<TABLE> <S> <C>

<PAGE>
<ARTICLE> 5
<LEGEND>
THIS SCHEDULE CONTAINS SUMMARY FINANCIAL INFORMATION EXTRACTED FROM CHIRON
CORPORATION'S CONSOLIDATED BALANCE SHEET DATED DECEMBER 31, 1997 AND 
CONSOLIDATED STATEMENT OF OPERATIONS FOR THE YEAR ENDED DECEMBER 31, 1997 
AND IS QUALIFIED IN ITS ENTIRETY BY REFERENCE TO SUCH FINANCIAL STATEMENTS.
</LEGEND>
<RESTATED>
<MULTIPLIER> 1,000
       
<S>                             <C>
<PERIOD-TYPE>                   YEAR
<FISCAL-YEAR-END>                          DEC-31-1997<F5>
<PERIOD-START>                             JAN-01-1997
<PERIOD-END>                               DEC-31-1997<F5>
<CASH>                                          98,483
<SECURITIES>                                   159,989<F1>
<RECEIVABLES>                                  366,962
<ALLOWANCES>                                    22,918
<INVENTORY>                                    165,652
<CURRENT-ASSETS>                               770,052
<PP&E>                                         831,521
<DEPRECIATION>                                 277,623
<TOTAL-ASSETS>                               1,768,478
<CURRENT-LIABILITIES>                          471,186
<BONDS>                                        397,217<F2>
<PREFERRED-MANDATORY>                                0
<PREFERRED>                                          0
<COMMON>                                         1,757
<OTHER-SE>                                     872,188<F3>
<TOTAL-LIABILITY-AND-EQUITY>                 1,768,478
<SALES>                                        252,729
<TOTAL-REVENUES>                               574,599
<CGS>                                          113,612
<TOTAL-COSTS>                                  113,612
<OTHER-EXPENSES>                               294,945<F4>
<LOSS-PROVISION>                                     0
<INTEREST-EXPENSE>                              31,610
<INCOME-PRETAX>                                 40,206
<INCOME-TAX>                                    14,424
<INCOME-CONTINUING>                             25,782
<DISCONTINUED>                                  45,437<F8>
<EXTRAORDINARY>                                      0
<CHANGES>                                            0
<NET-INCOME>                                    71,219
<EPS-PRIMARY>                                      .41<F6>
<EPS-DILUTED>                                      .40<F7>
<FN>
<F5>ACTUAL FISCAL YEAR END WAS DEC-28-1997, FOR PRESENTATION PURPOSES, DATES USED
IN THE CONSOLIDATED FINANCIAL STATEMENTS AND NOTES REFER TO THE FISCAL MONTH
END.
<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, ACCUMULATED OTHER
COMPREHENSIVE LOSS AND NOTES RECEIVABLE FROM STOCK SALES.
<F4>CONSISTS OF RESEARCH AND DEVELOPMENT, IMPAIRMENT LOSS ON LONG-LIVED ASSETS AND
OTHER OPERATING EXPENSES.
<F8>ON NOVEMBER 30, 1998, CHIRON CORPORATION COMPLETED THE SALE OF ITS IN VITRO
DIAGNOSTICS BUSINESS, CHIRON DIAGNOSTICS CORPORATION. THIS SCHEDULE FOR THE
YEAR ENDED DEC-31-1997 HAS BEEN RESTATED TO REFLECT THE RESULTS OF CHIRON
DIAGNOSTICS CORPORATION AS DISCONTINUED OPERATIONS.
<F6>REPRESENTS BASIC NET INCOME PER SHARE. BASIC INCOME PER SHARE FROM CONTINUING
OPERATIONS AND BASIC INCOME PER SHARE FROM DISCONTINUED OPERATIONS WERE $0.15
AND $0.26, RESPECTIVELY.
<F7>REPRESENTS DILUTED NET INCOME PER SHARE. DILUTED INCOME PER SHARE FROM
CONTINUING OPERATIONS AND DILUTED INCOME PER SHARE FROM DISCONTINUED OPERATIONS
WERE $0.14 AND $0.26, RESPECTIVELY.
</FN>
        

</TABLE>