<ARTICLE> 5
<RESTATED> 
<CIK> 0000932064
<NAME> SECURITY DYNAMICS TECHNOLOGIES INC.
<MULTIPLIER> 1,000
<CURRENCY> US DOLLARS
       
                             
<PERIOD-TYPE>                   YEAR
<FISCAL-YEAR-END>                          DEC-31-1997
<PERIOD-START>                             JAN-01-1997
<PERIOD-END>                               SEP-30-1997
<EXCHANGE-RATE>                                      1
<CASH>                                          36,988
<SECURITIES>                                    70,774
<RECEIVABLES>                                   20,257
<ALLOWANCES>                                       787
<INVENTORY>                                      2,744
<CURRENT-ASSETS>                               137,663
<PP&E>                                          21,290
<DEPRECIATION>                                   5,823
<TOTAL-ASSETS>                                 161,059
<CURRENT-LIABILITIES>                           27,669
<BONDS>                                              0
<PREFERRED-MANDATORY>                                0
<PREFERRED>                                          0
<COMMON>                                           380
<OTHER-SE>                                     129,978
<TOTAL-LIABILITY-AND-EQUITY>                   161,059<F1>
<SALES>                                         96,202
<TOTAL-REVENUES>                                96,202
<CGS>                                           19,995
<TOTAL-COSTS>                                   84,875
<OTHER-EXPENSES>                                     0
<LOSS-PROVISION>                                   327
<INTEREST-EXPENSE>                             (3,976)
<INCOME-PRETAX>                                 19,899
<INCOME-TAX>                                     7,508
<INCOME-CONTINUING>                             12,391
<DISCONTINUED>                                       0
<EXTRAORDINARY>                                      0
<CHANGES>                                            0
<NET-INCOME>                                    12,391
<EPS-PRIMARY>                                    0.314
<EPS-DILUTED>                                    0.312
<FN>
<F1>TOTAL LIABILITY AND EQUITY INCLUDES $3,032 MINORITY INTERESTS
</FN>