<TABLE> <S> <C>

<PAGE>
<ARTICLE> 5
<LEGEND>
THIS SCHEDULE CONTAINS SUMMARY FINANCIAL INFORMATION EXTRACTED FROM CHIRON
CORPORATION'S UNAUDITED CONDENSED CONSOLIDATED BALANCE SHEETS DATED MARCH 31 AND
JUNE 30, 1998 AND UNAUDITED CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS FOR
THE THREE AND SIX MONTHS ENDED MARCH 31 AND JUNE 30, 1998, RESPECTIVELY AND IS
QUALIFIED IN ITS ENTIRETY BY REFERENCE TO SUCH FINANCIAL STATEMENTS.
</LEGEND>
<RESTATED>
<MULTIPLIER> 1,000
       
<S>                             <C>                     <C>
<PERIOD-TYPE>                   3-MOS                   6-MOS
<FISCAL-YEAR-END>                          DEC-31-1998<F5>         DEC-31-1998<F5>
<PERIOD-START>                             JAN-01-1998             JAN-01-1998
<PERIOD-END>                               MAR-31-1998<F5>         JUN-30-1998<F5>
<CASH>                                         177,590                 158,120
<SECURITIES>                                   270,727<F1>             254,859<F1>
<RECEIVABLES>                                  295,532                 328,132
<ALLOWANCES>                                         0                       0
<INVENTORY>                                    133,224                 170,231
<CURRENT-ASSETS>                               863,843                 848,427
<PP&E>                                         724,254                 765,364
<DEPRECIATION>                                 256,123                 283,432
<TOTAL-ASSETS>                               1,755,401               1,802,840
<CURRENT-LIABILITIES>                          366,121                 378,088
<BONDS>                                        400,072<F2>             402,312<F2>
<PREFERRED-MANDATORY>                                0                       0
<PREFERRED>                                          0                       0
<COMMON>                                         1,771                   1,775
<OTHER-SE>                                     964,056<F3>             987,615<F3>
<TOTAL-LIABILITY-AND-EQUITY>                 1,755,401               1,802,840
<SALES>                                         69,220                 165,278
<TOTAL-REVENUES>                               133,287                 296,177
<CGS>                                           28,077                  71,310
<TOTAL-COSTS>                                   28,077                  71,310
<OTHER-EXPENSES>                                72,111<F4>             143,426<F4>
<LOSS-PROVISION>                                     0                       0
<INTEREST-EXPENSE>                               6,580                  12,629
<INCOME-PRETAX>                                 11,407                  29,327
<INCOME-TAX>                                     3,865                   1,683
<INCOME-CONTINUING>                              7,542                  27,644
<DISCONTINUED>                                  46,939<F8>              52,224<F8>
<EXTRAORDINARY>                                      0                       0
<CHANGES>                                            0                       0
<NET-INCOME>                                    54,481                  79,868
<EPS-PRIMARY>                                     0.31<F6>                0.45<F6>
<EPS-DILUTED>                                     0.30<F7>                0.44<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, ACCUMULATED 
OTHER COMPREHENSIVE LOSS AND NOTES RECEIVABLE FROM STOCK SALES.
<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 JAN-03-1999. ACTUAL INTERIM PERIOD ENDS WERE
MAR-29-1998 AND JUNE 28, 1998. FOR PRESENTATION PURPOSES, DATES USED IN THE 
CONDENSED 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 FOR THE THREE MONTHS ENDED MAR-31-1998 AND SIX MONTHS 
ENDED JUN-30-1998 WAS $0.04 AND $0.16, RESPECTIVELY. BASIC INCOME PER SHARE FROM
DISCONTINUED OPERATIONS FOR THE THREE MONTHS ENDED MAR-31-1998 AND SIX MONTHS
ENDED JUN-30-1998 WERE $0.27 AND $0.29, RESPECTIVELY.
<F7>REPRESENTS DILUTED NET INCOME PER SHARE. DILUTED INCOME PER SHARE FROM
CONTINUING OPERATIONS FOR THE THREE MONTHS ENDED MAR-31-1998 AND SIX MONTHS
ENDED JUN-30-1998 WAS $0.04 AND $0.15, RESPECTIVELY. DILUTED INCOME PER SHARE
FROM DISCONTINUED OPERATIONS FOR THE THREE MONTHS ENDED MAR-31-1998 AND SIX
MONTHS ENDED JUN-30-1998 WERE $0.26 AND $0.29, RESPECTIVELY.
<F8>ON NOVEMBER 30, 1998, CHIRON CORPORATION COMPLETED THE SALE OF ITS IN VITRO
DIAGNOSTICS BUSINESS, CHIRON DIAGNOSTICS CORPORATION. THIS SCHEDULE FOR THE 
THREE MONTHS ENDED MAR-31-1998 AND SIX MONTHS ENDED JUN-30-1998 HAS BEEN 
RESTATED TO REFLECT THE RESULTS OF CHIRON DIAGNOSTICS CORPORATION AS 
DISCONTINUED OPERATIONS.
</FN>
        

</TABLE>