THERMO ELECTRON CORP
S-4, 2000-04-24
MEASURING & CONTROLLING DEVICES, NEC
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<PAGE>   1

     AS FILED WITH THE SECURITIES AND EXCHANGE COMMISSION ON APRIL 24, 2000

                                                      REGISTRATION NO. 333-
- --------------------------------------------------------------------------------
- --------------------------------------------------------------------------------

                       SECURITIES AND EXCHANGE COMMISSION
                             WASHINGTON, D.C. 20549
                            ------------------------

                                    FORM S-4
                             REGISTRATION STATEMENT
                                     UNDER
                           THE SECURITIES ACT OF 1933
                            ------------------------

                          THERMO ELECTRON CORPORATION
             (EXACT NAME OF REGISTRANT AS SPECIFIED IN ITS CHARTER)

<TABLE>
<S>                                    <C>                                    <C>
               DELAWARE                                 3569                                04-2209186
     (STATE OR OTHER JURISDICTION           (PRIMARY STANDARD INDUSTRIAL                 (I.R.S. EMPLOYER
  OF INCORPORATION OR ORGANIZATION)         CLASSIFICATION CODE NUMBER)               IDENTIFICATION NUMBER)
</TABLE>

                                81 WYMAN STREET
                       WALTHAM, MASSACHUSETTS 02454-9046
                                 (781) 622-1000
              (ADDRESS, INCLUDING ZIP CODE, AND TELEPHONE NUMBER,
       INCLUDING AREA CODE, OF REGISTRANT'S PRINCIPAL EXECUTIVE OFFICES)
                            ------------------------

                          SANDRA L. LAMBERT, SECRETARY
                          THERMO ELECTRON CORPORATION
                                81 WYMAN STREET
                       WALTHAM, MASSACHUSETTS 02454-9046
                                 (781) 622-1000
           (NAME, ADDRESS, INCLUDING ZIP CODE, AND TELEPHONE NUMBER,
                   INCLUDING AREA CODE, OF AGENT FOR SERVICE)
                            ------------------------

                                   COPIES TO:

<TABLE>
<S>                                                      <C>
                SETH H. HOOGASIAN, ESQ.                                   DAVID E. REDLICK, ESQ.
                    GENERAL COUNSEL                                         HALE AND DORR LLP
              THERMO ELECTRON CORPORATION                                    60 STATE STREET
                    81 WYMAN STREET                                    BOSTON, MASSACHUSETTS 02109
           WALTHAM, MASSACHUSETTS 02454-9046                                  (617) 526-6000
                     (781) 622-1000
</TABLE>

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

    APPROXIMATE DATE OF COMMENCEMENT OF PROPOSED SALE TO THE PUBLIC:  As
promptly as practicable after this Registration Statement becomes effective and
the other conditions to the exchange offer are met or waived.
    If the securities being registered on this form are being offered in
connection with the formation of a holding company and there is compliance with
General Instruction G, check the following box. [ ]
    If this form is filed to register additional securities for an offering
pursuant to Rule 462(b) under the Securities Act, check the following box and
list the Securities Act registration statement number of the earlier effective
registration statement for the same offering. [ ]
    If this form is a post-effective amendment filed pursuant to Rule 462(d)
under the Securities Act, check the following box and list the Securities Act
registration statement number of the earlier effective registration statement
for the same offering. [ ]
                            ------------------------

                        CALCULATION OF REGISTRATION FEE

<TABLE>
<CAPTION>
- ---------------------------------------------------------------------------------------------------------------------------------
- ---------------------------------------------------------------------------------------------------------------------------------
                                                      AMOUNT            PROPOSED MAXIMUM     PROPOSED MAXIMUM
           TITLE OF EACH CLASS OF                      TO BE           OFFERING PRICE PER   AGGREGATE OFFERING      AMOUNT OF
       SECURITIES TO BE REGISTERED(1)              REGISTERED(2)             SHARE               PRICE(3)       REGISTRATION FEE
- ---------------------------------------------------------------------------------------------------------------------------------
<S>                                           <C>                     <C>                  <C>                  <C>
Common Stock, par value $1.00 per share
  (including preferred stock purchase rights
  attached thereto)(4).......................    17,394,047 shares            N/A              $381,773,739         $100,789
- ---------------------------------------------------------------------------------------------------------------------------------
- ---------------------------------------------------------------------------------------------------------------------------------
</TABLE>

(1) This registration statement relates to securities of the registrant
    exchangeable for shares of common stock of Thermo Instrument Systems Inc., a
    Delaware corporation, par value $.10 per share, in the exchange offer by the
    registrant for all the outstanding shares of Thermo Instrument common stock
    and in the proposed merger of Thermo Instrument with and into the
    registrant.

(2) Based on the maximum number of shares expected to be issued in connection
    with the exchange offer and the merger, calculated as the product of (a)
    20,463,584, representing the aggregate number of shares of Thermo Instrument
    common stock outstanding on March 31, 2000 (other than shares owned by the
    registrant) plus the number of such shares for which options were
    outstanding on March 31, 2000 and (b) the exchange ratio of 0.85 shares of
    the registrant's common stock for each share of Thermo Instrument common
    stock.

(3) Estimated solely for the purpose of calculating the registration fee in
    accordance with Rules 457(c) and 457(f) under the Securities Act of 1933,
    based upon (a) $18.65625, the average of the high and low prices per share
    of Thermo Instrument common stock on April 20, 2000 as reported in the
    consolidated transaction reporting system, multiplied by (b) 20,463,584,
    representing the aggregate number of shares of Thermo Instrument common
    stock outstanding on March 31, 2000 (other than shares owned by the
    registrant) plus the number of such shares for which options were
    outstanding on March 31, 2000.

(4) Shares of Thermo Electron common stock being registered hereby are
    accompanied by Thermo Electron's preferred stock purchase rights. Until the
    occurrence of certain prescribed events, such rights are not exercisable,
    are evidenced by the certificate for the Thermo Electron common stock and
    will be transferred along with and only with the Thermo Electron common
    stock.
                            ------------------------

    THE REGISTRANT HEREBY AMENDS THIS REGISTRATION STATEMENT ON SUCH DATE OR
DATES AS MAY BE NECESSARY TO DELAY ITS EFFECTIVE DATE UNTIL THE REGISTRANT SHALL
FILE A FURTHER AMENDMENT WHICH SPECIFICALLY STATES THAT THIS REGISTRATION
STATEMENT SHALL THEREAFTER BECOME EFFECTIVE IN ACCORDANCE WITH SECTION 8(a) OF
THE SECURITIES ACT OF 1933 OR UNTIL THE REGISTRATION STATEMENT SHALL BECOME
EFFECTIVE ON SUCH DATE AS THE SECURITIES AND EXCHANGE COMMISSION, ACTING
PURSUANT TO SECTION 8(a), MAY DETERMINE.

- --------------------------------------------------------------------------------
- --------------------------------------------------------------------------------
<PAGE>   2

     THE INFORMATION CONTAINED IN THIS PROSPECTUS IS NOT COMPLETE AND MAY BE
     CHANGED. WE MAY NOT SELL THESE SECURITIES UNTIL THE RELATED REGISTRATION
     STATEMENT FILED WITH THE SECURITIES AND EXCHANGE COMMISSION IS EFFECTIVE.
     THIS PROSPECTUS IS NOT AN OFFER TO SELL THESE SECURITIES AND WE ARE NOT
     SOLICITING AN OFFER TO BUY THESE SECURITIES IN ANY STATE WHERE THE OFFER OR
     SALE IS NOT PERMITTED.

                  Subject to Completion, dated April 24, 2000

                          THERMO ELECTRON CORPORATION

                               OFFER TO EXCHANGE
                          0.85 SHARES OF COMMON STOCK
                                       OF
                          THERMO ELECTRON CORPORATION
                                      FOR
                     EACH OUTSTANDING SHARE OF COMMON STOCK
                                       OF
                         THERMO INSTRUMENT SYSTEMS INC.
                            ------------------------

                                     MERGER
                                       OF
                         THERMO INSTRUMENT SYSTEMS INC.
                                      INTO
                          THERMO ELECTRON CORPORATION
                            ------------------------

                        THE OFFER AND WITHDRAWAL RIGHTS
               WILL EXPIRE AT 12:00 MIDNIGHT, NEW YORK CITY TIME,
             ON FRIDAY, MAY 19, 2000, UNLESS THE OFFER IS EXTENDED.

    We are offering to exchange 0.85 shares of Thermo Electron Corporation
common stock for each outstanding share of common stock of Thermo Instrument
Systems Inc. that stockholders of Thermo Instrument validly tender, and do not
properly withdraw, before the exchange offer expires. You may withdraw shares of
Thermo Instrument common stock that you tender pursuant to this exchange offer
at any time prior to the expiration of the exchange offer.
    If we complete the exchange offer, we intend to cause Thermo Instrument to
merge into Thermo Electron. In the merger, we will issue 0.85 shares of Thermo
Electron common stock for each outstanding share of Thermo Instrument common
stock, subject to any applicable appraisal rights. This prospectus also relates
to the shares of our common stock that we would issue in the merger.
    You should read this prospectus carefully. It sets forth the terms and
conditions of the exchange offer and the merger. It also describes our and
Thermo Instrument's businesses and finances. We have prepared this prospectus so
that you will have the information necessary to make a decision about the
exchange offer and whether to pursue your appraisal rights in connection with
the merger.
    OUR OBLIGATION TO EXCHANGE THERMO ELECTRON COMMON STOCK FOR THERMO
INSTRUMENT COMMON STOCK IS SUBJECT TO THE IMPORTANT CONDITIONS LISTED BELOW
UNDER "THE EXCHANGE OFFER -- CONDITIONS OF THE OFFER." THESE INCLUDE THE
CONDITION THAT STOCKHOLDERS OF THERMO INSTRUMENT VALIDLY TENDER, AND DO NOT
WITHDRAW, A SUFFICIENT NUMBER OF SHARES OF THERMO INSTRUMENT COMMON STOCK WHICH,
TOGETHER WITH SHARES OF THERMO INSTRUMENT COMMON STOCK OWNED BY US, CONSTITUTE
AT LEAST 90% OF THE OUTSTANDING SHARES OF THERMO INSTRUMENT COMMON STOCK UPON
THE EXPIRATION OF THE EXCHANGE OFFER. AS OF MARCH 31, 2000, WE OWNED 114,602,387
SHARES OF THERMO INSTRUMENT COMMON STOCK, REPRESENTING APPROXIMATELY 88.6% OF
THE OUTSTANDING SHARES OF THERMO INSTRUMENT COMMON STOCK ON THAT DATE.
    Our common stock trades on the New York Stock Exchange under the symbol
"TMO." On April 20, 2000, the last reported sale price for our common stock was
$19.1875. Thermo Instrument common stock trades on the American Stock Exchange
under the symbol "THI." On April 20, 2000, the last reported sale price for
Thermo Instrument common stock was $18.75.
    An investment in our common stock involves a high degree of risk. You should
carefully review the "Risk Factors" beginning on page 15 for a discussion of
important factors that you should consider in connection with our offer, the
merger and an investment in our common stock.
                            ------------------------

    We incorporate by reference into this prospectus important business and
financial information about Thermo Instrument and about us. This information is
not included in, or delivered with, this prospectus.
    We will provide you with a copy of any and all of the information that we
incorporate by reference in this prospectus, without charge, upon written or
oral request. If we do not specifically incorporate by reference in this
prospectus exhibits to the documents that we incorporate in this prospectus,
then we will not provide copies of those exhibits. TO OBTAIN TIMELY DELIVERY,
YOU MUST REQUEST THE INFORMATION NO LATER THAN MAY 12, 2000.
    You should direct any requests for documents relating to Thermo Instrument
or to us to: Sandra L. Lambert, Corporate Secretary, Thermo Electron
Corporation, 81 Wyman Street, Waltham, Massachusetts 02454 (telephone:
781-622-1000; facsimile: 781-768-6620).
                            ------------------------

    NEITHER THE SECURITIES AND EXCHANGE COMMISSION NOR ANY STATE SECURITIES
COMMISSION HAS APPROVED OR DISAPPROVED OF THESE SECURITIES OR PASSED UPON THE
ADEQUACY OR ACCURACY OF THIS PROSPECTUS. ANY REPRESENTATION TO THE CONTRARY IS A
CRIME.
                            ------------------------

               The date of this prospectus is             , 2000
<PAGE>   3

                               TABLE OF CONTENTS

<TABLE>
<S>                                                           <C>
QUESTIONS AND ANSWERS ABOUT THE EXCHANGE OFFER AND THE
  MERGER....................................................    1
SUMMARY.....................................................    4
RISK FACTORS................................................   15
FORWARD-LOOKING STATEMENTS..................................   21
INFORMATION ABOUT THERMO ELECTRON AND THERMO INSTRUMENT.....   22
BACKGROUND TO THE EXCHANGE OFFER AND THE MERGER.............   23
THE EXCHANGE OFFER..........................................   31
MARKET PRICES AND DIVIDENDS.................................   46
THE MERGER; APPRAISAL RIGHTS................................   47
FEDERAL INCOME TAX CONSEQUENCES.............................   49
COMPARISON OF THE RIGHTS OF HOLDERS OF OUR COMMON STOCK AND
  THE RIGHTS OF HOLDERS OF THERMO INSTRUMENT COMMON STOCK...   51
TRANSACTIONS WITH RELATED PARTIES...........................   57
LEGAL MATTERS...............................................   57
EXPERTS.....................................................   57
WHERE YOU CAN FIND MORE INFORMATION.........................   58
THERMO ELECTRON CORPORATION PRO FORMA CONSOLIDATED CONDENSED
  FINANCIAL STATEMENTS (UNAUDITED)..........................  F-1
ANNEX A.....................................................  A-1
ANNEX B.....................................................  B-1
ANNEX C.....................................................  C-1
</TABLE>

     THIS PROSPECTUS INCORPORATES IMPORTANT BUSINESS AND FINANCIAL INFORMATION
ABOUT THERMO ELECTRON AND THERMO INSTRUMENT THAT IS NOT INCLUDED OR DELIVERED
WITH THE PROSPECTUS. YOU MAY OBTAIN THIS INFORMATION WITHOUT CHARGE TO YOU UPON
WRITTEN OR ORAL REQUEST. YOU MUST ADDRESS YOUR REQUEST TO SANDRA L. LAMBERT,
CORPORATE SECRETARY, THERMO ELECTRON CORPORATION, 81 WYMAN STREET, WALTHAM,
MASSACHUSETTS 02454-9046, TELEPHONE (781) 622-1000. TO OBTAIN TIMELY DELIVERY,
YOU MUST REQUEST THE INFORMATION NO LATER THAN MAY 12, 2000.
<PAGE>   4

         QUESTIONS AND ANSWERS ABOUT THE EXCHANGE OFFER AND THE MERGER

Q: What is the exchange offer?

A: We are offering to exchange shares of our common stock for all of the
outstanding shares of Thermo Instrument common stock that we do not already own.

Q: What is the exchange ratio?

A: We are offering to exchange 0.85 shares of our common stock for each share of
Thermo Instrument common stock that stockholders of Thermo Instrument validly
tender in the exchange offer. This exchange ratio represents a valuation of the
Thermo Instrument common stock at a premium of 2.3% over its last reported sale
price on March 7, 2000, the day before we announced the exchange ratio, based on
the last reported sale price of our common stock on that date.

Q: What happens to any fractional shares?

A: We will not issue fractional shares of our common stock in the exchange offer
or the short-form merger in which we will cause Thermo Instrument to merge into
Thermo Electron. Instead, we will pay you cash in an amount equal to $19.1875
per whole share of our common stock for your fractional shares.

Q: How do I participate in the exchange offer?

