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):

                                January 21, 1997

                    ________________________________________


                         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 Number)

        1275 Hammerwood Avenue                                 94089
        Sunnyvale, CA                                          (Zip Code)

                                 (617) 622-1000
                         (Registrant's telephone number
                              including area code)
PAGE








        Item 5.   Other Events

             On January 21, 1997, Thermo Instrument Systems Inc. (the
        "Company")announced that it had commenced an all-cash tender
        offer for all of the outstanding shares of Life Sciences
        International PLC ("LSI"), a company listed on the London Stock
        Exchange, at a price of 135 pence per share (equivalent to
        approximately $2.25 per share)  The Board of Directors of LSI has
        recommended that its shareholders accept the offer. LSI has
        approximately 175 million shares outstanding.  The closing of the
        transaction is subject to certain conditions, including the
        tender of at least 90% of the LSI shares and antitrust regulatory
        clearances in the U.S., U.K. and Germany.  

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

        (c)  Exhibits

             99   Press Release dated January 21, 1997
PAGE







                                   SIGNATURES


             Pursuant to the requirements of the Securities Exchange Act
        of 1934, the Registrant has duly caused this amendment to be
        signed on its behalf by the undersigned thereunto duly
        authorized, on this 22nd day of January. 1997.


                                      THERMO INSTRUMENT SYSTEMS INC.



                                      By:  /s/Jonathan W. Painter
                                         ------------------------
                                           Jonathan W. Painter
                                           Treasurer