<TABLE> <S> <C>

<PAGE>
<ARTICLE> 5
<LEGEND>
THIS SCHEDULE CONTAINS SUMMARY FINANCIAL INFORMATION EXTRACTED FROM CHIRON
CORPORATION UNAUDITED CONDENSED CONSOLIDATED BALANCE SHEET DATED SEPTEMBER 30,
1998 AND UNAUDITED CONDENSED CONSOLIDATED STATEMENT OF OPERATIONS FOR THE NINE
MONTHS ENDED SEPTEMBER 30, 1998 AND IS QUALIFIED IN ITS ENTIRETY BY REFERENCE TO
SUCH FINANCIAL STATEMENTS.
</LEGEND>
<RESTATED>
<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>                                          124,462<F6>
<TOTAL-COSTS>                                  124,462<F6>
<OTHER-EXPENSES>                               217,364<F6><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-BASIC>                                       0.93
<EPS-DILUTED>                                     0.91
<FN>
<F1>CONSISTS OF 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 WAS JAN-03-1999. ACTUAL INTERIM PERIOD END WAS
SEPTEMBER 27, 1998. FOR PRESENTATION PURPOSES, DATES USED IN THE CONDENSED
CONSOLIDATED FINANCIAL STATEMENTS AND NOTES REFER TO THE FISCAL MONTH END.
<F6>DURING THE SECOND QUARTER OF 1999, THE COMPANY COMPLETED THE
IMPLEMENTATION OF AN INTEGRATED INFORMATION SYSTEM. AS A RESULT, CERTAIN
PREVIOUSLY REPORTED AMOUNTS HAVE BEEN RECLASSIFIED TO CONFORM WITH THE
SEPTEMBER 30, 1999 PRESENTATION.
</FN>


</TABLE>