A: To tender your shares, you should:

     - If you hold your shares in your own name, complete and sign the enclosed
       letter of transmittal. Once completed, you should return it with your
       share certificates to American Stock Transfer & Trust Company, the
       depositary for the exchange offer, at one of its addresses on the back
       cover of this prospectus.

     - If you hold your shares in "street name" through a broker, ask your
       broker to tender your shares.

Q: Will I have to pay any fees or commissions?

A: If you are the record owner of your shares and you tender your shares in the
exchange offer, you will not have to pay brokerage fees or incur similar
expenses. If you own your shares through a broker or other nominee and your
broker tenders the shares on your behalf, your broker may charge you a fee for
doing so. You should consult your broker or nominee to determine whether any
charges will apply.

Q: Can I withdraw shares that I have tendered?

A: You may withdraw shares that you have tendered at any time on or before May
19, 2000, or, if we extend the exchange offer, before the exchange offer
expires. Unless we have accepted your shares for exchange on or before June 22,
2000, you may also withdraw shares you have tendered which we have not accepted
for exchange at any time after that date.

Q: What are the conditions to the exchange offer?

A: Our obligation to complete the exchange offer is subject to a number of
conditions. Thermo Instrument stockholders must tender, and not withdraw, a
sufficient number of shares of Thermo Instrument common

                                        1
<PAGE>   5

stock so that when the exchange offer expires we own at least 90% of Thermo
Instrument's outstanding shares. As of March 31, 2000:

<TABLE>
<S>                                                             <C>
Our ownership of Thermo Instrument common stock as a
  percentage of outstanding shares was:.....................        88.6%
Based on that percentage, the number of shares of Thermo
  Instrument common stock that Thermo Instrument
  stockholders must tender for us to meet the 90% condition
  is:.......................................................    1,822,900
Our ownership of Thermo Instrument common stock as a
  percentage of the shares of Thermo Instrument common stock
  then outstanding, assuming that optionholders had
  exercised all outstanding Thermo Instrument options issued
  by Thermo Instrument or by us and debenture holders did
  not convert any of the two issues of Thermo Instrument's
  outstanding $422.5 million total principal amount of
  convertible debentures into Thermo Instrument common stock
  at their conversion prices of $35.65 per share and $34.456
  per share, would have been:...............................        84.8%
Based on that percentage, the number of shares of Thermo
  Instrument common stock that Thermo Instrument
  stockholders must tender for us to meet the 90% condition
  is:.......................................................    6,967,438
</TABLE>

Our obligation to complete the exchange offer is also subject to the other
conditions described below under "The Exchange Offer -- Conditions Of The
Offer."

Q: How long will it take to complete the exchange offer and the merger?

A: The exchange offer will expire at 12:00 midnight on May 19, 2000. We can
elect at any time to extend the exchange offer. We will need to extend the
exchange offer if the registration statement of which this prospectus is a part
is not effective by May 19, 2000. If we complete the exchange offer, we expect
to close the merger as promptly as practicable after we have completed the
exchange offer.

Q: What will happen after you complete the exchange offer?

A: We plan to take Thermo Instrument private by acquiring all of the outstanding
shares of Thermo Instrument common stock that we do not currently own. The
exchange offer is the first step in this plan. If we complete the exchange
offer, we will own at least 90% of Thermo Instrument's outstanding shares. We
would then cause Thermo Instrument to merge with and into Thermo Electron in a
so-called "short-form" merger. A short-form merger would not require approval of
Thermo Instrument's board of directors or the stockholders of Thermo Instrument
other than Thermo Electron.

Q. What will happen to my shares if you complete the exchange offer and I have
not tendered my shares?

A: If you do not tender your shares of Thermo Instrument common stock and we
complete the exchange offer, your shares will remain outstanding until the
closing of the merger of Thermo Instrument and Thermo Electron. After the
merger, each of your shares will be converted, subject to appraisal rights, into
the right to receive 0.85 shares of our common stock.

Q: What are the federal income tax consequences to me of the exchange offer and
the merger?

A: For federal income tax purposes, your receipt of shares of our common stock
in the exchange offer or the merger would be tax-free. However, your receipt of
cash in lieu of fractional shares of our common stock in the exchange offer or
the merger would be taxable to you.

                                        2
<PAGE>   6

Q: Is Thermo Electron's financial condition relevant to my decision to tender my
   shares in the exchange offer or to pursue my appraisal rights in connection
   with the merger?

A: Yes. If you tender your shares of Thermo Instrument common stock and we close
the exchange offer, you will receive shares of our common stock in exchange for
your Thermo Instrument common stock. Similarly, if you do not tender your shares
of Thermo Instrument common stock, you will receive shares of our common stock
in the merger unless you pursue your appraisal rights. You should consider our
financial condition before you decide to become one of our stockholders through
the exchange offer or the merger. In considering our financial condition, you
should review this prospectus and the documents that we incorporate by reference
in this prospectus, because they contain detailed business, financial and other
information about us.

Q: Where can I find more information about Thermo Electron and Thermo
Instrument?

A: You can find more information about Thermo Electron and Thermo Instrument
from various documents that we file and that Thermo Instrument files with the
SEC. You can obtain copies of these documents in the manner described under
"Where You Can Find More Information" on page 58.

Q: What should I do if I have questions?

A: If you have any questions about the exchange offer, you should call our
information agent, D.F. King & Co., Inc. If you are a banker or broker, call
collect at (212) 269-5550. All others should call toll-free at (800) 290-6433.

                                        3
<PAGE>   7

                                    SUMMARY

     Before you make any decision with respect to the exchange offer or the
merger, you should read the following summary together with the more detailed
information included elsewhere, or that we incorporate by reference, in this
prospectus.

- - THE COMPANIES

     - Thermo Electron Corporation (page 22).  Thermo Electron Corporation, a
       Delaware corporation, develops, manufactures and sells measurement and
       detection instruments that our customers use to collect, monitor and
       analyze data. We conduct this business in significant part through Thermo
       Instrument. As discussed below, we are in the process of spinning off a
       business that serves the healthcare industry with a range of medical
       products for diagnosis and monitoring, and our paper recycling and
       papermaking equipment business. We are also in the process of selling
       various non-core businesses. We plan to take Thermo Ecotek Corporation,
       our electric power generation business, private. Although we no longer
       consider it a core business under our new strategy, we expect to retain
       Thermo Ecotek after it is taken private while we continue to evaluate how
       to best exit that business and create maximum value for our stockholders.

      Our common stock is listed on the New York Stock Exchange under the symbol
      "TMO." Our principal executive offices are located at 81 Wyman Street,
      P.O. Box 9046, Waltham, Massachusetts 02454-9046, and our telephone number
      is (781) 622-1000.

     - Thermo Instrument Systems Inc. (page 22).  Thermo Instrument Systems
       Inc., a Delaware corporation, is a worldwide leader in developing,
       manufacturing and marketing measurement instruments used to monitor,
       collect and analyze information. Thermo Instrument's customers use these
       systems for multiple applications in a range of industries, including
       industrial processing, food and beverage production, life sciences
       research and medical diagnostics. Thermo Instrument common stock is
       listed on the American Stock Exchange under the symbol "THI." Thermo
       Instrument's principal executive offices are located at 81 Wyman Street,
       P.O. Box 9046, Waltham, Massachusetts 02454-9046, and its telephone
       number is (781) 622-1000.

     - Affiliation of Thermo Instrument and Thermo Electron (pages 25 and
       27).  We own a majority of Thermo Instrument's common stock. Several
       officers of Thermo Instrument are also officers or directors of Thermo
       Electron. See "Background To The Exchange Offer And The Merger."

     - The Thermo Electron reorganization (page 23).  On January 31, 2000, we
       announced that our board of directors had authorized our management to
       proceed with a major reorganization of our operations. As part of this
       reorganization, we plan to:

        - acquire the public minority interest in most of our subsidiaries that
          have minority investors;

        - spin off a business that serves the healthcare industry with a range
          of medical products for diagnosis and monitoring, and our paper
          recycling and papermaking equipment business; and

        - divest a variety of non-core businesses.

      The primary goal of the reorganization is to allow us to focus on our core
      business and each of our spun-off subsidiaries to focus on its core
      business. The purpose of the exchange offer and merger described in this
      prospectus is to allow us to acquire the minority public interest in
      Thermo Instrument as part of our overall reorganization. The exchange
      offer and merger also would provide the public stockholders of Thermo
      Instrument with a continuing equity interest in the restructured company.
      We plan to retain Thermo Instrument as part of our core instrument
      business.

     - The Thermo Instrument reorganization.  Thermo Instrument has historically
       conducted its business through wholly-owned subsidiaries and divisions,
       as well as majority-owned subsidiaries that are partially owned by public
       or private investors. On January 31, 2000, Thermo Instrument announced
       its intention to acquire, through cash tender offers and mergers, the
       interests of public

                                        4
<PAGE>   8

       stockholders in five subsidiaries that it does not wholly own. Thermo
       Instrument expects to complete these acquisitions in the second quarter
       of 2000. Thermo Instrument's total cost of acquiring the public minority
       interests in these subsidiaries will be approximately $231 million. We
       agreed to loan Thermo Instrument up to $400 million to finance these
       acquisitions and related expenses. If Thermo Instrument successfully
       completes these tender offers and mergers, Thermo Instrument will not own
       any subsidiary with publicly-held minority interests, other than its
       interest in Spectra-Physics Lasers, Inc. Thermo Instrument is acquiring
       the publicly-held minority interests in these subsidiaries as part of our
       reorganization described above.

- - PRINCIPAL TERMS OF THE EXCHANGE OFFER

     - Exchange offer for all outstanding Thermo Instrument shares (page
       31).  We are offering to acquire all of the outstanding shares of common
       stock of Thermo Instrument that we do not currently own in exchange for
       shares of our common stock.

     - Exchange ratio (page 31).  We are offering to exchange 0.85 shares of our
       common stock for each share of Thermo Instrument common stock that Thermo
       Instrument stockholders validly tender in the exchange offer. We
       sometimes refer to this ratio of 0.85 to 1 as the "exchange ratio." The
       following table shows the last reported sale price of Thermo Instrument
       common stock on the American Stock Exchange and our common stock on the
       New York Stock Exchange on March 7, 2000, the last trading date before we
       announced the exchange ratio, and on April 20, 2000, the last trading
       date before the commencement of the exchange offer.

<TABLE>
<CAPTION>
      DATE                                                     THERMO INSTRUMENT    THERMO ELECTRON
      ----                                                     -----------------    ---------------
      <S>                                                      <C>                  <C>
      March 7, 2000..........................................      $19.9375            $  24.00
      April 20, 2000.........................................      $  18.75            $19.1875
</TABLE>

      The exchange ratio represents a valuation of the Thermo Instrument common
      stock at a premium of 2.3% over its last reported sale price on March 7,
      2000, based on the last reported sale price of our common stock on that
      date. For more information regarding the trading ranges of our common
      stock and Thermo Instrument common stock, see "-- Comparative Per Share
      Market Information."

     - Cash in lieu of fractional shares (page 31).  We will not issue
       fractional shares of our common stock in the exchange offer or the
       merger. Instead, we will pay an amount in cash equal to $19.1875 per
       whole share of our common stock for fractional shares.

     - Expiration of the exchange offer (page 31).  The exchange offer will
       expire at 12:00 midnight on Friday, May 19, 2000. We can elect at any
       time to extend the exchange offer. If we extend the exchange offer, we
       will issue a press release announcing the extension. See "The Exchange
       Offer -- Terms Of The Offer; Expiration Date."

     - Procedures for accepting the exchange offer and tendering shares (page
       34).  To exchange your shares of Thermo Instrument common stock for
       shares of our common stock in the exchange offer, you must follow the
       procedures described below under "The Exchange Offer -- Procedures For
       Accepting The Offer And Tendering Shares" and in the accompanying letter
       of transmittal before the exchange offer expires.

     - Issuance of Thermo Electron shares for tendered shares (page 33).  If we
       satisfy or waive all of the conditions of the exchange offer and we
       accept for exchange shares of Thermo Instrument common stock that you
       tendered, we will issue you shares of our common stock in exchange for
       your shares of Thermo Instrument common stock promptly after the exchange
       offer expires. See "The Exchange Offer -- Acceptance For Exchange And
       Exchange Of Shares."

     - Withdrawal rights (page 38).  You may withdraw shares of Thermo
       Instrument common stock that you have tendered at any time on or before
       May 19, 2000, or, if we extend the exchange offer, before the exchange
       offer expires. Unless accepted for exchange on or before June 22, 2000,
       you may also withdraw shares that you have tendered and which we have not
       accepted for exchange at

                                        5
<PAGE>   9

       any time after June 22, 2000. For your withdrawal to be effective,
       American Stock Transfer & Trust Company, the depositary for the exchange
       offer, must receive your notice of withdrawal at one of the addresses on
       the back cover of this prospectus before the exchange offer expires. For
       more information on your withdrawal rights, see "The Exchange
       Offer -- Withdrawal Rights."

     - Conditions of the exchange offer (page 39).  Our obligation to complete
       the exchange offer is subject to a number of conditions. In particular,
       Thermo Instrument stockholders must tender, and not withdraw, enough
       shares of Thermo Instrument common stock so that at the time the exchange
       offer expires we own at least 90% of Thermo Instrument's outstanding
       shares of common stock. In addition, our obligation to complete the
       exchange offer is subject to the condition that the SEC declare effective
       the registration statement of which this prospectus is a part. You can
       tender your shares of Thermo Instrument common stock before the
       registration statement is effective but we cannot accept these shares for
       exchange before the registration statement is effective or before the
       exchange offer expires. If the SEC has not declared the registration
       statement effective by the expiration date, we will extend or withdraw
       the exchange offer. For more information regarding the conditions to our
       obligation to complete the exchange offer, see "The Exchange
       Offer -- Conditions Of The Offer." We are not aware of any other material
       filing, approval or other action by any federal or state governmental or
       administrative authority that we must obtain in connection with our
       acquisition of shares of Thermo Instrument common stock as contemplated
       in this prospectus.

- - THE MERGER

     - Subsequent merger (page 47).  We plan to take Thermo Instrument private
       by acquiring all of the outstanding shares of Thermo Instrument common
       stock that we do not currently own. The exchange offer is the first step
       in this plan. If we complete the exchange offer, we will own at least 90%
       of Thermo Instrument's outstanding shares of common stock. We would then
       cause Thermo Instrument to merge with and into Thermo Electron in a
       so-called "short-form" merger. A short-form merger would not require
       approval of Thermo Instrument's board of directors or the stockholders of
       Thermo Instrument other than Thermo Electron.

     - No public stockholder action for merger; appraisal rights (page 47).  We
       do not intend to enter into a merger agreement with Thermo Instrument or
       to seek the approval of the directors of Thermo Instrument for the
       merger. Even if you do not tender your shares of Thermo Instrument common
       stock in the exchange offer, you would not be entitled to vote your
       shares with respect to the merger. If you do not tender your shares and
       we complete the merger, you would have a right to demand a judicial
       appraisal of the fair value of your shares of Thermo Instrument common
       stock. You could lose your right to an appraisal, however, if you fail to
       follow the statutory procedure. See "The Merger; Appraisal Rights."

     - Merger consideration (page 47).  In the merger, we would issue 0.85
       shares of our common stock for each share of Thermo Instrument common
       stock that we do not already own. This is the same consideration for each
       share of Thermo Instrument common stock that we are offering in this
       exchange offer. See "Background To The Exchange Offer And The
       Merger -- The Merger."

- - SHARE OWNERSHIP INFORMATION

     - Thermo Instrument shares outstanding.  As of March 31, 2000, Thermo
       Instrument had outstanding:

        - 129,361,430 shares of common stock;

        - options to purchase 5,600,038 shares of common stock;

        - $250 million principal amount of 4% convertible subordinated
          debentures due January 2005 convertible into a total of 7,012,623
          shares of common stock; and

                                        6
<PAGE>   10

        - $172.5 million principal amount of 4.5% senior convertible debentures
          due October 2003 convertible into a total of 5,006,385 shares of
          common stock.

