<ARTICLE>           5
<LEGEND>
THIS SCHEDULE CONTAINS SUMMARY FINANCIAL INFORMATION EXTRACTED FROM THERMO OPTEK
CORPORATION'S QUARTERLY REPORT ON FORM 10-Q FOR THE PERIOD ENDED OCTOBER 2, 1999
AND IS QUALIFIED IN ITS ENTIRETY BY REFERENCE TO SUCH FINANCIAL STATEMENTS.
</LEGEND>
<MULTIPLIER>        1,000

                              
<PERIOD-TYPE>                                 9-MOS
<FISCAL-YEAR-END>                             JAN-01-2000
<PERIOD-END>                                  OCT-02-1999
<CASH>                                                 52,107
<SECURITIES>                                                0
<RECEIVABLES>                                          98,672
<ALLOWANCES>                                            4,197
<INVENTORY>                                            69,881
<CURRENT-ASSETS>                                      263,667
<PP&E>                                                101,928
<DEPRECIATION>                                         42,533
<TOTAL-ASSETS>                                        558,584
<CURRENT-LIABILITIES>                                 133,143
<BONDS>                                                64,700
<PREFERRED-MANDATORY>                                       0
<PREFERRED>                                                 0
<COMMON>                                                  518
<OTHER-SE>                                            342,351
<TOTAL-LIABILITY-AND-EQUITY>                          558,584
<SALES>                                               327,886
<TOTAL-REVENUES>                                      327,886
<CGS>                                                 175,514
<TOTAL-COSTS>                                         175,514
<OTHER-EXPENSES>                                       21,756
<LOSS-PROVISION>                                         (170)
<INTEREST-EXPENSE>                                      3,745
<INCOME-PRETAX>                                        44,902
<INCOME-TAX>                                           17,905
<INCOME-CONTINUING>                                    26,997
<DISCONTINUED>                                              0
<EXTRAORDINARY>                                             0
<CHANGES>                                                   0
<NET-INCOME>                                           26,997
<EPS-BASIC>                                            0.53
<EPS-DILUTED>                                            0.51