<TABLE> <S> <C>
<PAGE>
<ARTICLE> 5
<LEGEND>
THIS SCHEDULE CONTAINS SUMMARY FINANCIAL INFORMATION EXTRACTED FROM CHIRON
CORPORATION'S UNAUDITED CONSOLIDATED BALANCE SHEET DATED JUNE 30, 2000 AND
UNAUDITED CONDENSED CONSOLIDATED STATEMENT OF OPERATIONS FOR THE SIX MONTHS
ENDED JUNE 30, 2000 AND IS QUALIFIED IN ITS ENTIRETY BY REFERENCE TO SUCH
FINANCIAL STATEMENTS.
</LEGEND>
<MULTIPLIER> 1,000
<S> <C>
<PERIOD-TYPE> 6-MOS
<FISCAL-YEAR-END> DEC-31-2000
<PERIOD-START> JAN-01-2000
<PERIOD-END> JUN-30-2000
<CASH> 474,450
<SECURITIES> 952,213<F1>
<RECEIVABLES> 213,456<F2>
<ALLOWANCES> 10,537
<INVENTORY> 102,894
<CURRENT-ASSETS> 1,513,109
<PP&E> 538,740
<DEPRECIATION> 242,646
<TOTAL-ASSETS> 2,428,434
<CURRENT-LIABILITIES> 537,430
<BONDS> 695<F3>
0
0
<COMMON> 1,828
<OTHER-SE> 1,837,472<F4>
<TOTAL-LIABILITY-AND-EQUITY> 2,428,434
<SALES> 318,627
<TOTAL-REVENUES> 457,600
<CGS> 99,530
<TOTAL-COSTS> 99,530
<OTHER-EXPENSES> 152,719<F5>
<LOSS-PROVISION> 4,183
<INTEREST-EXPENSE> 9,359
<INCOME-PRETAX> 141,250
<INCOME-TAX> 43,754
<INCOME-CONTINUING> 97,496
<DISCONTINUED> 2,342
<EXTRAORDINARY> 0
<CHANGES> 0
<NET-INCOME> 99,838
<EPS-BASIC> 0.55
<EPS-DILUTED> 0.52
<FN>
<F1>CONSISTS OF SHORT-TERM AND NONCURRENT INVESTMENTS IN MARKETABLE DEBT AND EQUITY
SECURITIES.
<F2>CONSISTS OF ACCOUNTS RECEIVABLE AND CURRENT AND NONCURRENT PORTIONS OF NOTES
RECEIVABLE.
<F3>CONSISTS OF CONVERTIBLE SUBORDINATED DEBENTURES AND NOTES PAYABLE, NET OF
CURRENT MATURITIES.
<F4>CONSISTS OF ADDITIONAL PAID-IN CAPITAL, ACCUMULATED DEFICIT, COST OF TREASURY
STOCK, AND ACCUMULATED OTHER COMPREHENSIVE INCOME.
<F5>CONSISTS OF RESEARCH AND DEVELOPMENT, RESTRUCTURING AND REORGANIZATION CHARGES
AND OTHER OPERATING EXPENSES.
</FN>
</TABLE>