     - Ownership of Thermo Instrument common stock by Thermo Electron and
       officers and directors of Thermo Electron and Thermo Instrument.  On
       March 31, 2000, we owned 114,602,387 shares of Thermo Instrument common
       stock, or approximately 88.6% of the outstanding shares of Thermo
       Instrument common stock. Assuming that optionholders exercised all
       outstanding options to purchase Thermo Instrument common stock and
       debenture holders did not convert any of Thermo Instrument's outstanding
       4% convertible subordinated debentures into Thermo Instrument common
       stock at the current conversion price of $35.65 per share or 4.5% senior
       convertible debentures into Thermo Instrument common stock at the current
       conversion price of $34.456 per share, we would have owned 84.8% of the
       outstanding shares of Thermo Instrument common stock on that date. In
       addition, on January 31, 2000, our directors and executive officers owned
       less than 1% of the outstanding shares of our common stock and less than
       1% of the outstanding shares of Thermo Instrument common stock. On
       January 31, 2000, the directors and executive officers of Thermo
       Instrument who are not also our directors or executive officers owned
       less than 1% of the outstanding shares of Thermo Instrument common stock
       and less than 1% of the outstanding shares of our common stock. On that
       date, our executive officers and directors also owned options to purchase
       2,660,715 shares of our common stock and 733,790 shares of Thermo
       Instrument common stock.

     - Ownership of Thermo Electron after the exchange offer and the merger.  If
       we acquire all of the outstanding shares of Thermo Instrument common
       stock pursuant to the exchange offer and the merger, former stockholders
       of Thermo Instrument would acquire through the exchange offer and the
       merger approximately 8% of the then outstanding shares of our common
       stock, based upon the number of shares of Thermo Instrument common stock
       and of our common stock outstanding on March 31, 2000 and the assumption
       that no Thermo Instrument optionholders exercise their options and that
       no Thermo Instrument debenture holders convert their debentures. In our
       reorganization, we are also offering shares of our common stock in
       connection with acquiring the minority interests in a number of our other
       public subsidiaries. We would issue approximately 9.8 million additional
       shares of our common stock in these other transactions, assuming that
       optionholders do not exercise any options to purchase shares of common
       stock of the subject companies and debenture holders do not convert any
       convertible debt securities of the subject companies.

- - RISK FACTORS (PAGE 15)

     Before you make any decision about the exchange offer or the merger, you
should read carefully this prospectus and the documents that we incorporate by
reference in this prospectus. You should also carefully consider the risks of
the exchange offer and the merger, our reorganization and our business that we
identify in this prospectus and in the documents that we incorporate by
reference in this prospectus. These risks include the following:

     - we may not complete our reorganization as proposed, including the two
       proposed spin-offs, the acquisition of the minority interests in most of
       our subsidiaries and the dispositions of our non-core businesses;

     - we may not realize the anticipated benefits of our reorganization;

     - the fixed exchange ratio in this exchange offer and the merger may work
       to your disadvantage if Thermo Instrument common stock increases in value
       or our common stock decreases in value;

     - the trading price for our common stock has been and may continue to be
       volatile; and

     - our business is subject to a number of risks, including intense
       competition, rapid technological changes, significant governmental
       regulation and difficulties of international operations.

                                        7
<PAGE>   11

     You should carefully review "Risk Factors" beginning on page 15 for a more
complete discussion of these and other risk factors relating to the exchange
offer, the merger, our reorganization and our business.

- - FEDERAL INCOME TAX CONSEQUENCES (PAGE 49)

     For federal income tax purposes, your receipt of shares of our common stock
pursuant to the exchange offer or the merger would be tax-free. However, you
would recognize taxable income upon the receipt of cash in lieu of fractional
shares of our common stock in the exchange offer or the merger.

     For a more detailed discussion of the tax consequences of the exchange
offer and the merger, you should carefully review "Federal Income Tax
Consequences." We urge you to consult with your own tax advisor.

- - CONSEQUENCES OF THE OFFER AND THE MERGER (PAGE 27)

     Completion of the exchange offer and the merger would have the following
consequences:

     - The shares of Thermo Instrument would no longer be listed on the American
       Stock Exchange; and

     - Thermo Instrument would no longer be subject to the requirements of the
       Securities Exchange Act of 1934, including requirements to file annual
       and other periodic reports.

     If you do not tender your shares of Thermo Instrument common stock and we
complete the exchange offer, your shares will remain outstanding until the
merger of Thermo Instrument and Thermo Electron. After the merger, each of your
shares will convert, subject to appraisal rights, into the right to receive 0.85
shares of our common stock.

- - EFFECT OF THE MERGER ON THERMO INSTRUMENT STOCK OPTIONS AND DEBENTURES (PAGES
29 AND 30)

     - Stock options.  In connection with the exchange offer and the merger, we
       will assume Thermo Instrument's stock option plans and any outstanding
       options to purchase shares of Thermo Instrument common stock under those
       plans. After we have assumed these options, they will be exercisable for
       shares of our common stock. The number of shares of our common stock
       underlying each assumed option will equal the number of shares of Thermo
       Instrument common stock underlying the option before the merger
       multiplied by the exchange ratio. The exercise price for each assumed
       option will be calculated by dividing the exercise price of the Thermo
       Instrument stock option before the merger by the exchange ratio, rounded
       up to the nearest whole cent.

     - Debentures.  In connection with the merger, we will assume Thermo
       Instrument's 4% convertible subordinated debentures due January 2005 and
       its 4.5% senior convertible debentures due October 2003. After we assume
       these debentures, they will be convertible into shares of our common
       stock, instead of shares of Thermo Instrument common stock. A total of
       $250 million principal amount of the 4% debentures was outstanding and a
       total of $172.5 million principal amount of the 4.5% debentures was
       outstanding as of March 31, 2000. As of that date, the 4% debentures were
       convertible into a total of 7,012,623 shares of Thermo Instrument common
       stock at a conversion price of $35.65 per share and the 4.5% debentures
       were convertible into a total of 5,006,385 shares of Thermo Instrument
       common stock at a conversion price of $34.456 per share. After the
       merger, the 4% debentures would be convertible into a total of 5,960,729
       shares of our common stock at a conversion price of $41.94 per share and
       the 4.5% debentures would be convertible into a total of 4,255,427 shares
       of our common stock at a conversion price of $40.54 per share. Holders of
       these debentures will not have the right to require Thermo Instrument to
       redeem their debentures as a result of the merger.

                                        8
<PAGE>   12

- - POTENTIAL CONFLICTS OF INTEREST (PAGE 25)

     In setting the exchange ratio, our financial interest was adverse to the
financial interest of the public stockholders of Thermo Instrument. We set the
exchange ratio on our own and without any negotiations with Thermo Instrument.

- - APPRAISAL RIGHTS (PAGE 47)

     If you tender your shares of Thermo Instrument common stock in the exchange
offer, you will not be entitled to exercise appraisal rights under the Delaware
General Corporation Law. If you do not tender your shares in the exchange offer,
upon the merger of Thermo Instrument into Thermo Electron, you will have a right
to dissent and demand payment of the judicially appraised fair value of your
Thermo Instrument shares under the Delaware General Corporation Law. This value
may be more or less than the market value of the 0.85 shares of our common stock
issuable for each share of Thermo Instrument common stock in the exchange offer
and the merger. See "The Merger; Appraisal Rights."

- - COMPARISON OF STOCKHOLDERS' RIGHTS (PAGE 51)

     If you tender your shares of Thermo Instrument common stock in the exchange
offer or do not exercise appraisal rights in the merger, you will become a
stockholder of Thermo Electron. Your rights as a stockholder of Thermo Electron
will be governed by our certificate of incorporation and bylaws. Unlike Thermo
Instrument, we have a classified board of directors and we have adopted a
stockholders rights plan. The classified board, the rights plan and other
provisions of our certificate of incorporation and bylaws may make it more
difficult for a third party to acquire us, even if an acquisition is favored by
many of our stockholders. See "Comparison Of The Rights Of Holders Of Our Common
Stock And The Rights Of Holders Of Thermo Instrument Common Stock."

- - SUMMARY HISTORICAL AND UNAUDITED PRO FORMA COMBINED SELECTED FINANCIAL
  INFORMATION (PAGES 10 AND 12)

     We will exchange shares of our common stock for shares of Thermo Instrument
common stock that we accept in the exchange offer or we acquire in the merger.
You should consider our financial condition before you decide to become one of
our stockholders through the exchange offer or the merger. In considering our
financial condition, you should review the documents that we incorporate by
reference in this prospectus because they contain detailed business, financial
and other information about us and about Thermo Instrument.

                                        9
<PAGE>   13

               SELECTED FINANCIAL INFORMATION -- THERMO ELECTRON

     We have derived the selected financial information presented below as of
and for the fiscal years ended January 1, 2000, and January 2, 1999, and for the
fiscal year ended January 3, 1998, from our consolidated financial statements,
which Arthur Andersen LLP, independent public accountants, audited, as indicated
in their report. We incorporate these financial statements by reference into
this prospectus from our Annual Report on Form 10-K for the fiscal year ended
January 1, 2000. We have derived the selected financial information presented
below as of January 3, 1998, and as of and for the fiscal years ended December
28, 1996 and December 30, 1995, from our consolidated financial statements,
which Arthur Andersen LLP audited, but which we have not included or
incorporated by reference in this prospectus. You should read this information
in conjunction with our consolidated financial statements and the related notes
that we incorporate by reference into this prospectus.

<TABLE>
<CAPTION>
                                                                FISCAL YEAR(1)
                                        --------------------------------------------------------------
                                         1999(2)      1998(3)        1997       1996(4)        1995
                                        ----------   ----------   ----------   ----------   ----------
                                                   (IN THOUSANDS EXCEPT PER SHARE AMOUNTS)
<S>                                     <C>          <C>          <C>          <C>          <C>
STATEMENT OF OPERATIONS DATA:
Revenues..............................  $2,471,193   $2,055,805   $1,979,602   $1,573,005   $1,059,064
Income (Loss) from Continuing
  Operations Before Extraordinary
  Items...............................     (14,580)     114,676      174,665      164,172       76,167
Net Income (Loss).....................    (174,573)     181,901      239,328      190,816      139,582
Earnings (Loss) per Share from
  Continuing Operations Before
  Extraordinary Items:
  Basic...............................        (.09)         .71         1.15         1.16          .60
  Diluted.............................        (.11)         .67         1.05         1.03          .55
Earnings (Loss) per Share:
  Basic...............................       (1.10)        1.12         1.57         1.35         1.10
  Diluted.............................       (1.13)        1.08         1.41         1.17          .95
BALANCE SHEET DATA (AT END OF PERIOD):
Working Capital.......................  $1,450,858   $2,163,010   $2,001,963   $2,218,617   $1,317,146
Total Assets..........................   5,181,842    5,421,060    4,961,046    4,546,942    3,247,952
Long Term Obligations.................   1,565,974    1,808,582    1,518,687    1,531,668    1,079,761
Minority Interest.....................     364,278      399,512      464,191      364,163      200,868
Common Stock of Subsidiaries Subject
  to Redemption.......................       7,692       40,500       40,500        2,613           --
Shareholders' Investment..............   2,014,486    2,254,802    2,007,862    1,755,576    1,311,311
OTHER DATA (UNAUDITED):
Book Value per Share..................  $    12.87   $    14.23   $    12.62   $    11.71   $     9.82
Cash Dividends Declared per Share.....          --           --           --           --           --
Ratio of Earnings to Fixed
  Charges(5)..........................        1.32x        3.35x
</TABLE>

- ---------------
(1) Our 1999, 1998, 1997, 1996 and 1995 fiscal years ended January 1, 2000,
    January 2, 1999, January 3, 1998, December 28, 1996 and December 30, 1995,
    respectively.

(2) Reflects a $182.4 million pretax charge for restructuring and related costs.

(3) Reflects a $32.5 million pretax charge for restructuring and related costs,
    the issuance of $150.0 million principal amount of our notes and our public
    offering of common stock for net proceeds of $290.1 million.

(4) Reflects the issuance of $585.0 million principal amount of our convertible
    debentures.

(5) For purposes of computing the ratios of earnings to fixed charges,
    "earnings" represent income from continuing operations before taxes and
    minority interest, plus fixed charges. "Fixed charges" consist of interest
    on indebtedness and amortization of debt expense and one-third of rental
    expense, which is treated as the interest component of rental expense.

                                       10
<PAGE>   14

              SELECTED FINANCIAL INFORMATION -- THERMO INSTRUMENT

     We have derived the selected financial information presented below as of
and for the fiscal years ended January 1, 2000, and January 2, 1999, and for the
fiscal year ended January 3, 1998, from Thermo Instrument's consolidated
financial statements, which Arthur Andersen LLP, independent public accountants,
audited, as indicated in their report. We incorporate these financial statements
by reference into this prospectus from Thermo Instrument's Annual Report on Form
10-K for the fiscal year ended January 1, 2000. We have derived the selected
financial information presented below as of January 3, 1998, and as of and for
the fiscal years ended December 28, 1996 and December 30, 1995, from Thermo
Instrument's consolidated financial statements, which Arthur Andersen LLP
audited, but which we have not included or incorporated by reference in this
prospectus. You should read this information in conjunction with Thermo
Instrument's consolidated financial statements and the related notes that we
incorporate by reference into this prospectus.

<TABLE>
<CAPTION>
                                                               FISCAL YEAR(1)
                                       --------------------------------------------------------------
                                        1999(2)      1998(3)      1997(4)      1996(5)        1995
                                       ----------   ----------   ----------   ----------   ----------
                                                  (IN THOUSANDS EXCEPT PER SHARE AMOUNTS)
<S>                                    <C>          <C>          <C>          <C>          <C>
STATEMENT OF INCOME DATA:
Revenues.............................  $2,093,537   $1,659,981   $1,592,314   $1,209,362   $  782,662
Income Before Extraordinary Item.....      87,799      103,565      147,258      132,751       79,306
Net Income...........................      87,799      104,084      147,258      132,751       79,306
Earnings per Share:
  Basic..............................         .74          .86         1.21         1.12          .70
  Diluted............................         .67          .79         1.09         1.01          .64
BALANCE SHEET DATA (AT END OF
  PERIOD):
Working Capital......................  $  368,800   $  745,955   $  612,666   $  636,703   $  489,895
Total Assets.........................   2,885,358    2,565,774    2,351,153    1,924,400    1,372,813
Long Term Obligations................     596,494      743,443      673,194      554,214      441,034
Shareholders' Investment.............     984,566      945,007      877,558      746,267      542,705
OTHER DATA (UNAUDITED):
Book Value per Share.................  $     8.29   $     7.92   $     7.19   $     6.16   $     4.74
Cash Dividends Declared per Share....          --           --           --           --           --
Ratio of Earnings to Fixed
  Charges(6).........................        3.78x        4.45x
</TABLE>

- ---------------
(1) Thermo Instrument's 1999, 1998, 1997, 1996 and 1995 fiscal years ended
    January 1, 2000, January 2, 1999, January 3, 1998, December 28, 1996 and
    December 30, 1995, respectively.

(2) Reflects a pretax charge of $21.7 million for restructuring and related
    costs, consisting of restructuring and unusual costs, net, of $15.0 million
    and inventory provisions of $6.7 million. Also reflects the February 1999
    acquisition of Spectra-Physics AB, the reclassification as short-term of an
    aggregate of $130.0 million of 5% subordinated convertible debentures of
    ThermoQuest Corporation and Thermo Optek Corporation due August and October
    2000, respectively, and the classification as noncurrent of Thermo
    Instrument's $140.0 million 3 3/4% senior convertible note as a result of
    its conversion by Thermo Electron in February 2000.

