MARKETABLE DEBT
SECURITIES.
<F2>CONSISTS OF CONVERTIBLE SUBORDINATED DEBENTURES, CAPITAL LEASE OBLIGATIONS AND
NOTES PAYABLE, NET OF CURRENT MATURITIES.
<F3>CONSISTS OF ADDITIONAL PAID-IN CAPITAL, ACCUMULATED DEFICIT, CUMULATIVE
FOREIGN CURRENCY TRANSLATION ADJUSTMENT, UNREALIZED GAIN FROM INVESTMENTS AND
NOTES RECEIVABLE FROM STOCK SALES.
<F4>CONSISTS OF RESEARCH AND DEVELOPMENT, IMPAIRMENT LOSS ON LONG-LIVED ASSETS AND
OTHER OPERATING EXPENSES.
<F5>ACTUAL FISCAL YEAR END WILL BE, AND PERIOD END WAS, DEC-28-1997 AND
SEP-28-1997, RESPECTIVELY. FOR PRESENTATION PURPOSES, DATES USED IN THE
CONSOLIDATED FINANCIAL STATEMENTS AND NOTES REFER TO THE CALENDAR MONTH END.
<F6>REPRESENTS NET INCOME PER SHARE.
</FN>
        

</TABLE>