SECURITIES AND EXCHANGE COMMISSION

                             Washington, D.C. 20549

                   -------------------------------------------


                                    FORM 8-K

                                 CURRENT REPORT



                       Pursuant to Section 13 or 15(d) of
                       the Securities Exchange Act of 1934



                                 Date of Report
                       (Date of earliest event reported):

                                February 22, 1999

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                         THERMO INSTRUMENT SYSTEMS INC.
             (Exact name of Registrant as specified in its charter)


Delaware                         1-9786                           04-2925809
(State or other               (Commission                      (I.R.S. Employer
jurisdiction of               File Number)                      Identification
incorporation or                                                    Number)
organization)


860 West Airport Freeway
Suite 301
Hurst, Texas                                                        76054
(Address of principal executive offices)                          (Zip Code)


                                 (817) 485-6663
                         (Registrant's telephone number
                              including area code)






Item 5.  Other Events.

     On January 7, 1999,  Thermo  Instrument  Systems  Inc.  (the  "Registrant")
announced  that it would  commence a tender  offer (the  "Offer") for all of the
outstanding  shares of  Spectra-Physics  AB, a publicly  traded company with its
shares  listed on the  Stockholm  Stock  Exchange,  and the  parent  company  of
Spectra-Physics  Lasers,  Inc., a publicly traded company with its shares listed
on NASDAQ.  On February  22,  1999,  the  Registrant  announced  that all of the
conditions  of its  Offer  had  been  satisfied  and  that  the  Offer  was then
unconditional  in all  respects.  As of February 22, 1999,  the  Registrant  had
purchased  and  received   acceptances  for  approximately   17.3  million,   or
approximately 98 percent,  of all outstanding  Spectra-Physics  AB shares,  at a
price  of 160  Swedish  krona  per  share  (approximately  $20 per  share).  The
Registrant  expects  to  acquire  any  remaining  outstanding  shares  under the
compulsory acquisition rules applicable to Swedish companies.

     The   businesses   acquired   manufacture  a  wide  range  of   laser-based
instrumentation   systems,   primarily  for  the   process-control,   industrial
measurement,   construction,   research,  commercial,  and  government  markets.
Spectra-Physics AB's revenues for 1998 were approximately $442 million.

     The  purchase  price  for the 98% of the  outstanding  shares  of  Spectra-
Physics AB that have been  purchased by the Registrant  was  approximately  $355
million.  To finance  the Offer,  the  Registrant  utilized  approximately  $155
million of available  cash and $200 million of borrowings  from Thermo  Electron
Corporation  ("Thermo  Electron"),  the  Registrant's  parent  corporation.  The
indebtedness  to  Thermo  Electron  bears  interest  at  a  variable  commercial
paper-based rate, which rate is initially 5.03%, and is due August 27, 1999.

    




     Item 7. Financial Statements, Pro Forma Financial Information and Exhibits

         (a)     Financial Statements of Business Acquired:  Not applicable. 

         (b)     Pro Forma  Financial  Information:  Not applicable.

         (c)      Exhibits: Not applicable.








                                    SIGNATURES

      Pursuant to the  requirements of the Securities  Exchange Act of 1934, the
Registrant  has duly  caused  this  report  to be  signed  on its  behalf by the
undersigned, thereunto duly authorized, on this 9th day of March, 1999.



                                                  THERMO INSTRUMENT SYSTEMS INC.


                                                  By: /s/ Theo Melas-Kyriazi
                                                      Theo Melas-Kyriazi
                                                      Chief Financial Officer