(3) Reflects a pretax charge of $31.8 million, consisting of restructuring and
    unusual costs, net, of $23.2 million and inventory provisions of $8.6
    million. Also reflects nontaxable gains of $18.6 million from the issuance
    of stock by subsidiaries and the January 1998 issuance of $250.0 million
    principal amount of 4% subordinated convertible debentures due 2005.

(4) Reflects the March 1997 acquisition of Life Sciences International PLC and
    nontaxable gains of $46.4 million from the issuance of stock by
    subsidiaries.

(5) Reflects the March 1996 acquisition of a substantial portion of the
    businesses constituting the Scientific Instruments Division of Fisons plc,
    the October 1996 issuance of $172.5 million principal amount of 4 1/2%
    senior convertible debentures due 2003 and nontaxable gains of $71.7 million
    from the issuance of stock by subsidiaries.

(6) For purposes of computing the ratios of earnings to fixed charges,
    "earnings" represent income before taxes and minority interest, plus fixed
    charges. "Fixed charges" consist of interest on indebtedness and
    amortization of debt expense and one-third of rental expense, which is
    treated as the interest component of rental expense.

                                       11
<PAGE>   15

          UNAUDITED PRO FORMA COMBINED SELECTED FINANCIAL INFORMATION
                         AND COMPARATIVE PER SHARE DATA

     The following table presents unaudited pro forma combined selected
financial information for us and for Thermo Instrument, historical selected
financial information for us and for Thermo Instrument, and unaudited pro forma
combined per share data for us and for Thermo Instrument. We derived the
historical financial information from our financial statements and those of
Thermo Instrument, which we incorporate by reference into this prospectus. We
derived the pro forma information from the pro forma consolidated condensed
financial information included elsewhere in this prospectus. The unaudited pro
forma consolidated condensed statement of operations data sets forth our results
of operations for the fiscal year ended January 1, 2000, assuming that we had
successfully completed the exchange offer and the merger as of the beginning of
fiscal 1999. The unaudited pro forma consolidated condensed balance sheet data
set forth our financial position as of January 1, 2000, assuming that we had
successfully completed the exchange offer and the merger on January 1, 2000.

     This data is not necessarily indicative of the results of the future
operations of the combined entity or the actual results that would have occurred
had we completed the exchange offer and the merger prior to the periods
indicated.

<TABLE>
<CAPTION>
                                                              FISCAL YEAR ENDED
                                                               JANUARY 1, 2000
                                                              -----------------
                                                                (IN THOUSANDS
                                                              EXCEPT PER SHARE
                                                                  AMOUNTS)
<S>                                                           <C>
PRO FORMA COMBINED:
STATEMENT OF OPERATIONS DATA:
  Revenues..................................................     $2,471,193
  Loss from Continuing Operations Before Extraordinary
     Items..................................................         (7,572)
BALANCE SHEET DATA (AT END OF PERIOD):
  Working Capital...........................................     $1,450,858
  Total Assets..............................................      5,354,813
  Long-term Obligations.....................................      1,565,974
  Minority Interest.........................................        244,380
  Common Stock of Subsidiaries Subject to Redemption........          7,692
  Shareholders' Investment..................................      2,307,355
                                                                 ----------

PER SHARE DATA:
THERMO ELECTRON (HISTORICAL):
  Book Value per Common Share...............................     $    12.87
  Cash Dividends Declared per Share.........................             --
  Loss per Share from Continuing Operations Before
     Extraordinary Items:
     Basic..................................................     $     (.09)
     Diluted................................................     $     (.11)
  Ratio of Earnings to Fixed Charges(2).....................           1.32x
PRO FORMA:
COMBINED PER SHARE OF THERMO ELECTRON STOCK:
  Book Value per Common Share...............................     $    13.65
  Cash Dividends Declared per Share.........................             --
  Loss per Share from Continuing Operations Before
     Extraordinary Items:
     Basic..................................................     $     (.04)
     Diluted................................................     $     (.06)
  Ratio of Earnings to Fixed Charges(2).....................           1.29x
</TABLE>

                                       12
<PAGE>   16

<TABLE>
<CAPTION>
                                                              FISCAL YEAR ENDED
                                                               JANUARY 1, 2000
                                                              -----------------
                                                                (IN THOUSANDS
                                                              EXCEPT PER SHARE
                                                                  AMOUNTS)
<S>                                                           <C>
COMBINED PER THERMO ELECTRON SHARE EQUIVALENT(1):
  Book Value per Common Share...............................     $    11.60
  Cash Dividends Declared per Share.........................             --
  Loss per Share from Continuing Operations Before
     Extraordinary Items:
     Basic..................................................     $     (.04)
     Diluted................................................     $     (.05)
  Ratio of Earnings to Fixed Charges(2).....................           1.10x
THERMO INSTRUMENT (HISTORICAL):
  Book Value per Common Share...............................     $     8.29
  Cash Dividends Declared per Share.........................             --
  Earnings per Share:
     Basic..................................................     $      .74
     Diluted................................................     $      .67
  Ratio of Earnings to Fixed Charges(2).....................           3.78x
</TABLE>

- ---------------
(1) Pro forma combined per Thermo Electron share equivalent data has been
    calculated based on the pro forma combined data for Thermo Electron common
    stock, multiplied by an exchange ratio of 0.85. See "-- Principal Terms of
    the Exchange Offer -- Exchange ratio" for a description of the exchange
    ratio. The exchange ratio is the 0.85 shares of our common stock which you
    would have received for each share of Thermo Instrument common stock in the
    exchange offer or the merger.

(2) For purposes of computing the ratios of earnings to fixed charges,
    "earnings" represent income from continuing operations before taxes and
    minority interest, plus fixed charges. "Fixed charges" consist of interest
    on indebtedness and amortization of debt expense and one-third of rental
    expense, which is treated as the interest component of rental expense.

                                       13
<PAGE>   17

- - COMPARATIVE PER SHARE MARKET INFORMATION (PAGE 46)

     Our common stock is traded on the New York Stock Exchange under the symbol
"TMO." Thermo Instrument common stock is traded on the American Stock Exchange
under the symbol "THI."

     The following table presents the closing prices per share of Thermo
Instrument common stock and the closing prices per share of our common stock on:

     - March 7, 2000, the last trading day before our public announcement of the
       terms, including the exchange ratio, of the exchange offer and the
       merger; and

     - April 20, 2000, the last trading date before we commenced the exchange
       offer.

     The table also presents, in the line entitled "Equivalent Per Share Price,"
the price per share of Thermo Instrument common stock based upon the exchange
ratio of 0.85 shares of our common stock for each share of Thermo Instrument
common stock.

<TABLE>
<CAPTION>
                                                            MARCH 7, 2000    APRIL 20, 2000
                                                            -------------    --------------
<S>                                                         <C>              <C>
Thermo Instrument.........................................    $19.9375          $18.75
Thermo Electron...........................................    $24.00            $19.1875
Equivalent Per Share Price................................    $20.40            $16.31
</TABLE>

     You should obtain current stock price quotations for our common stock and
the Thermo Instrument common stock.

- - FOR MORE INFORMATION (PAGE 58)

     You can obtain more information about Thermo Instrument and about us from
our respective public filings with the SEC. See "Where You Can Find More
Information."

     If you have any questions about the exchange offer, you should call the
information agent, D.F. King & Co., Inc. If you are a banker or broker, call
collect at (212) 269-5550. All others should call toll-free at (800) 290-6433.

                                       14
<PAGE>   18

                                  RISK FACTORS

     The exchange offer, the merger and an investment in our common stock
involve a high degree of risk. If any of the following events occurs, our
business, financial condition and results of operations would likely suffer,
possibly materially.

RISK RELATED TO THE EXCHANGE OFFER AND THE MERGER

BECAUSE WE WILL NOT ADJUST THE EXCHANGE RATIO TO REFLECT CHANGES IN OUR OR
THERMO INSTRUMENT'S STOCK PRICE, THE FIXED EXCHANGE RATIO USED IN THE EXCHANGE
OFFER MAY PROVE UNFAVORABLE TO YOU.

     We have fixed the exchange ratio at 0.85 shares of our common stock for
each share of Thermo Instrument common stock. We will not adjust the exchange
ratio to reflect fluctuations in the market value of shares of our common stock
or Thermo Instrument common stock. We will use the same exchange ratio in the
exchange offer and the merger. If you tender your shares of Thermo Instrument
common stock and we complete the exchange offer or if you do not tender your
shares of Thermo Instrument common stock and do not properly exercise your
appraisal rights in connection with the merger, you will be locked into the
exchange ratio and you will not be able to capture gains from possible increases
in the value of Thermo Instrument common stock. You may incur losses from
possible decreases in the value of our common stock.

RISKS RELATED TO OUR REORGANIZATION

BECAUSE OUR REORGANIZATION IS VERY COMPLEX AND WILL REQUIRE GOVERNMENTAL AND
THIRD PARTY CONSENTS AND APPROVALS, WE MAY NOT BE ABLE TO SUCCESSFULLY COMPLETE
THIS REORGANIZATION OR TO DO SO ON THE TIME SCHEDULE WE CONTEMPLATE.

     Our reorganization consists of:

     - the acquisition of the public minority interest in most of our
       subsidiaries that have minority investors;

     - the spin off of two of our businesses; and

     - the sale of a variety of non-core businesses.

To accomplish these objectives, we will need to obtain a variety of governmental
and third party consents and approvals. In particular, in addition to the
Internal Revenue Service ruling that we discuss below, we will need to obtain:

     - approval of the spin-offs and some of the other transactions by our board
       of directors;

     - when we are making a tender or exchange offer, the tender by minority
       stockholders of enough shares to allow us to own at least 90% of the
       target subsidiary's outstanding shares;

     - the satisfactory resolution of any comments raised by the SEC on various
       registration statements, tender offer documents and other filings; and

     - the receipt of any necessary third party contractual consents.

     If we do not receive these consents and approvals, we may not be able to
effect some aspects of our reorganization. If we are not able to effect all
aspects of the reorganization, we may not achieve some or all of the anticipated
benefits of our reorganization. Until we have completed the entire
reorganization, we will continue to own and operate a diverse group of
businesses, some of which may continue to have minority stockholders.

     Our reorganization is time-consuming and expensive, and consumes management
resources. The failure of our management to complete the proposed reorganization
in a timely manner could negatively affect the public market's confidence in our
management, which in turn may adversely affect the market price of our common
stock.

                                       15
<PAGE>   19

WE DO NOT EXPECT TO PROCEED WITH OUR TWO PLANNED SPIN-OFFS UNTIL WE RECEIVE A
FAVORABLE RULING FROM THE INTERNAL REVENUE SERVICE, WHICH THE INTERNAL REVENUE
SERVICE MAY NOT ISSUE OR WHICH MAY TAKE A SUBSTANTIAL PERIOD OF TIME FOR US TO
OBTAIN.

     We do not expect to spin-off our business that serves the healthcare
industry with a range of medical products for diagnosis and monitoring or our
paper recycling and papermaking equipment business unless we obtain a favorable
ruling from the Internal Revenue Service. The Internal Revenue Service may not
grant the necessary ruling or may seek to impose conditions to the granting of
the ruling that are not acceptable to us. We do not expect the Internal Revenue
Service to issue a tax ruling before the end of 2000, and additional delays are
possible.

AS PART OF OUR REORGANIZATION, WE ARE SEEKING TO DIVEST A SIGNIFICANT NUMBER OF
BUSINESSES; WE MAY NOT SUCCEED IN SELLING ALL OF THESE BUSINESSES IN A TIMELY
MANNER OR AT PRICES WE CONSIDER ACCEPTABLE.

     We plan to sell a significant number of businesses as part of our
reorganization. This process will entail a number of risks:

     - We may not find buyers for all of these businesses.

     - The timing of these dispositions is uncertain.

     - We cannot be certain that the terms, including price, for the sale of
       these businesses will be acceptable to us.

     - Each of these sales will be subject to various conditions, including
       conditions in the agreements governing the transaction and the receipt of
       necessary governmental approvals.

EVEN IF WE SUCCEED IN COMPLETING OUR REORGANIZATION, WE WILL FACE A NUMBER OF
CHALLENGES IN INTEGRATING OUR INSTRUMENT BUSINESS.

     Currently we operate our instrument business directly and through a number
of majority-owned subsidiaries, including Thermo Instrument, Thermedics Inc. and
their publicly traded subsidiaries. We have conducted these operations largely
as autonomous, unaffiliated businesses. As part of our reorganization, we plan
to manage these operations in a more coordinated manner. The following factors
may make it difficult for us to successfully integrate and consolidate our
instrument operations:

     - Our success in integrating these businesses will depend on our ability to
       coordinate geographically separate organizations and integrate personnel
       with different business backgrounds and corporate cultures.

     - Our ability to combine these businesses will require coordination of
       administrative, sales and marketing, distribution and accounting and
       finance functions and expansion of information and management systems.

     - The integration process could disrupt our instrument business.

     - Retaining key employees of these businesses may be difficult.

OUR REORGANIZATION CONTEMPLATES THE ISSUANCE OF A SIGNIFICANT NUMBER OF
ADDITIONAL SHARES OF OUR COMMON STOCK, WHICH MAY DEPRESS THE MARKET PRICE OF OUR
SHARES.

     We expect to issue a substantial number of shares of our common stock or
securities exercisable for shares of our common stock in connection with the
exchange offer, the merger and our reorganization. At March 31, 2000,
156,904,025 shares of our common stock were outstanding. The number of shares of
our

                                       16
<PAGE>   20

common stock outstanding may increase by as many as 58.1 million shares because,
as part of our reorganization:

     - We plan to exchange shares of our common stock for the common stock held
       by minority stockholders in a number of our public subsidiaries,
       including Thermo Instrument. We expect to issue a total of approximately
       22.3 million shares of our common stock in these transactions.

     - We plan to assume employee stock options in these transactions, including
       the merger with Thermo Instrument, that would be exercisable for
       approximately 17.9 million shares of our common stock. In addition, we
       may be required to issue additional stock options to retain our key
       employees.

     - The debentures issued by some of our subsidiaries, including Thermo
       Instrument, will become convertible into shares of our common stock.
       Based on the total principal amounts outstanding of these debentures and
       the conversion prices at March 31, 2000, these debentures would be
       convertible into approximately 17.9 million shares of our common stock.

     The increase in the number of outstanding shares of our common stock, as
well as the potential future issuance of shares of our common stock upon
conversion of debentures or exercise of employee stock options, may depress the
market price of our common stock.

WE ARE UNABLE TO PREDICT THE LIQUIDITY OR PROSPECTIVE PERFORMANCE OF THE COMMON
STOCK OF THE COMPANIES THAT WE INTEND TO SPIN OFF.

     We are unable to predict the liquidity or market performance of the shares
of the businesses we plan to spin off. Although Thermo Fibertek Inc., the
company that conducts our paper recycling and papermaking equipment business,
has publicly traded shares, the historic prices of these shares may not be
representative of the trading price of Thermo Fibertek's common stock after the
number of shares held by its stockholders other than us increases as a result of
the spin-off. We currently conduct our business that serves the healthcare
industry with a range of medical products for diagnosis and monitoring both
directly and through some of our subsidiaries. There is currently no public
trading market for the shares of the company that will conduct this business
following the proposed spin-off. The businesses that we are spinning off may not
have the financial resources and management skills necessary to succeed as
independent entities.

AS A RESULT OF THE SPIN-OFF OF THERMO FIBERTEK AND ITS SUBSIDIARIES, WE WILL
REMAIN AS THE GUARANTOR OF INDEBTEDNESS AND STOCK REDEMPTION RIGHTS OF THESE
COMPANIES EVEN THOUGH WE WILL NO LONGER CONTROL THEIR BUSINESS OR OPERATIONS.

