SECURITIES AND EXCHANGE COMMISSION
                             WASHINGTON, D.C. 20549

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



                                 SCHEDULE 14D-9



          SOLICITATION/RECOMMENDATION STATEMENT UNDER SECTION 14(d)(4)
                     OF THE SECURITIES EXCHANGE ACT OF 1934



                         Thermo Instrument Systems Inc.
                         ------------------------------
                            (Name of Subject Company)

                         Thermo Instrument Systems Inc.
                        -------------------------------
                      (Name of Person(s) Filing Statement)


                          Common Stock, $.10 par value
                       ---------------------------------
                         (Title of Class of Securities)


                                   883559 10 6
                            -----------------------
                      (CUSIP Number of Class of Securities)

                             Seth H. Hoogasian, Esq.
                         c/o Thermo Electron Corporation
                                 81 Wyman Street
                        Waltham, Massachusetts 02454-9046
                                 (781) 622-1000
                           --------------------------
(Name, Address, and Telephone Number of Person Authorized to Receive Notices and
          Communications on Behalf of the Person(s) Filing Statement)


[X] Check the box if the filing relates solely to preliminary communications
made before the commencement of a tender offer.





Investor Contact: 781-622-1111
Media Contact: 781-622-1252

        Thermo Instrument to Take Additional Public Subsidiaries Private;
               Announces Thermo Electron's Proposed Exchange Offer


WALTHAM, Mass., January 31, 2000 - Thermo Instrument Systems Inc. (ASE-THI)
announced today that it plans to take private Thermo Optek Corporation,
ThermoQuest Corporation, Thermo BioAnalysis Corporation, Metrika Systems
Corporation, and ONIX Systems Inc. In addition, Thermo Instrument announced that
its parent company, Thermo Electron Corporation (NYSE-TMO), plans to take it
private. These actions are part of a major reorganization plan under which
Thermo Electron will spin in, spin off, and sell various businesses to focus
solely on its core measurement and detection instruments business.

         Because Thermo Instrument currently owns more than 90 percent of the
outstanding shares of Thermo Optek and ThermoQuest common stock, these two
companies are expected to be spun in for cash through a "short-form" merger, at
$15.00 and $17.00 per share, respectively.

         In addition, Thermo Instrument will make cash tender offers of $28.00
per share for Thermo BioAnalysis, $9.00 per share for Metrika Systems, and $9.00
per share for ONIX Systems, in order to bring its own equity ownership in each
of these companies to at least 90 percent. If successful, each of these
companies would then be spun into Thermo Instrument through a short-form merger
at the same cash prices as the tender offers.

         Thermo Instrument currently owns approximately 67.3 percent, 70.5
percent, and 80.3 percent of the outstanding shares of Thermo BioAnalysis,
Metrika Systems, and ONIX Systems common stock, respectively. Thermo Electron,
which currently owns approximately 20.8 percent, 8.5 percent, and 2.1 percent of
the outstanding shares of Thermo BioAnalysis, Metrika Systems, and ONIX Systems
common stock, respectively, will tender its shares to Thermo Instrument in these
tender offers.

         Following these tender offers, Thermo Instrument, in turn, would be
taken private. Thermo Electron has announced that it plans to conduct an
exchange offer for any and all of the outstanding shares of Thermo Instrument
common stock held by minority shareholders. In the exchange offer, holders of
Thermo Instrument common stock would receive shares of Thermo Electron common
stock in exchange for their Thermo Instrument shares. Thermo Electron expects to
announce the exchange ratio for this transaction shortly after Thermo Instrument
conducts the tender offers for Thermo BioAnalysis, Metrika Systems, and ONIX
Systems.

         Thermo Electron, which currently owns approximately 87.8 percent of the
outstanding shares of Thermo Instrument common stock, will condition the
exchange offer on receiving acceptances from holders of enough shares so that,
when combined with its current share ownership, Thermo Electron's ownership
reaches at least 90 percent. If Thermo Electron achieves this
90-percent-ownership threshold, it will acquire all remaining outstanding shares
of Thermo Instrument through a short-form merger. In the short-form merger,
minority shareholders who do not participate in the exchange offer would also
receive shares of Thermo Electron common stock in exchange for their Thermo
Instrument common stock at the same ratio.

         The tender offers and exchange offer will require Securities and
Exchange Commission clearance of necessary filings; the exchange offer will
require establishment of the exchange ratio. The short-form

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merger would not require Thermo Instrument board or shareholder approval. In
addition, depending on the exchange ratio that is set and the number of Thermo
Electron shares outstanding at the time of the transaction, the issuance of
Thermo Electron common stock in the Thermo Instrument spin-in may require
approval of Thermo Electron's shareholders, according to New York Stock Exchange
rules.

         Thermo Instrument plans to conduct its subsidiary tender offers during
the second quarter of 2000. If Thermo Instrument successfully obtains ownership
of at least 90 percent of the outstanding Thermo BioAnalysis, Metrika Systems,
and ONIX Systems shares, it expects to complete these spin-ins by the end of the
second quarter of 2000. The Thermo Optek and ThermoQuest transactions are also
expected to be completed by the end of the second quarter of 2000. Thermo
Electron plans to conduct the exchange offer for Thermo Instrument's common
stock during the third quarter of 2000. If Thermo Electron successfully obtains
ownership of at least 90 percent of the outstanding Thermo Instrument shares, it
expects to complete the spin-in of Thermo Instrument by the end of the third
quarter of 2000.

