<TABLE> <S> <C>

<PAGE>
<ARTICLE> 5
<LEGEND>
THIS SCHEDULE CONTAINS SUMMARY FINANCIAL INFORMATION EXTRACTED FROM SIEBEL
SYSTEMS, INC. QUARTERLY REPORT ON FORM 10-Q FOR THE QUARTERS ENDED JUNE 30, 1997
AND 1998, RESPECTIVELY, AND IS QUALIFIED IN ITS ENTIRETY BY REFERENCE TO SUCH
FINANCIAL STATEMENTS. THE SUMMARY FINANCIAL INFORMATION FOR THE PERIODS ENDED
JUNE 30, 1997 AND DECEMBER 31, 1997 HAVE BEEN RESTATED TO REFLECT THE EFFECT OF 
THE POOLING OF INTERESTS BETWEEN SIEBEL SYSTEMS, INC. AND SCOPUS TECHNOLOGY, 
INC., WHICH OCCURRED ON MAY 18, 1998.
</LEGEND>
<RESTATED> 
<MULTIPLIER> 1,000
<CURRENCY> US DOLLARS
       
<S>                             <C>                     <C>                     <C>
<PERIOD-TYPE>                   6-MOS                   YEAR                   6-MOS
<FISCAL-YEAR-END>                          DEC-31-1997             DEC-31-1997             DEC-31-1998
<PERIOD-START>                             JAN-01-1997             JAN-01-1997             JAN-01-1998
<PERIOD-END>                               JUN-30-1997             DEC-31-1997             JUN-30-1998
<EXCHANGE-RATE>                                      1                       1                       1
<CASH>                                          75,414                  70,202                  63,275
<SECURITIES>                                    75,936                  91,999                 116,136
<RECEIVABLES>                                   40,758                  63,056                 110,663
<ALLOWANCES>                                         0                       0                       0
<INVENTORY>                                          0                       0                       0
<CURRENT-ASSETS>                               201,785                 236,736                 303,222
<PP&E>                                          19,490                  24,843                  24,815
<DEPRECIATION>                                       0                       0                       0
<TOTAL-ASSETS>                                 226,920                 268,164                 334,120
<CURRENT-LIABILITIES>                           40,347                  58,634                 103,302
<BONDS>                                              0                       0                       0
<PREFERRED-MANDATORY>                                0                       0                       0
<PREFERRED>                                          0                       0                       0
<COMMON>                                       162,409                 195,518                 209,569
<OTHER-SE>                                      23,959                  13,850                  21,087
<TOTAL-LIABILITY-AND-EQUITY>                   226,920                 268,164                 334,120
<SALES>                                         62,949                 156,971                 123,342
<TOTAL-REVENUES>                                83,161                 207,628                 164,188
<CGS>                                            1,497                   4,393                   3,302
<TOTAL-COSTS>                                   13,325                  33,180                  29,334
<OTHER-EXPENSES>                                58,512                 167,829                 118,520
<LOSS-PROVISION>                                     0                       0                       0
<INTEREST-EXPENSE>                                   0                       0                       0
<INCOME-PRETAX>                                 13,906                  11,993                  19,262
<INCOME-TAX>                                     5,264                  13,180                  10,324
<INCOME-CONTINUING>                              8,642                  (1,187)                  8,938
<DISCONTINUED>                                       0                       0                       0
<EXTRAORDINARY>                                      0                       0                       0
<CHANGES>                                            0                       0                       0
<NET-INCOME>                                     8,642                  (1,187)                  8,938
<EPS-PRIMARY>                                     0.10                   (0.01)                   0.10
<EPS-DILUTED>                                     0.09                   (0.01)                   0.09
        

</TABLE>