     We have guaranteed the payment of principal and interest on $153 million
principal amount of debentures issued by Thermo Fibertek. These debentures
mature in July 2004. We have also guaranteed the financial obligations of Thermo
Fibergen Inc., a subsidiary of Thermo Fibertek, under stock redemption rights
granted by Thermo Fibergen. We are contingently liable for $60.1 million under
these stock redemption rights, some of which terminate in September 2000 and the
remainder of which terminate in September 2001. We will remain liable as a
guarantor for these obligations following the spin-offs, although we will no
longer control the business or operations of Thermo Fibertek or of its
subsidiaries.

RISKS RELATED TO OUR BUSINESS AND FINANCIAL CONDITION

OUR STOCK PRICE MAY BE VOLATILE, WHICH COULD CAUSE YOU TO LOSE PART OR ALL OF
YOUR INVESTMENT.

     The market price for our common stock can be very volatile. The market
price for our common stock may be affected by a number of factors, including:

     - the risks described in this prospectus;

     - our financial results; and

     - general market conditions.

                                       17
<PAGE>   21

In addition, the stock market has experienced extreme price and volume
fluctuations. This volatility has significantly affected the market prices of
securities for reasons frequently unrelated to or disproportionate to the
operating performance of the specific companies. These broad market fluctuations
may adversely affect the market price of our common stock.

WE MAY NOT BE ABLE TO COMPLETE PENDING OR FUTURE ACQUISITIONS, AND WE MAY NOT BE
ABLE TO INTEGRATE ANY ACQUIRED BUSINESSES INTO OUR EXISTING BUSINESS OR MAKE THE
ACQUIRED BUSINESSES PROFITABLE.

     One of our strategies is to supplement our internal growth by acquiring
businesses and technologies that complement or augment our existing product
lines. Some of the businesses we have acquired have had low levels of
profitability. In addition, businesses we may seek to acquire may be marginally
profitable or unprofitable. For these acquired businesses to achieve acceptable
levels of profitability, we must change their operations and improve their
market penetration. We may not be successful in this regard.

     We may be unable to identify or complete promising acquisitions for many
reasons, including:

     - competition among buyers;

     - the need for regulatory approvals, including antitrust approvals; and

     - the high valuations of businesses resulting from historically high stock
       prices.

     We may have to pay, and have paid, substantial premiums over the fair value
of the net assets of the companies we acquire. We have acquired significant
intangible assets, including approximately $1.2 billion of cost in excess of net
assets of acquired companies, or goodwill, recorded on our balance sheet as of
January 1, 2000. We expect to record additional goodwill in 2000 as a result of
our plans to acquire the minority interests in most of our publicly-traded
subsidiaries. Our ability to realize the value of this asset will depend on
future cash flows of the acquired businesses. These cash flows in turn depend on
how well we have identified these acquired businesses as desirable acquisition
candidates and how well we can integrate these acquired businesses.

     To finance our acquisitions, we may have to raise additional funds, either
through public or private financings. We may be unable to obtain such funds or
may be able to do so only on unfavorable terms.

IT MAY BE DIFFICULT FOR US TO EXPAND BECAUSE SOME OF THE MARKETS FOR OUR
PRODUCTS ARE NOT GROWING.

     Some of the markets in which we compete have been flat or declining over
the past several years. To address this issue, we have pursued a number of
potential growth strategies, including:

     - acquiring complementary businesses;

     - developing new applications for our technologies; and

     - strengthening our presence in selected geographic markets.

These strategies may not result in growth of our business, and we may not be
able to successfully implement these strategies.

WE HAVE SIGNIFICANT INTERNATIONAL OPERATIONS WHICH CAN ENTAIL ADDITIONAL RISKS.

     We are a global company with substantial operations outside of the United
States. We intend to continue to expand our international operations. In 1999,
our international revenues from continuing operations, including export revenues
from the U.S., accounted for approximately 63% of our total revenues. Our
international revenues are subject to many risks, including the following:

     - changes in exchange rates may adversely affect demand for our products
       and the profitability in U.S. dollars of products and services we provide
       in foreign markets, where payment for our products and services is made
       in the local currency;

                                       18
<PAGE>   22

     - we may find it hard to enforce agreements and collect receivables using a
       foreign country's legal system;

     - our foreign customers may have longer payment cycles;

     - foreign countries may impose additional withholding taxes or otherwise
       tax our foreign income, impose tariffs, or adopt other restrictions on
       foreign trade;

     - U.S. export licenses may be difficult to obtain;

     - intellectual property rights may be harder to enforce in foreign
       countries;

     - foreign countries may have unexpected changes in regulatory requirements;

     - we may have difficulty managing and staffing our foreign operations
       because of, among other factors, language and cultural differences;

     - foreign countries in which we operate may be characterized by
       unpredictable political instability; and

     - our revenues could be affected by seasonal reductions in business
       activity in some foreign countries.

     Of these factors, exchange rate fluctuations, in particular, have had an
adverse impact upon our business and results of operations.

     A portion of our revenues come from exports to Asia. Some countries in Asia
experienced a severe economic crisis in the late 1990's, involving sharply
reduced economic activity and liquidity, highly volatile
foreign-currency-exchange and interest rates, and unstable stock markets.
Unstable conditions in Asia depressed our export sales to Asia in 1998 and early
1999. Unstable economic conditions in this region and other parts of the world
may adversely affect our future export sales.

WE MUST DEVELOP NEW PRODUCTS, ADAPT TO RAPID AND SIGNIFICANT TECHNOLOGICAL
CHANGE AND RESPOND TO INTRODUCTIONS OF NEW PRODUCTS TO REMAIN COMPETITIVE.

     Our growth strategy includes significant investment in product development.
We intend to increase our investment in research and development. We sell our
products in several industries that are characterized by rapid and significant
technological changes, frequent new product and service introductions and
enhancements and evolving industry standards. Without the timely introduction of
new products, services and enhancements, our products and services will likely
become technologically obsolete over time, in which case our revenue and
operating results would suffer.

     Our customers use many of our products to develop, test and manufacture
their new products. As a result, we must anticipate industry trends and develop
products in advance of the commercialization of our customers' products. If we
fail to adequately predict our customers' needs and future activities, we may
invest heavily in research and development of products and services that do not
lead to significant revenue.

     Many of our products and products under development are technologically
innovative and require significant planning, design, development and testing at
the technological, product and manufacturing-process levels. These activities
require us to make significant investments.

     Products in our markets undergo rapid and significant technological change
because of quickly changing industry standards and the introduction of new
products and technologies that make existing products and technologies
uncompetitive or obsolete. Our competition may adapt more quickly to new
technologies and changes in our customers' requirements than we can. The
products we are currently developing, or those we will develop in the future,
may not be technologically feasible or accepted by the marketplace, and our
products or technologies could become uncompetitive or obsolete.

                                       19
<PAGE>   23

CHANGES IN GOVERNMENTAL REGULATIONS MAY REDUCE DEMAND FOR OUR PRODUCTS OR
INCREASE OUR EXPENSES.

     We compete in many markets in which we or our customers must comply with
federal, state, local and foreign regulations, such as environmental, health and
safety and food and drug regulations. We develop, configure and market our
products to meet customer needs created by these regulations. Any significant
change in these regulations could reduce demand for our products. For example,
demand for electromagnetic compatibility test instruments made by one of our
subsidiaries decreased because of the declining importance of IEC 801, the
European Union directive on electromagnetic compatibility.

DEMAND FOR SOME OF OUR PRODUCTS DEPENDS ON CAPITAL SPENDING POLICIES OF OUR
CUSTOMERS AND ON GOVERNMENT FUNDING POLICIES.

     Our customers include manufacturers of semiconductors and products
incorporating semiconductors, pharmaceutical and chemical companies,
laboratories, universities, healthcare providers, government agencies and public
and private research institutions. Many factors, including public policy
spending provisions, available resources and economic cycles have a significant
effect on the capital spending policies of these entities. These policies in
turn can have a significant effect on the demand for our products. For example,
a reduction in discretionary capital spending by petrochemical, oil and gas, and
mining companies, due to difficult market conditions, has adversely affected our
businesses operating in the process control industry. Similarly, softness in the
semiconductor industry has resulted in lower revenues at some of our businesses.
Also, our Thermedics Detection Inc. subsidiary has experienced lower demand for
its detection instruments as a result of a shift in the process of recycling
plastic containers in Europe, from sanitizing and reusing recyclables, to
melting and re-forming plastic containers.

OBTAINING AND ENFORCING PATENT PROTECTION FOR OUR PROPRIETARY PRODUCTS,
PROCESSES AND TECHNOLOGIES MAY BE DIFFICULT AND EXPENSIVE.

     Patent and trade secret protection is crucial to us, because developing and
marketing new technologies and products is time-consuming and expensive. We own
many U.S. and foreign patents, and intend to apply for additional patents as
appropriate to cover our products. We may not obtain issued patents from any
pending or future patent applications owned by or licensed to us. The claims
allowed under any issued patents may not be broad enough to protect our
technology.

     We may incur significant expense in any legal proceedings to protect our
proprietary rights. In addition, third parties may seek to challenge, invalidate
or circumvent any issued patents owned by or licensed to us, and the rights
granted under those patents may not provide competitive advantages to us.
Defending infringement and/or invalidity claims would be expensive and divert
management's attention. In addition, those claims could result in awards of
substantial damages, which could have a significant adverse effect on our
results of operations, or court orders that could effectively prevent us from
making, using or selling our products and services in the United States or
abroad.

                                       20
<PAGE>   24

                           FORWARD-LOOKING STATEMENTS

     This prospectus and the information that we incorporate by reference into
this prospectus include statements that are subject to risks and uncertainties
and are based on the beliefs and assumptions of our and Thermo Instrument's
management, based on information currently available to each company's
management. When we use words such as "believes," "expects," "anticipates,"
"intends," "plans," "estimates," "should," "likely" or similar expressions, we
are making forward-looking statements. Forward-looking statements include the
information concerning possible or assumed future results of our and Thermo
Instrument's operations set forth:

     - under "Summary," "Risk Factors," "Information About Thermo Electron And
       Thermo Instrument," "Background To The Exchange Offer And The Merger,"
       "Transactions With Related Parties" and "Unaudited Pro Forma Financial
       Statements" in this prospectus; and

     - under "Business" and "Management's Discussion and Analysis of Financial
       Condition and Results of Operations" in our and Thermo Instrument's
       Annual Reports on Form 10-K that we incorporate by reference into this
       prospectus.

     Forward-looking statements are not guarantees of performance. They involve
risks, uncertainties and assumptions. The future results and stockholder values
of Thermo Electron and Thermo Instrument may differ materially from those
expressed in the forward-looking statements. Many of the important factors that
will determine these results and values are beyond our ability to control or
predict. You should not put undue reliance on any forward-looking statements.
For a discussion of some of the factors that may cause actual results to differ
materially from those suggested by the forward-looking statements, you should
read carefully the section of this prospectus captioned "Risk Factors" that
starts on page 15.

                                       21
<PAGE>   25

            INFORMATION ABOUT THERMO ELECTRON AND THERMO INSTRUMENT

THERMO ELECTRON

     Thermo Electron Corporation, a Delaware corporation, develops, manufactures
and sells measurement and detection instruments that our customers use to
collect, monitor and analyze data. We conduct these businesses in significant
part through Thermo Instrument. We are in the process of spinning off our
business that serves the healthcare industry with a range of medical products
for diagnosis and monitoring, and our paper recycling and papermaking equipment
business. We are also in the process of selling various non-core businesses. We
plan to take Thermo Ecotek, our electric power generation business, private.
Although we no longer consider it a core business under our new strategy, we
expect to retain Thermo Ecotek after it is taken private while we continue to
evaluate how to best exit that business and create maximum value for our
stockholders.

     Our common stock is listed on the New York Stock Exchange under the symbol
"TMO." Our principal executive offices are located at 81 Wyman Street, P.O. Box
9046, Waltham, Massachusetts 02454-9046, and our telephone number is (781)
622-1000.

     The name, business address, principal occupation, five-year employment
history and citizenship of each of our directors and executive officers is
included in Annex A to this prospectus. Except as set forth in Annex B to this
prospectus, none of our executive officers or directors purchased or sold any
shares of Thermo Instrument common stock during the 60-day period ended on April
20, 2000.

     During the past five years, we have not been convicted in a criminal
proceeding, excluding traffic violations or similar misdemeanors, or been a
party to any judicial or administrative proceeding, except for any matters that
were dismissed without sanction or settlement, that resulted in a judgment,
decree or final order enjoining us from future violations of, or prohibiting
activities subject to, federal or state securities laws, or a finding of any
violation of federal or state securities laws.

     We are subject to the disclosure requirements of the Exchange Act and are
required to file reports, proxy statements and other information with the SEC
relating to our business, financial condition and other matters. You can inspect
and copy, at prescribed rates, these reports, proxy statements and other
information at the offices of the SEC and the New York Stock Exchange. See
"Where You Can Find More Information."

THERMO INSTRUMENT

     Thermo Instrument Systems Inc., a Delaware corporation, is a worldwide
leader in developing, manufacturing and marketing measurement instruments used
to monitor, collect and analyze information. Thermo Instrument's customers use
these systems for multiple applications in a range of industries, including
industrial processing, food and beverage production, life sciences research and
medical diagnostics.

     Thermo Instrument common stock is listed on the American Stock Exchange
under the symbol "THI." Thermo Instrument's principal executive offices are
located at 81 Wyman Street, P.O. Box 9046, Waltham, Massachusetts 02454-9046,
and its telephone number is (781) 622-1000.

     The name, business address, principal occupation, five-year employment
history and citizenship of each of Thermo Instrument's directors and executive
officers is included in Annex A to this prospectus. None of Thermo Instrument's
executive officers or directors purchased or sold any shares of Thermo
Instrument common stock during the 60-day period ended on April 20, 2000.

     Thermo Instrument is subject to the disclosure requirements of the Exchange
Act and is required to file reports, proxy statements and other information with
the SEC relating to its business, financial condition and other matters. You can
inspect and copy, at prescribed rates, these reports, proxy statements and other
information at the offices of the SEC and the American Stock Exchange. See
"Where You Can Find More Information."

                                       22
<PAGE>   26

                BACKGROUND TO THE EXCHANGE OFFER AND THE MERGER

OUR REORGANIZATION; PURPOSE AND REASONS FOR THE EXCHANGE OFFER AND THE MERGER

     Our Reorganization.  On January 31, 2000, we announced that our board of
directors had authorized our management to proceed with a major reorganization
of our operations. The reorganization reflects a significant change in strategic
direction for us, both in terms of our business focus and operating structure.

     - Until we adopted the reorganization plan, we had historically been
       engaged in a diversified group of businesses, including the instruments
       business. If we complete all aspects of the reorganization, we will focus
       primarily on a variety of segments in the instruments business. The
       businesses that we currently conduct through Thermo Instrument would be
       central to this new focus.

     - We have historically pursued a strategy of publicly offering minority
       interests in some of our subsidiaries. These subsidiaries, in turn,
       pursued the same strategy. Our management has reevaluated the benefits
       and detriments of this corporate structure and concluded that we would
       benefit if we reorganized our instrument businesses under a single parent
       company without minority interests. To acquire the minority interests in
       our subsidiaries, this new strategy includes exchanging shares of our
       common stock for publicly held shares of the common stock of a number of
       our subsidiaries, and tender offers and mergers by Thermo Instrument and
       Thermedics involving publicly held shares of common stock of their
       subsidiaries.

     As part of our reorganization, we intend to spin-off or dispose of all of
our businesses other than the instrument business and our electric power
generation business. We do not expect to complete the spin-offs until the end of
2000 or early 2001. If you receive shares of our common stock in the exchange
offer or the merger and hold them at the time we complete the spin-offs, you
will receive shares of common stock of companies that will conduct our business
that serves the healthcare industry with a range of medical products for
diagnosis and monitoring and our paper recycling and papermaking equipment
business. See "Risk Factors -- Risks Related to Our Reorganization -- We are
unable to predict the liquidity or prospective performance of the common stock
of the companies that we intend to spin off." In addition, we will continue to
hold non-core assets until we sell them, which may not occur until after we
complete the proposed spin-offs. During the fiscal year ended January 1, 2000,
revenue from these non-core businesses and the businesses we are spinning off
was approximately $1.83 billion and net loss from the non-core businesses and
the businesses we are spinning off was approximately $111.5 million.

