<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, 1998 AND
UNAUDITED CONDENSED STATEMENT OF OPERATIONS FOR THE NINE MONTHS ENDED SEPTEMBER
30, 1998 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-31-1998<F5>
<PERIOD-START>                             JAN-01-1998
<PERIOD-END>                               SEP-30-1998<F5>
<CASH>                                          80,468
<SECURITIES>                                   339,496<F1>
<RECEIVABLES>                                  348,015
<ALLOWANCES>                                         0
<INVENTORY>                                    177,441
<CURRENT-ASSETS>                               886,260
<PP&E>                                         820,781
<DEPRECIATION>                                 306,505
<TOTAL-ASSETS>                               1,960,449
<CURRENT-LIABILITIES>                          373,593
<BONDS>                                        405,865<F2>
<PREFERRED-MANDATORY>                                0
<PREFERRED>                                          0
<COMMON>                                         1,782
<OTHER-SE>                                   1,140,116<F3>
<TOTAL-LIABILITY-AND-EQUITY>                 1,960,449
<SALES>                                        278,091
<TOTAL-REVENUES>                               512,147
<CGS>                                          120,917
<TOTAL-COSTS>                                  120,917
<OTHER-EXPENSES>                               222,385<F4>
<LOSS-PROVISION>                                     0
<INTEREST-EXPENSE>                              18,638
<INCOME-PRETAX>                                 77,097
<INCOME-TAX>                                    15,539
<INCOME-CONTINUING>                             61,558
<DISCONTINUED>                                 102,745
<EXTRAORDINARY>                                      0
<CHANGES>                                            0
<NET-INCOME>                                   164,303
<EPS-PRIMARY>                                     0.93<F6>
<EPS-DILUTED>                                     0.91<F7>
<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 AND ACCUMULATED
OTHER COMPREHENSIVE LOSS.
<F4>CONSISTS OF RESEARCH AND DEVELOPMENT, WRITE-OFF OF PURCHASED IN-PROCESS
TECHNOLOGIES, RESTRUCTURING AND REORGANIZATION CHARGES AND OTHER OPERATING
EXPENSES.
<F5>ACTUAL FISCAL YEAR END WILL BE, AND PERIOD END WAS, JAN-03-1999 AND
SEP-27-1998, RESPECTIVELY.  FOR PRESENTATION PURPOSES, DATES USED IN THE 
CONSOLIDATED FINANCIAL STATEMENTS AND NOTES REFER TO THE FISCAL MONTH END.
<F6>REPRESENTS BASIC NET INCOME PER SHARE.  BASIC INCOME PER SHARE FROM CONTINUING
OPERATIONS AND BASIC INCOME PER SHARE FROM DISCONTINUED OPERATIONS WERE $0.35
AND $0.58, RESPECTIVELY.
<F7>REPRESENTS DILUTED NET INCOME PER SHARE.  DILUTED INCOME PER SHARE FROM
CONTINUING OPERATIONS AND DILUTED INCOME PER SHARE FROM DISCONTINUED OPERATIONS
WERE $0.34 AND $0.57, RESPECTIVELY.
</FN>
        

</TABLE>