<TABLE> <S> <C>

<PAGE>
<ARTICLE> 5
<LEGEND>
THIS SCHEDULE CONTAINS SUMMARY FINANCIAL INFORMATION EXTRACTED FROM THE 
CONSOLIDATED FINANCIAL STATEMENTS OF PERITUS SOFTWARE SERVICES, INC. FOR THE 
THREE AND NINE MONTHS ENDED SEPTEMBER 30, 1998 AND IS QUALIFIED IN ITS ENTIRETY 
BY REFERENCE TO SUCH FINANCIAL STATEMENTS.
</LEGEND>
       
<S>                             <C>                     <C>
<PERIOD-TYPE>                   3-MOS                   9-MOS
<FISCAL-YEAR-END>                          DEC-31-1998             DEC-31-1998
<PERIOD-START>                             JUL-01-1998             JAN-01-1998
<PERIOD-END>                               SEP-30-1998             SEP-30-1998
<CASH>                                           4,004                   4,004
<SECURITIES>                                     2,500                   2,500
<RECEIVABLES>                                    6,299                   6,299
<ALLOWANCES>                                     (745)                   (745)
<INVENTORY>                                          0                       0
<CURRENT-ASSETS>                                 2,956                   2,956
<PP&E>                                           9,081                   9,081
<DEPRECIATION>                                 (3,842)                 (3,842)
<TOTAL-ASSETS>                                  20,929                  20,929
<CURRENT-LIABILITIES>                            9,555                   9,555
<BONDS>                                              0                       0
<PREFERRED-MANDATORY>                                0                       0
<PREFERRED>                                          0                       0
<COMMON>                                           163                     163
<OTHER-SE>                                       9,866                   9,866
<TOTAL-LIABILITY-AND-EQUITY>                    20,929                  20,929
<SALES>                                          5,293                  25,809
<TOTAL-REVENUES>                                 5,293                  25,809
<CGS>                                            4,851                  14,989
<TOTAL-COSTS>                                    4,851                  14,989
<OTHER-EXPENSES>                                16,672                  32,579
<LOSS-PROVISION>                                     0                       0
<INTEREST-EXPENSE>                                (95)                   (440)
<INCOME-PRETAX>                               (16,135)                (21,319)
<INCOME-TAX>                                         0                      25
<INCOME-CONTINUING>                           (16,135)                (21,344)
<DISCONTINUED>                                       0                       0
<EXTRAORDINARY>                                      0                       0
<CHANGES>                                            3                      15
<NET-INCOME>                                  (16,132)                (21,329)
<EPS-PRIMARY>                                    (.99)                  (1.32)
<EPS-DILUTED>                                    (.99)                  (1.32)
        

</TABLE>