     We plan to take Thermo Ecotek, our electric power generation business,
private. Although we no longer consider it a core business under our new
strategy, we expect to retain Thermo Ecotek after it is taken private while we
continue to evaluate how to best exit that business and create maximum value for
our stockholders.

     Purpose of the Exchange Offer and the Merger.  The purpose of this exchange
offer and the merger is to acquire the minority public interest in Thermo
Instrument as part of our overall reorganization. We are seeking through the
reorganization to:

     - eliminate the complexity of our corporate structure; and

     - focus on and integrate our instruments business.

     We anticipate that our stockholders may realize the following benefits from
the exchange offer and the merger:

     - By conducting our operations in a more coordinated manner with our other
       instruments subsidiaries, we would achieve greater marketing, operating
       and administrative efficiency.

     - We would eliminate additional burdens on management associated with
       public reporting and other tasks resulting from Thermo Instrument's
       public company status. For example, Thermo Instrument's management would
       no longer need to dedicate time and resources to stockholder and analyst
       inquiries and investor and public relations.

                                       23
<PAGE>   27

     - We would lower costs, particularly those associated with being a public
       company. For example, as a privately-held entity, Thermo Instrument would
       no longer be required to file quarterly, annual or other periodic reports
       with the SEC or publish and distribute to its stockholders annual reports
       and proxy statements. We anticipate that eliminating these costs,
       including fees for an audit by an independent accounting firm and legal
       fees, will result in savings of approximately $450,000 per year.

CERTAIN PROJECTED FINANCIAL DATA

     Thermo Instrument does not, as a matter of course, make public forecasts or
projections as to future sales, earnings or other income statement data, cash
flows or balance sheet and financial position information. However, in
connection with the exchange offer and the merger, we had access to Thermo
Instrument's projections for the fourth quarter of fiscal 1999 and for fiscal
1999 and 2000. These projections were prepared by management of Thermo
Instrument in the course of its regular business planning.

     We have included a summary of these Thermo Instrument projections below.
These projections do not reflect any of the effects of the exchange offer or the
merger or other changes that may in the future be appropriate concerning Thermo
Instrument and its assets, business, operations, properties, policies, corporate
structure, capitalization and management in light of the circumstances then
existing. We and Thermo Instrument believe that the assumptions were reasonable
at the time Thermo Instrument prepared the projections, given the information
known by our and Thermo Instrument's management.

     Thermo Instrument did not prepare its projections for the fourth quarter of
fiscal 1999 and for fiscal 1999 and 2000 with a view toward public disclosure or
compliance with published guidelines of the SEC or the American Institute of
Certified Public Accountants regarding forward-looking information or generally
accepted accounting principles. Neither Thermo Instrument's independent
auditors, nor any other independent accountants, have compiled, examined or
performed any procedures with respect to the prospective financial information
contained in these projections nor have they expressed any opinion or given any
form of assurance on this information or its achievability. They assume no
responsibility for, and disclaim any association with, this prospective
financial information.

     In preparing its projections for the fourth quarter of fiscal 1999 and for
fiscal 1999 and 2000, Thermo Instrument necessarily made numerous assumptions,
many of which are beyond our or Thermo Instrument's control and may prove not to
have been, or may no longer be, accurate. Except as otherwise indicated, this
information does not reflect revised prospects for Thermo Instrument's business,
changes in general business and economic conditions or any other transaction or
event that has occurred or that may occur and that Thermo Instrument did not
anticipate at the time it prepared this information. Accordingly, this
information is not necessarily indicative of current values or future
performance, which may be significantly more favorable or less favorable than as
set forth below, and you should not regard our including these projections in
this prospectus as a representation that they will be achieved.

     THE THERMO INSTRUMENT PROJECTIONS FOR THE FOURTH QUARTER OF FISCAL 1999 AND
FOR FISCAL 1999 AND 2000 ARE NOT GUARANTEES OF PERFORMANCE. THEY INVOLVE RISKS,
UNCERTAINTIES AND ASSUMPTIONS. THE FUTURE FINANCIAL RESULTS AND STOCKHOLDER
VALUE OF THERMO INSTRUMENT MAY DIFFER MATERIALLY FROM THOSE EXPRESSED IN THESE
PROJECTIONS. MANY OF THE FACTORS THAT WILL DETERMINE THESE RESULTS AND VALUES
ARE BEYOND THERMO INSTRUMENT'S ABILITY TO CONTROL OR PREDICT. YOU SHOULD NOT
PLACE UNDUE RELIANCE ON THESE PROJECTIONS. THERMO INSTRUMENT'S FUTURE FINANCIAL
RESULTS MAY VARY MATERIALLY FROM THESE PROJECTIONS. NEITHER THERMO INSTRUMENT
NOR WE INTEND TO UPDATE OR REVISE THESE PROJECTIONS.

                                       24
<PAGE>   28

                         THERMO INSTRUMENT PROJECTIONS
                                 (IN THOUSANDS)

<TABLE>
<CAPTION>
                                                           FOURTH         FISCAL        FISCAL
                                                           QUARTER         YEAR          YEAR
                                                         FISCAL 1999       1999          2000
                                                         -----------    ----------    ----------
<S>                                                      <C>            <C>           <C>
SELECTED INCOME STATEMENT DATA:
Revenues...............................................  $  570,144     $2,092,567    $2,291,414
                                                         ----------     ----------    ----------
Costs and Operating Expenses
  Cost of revenues.....................................     304,207      1,128,745     1,209,458
  Operating expenses...................................     199,199        743,024       825,402
  Restructuring costs, net.............................         328          1,871           279
                                                         ----------     ----------    ----------
                                                            503,734      1,873,640     2,035,139
                                                         ----------     ----------    ----------
Operating Income.......................................      66,410        218,927       256,275
Interest Income........................................       4,742         22,341        18,456
Interest Expense.......................................     (13,454)       (52,818)      (54,834)
Equity in Loss of Affiliates...........................       2,343         (7,947)         (646)
Gain on Sale of Investments............................          --          1,116            --
Other Expense, Net.....................................          (1)        (3,387)           (1)
                                                         ----------     ----------    ----------
Income Before Provision for Income Taxes and Minority
  Interest.............................................      60,040        178,232       219,250
Provision for Income Taxes.............................      25,218         77,230        92,084
Minority Interest Expense..............................       5,326         16,402        20,219
                                                         ----------     ----------    ----------
Net Income.............................................  $   29,496     $   84,600    $  106,947
                                                         ==========     ==========    ==========
SELECTED BALANCE SHEET DATA:
Accounts Receivable, Net...............................  $  478,370     $  478,370    $  494,514
Inventories............................................     338,660        338,660       326,721
Prepaid Income Taxes and Other Current Assets..........     121,052        121,052       133,277
                                                         ----------     ----------    ----------
Total Current Assets Excluding Cash and Investments....     938,082        938,082       954,512
Property, Plant and Equipment:
  Balance, Beginning of Period.........................     290,211        220,231       289,488
  Additions............................................      18,024         52,636        61,618
  Depreciation Expense.................................     (14,098)       (48,555)      (54,619)
  Sales................................................         299         70,124            78
                                                         ----------     ----------    ----------
  Balance, End of Period...............................     294,436        294,436       296,565
Cost in Excess of Net Assets of Acquired Companies.....   1,081,751      1,081,751     1,048,743
</TABLE>

CONFLICTS OF INTEREST

     Thermo Electron.  In setting the exchange ratio, our financial interest was
adverse to the financial interest of the public stockholders of Thermo
Instrument. We set the exchange ratio on our own and without any negotiations
with Thermo Instrument.

     Our Directors.  The members of our board of directors own, or hold options
to purchase, shares of our common stock and/or shares of common stock of Thermo
Instrument. These positions and equity interests presented these directors with
actual or potential conflicts of interest in determining the exchange ratio and
the other terms of the exchange offer and the merger.

     Officers and Directors of Thermo Instrument.  We set the exchange ratio on
our own and without negotiation with Thermo Instrument. The board of directors
of Thermo Instrument has formed a special

                                       25
<PAGE>   29

committee to evaluate the exchange offer and to make a recommendation to Thermo
Instrument's stockholders as to whether to accept or reject the exchange offer.
Mr. Polyvios C. Vintiadis, the only director of Thermo Instrument who is not an
employee of Thermo Electron or one of our affiliates, is the sole member of this
special committee.

     The special committee of the board of directors of Thermo Instrument has
not yet made a recommendation with respect to the exchange offer. Thermo
Instrument must file a Schedule 14D-9 with the SEC, which will include Thermo
Instrument's recommendation with respect to the exchange offer, no later than
May 5, 2000. Thermo Instrument also must publish or send you its recommendation.
YOU SHOULD CAREFULLY CONSIDER THERMO INSTRUMENT'S RECOMMENDATION BEFORE
DETERMINING WHETHER TO TENDER YOUR SHARES IN THE EXCHANGE OFFER OR TO PURSUE
YOUR APPRAISAL RIGHTS IN CONNECTION WITH THE MERGER.

     In considering any position that Thermo Instrument may take with respect to
the exchange offer and the merger, you should be aware that the officers and
several directors of Thermo Instrument have interests in connection with the
exchange offer and the merger that present them with actual or potential
conflicts of interest, as summarized below.

     Officers and directors of Thermo Instrument who own shares of Thermo
Instrument common stock will receive shares of our common stock in the exchange
offer or the merger at the same exchange ratio and on the same terms as the
Thermo Instrument public stockholders.

     Several members of the board of directors and executive officers of Thermo
Instrument are directors or officers of ours and of our other affiliates, as set
forth below:

     - Mr. Earl R. Lewis, the chief executive officer, president and a director
       of Thermo Instrument, is our chief operating officer, measurement and
       detection, and a director of our affiliates FLIR Systems Inc., SpectRx
       Inc. and Spectra-Physics Lasers, Inc.;

     - Mr. Theo Melas-Kyriazi, the chief financial officer of Thermo Instrument,
       is also our chief financial officer; and

     - Mr. Vintiadis is also a director of our affiliates, Thermo TerraTech Inc.
       and Spectra-Physics Lasers, Inc.

Consequently, these directors and officers receive or have received compensation
not only from Thermo Instrument but also from us and/or our other affiliates.

     As of January 31, 2000, the members of the board of directors and executive
officers of Thermo Instrument owned a total of 168,043 shares of Thermo
Instrument common stock. These individuals would receive in exchange for their
shares of Thermo Instrument common stock a total of 142,836 shares of our common
stock, assuming that they tender all of their shares of Thermo Instrument common
stock in the exchange offer.

     In addition, as of January 31, 2000, the members of the board of directors
and executive officers of Thermo Instrument held options to acquire a total of
1,270,168 shares of Thermo Instrument common stock, with exercise prices ranging
from $4.88 to $27.89. We would assume these options and convert them into
options to acquire shares of our common stock on the same terms as all of the
other holders of Thermo Instrument options in connection with the exchange offer
and the merger. See "-- Treatment of Thermo Instrument Options."

     As of January 31, 2000, Mr. Vintiadis had accumulated deferred units
representing 5,590 shares of Thermo Instrument common stock under Thermo
Instrument's deferred compensation plan for directors. These units would be
converted into the right to receive 4,751.5 shares of our common stock in the
merger. See "-- Treatment of Thermo Instrument Deferred Compensation Plan for
Directors."

     Indemnification Agreements.  We have entered into separate indemnification
agreements with each of Thermo Instrument's executive officers and directors.
These agreements require us to indemnify and advance expenses to the indemnified
director or officer if he or she, by reason of his or her status as a director
or officer of Thermo Instrument, or service as a director, officer or fiduciary
of another enterprise
                                       26
<PAGE>   30

at our request, is made or threatened to be made a party to any threatened,
pending or completed action, suit or other proceeding, whether civil, criminal,
administrative or investigative. We are only required to provide these benefits
if the director or officer seeking indemnification acted in good faith and in a
manner he or she reasonably believed to be in or not opposed to our best
interests, and, with respect to any criminal action or proceeding, had no
reasonable cause to believe his or her conduct was unlawful. We are required to
provide indemnification to the maximum extent permitted by Delaware law in the
case of any threatened, pending or completed action, suit or proceeding by or in
our right.

THE MERGER

     If we successfully complete the exchange offer, we plan to cause Thermo
Instrument to merge into us in a so-called "short-form" merger. This merger
would occur as promptly as practicable after completion of the exchange offer.
Under the Delaware General Corporation Law, if we own at least 90% of the
outstanding shares of Thermo Instrument common stock, we would have the power to
approve, adopt and complete the merger without a vote of Thermo Instrument's
stockholders or board of directors. Our stockholders would own all of the
outstanding shares of the surviving corporation after the merger.

     On the effective date of the merger, each outstanding share of Thermo
Instrument common stock, other than shares of Thermo Instrument common stock
held by us or Thermo Instrument and shares of Thermo Instrument common stock
held by stockholders, if any, who are entitled to and perfect their appraisal
rights under Section 262 of the Delaware General Corporation Law, would be
cancelled and converted into the right to receive 0.85 shares of our common
stock.

EFFECTS OF THE EXCHANGE OFFER AND THE MERGER

     General.  Upon completion of the exchange offer and the merger, we would
have complete control over the conduct of Thermo Instrument's business and would
have a 100% interest in the net book value and net earnings of Thermo
Instrument. In addition, we would receive the benefit of complete control over
any future increases in the value of Thermo Instrument and would bear the
complete risk of any losses incurred in the operation of Thermo Instrument and
any decrease in the value of Thermo Instrument. Our ownership of Thermo
Instrument, before the transactions contemplated by the exchange offer and the
merger, totaled approximately 88.6%.

     Possible Effect of the Exchange Offer on the Market for Thermo Instrument
Common Stock.  After the completion of the exchange offer and before the
effective date of the merger, our exchange of shares of our common stock for
shares of Thermo Instrument common stock pursuant to the exchange offer would
reduce the number of shares of Thermo Instrument common stock that might
otherwise trade publicly and may reduce the number of holders of shares of
Thermo Instrument common stock. These exchanges could adversely affect the
liquidity and market value of the remaining shares of Thermo Instrument common
stock held by the public.

     American Stock Exchange Listing.  If we complete the exchange offer and the
merger, the shares of Thermo Instrument common stock would not meet the
requirements for continued listing on the American Stock Exchange and would be
delisted. Assuming that the merger occurs shortly after the completion of the
exchange offer, we do not expect the American Stock Exchange to delist the
shares of Thermo Instrument common stock until after the effective date of the
merger. However, as discussed below, it is possible that the American Stock
Exchange could take this action.

     The shares of Thermo Instrument common stock may not meet the quantitative
requirements for continued listing on the American Stock Exchange following the
closing of the exchange offer and prior to the effective date of the merger.
Whether the shares of Thermo Instrument common stock meets those requirements
will depend upon:

     - the aggregate market value and the number of shares of Thermo Instrument
       common stock that we do not exchange for shares of our common stock
       pursuant to the exchange offer; and

     - the number of Thermo Instrument public stockholders who are not
       affiliated with us.
                                       27
<PAGE>   31

     To be listed on the American Stock Exchange, an issuer must have at least
200,000 publicly held shares, held by at least 300 stockholders, with a market
value of at least $1,000,000 and have stockholders' equity of at least
$2,000,000 or $4,000,000, depending on profitability levels during the issuer's
four most recent fiscal years.