         Obligations under Thermo Instrument's 4% convertible subordinated
debentures due January 15, 2005, and its 4 1/2% convertible senior debentures
due October 15, 2003, would be assumed by Thermo Electron in the short-form
merger, and the debentures would be convertible into Thermo Electron common
stock.

         Spectra-Physics Lasers, Inc., acquired indirectly by Thermo Instrument
as part of its February 1999 acquisition of Spectra-Physics AB, will remain a
public subsidiary while Thermo Instrument and Thermo Electron continue to
evaluate the Spectra-Physics Lasers business. Thermo Instrument owns
approximately 80.4 percent of the outstanding shares of Spectra-Physics Lasers
common stock.

         Thermo Instrument Systems Inc. is a leading provider of analytical
instruments used to identify complex chemical compounds, toxic metals, and other
elements in a broad range of liquids and solids. The company also develops and
manufactures instruments used to monitor radioactivity and air pollution; life
science instruments and consumables; and imaging, inspection, measurement, and
control instruments for various industrial processes. More information is
available on the Internet at http://www.thermo.com/subsid/thi1.html.

OTHER IMPORTANT INFORMATION:
THE TENDER OFFERS DESCRIBED IN THIS ANNOUNCEMENT FOR THE OUTSTANDING SHARES OF
THERMO BIOANALYSIS, METRIKA SYSTEMS, AND ONIX SYSTEMS COMMON STOCK HAVE NOT YET
COMMENCED. AS SOON AS THE TENDER OFFERS COMMENCE, WE WILL FILE TENDER OFFER
STATEMENTS WITH THE SECURITIES AND EXCHANGE COMMISSION. YOU SHOULD READ THE
TENDER OFFER STATEMENTS WHEN THEY BECOME AVAILABLE BECAUSE THEY WILL CONTAIN
IMPORTANT INFORMATION ABOUT THE TENDER OFFERS. YOU CAN OBTAIN THE TENDER OFFER
STATEMENTS AND OTHER DOCUMENTS THAT ARE FILED WITH THE SECURITIES AND EXCHANGE
COMMISSION FOR FREE ON THE SECURITIES AND EXCHANGE COMMISSION'S WEB SITE AT
http://www.sec.gov. IF YOU WRITE US OR CALL US, WE WILL SEND YOU THESE DOCUMENTS
FOR FREE WHEN THEY ARE AVAILABLE:


         * TENDER OFFER STATEMENTS (EXCEPT FOR EXHIBITS)
         * OFFERS TO PURCHASE
         * LETTERS OF TRANSMITTAL
         * NOTICES OF GUARANTEED DELIVERY


                                     -more-







YOU CAN CALL US AT (781) 622-1111 OR WRITE TO US AT:

         INVESTOR RELATIONS DEPARTMENT
         THERMO INSTRUMENT SYSTEMS INC.
         81 WYMAN STREET, P.O. BOX 9046
         WALTHAM, MA 02454-9046

THE EXCHANGE OFFER BY THERMO ELECTRON FOR OUR COMMON STOCK DESCRIBED IN THIS
ANNOUNCEMENT HAS NOT YET COMMENCED. ONCE THE EXCHANGE OFFER COMMENCES, WE WILL
FILE A SOLICITATION/RECOMMENDATION STATEMENT WITH THE SECURITIES AND EXCHANGE
COMMISSION. YOU SHOULD READ THIS DOCUMENT WHEN IT BECOMES AVAILABLE BECAUSE IT
WILL CONTAIN IMPORTANT INFORMATION ABOUT THE EXCHANGE OFFER. YOU CAN OBTAIN THE
SOLICITATION/RECOMMENDATION STATEMENT AND OTHER DOCUMENTS THAT WILL BE FILED
WITH THE SECURITIES AND EXCHANGE COMMISSION FOR FREE WHEN THEY ARE AVAILABLE ON
THE SECURITIES AND EXCHANGE COMMISSION'S WEB SITE AT http://www.sec.gov. ALSO,
IF YOU WRITE US OR CALL US AT THE ABOVE ADDRESS AND PHONE NUMBER, WE WILL SEND
YOU THE SOLICITATION/RECOMMENDATION STATEMENT FOR FREE WHEN IT IS AVAILABLE.

The following constitutes a "Safe Harbor" statement under the Private Securities
Litigation Reform Act of 1995: This press release contains forward-looking
statements that involve a number of risks and uncertainties. Important factors
that could cause actual results to differ materially from those indicated by
such forward-looking statements are set forth under the heading "Forward-looking
Statements" in Exhibit 13 to the company's annual report on Form 10-K for the
year ended January 2, 1999. These include risks and uncertainties relating to:
the company's acquisition and spinout strategies, competition and technological
change, intellectual property rights and litigation, dependence on certain key
industries and international operations, possible changes in governmental
regulations, capital spending and government funding policies, and the potential
impact of the year 2000 on processing date-sensitive information.



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