<ARTICLE>           5
<LEGEND>
THIS SCHEDULE CONTAINS SUMMARY FINANCIAL INFORMATION EXTRACTED FROM THERMO OPTEK
CORPORATION'S ANNUAL REPORT ON FORM 10-K FOR THE YEAR ENDED JANUARY 2, 1999 AND
IS QUALIFIED IN ITS ENTIRETY BY REFERENCE TO SUCH FINANCIAL STATEMENTS.
</LEGEND>
<MULTIPLIER>        1,000
       
                              
<PERIOD-TYPE>                                 YEAR
<FISCAL-YEAR-END>                             JAN-02-1999
<PERIOD-END>                                  JAN-02-1999
<CASH>                                                 59,427
<SECURITIES>                                                0
<RECEIVABLES>                                         110,719
<ALLOWANCES>                                            4,960
<INVENTORY>                                            63,697
<CURRENT-ASSETS>                                      247,195
<PP&E>                                                100,446
<DEPRECIATION>                                         37,552
<TOTAL-ASSETS>                                        561,668
<CURRENT-LIABILITIES>                                 149,404
<BONDS>                                                71,761
<PREFERRED-MANDATORY>                                       0
<PREFERRED>                                                 0
<COMMON>                                                  518
<OTHER-SE>                                            326,533
<TOTAL-LIABILITY-AND-EQUITY>                          561,668
<SALES>                                               447,301
<TOTAL-REVENUES>                                      447,301
<CGS>                                                 240,613
<TOTAL-COSTS>                                         240,613
<OTHER-EXPENSES>                                       24,963
<LOSS-PROVISION>                                          519
<INTEREST-EXPENSE>                                      7,254
<INCOME-PRETAX>                                        59,026
<INCOME-TAX>                                           25,443
<INCOME-CONTINUING>                                    33,583
<DISCONTINUED>                                              0
<EXTRAORDINARY>                                           280
<CHANGES>                                                   0
<NET-INCOME>                                           33,863
<EPS-PRIMARY>                                            0.66
<EPS-DILUTED>                                            0.63