     If the shares of Thermo Instrument common stock no longer meet the
requirements for listing on the American Stock Exchange, it is possible that the
shares would continue to trade in the over-the-counter market before the
effective date of the merger and that price or other quotations might still be
available from other sources. The extent of the public market for the shares of
Thermo Instrument common stock and the availability of such quotations would,
however, depend upon such factors as:

     - the number of holders and/or the aggregate market value of such shares of
       Thermo Instrument common stock remaining at the time;

     - the interest in maintaining a market in those shares of Thermo Instrument
       common stock on the part of securities firms; and

     - the possible termination of registration of shares of Thermo Instrument
       common stock under the Exchange Act, as described below.

     We cannot predict whether a reduction in the number of shares of Thermo
Instrument common stock that might otherwise trade publicly would have an
adverse or beneficial effect on the market price for or marketability of the
shares of Thermo Instrument common stock or whether it would cause future market
prices to be greater or less than the price paid in the exchange offer and the
merger.

     Exchange Act Registration.  The shares of Thermo Instrument common stock
are currently registered under the Exchange Act. If we complete the exchange
offer and the merger, Thermo Instrument's reporting obligations under the
Exchange Act would terminate.

     Before the effective date of the merger, the exchange of shares of Thermo
Instrument common stock for shares of our common stock pursuant to the exchange
offer may result in the shares of Thermo Instrument common stock becoming
eligible for deregistration under the Exchange Act. Thermo Instrument may apply
to the SEC for termination of the registration of its common stock if the common
stock is not listed on a national securities exchange and there are fewer than
300 record holders of the shares of Thermo Instrument common stock. See
"-- American Stock Exchange Listing."

     If Thermo Instrument terminates the registration of its common stock under
the Exchange Act:

     - Thermo Instrument would no longer be required to provide its stockholders
       with annual, quarterly and other reports under the Exchange Act;

     - Thermo Instrument would no longer be required to comply with other
       provisions of the Exchange Act, such as the short-swing profit recovery
       provisions of Section 16(b), the requirement of furnishing a proxy
       statement in connection with stockholders' meetings pursuant to Section
       14(a) and the requirements of Rule 13e-3 under the Exchange Act with
       respect to "going private" transactions;

     - "affiliates" of Thermo Instrument and persons holding "restricted
       securities" of Thermo Instrument may be deprived of the ability to
       dispose of their securities pursuant to Rule 144 under the Securities
       Act; and

     - the shares of Thermo Instrument common stock would no longer be "margin
       securities" or eligible for listing on the American Stock Exchange.

     We presently intend to cause Thermo Instrument to terminate the
registration of the shares of Thermo Instrument common stock under the Exchange
Act as soon after the completion of the exchange offer or the merger as the
requirements for termination of registration are met.

     Margin Regulations.  The shares of Thermo Instrument common stock are
currently "margin securities" under the rules of the Board of Governors of the
Federal Reserve System. As a result, brokers
                                       28
<PAGE>   32

are allowed to extend credit, known as purpose loans, on the collateral of
shares of Thermo Instrument common stock for the purpose of buying, carrying or
trading in securities. If we complete the exchange offer and the merger, shares
of Thermo Instrument common stock would no longer be "margin securities."
Following the exchange of shares of Thermo Instrument common stock pursuant to
the exchange offer and before the effective date of the merger, depending upon
factors such as the number of record holders of the shares of Thermo Instrument
common stock and the number and market value of publicly held shares of Thermo
Instrument common stock, the shares of Thermo Instrument common stock might no
longer constitute "margin securities" for purposes of the Federal Reserve
Board's margin regulations and you could not then use your shares of Thermo
Instrument common stock as collateral for purpose loans made by brokers. In
addition, if Thermo Instrument terminated the registration of shares of its
common stock under the Exchange Act, the shares of its common stock would no
longer constitute "margin securities."

     Treatment of Thermo Instrument Options.  Thermo Instrument has issued
options to acquire shares of its common stock pursuant to Thermo Instrument's
Equity Incentive Plan, Directors Stock Option Plan and Employees Equity
Incentive Plan. In connection with the exchange offer and the merger, we would
assume Thermo Instrument's plans and each outstanding option under these plans.
Each option that we assume would continue to have, and be subject to, the same
terms and conditions applicable to the option immediately before the effective
date of the merger, except that:

     - each option would be exercisable, or would become exercisable in
       accordance with its terms, for that number of whole shares of our common
       stock equal to the product of the number of shares of Thermo Instrument
       common stock that were issuable upon exercise of the option immediately
       before the effective date of the merger multiplied by the exchange ratio,
       rounded down to the nearest whole number of shares of our common stock;
       and

     - the per share exercise price for the shares of our common stock issuable
       upon exercise of such assumed option would be equal to the quotient
       determined by dividing the exercise price per share at which the option
       was exercisable immediately before the effective date of the merger by
       the exchange ratio, rounded up to the nearest whole cent.

     Treatment of Thermo Instrument Employees' Stock Purchase Plan.  In
connection with the exchange offer and the merger, we would assume each
outstanding option to purchase shares of Thermo Instrument common stock under
Thermo Instrument's Employees' Stock Purchase Plan. Each stock option under the
plan that we assume would continue to have, and be subject to, the same terms
and conditions as set forth in the plan immediately before the effective date of
the merger, except that:

     - the assumed stock option would be exercisable, or would become
       exercisable in accordance with its terms, for that number of whole shares
       of our common stock equal to the product of the number of shares of
       Thermo Instrument common stock that were issuable upon exercise of the
       assumed stock option immediately before the effective date of the merger
       multiplied by the exchange ratio, rounded down to the nearest whole
       number of shares of our common stock;

     - the purchase price per share of our common stock would be the lower of:

        -- 85% of the per share market value of the shares of Thermo Instrument
           common stock on the grant date of the assumed stock option divided by
           the exchange ratio, with the resulting price rounded up to the
           nearest whole cent; and

        -- 85% of the per share market value of our common stock as of the
           exercise date of the assumed stock option; and

     - the $25,000 limit under Section 9.2(i) of the plan would be applied by
       taking into account our assumption of the stock options in accordance
       with Section 423(b)(8) of the Internal Revenue Code of 1986 and
       regulations under that section.

     Treatment of Thermo Instrument Deferred Compensation Plan for
Directors.  In connection with the exchange offer and the merger, we would
assume Thermo Instrument's deferred compensation plan for directors and the
units for Thermo Instrument common stock outstanding under the plan would be
                                       29
<PAGE>   33

converted into units for our common stock at the exchange ratio. Based on the
units accumulated on January 1, 2000, Mr. Vintiadis would receive units for
4,751.5 shares of our common stock.

     Treatment of Thermo Instrument Debentures.  From and after the effective
date of the merger, we would assume Thermo Instrument's 4% convertible
subordinated debentures due January 2005 and Thermo Instrument's 4.5% senior
convertible debentures due October 2003. These debentures would be convertible
into shares of our common stock, instead of Thermo Instrument common stock. As
of March 31, 2000, a total of $250 million principal amount of the 4% debentures
was outstanding and a total of $172.5 million principal amount of the 4.5%
debentures was outstanding. At that date, the 4% debentures were convertible
into a total of 7,012,623 shares of Thermo Instrument common stock at a
conversion price of $35.65 per share and the 4.5% debentures were convertible
into a total of 5,006,385 shares of Thermo Instrument common stock at a
conversion price of $34.456 per share. Holders of Thermo Instrument debentures
would not have the right to require Thermo Instrument to redeem their debentures
as a result of the merger. After the merger, the 4% debentures would be
initially convertible into a total of 5,960,729 shares of our common stock at a
conversion price of $41.94 per share and the 4.5% debentures would be initially
convertible into a total of 4,255,427 shares of our common stock at a conversion
price of $40.54 per share.

     Accounting Treatment.  The exchange offer and the merger would be accounted
for as the acquisition of a minority interest by us using the purchase method of
accounting.

     Tax Consequences.  For federal income tax purposes, your receipt of shares
of our common stock pursuant to the exchange offer or the merger would be
tax-free. However, you would be taxed upon your receipt of cash in lieu of
fractional shares of our common stock in the exchange offer or the merger. See
"Federal Income Tax Consequences."

CONDUCT OF THERMO INSTRUMENT'S BUSINESS AFTER THE OFFER AND THE MERGER

     Following our reorganization, we plan to retain Thermo Instrument as part
of our core measurement and detection instruments business. We intend to
evaluate ways in which we can more efficiently integrate and operate our
instruments business, including Thermo Instrument's business. We do not
currently have any commitment or agreement for the sale of all or any material
portion of Thermo Instrument's business.

     Except as otherwise described in this prospectus, we have not as of the
date of this prospectus approved any specific plans or proposals for:

     - any extraordinary corporate transaction involving Thermo Instrument's
       business after the completion of the exchange offer and the merger; or

     - any sale or transfer of a material amount of assets currently held by
       Thermo Instrument after the completion of the exchange offer and the
       merger.

CONDUCT OF THERMO INSTRUMENT'S BUSINESS IF THE OFFER IS NOT COMPLETED

     If we do not complete the exchange offer because, on the date the exchange
offer expires, we do not own at least 90% of Thermo Instrument's outstanding
shares or because another condition to the exchange offer is not satisfied or
waived, we expect that Thermo Instrument's current management will continue to
operate Thermo Instrument's business substantially as presently operated. In
that event, we may consider:

     - engaging in open market or privately negotiated purchases of shares of
       Thermo Instrument common stock to increase our ownership of shares of
       Thermo Instrument common stock to at least 90% of the outstanding shares
       of Thermo Instrument common stock;

     - proposing that we and Thermo Instrument enter into a long-form merger
       agreement, which would require the consent of Thermo Instrument's board
       of directors, and vote all of our shares of Thermo Instrument common
       stock in favor of such merger; or

                                       30
<PAGE>   34

     - keeping outstanding the public minority interest in Thermo Instrument, in
       which case the Thermo Instrument public stockholders would not receive
       shares of our common stock for their shares of Thermo Instrument common
       stock and the trading price for the shares of Thermo Instrument common
       stock could decline, including to a price that is less than the value of
       the shares of our common stock that we propose to issue in exchange for
       shares of Thermo Instrument common stock in the exchange offer and the
       merger.

     If we were to pursue any of these alternatives, it may take considerably
longer for you to receive any consideration for your shares of Thermo Instrument
common stock, other than through sales in the open market, than if you had
tendered your shares in the exchange offer. Any such transaction may result in
proceeds per share to you that are more or less than the value of the shares of
our common stock that we propose to issue in exchange for shares of Thermo
Instrument common stock in the exchange offer and the merger.

                               THE EXCHANGE OFFER

TERMS OF THE EXCHANGE OFFER; EXPIRATION OF THE EXCHANGE OFFER

     Offer For All Outstanding Shares.  We are offering to acquire all the
shares of Thermo Instrument common stock, par value $.10 per share, outstanding
on the expiration date that we do not currently own.

     Exchange Ratio.  We are offering to exchange 0.85 shares of our common
stock for each outstanding share of common stock of Thermo Instrument that
Thermo Instrument stockholders validly tender and do not properly withdraw.

     Fractional Shares.  We will not issue fractional shares of our common stock
in the exchange offer or the merger. Instead, we will pay an amount in cash
equal to $19.1875 for each whole share of our common stock in lieu of any
fractional share that we would otherwise issue to you.

     Withdrawal Rights.  You may withdraw shares that you have tendered at any
time on or before May 19, 2000. If we extend the exchange offer, all shares of
Thermo Instrument common stock that you have previously tendered and not
properly withdrawn would remain subject to the exchange offer, although you
would have the right to withdraw your shares of Thermo Instrument common stock.
Unless we accept your shares for exchange on or before June 22, 2000, you may
also withdraw shares that you have tendered at any time after that date. See
"-- Withdrawal Rights."

     Expiration Date.  This exchange offer will expire at 12:00 midnight, New
York City time, on Friday, May 19, 2000, unless we, in our sole discretion,
extend the period during which the exchange offer is open.

     Extension of Expiration Date.  If allowed by the rules of the SEC, we may
extend the period during which the exchange offer is open. We may exercise this
right in our sole discretion at any time and for any reason, including the
failure to satisfy any of the conditions specified below under "-- Conditions Of
The Offer." We can extend the period during which the exchange offer is open by
providing oral or written notice to American Stock Transfer & Trust Company, the
depositary for the exchange offer. If we extend the period during which the
exchange offer is open, we will make an announcement no later than 9:00 a.m.,
New York City time, on the next business day after the previously scheduled
expiration of the exchange offer. Any extension would delay our acceptance for
exchange and the actual exchange of any shares of Thermo Instrument common stock
that you tender.

     Termination, Amendment and Waiver.  If allowed by the rules of the SEC, we
may also, in our sole discretion, at any time before the exchange offer expires:

     - terminate the exchange offer and not accept for exchange, or exchange,
       any shares of Thermo Instrument common stock if any of the conditions
       described in "-- Conditions Of The Offer" has not been satisfied or upon
       the occurrence and during the continuance of any of the events specified
       in "-- Conditions Of The Offer" or

                                       31
<PAGE>   35

     - waive any condition or amend the exchange offer in any respect,

in each case by giving oral or written notice of termination, waiver or
amendment to the depositary and by making a public announcement thereof. If we
terminate or withdraw the exchange offer, we will promptly return any shares of
Thermo Instrument common stock that you have tendered. We may not delay
acceptance for exchange, or the exchange, of any shares of Thermo Instrument
common stock upon the occurrence of any of the conditions specified in
"-- Conditions Of The Offer" without extending the period during which the
exchange offer is open.

     If the number of shares of Thermo Instrument common stock tendered is
insufficient to satisfy the minimum tender condition or any other condition
specified in "-- Conditions Of The Offer" is not fulfilled by the expiration of
the exchange offer, we may:

     - decline to exchange shares of our common stock for any of the shares of
       Thermo Instrument common stock tendered, return to you all shares of
       Thermo Instrument common stock that you tendered and terminate the
       exchange offer;

     - extend the exchange offer and retain all tendered shares of Thermo
       Instrument common stock until the expiration of the exchange offer, as
       extended, subject to the terms and conditions of the exchange offer,
       including your rights to withdraw your shares of Thermo Instrument common
       stock; or

     - waive or amend the condition and, subject to complying with the rules of
       the SEC, accept for exchange and exchange shares of our common stock for
       all shares of Thermo Instrument common stock validly tendered.

     We will publicly announce any extension, termination or amendment of the
exchange offer as promptly as practicable. Without limiting the manner in which
we may choose to make any public announcement, except as provided by applicable
law, including Rules 14d-4(c), 14d-6(d) and 14e-1 under the Exchange Act, which
require that material changes be promptly disseminated to holders of shares of
Thermo Instrument common stock, we will have no obligation to publish, advertise
or otherwise communicate any public announcement other than by issuing a release
to the Dow Jones News Service.

     Material Change to Exchange Offer.  If we make a material change in the
terms of the exchange offer or the information concerning the exchange offer, or
waive a material condition of the exchange offer, we will disseminate additional
exchange offer materials, including by public announcement as described above,
and extend the exchange offer to the extent required by Rules 14d-4(d), 14d-6(d)
and 14e-1 under the Exchange Act. The minimum period during which we will keep
the exchange offer open following material changes in the terms of the exchange
offer or information concerning the exchange offer, other than a change in
price, a change in percentage of securities sought or a change in any dealer's
soliciting fee, will depend upon the facts and circumstances, including the
relative materiality of the changes.

