<TABLE> <S> <C>

<PAGE>
 
<ARTICLE> 5
<RESTATED> 
<MULTIPLIER> 1,000
       
<S>                             <C>                      <C>                       <C>                    
<PERIOD-TYPE>                   3-MOS                    6-MOS                     9-MOS                  
<FISCAL-YEAR-END>                          SEP-30-1997              SEP-30-1997               SEP-30-1997 
<PERIOD-START>                             OCT-01-1996              OCT-01-1996               OCT-01-1996 
<PERIOD-END>                               DEC-31-1996              MAR-31-1997               JUN-30-1997 
<CASH>                                          49,139                   44,579                    38,503 
<SECURITIES>                                    21,750                   24,057                    31,084 
<RECEIVABLES>                                    4,100                    7,382                     6,785 
<ALLOWANCES>                                       754                      858                       992 
<INVENTORY>                                        680                      700                       433 
<CURRENT-ASSETS>                                80,055                   82,682                    83,881 
<PP&E>                                           7,136                    8,277                    10,482 
<DEPRECIATION>                                   3,437                    3,844                     4,699 
<TOTAL-ASSETS>                                  83,826                   89,140                    95,980 
<CURRENT-LIABILITIES>                           19,455                   23,401                    24,245 
<BONDS>                                              0                        0                         0 
<PREFERRED-MANDATORY>                                0                        0                         0 
<PREFERRED>                                          0                        0                         0 
<COMMON>                                        51,262                   52,540                    54,983 
<OTHER-SE>                                           0                        0                         0 
<TOTAL-LIABILITY-AND-EQUITY>                    83,826                   89,140                    95,980 
<SALES>                                         19,207                   43,019                    69,386 
<TOTAL-REVENUES>                                19,207                   43,019                    69,386 
<CGS>                                            1,993                    4,406                     7,157 
<TOTAL-COSTS>                                    1,993                    4,406                     7,157 
<OTHER-EXPENSES>                                12,121                   34,087                    54,821 
<LOSS-PROVISION>                                     0                        0                         0 
<INTEREST-EXPENSE>                                  12                       20                        35 
<INCOME-PRETAX>                                  5,574                    5,830                     9,733 
<INCOME-TAX>                                     1,417                    1,457                     2,418 
<INCOME-CONTINUING>                              4,157                    4,373                     7,315 
<DISCONTINUED>                                       0                        0                         0 
<EXTRAORDINARY>                                      0                        0                         0 
<CHANGES>                                            0                        0                         0 
<NET-INCOME>                                     4,157                    4,373                     7,315 
<EPS-PRIMARY>                                     0.15                     0.16                      0.26 
<EPS-DILUTED>                                     0.14                     0.15                      0.25  
        

</TABLE>