Filer:  Thermo Electron Corporation
                                Subject Company:  Thermo Instrument Systems Inc.
                                  Subject Company Exchange Act File No.:  1-9786
                                          Registration Statement No.:  333-35478

Press release:

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


              Thermo Electron Further Extends Exchange Offer for
                  Thermo Instrument Shares to June 29, 2000

WALTHAM, Mass., June 14, 2000 - Thermo Electron Corporation (NYSE-TMO) announced
that it has further  extended the exchange offer for Thermo  Instrument  Systems
Inc.  (ASE-THI)  common  stock until  midnight on June 29,  2000.  The offer was
extended  because  Thermo  Electron does not expect the  Securities and Exchange
Commission  (SEC) to declare Thermo  Electron's  registration  statement for the
exchange offer  effective  prior to the previously  announced  expiration  date.
Thermo Electron expects to file today an amendment to its registration statement
responding to comments from the SEC. The company may not accept shares of Thermo
Instrument  common stock tendered in the exchange  offer until the  registration
statement is declared  effective by the SEC.  Other terms and  conditions of the
exchange offer remain unchanged.

      According to a  preliminary  report from the  depositary  for the exchange
offer,  approximately  12.2 million shares of Thermo Instrument common stock had
been tendered and not withdrawn  pursuant to the exchange  offer as of the close
of business on Tuesday,  June 13, 2000. These shares  represent  approximately 9
percent of total Thermo  Instrument shares  outstanding,  and when combined with
shares held by Thermo Electron, represent approximately 98 percent.

      Because of the extension  announced  today,  holders of Thermo  Instrument
common stock may tender or withdraw  their  shares  until  midnight on Thursday,
June 29, 2000, unless the exchange offer is further extended. The exchange offer
previously had been scheduled to expire at midnight on June 16, 2000.

       On April 24, 2000,  Thermo  Electron  mailed a preliminary  prospectus to
registered  holders of Thermo Instrument shares regarding the exchange offer and
the  merger,  accompanied  by a letter of  transmittal  that  Thermo  Instrument
shareholders  can use to tender their shares in the exchange  offer.  Beneficial
owners of Thermo  Instrument shares holding in street name through their brokers
can receive the  preliminary  prospectus  and letter of  transmittal  from their
broker and should contact their broker for those documents.  In any case, copies
of the  preliminary  prospectus and letter of transmittal  may be requested from
D.F. King & Co., Inc., the information  agent for the exchange offer, by calling
(800) 290-6433.

         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 company  focused on its core  measurement  and  detection
instruments  business.   More  information  is  available  on  the  Internet  at
http://www.thermo.com.


Other Important Information:

We urge investors and security holders to read the following documents when they
become  available  regarding the exchange offer and the merger described in this
announcement, because they contain important information:

- -    Thermo Electron's preliminary prospectus, any prospectus supplement,  final
     prospectus, and other exchange offer materials.

- -    Thermo  Electron's  registration  statement on form S-4 and Schedule TO, as
     amended,  which contain or  incorporate  by reference the documents  listed
     above and other information.

- -    Thermo  Instrument's   solicitation/recommendation  statement  on  schedule
     14D-9.

These  documents and  amendments to these  documents  have been or will be filed
with the SEC. When these and other documents are filed with the SEC, they may be
obtained for free at the SEC's Web site at www.sec.gov.  You may also obtain for
free each of these documents,  when available, from us. 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 1, 2000. These include risks and  uncertainties  relating to:
the company's corporate  reorganization,  acquisition strategy, growth strategy,
international operations, product development and technological change, possible
changes  in  governmental  regulations,  changes  in both  capital  spending  by
commercial  customers  and  government  funding  policies,   and  dependence  on
intellectual property rights.