<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 JULY 3, 1999
AND IS QUALIFIED IN ITS ENTIRETY BY REFERENCE TO SUCH FINANCIAL STATEMENTS.
</LEGEND>
<MULTIPLIER>        1,000

                              
<PERIOD-TYPE>                                 6-MOS
<FISCAL-YEAR-END>                             JAN-01-2000
<PERIOD-END>                                  JUL-03-1999
<CASH>                                                 55,054
<SECURITIES>                                                0
<RECEIVABLES>                                          95,594
<ALLOWANCES>                                            4,321
<INVENTORY>                                            67,609
<CURRENT-ASSETS>                                      246,969
<PP&E>                                                 98,885
<DEPRECIATION>                                         40,089
<TOTAL-ASSETS>                                        539,196
<CURRENT-LIABILITIES>                                 131,906
<BONDS>                                                69,082
<PREFERRED-MANDATORY>                                       0
<PREFERRED>                                                 0
<COMMON>                                                  518
<OTHER-SE>                                            324,513
<TOTAL-LIABILITY-AND-EQUITY>                          539,196
<SALES>                                               216,305
<TOTAL-REVENUES>                                      216,305
<CGS>                                                 115,846
<TOTAL-COSTS>                                         115,846
<OTHER-EXPENSES>                                       14,196
<LOSS-PROVISION>                                          (85)
<INTEREST-EXPENSE>                                      2,544
<INCOME-PRETAX>                                        28,436
<INCOME-TAX>                                           11,387
<INCOME-CONTINUING>                                    17,049
<DISCONTINUED>                                              0
<EXTRAORDINARY>                                             0
<CHANGES>                                                   0
<NET-INCOME>                                           17,049
<EPS-BASIC>                                            0.33
<EPS-DILUTED>                                            0.32