Filer:  Thermo Electron Corporation
                                Subject Company:  Thermo Instrument Systems Inc.
                                  Subject Company Exchange Act File No.:  1-9786
                                   Registration Statement No.:  333-____________

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

                  Thermo Electron Announces Exchange Ratios
            for its Thermo Instrument and Thermedics Subsidiaries

WALTHAM, Mass., March 8, 2000 - Thermo Electron Corporation (NYSE-TMO) announced
today that, in connection with its regularly scheduled board meeting, it has set
exchange ratios for its Thermo Instrument  Systems Inc. (ASE-THI) and Thermedics
Inc.  (ASE-TMD)  subsidiaries,  and is proceeding with its previously  announced
plan to take these two  companies  private.  Under the plan,  Thermo  Instrument
shareholders  would  receive  0.85 shares of Thermo  Electron  common  stock and
Thermedics  shareholders 0.45 shares of Thermo Electron common stock in exchange
for their Thermo Instrument or Thermedics common stock, respectively.

      Thermo  Electron  expects  to  conduct  exchange  offers  for  any and all
outstanding   Thermo   Instrument  and   Thermedics   shares  held  by  minority
shareholders  during the second quarter of 2000. Thermo Electron  currently owns
approximately 88.7 percent of the outstanding shares of Thermo Instrument common
stock and 75.7 percent of Thermedics,  and will condition each exchange offer on
receiving  acceptances from holders of enough shares so that, when combined with
its current share ownership,  Thermo  Electron's  ownership in each of these two
companies reaches at least 90 percent. In each case, if Thermo Electron achieves
this  90-percent-ownership  threshold, it will acquire all remaining outstanding
shares of Thermo  Instrument  and Thermedics  common stock through  "short-form"
mergers. In the short-form mergers, minority shareholders who do not participate
in the exchange offers would also receive shares of Thermo Electron common stock
at the same exchange ratio that is being offered in the exchange offers.

      Upon completion of the respective spin-ins,  outstanding obligations under
the Thermo Instrument and Thermedics  convertible  debentures will be assumed by
Thermo  Electron,  and these  debentures  will  become  convertible  into Thermo
Electron common stock.

      Each of the exchange  offers and proposed  subsequent  short-form  mergers
require Securities and Exchange Commission  clearance of necessary filings;  the
short-form  mergers would not require Thermo  Instrument or Thermedics  board or
shareholder approval.


      In each case,  if Thermo  Electron  successfully  obtains  ownership of at
least 90 percent of the outstanding  Thermo Instrument and Thermedics shares, it
expects to complete the spin-ins by the end of the second quarter of 2000.

      Thermo  Electron  Corporation  is a leading  provider  of  analytical  and
monitoring instruments used in a broad range of applications, from life sciences
research to  telecommunications  to food and beverage  production.  In addition,
Thermo  Electron  serves  the  healthcare  market  through a family  of  medical
products,  and is a major  producer  of paper  recycling  systems  and  provides
water-clarification  and fiber-recovery  products and services.  As announced on
January 31, 2000,  the company has initiated a major  reorganization  that would
transform it into one publicly traded entity focused on its core measurement and
detection  instruments  business.  The  company's  medical  products  and  paper
recycling   businesses  will  be  spun  off  as  dividends  to  Thermo  Electron
shareholders.    More    information   is   available   on   the   Internet   at
http://www.thermo.com.
                                    - more -

Other Important Information:
The transactions described in this announcement have not yet commenced.  As soon
as we commence our exchange offers for Thermo Instrument and Thermedics, we will
file tender offer  statements and  registration  statements on Form S-4 with the
Securities  and  Exchange  Commission  (SEC).  You  should  read  each of  these
documents  when  they  become  available  because  they will  contain  important
information  about the  proposed  transactions.  You can obtain the tender offer
statements, registration statements, and other documents that are filed with the
SEC  for   free   when   they  are   available   on  the   SEC'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, as applicable to the particular transaction:

    Tender Offer Statements (except for exhibits)
    Registration Statements on Form S-4
    Offers to Purchase
    Letters of Transmittal
    Notices of Guaranteed Delivery

You can call us at (781) 622-1111 or write to us at:

      Investor Relations Department
      Thermo Electron Corporation
      81 Wyman Street, P.O. Box 9046
      Waltham, MA 02454-9046

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  spinout and acquisition  strategies,  competition,  international
operations,  technological change, possible changes in governmental regulations,
capital spending and government funding policies, and dependence on intellectual
property rights.


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