     With respect to a change in price or, subject to limitations, a change in
the percentage of securities sought or a change in any dealer's soliciting fee,
we will keep the exchange offer open for a minimum ten business day period from
the date of the change to allow for adequate dissemination to stockholders.
Accordingly, if, before the exchange offer expires, we:

     - decrease the number of shares of Thermo Instrument common stock sought in
       the exchange offer,

     - increase the consideration offered in the exchange offer, or

     - add a dealer's soliciting fee,

and if the exchange offer is scheduled to expire at any time earlier than the
period ending on the tenth business day from the date that we first publish,
send or give to stockholders notice of such increase, decrease or addition, we
will extend the exchange offer at least until the ten business day period
expires. For purposes of the exchange offer, a "business day" means any day
other than a Saturday, Sunday or federal holiday and consists of the time period
from 12:01 a.m. through 12:00 midnight, New York City time.
                                       32
<PAGE>   36

     Mailing of the Prospectus.  Thermo Instrument has provided us with its
stockholder list and security position listings for the purpose of disseminating
materials relating to the exchange offer to holders of shares of Thermo
Instrument common stock. We will mail this prospectus and a related letter of
transmittal and, if required, other relevant materials to record holders of
shares of Thermo Instrument common stock. We will also furnish those materials
to brokers, dealers, commercial banks, trust companies and similar persons whose
names, or the names of whose nominees, appear on Thermo Instrument's stockholder
list or who are listed as participants in a clearing agency's security position
listing for subsequent transmittal to beneficial owners of shares of Thermo
Instrument common stock.

     Subsequent Offering Period.  Although we do not currently intend to, we may
elect to provide a subsequent offering period. Any subsequent offering period
would last between three and 20 business days after our acceptance of Thermo
Instrument shares in the exchange offer. We will comply with the requirements
under Exchange Act Rule 14d-11 if we elect to provide a subsequent offering
period. You will not have the right to withdraw any Thermo Instrument shares
that you tender during any subsequent offering period.

ACCEPTANCE FOR EXCHANGE AND EXCHANGE OF SHARES

     Timing of Exchange of Shares.  Upon the terms and subject to the conditions
of this exchange offer, including, if we extend or amend the exchange offer, the
terms and conditions of any such extension or amendment, we will accept for
exchange, and will exchange for shares of our common stock, all shares of Thermo
Instrument common stock validly tendered before the exchange offer expires and
not properly withdrawn, including shares of Thermo Instrument common stock
validly tendered and not withdrawn during any extension of the exchange offer,
if we extend the exchange offer, subject to the terms and conditions of the
extension, promptly after the expiration of the exchange offer. In addition,
subject to complying with Rule 14e-1 under the Exchange Act, we may, in our sole
discretion, delay the acceptance for exchange or exchange of shares of Thermo
Instrument common stock to comply, in whole or in part, with any law.

     In all cases, we will exchange shares of our common stock for shares of
Thermo Instrument common stock tendered and accepted for exchange pursuant to
the exchange offer only after timely receipt by the depositary of:

     - certificates evidencing shares of Thermo Instrument common stock or
       timely confirmation, known as a book-entry confirmation, of a book-entry
       transfer of shares of Thermo Instrument common stock into the
       depositary's account at The Depository Trust Company pursuant to the
       procedures set forth below under "-- Procedures For Accepting The Offer
       And Tendering Shares;"

     - a properly completed and duly executed letter of transmittal, or a
       facsimile of that document, with any required signature guarantees, or an
       agent's message in connection with a book-entry transfer; and

     - any other documents required by the letter of transmittal.

Accordingly, we may issue shares of our common stock to tendering stockholders
at different times if delivery of their shares of Thermo Instrument common stock
and other required documents occurs at different times.

     Agent's Message.  The term "agent's message" means a message transmitted by
The Depository Trust Company to, and received by, the depositary and forming a
part of a book-entry confirmation, which states that The Depository Trust
Company has received an express acknowledgment from the participant in The
Depository Trust Company tendering the shares of Thermo Instrument common stock
which are the subject of the book-entry confirmation, that the participant has
received and agrees to be bound by the terms of the letter of transmittal and
that we may enforce the agreement against such participant.

     Acceptance of Shares.  For purposes of the exchange offer, we will have
accepted for exchange, and thereby exchanged, shares of our common stock for
shares of Thermo Instrument common stock validly

                                       33
<PAGE>   37

tendered and not properly withdrawn if, as and when we give oral or written
notice to the depositary of our acceptance for exchange of such shares of Thermo
Instrument common stock pursuant to the exchange offer. Upon the terms and
subject to the conditions of the exchange offer, we will issue shares of our
common stock in exchange for shares of Thermo Instrument common stock that we
accept for exchange by depositing the total number of shares of our common stock
issuable in exchange for shares of Thermo Instrument common stock with the
depositary.

     The depositary will act as agent for tendering stockholders for the purpose
of receiving shares of our common stock and transmitting these shares to
stockholders whose shares of Thermo Instrument common stock we have accepted for
exchange. UNDER NO CIRCUMSTANCES WILL WE PAY INTEREST ON THE MARKET VALUE OF
SHARES OF OUR COMMON STOCK OR ON THE AMOUNT OF ANY CASH PAYABLE TO A TENDERING
STOCKHOLDER IN LIEU OF FRACTIONAL SHARES OF OUR COMMON STOCK, REGARDLESS OF ANY
EXTENSION OF THE EXCHANGE OFFER OR DELAY IN MAKING SUCH EXCHANGE. When we
deposit shares of our common stock with the depositary for the purpose of
issuing these shares to validly tendering stockholders, our obligation to make
such exchange will be satisfied and from then on tendering stockholders must
look solely to the depositary for the shares of our common stock owed to them by
reason of the acceptance for exchange of shares of Thermo Instrument common
stock pursuant to the exchange offer.

     Shares Not Accepted for Exchange.  If for any reason we do not accept any
shares of Thermo Instrument common stock that you tender pursuant to the terms
and conditions of the exchange offer, or if you submit share certificates
representing more shares of Thermo Instrument common stock than you are
tendering, we will return share certificates representing shares of Thermo
Instrument common stock that we do not accept for exchange or that you do not
tender, without expense, to you. In the case of shares of Thermo Instrument
common stock that you tender by book-entry transfer, we will credit your account
at The Depository Trust Company for any shares that we do not accept for
exchange as promptly as practicable following expiration or termination of the
exchange offer.

     Other Terms.  If we increase the exchange ratio or otherwise increase the
consideration in the exchange offer before the exchange offer expires, we will
apply the higher rate or increased consideration to all shares of Thermo
Instrument common stock that you tender in the exchange offer, whether or not
you tendered or we exchanged such shares of Thermo Instrument common stock
before we increased the in exchange ratio or other consideration.

     We may transfer or assign to one or more of our affiliates our right to
exchange shares of our common stock for shares of Thermo Instrument common stock
tendered pursuant to the exchange offer. We may exercise this right in whole or
in part from time to time. If we exercise this right, we will still be required
to comply with our obligations under the exchange offer. Your right to receive
shares of our common stock in exchange for your shares of Thermo Instrument
common stock that you validly tender and that we accept for exchange pursuant to
the exchange offer will not be prejudiced by any such transfer or assignment by
us.

PROCEDURES FOR ACCEPTING THE OFFER AND TENDERING SHARES

     General.  Except as set forth below, for you to validly tender your shares
of Thermo Instrument common stock pursuant to the exchange offer, the depositary
must receive either:

     - your letter of transmittal, or a facsimile of your letter of transmittal,
       properly completed and duly executed, together with any required
       signature guarantees, or

     - an agent's message in connection with a book-entry delivery of shares of
       Thermo Instrument common stock,

                                       34
<PAGE>   38

together with any other documents required by the letter of transmittal. The
depositary must receive these documents at one of its addresses set forth on the
back cover of this prospectus before the exchange offer expires. In addition,
either

     - the depositary must receive share certificates evidencing your tendered
       shares of Thermo Instrument common stock at one of the addresses set
       forth on the back cover of this prospectus or you must tender your shares
       of Thermo Instrument common stock pursuant to the procedures for
       book-entry transfer set forth below, and the depositary must receive a
       book-entry confirmation, in each case before the exchange offer expires;
       or

     - you must comply with the guaranteed delivery procedures set forth below.

     We will not accept alternative, conditional or contingent tenders. We will
not accept for exchange fractional shares of Thermo Instrument common stock. By
execution of the letter of transmittal included with this prospectus, or a
facsimile thereof, you will waive any right to receive any notice of the
acceptance for exchange of your shares of Thermo Instrument common stock.

     THE METHOD OF DELIVERY OF SHARE CERTIFICATES, THE LETTER OF TRANSMITTAL AND
ALL OTHER REQUIRED DOCUMENTS, INCLUDING DELIVERY THROUGH THE DEPOSITORY TRUST
COMPANY, IS AT YOUR SOLE OPTION AND RISK. EXCEPT AS OTHERWISE PROVIDED UNDER
THIS HEADING "PROCEDURES FOR ACCEPTING THE OFFER AND TENDERING SHARES," WE WILL
TREAT YOUR SHARE CERTIFICATES, LETTER OF TRANSMITTAL AND OTHER REQUIRED
DOCUMENTS AS DELIVERED ONLY WHEN THEY ARE ACTUALLY RECEIVED BY THE DEPOSITARY.
IF YOU USE THE MAIL FOR DELIVERY, WE RECOMMEND THAT YOU USE REGISTERED MAIL WITH
RETURN RECEIPT REQUESTED, PROPERLY INSURED. IN ALL CASES, YOU SHOULD ALLOW
SUFFICIENT TIME TO ENSURE TIMELY DELIVERY.

     Book-Entry Transfer.  Within two business days after the commencement date
of the exchange offer, the depositary will request that The Depository Trust
Company establish an account with respect to the shares of Thermo Instrument
common stock for purposes of the exchange offer. Any financial institution that
is a participant in the system of The Depository Trust Company may make
book-entry delivery of your shares of Thermo Instrument common stock by causing
The Depository Trust Company to transfer your shares into the depositary's
account at The Depository Trust Company in accordance with The Depository Trust
Company's procedures for such transfer. Although you may deliver your shares of
Thermo Instrument common stock through book-entry transfer into the depositary's
account at The Depository Trust Company, the depositary must receive:

     - your letter of transmittal, or a facsimile of your letter of transmittal,
       properly completed and duly executed, together with any required
       signature guarantees, or an agent's message, and

     - any other documents required by the letter of transmittal,

at one of its addresses set forth on the back cover of this prospectus before
the exchange offer expires for you to validly tender your shares of Thermo
Instrument common stock pursuant to the exchange offer, or you must comply with
the guaranteed delivery procedures described below.

     DELIVERY OF DOCUMENTS TO THE DEPOSITORY TRUST COMPANY IN ACCORDANCE WITH
THE DEPOSITORY TRUST COMPANY'S PROCEDURES DOES NOT CONSTITUTE DELIVERY TO THE
DEPOSITARY.

     Signature Guarantees.  Except as described below, a firm that is a bank,
broker, dealer, credit union, savings association or other entity which is a
member in good standing of:

     - the Securities Transfer Agents Medallion Program,

     - the Stock Exchanges' Medallion Program, or

     - the New York Stock Exchange, Inc. Medallion Signature Program

                                       35
<PAGE>   39

must guarantee signature on your letter of transmittal. Each firm that is a
member of these medallion programs is referred to in this prospectus as an
"eligible institution." We will not require a signature guarantee on your letter
of transmittal if:

     - you are the registered holder of shares of Thermo Instrument common stock
       and do not complete either the box entitled "Special Delivery
       Instructions" or the box entitled "Special Issuance Instructions" on your
       letter of transmittal; or

     - you tender shares of Thermo Instrument common stock for the account of an
       eligible institution.

For more information regarding these procedures, you should review Instruction 1
of the letter of transmittal.

     If your share certificates are registered in the name of a person other
than the person who signs the letter of transmittal, or if you direct us to make
payment or to return your share certificates for exchanged shares of Thermo
Instrument common stock to a person other than the registered holders, then the
tendered share certificates must be endorsed or accompanied by appropriate stock
powers signed exactly as the names of the registered holders appear on the share
certificates, with the signatures on the share certificates or stock powers
guaranteed by an eligible institution as provided above and in the letter of
transmittal. See Instructions 1 and 5 of the letter of transmittal.

     Guaranteed Delivery.  If you wish to tender shares of Thermo Instrument
common stock pursuant to the exchange offer and your share certificates are not
immediately available or you cannot deliver all of the required documents to the
depositary before the exchange offer expires or you cannot comply with the
procedures for book-entry transfer on a timely basis, you may still tender your
shares of Thermo Instrument common stock, so long as all of the following
conditions are satisfied:

     - you make your tender by or through an eligible institution;

     - the depositary receives a properly completed and duly executed notice of
       guaranteed delivery, substantially in the form provided with this
       prospectus, as provided below before the exchange offer expires; and

     - the depositary receives within three American Stock Exchange trading days
       after the date of execution of the notice of guaranteed delivery the
       share certificates, or a book-entry confirmation, for your tendered
       shares of Thermo Instrument common stock, in proper form for transfer, in
       each case together with a properly completed and duly executed letter of
       transmittal, or a facsimile of a properly completed and duly executed
       letter of transmittal, with any required signature guarantees or, in the
       case of a book-entry transfer, an agent's message and any other documents
       required by the letter of transmittal.

You may deliver the notice of guaranteed delivery by hand or transmit it by
telegram, facsimile transmission or mail to the depositary. You must include a
guarantee by an eligible institution in the form set forth in the notice of
guaranteed delivery.

     Timing for Exchange.  In all cases, we will exchange shares of Thermo
Instrument common stock that you have tendered and we have accepted for exchange
pursuant to the exchange offer only after timely receipt by the depositary of:

     - share certificates for Thermo Instrument shares, or book-entry
       confirmation of the transfer of the shares of Thermo Instrument common
       stock into the depositary's account at The Depository Trust Company;

     - a properly completed and duly executed letter of transmittal, or a
       facsimile of a properly completed and duly executed letter of
       transmittal, together with any required signature guarantees or, in the
       case of a book-entry transfer, an agent's message; and

     - any other documents required by the letter of transmittal.

                                       36
<PAGE>   40

Accordingly, tendering stockholders of Thermo Instrument may receive shares of
our common stock at different times depending upon when share certificates or
book-entry confirmations for their shares of Thermo Instrument common stock are
received by the depositary.

     Backup Federal Income Tax Withholding.  Under U.S. federal income tax laws,
the depositary may be required to withhold 31% of the amount of any cash
payments made to you in lieu of fractional shares of our common stock. To
prevent backup federal income tax withholding with respect to any reportable
cash payments made to you in the exchange offer, you must provide the depositary
with your correct taxpayer identification number and certify that you are not
subject to backup federal income tax withholding by completing the Substitute
Form W-9 included in the letter of transmittal. See Instruction 9 of the letter
of transmittal.

     Appointment as Proxy.  By executing the letter of transmittal, you
irrevocably appoint our designees as your attorneys-in-fact and proxies in the
manner set forth in the letter of transmittal, each with full power of
substitution with respect to any shares of Thermo Instrument common stock you
tendered, and with respect to any and all other shares of Thermo Instrument
common stock or other securities issued or issuable in respect of such shares of
Thermo Instrument common stock on or after April 24, 2000. This appointment will
not be effective until we accept your tendered shares of Thermo Instrument
common stock for exchange and deposit shares of our common stock as the exchange
consideration with the depositary. All such proxies will be irrevocable and
coupled with an interest in your tendered shares of Thermo Instrument common
stock. When this appointment becomes effective, all other powers of attorney and
proxies that you have given will be revoked, and you may not give any subsequent
powers of attorney or proxies or execute any subsequent written consents and, if
given or executed, we will treat them as ineffective.

     Upon our deposit of shares of our common stock as the exchange
consideration with the depositary, our designees will, with respect to your
shares of Thermo Instrument common stock and other securities for which the
appointment is effective, be empowered to exercise all of your voting and other
rights as they in their sole discretion consider proper. We may exercise these
rights at any time Thermo Instrument stockholders vote. We reserve the right to
require that, for us to treat your shares of Thermo Instrument common stock as
validly tendered, we be able to exercise full voting and other rights of a
record and beneficial holder immediately upon our acceptance for exchange of
your shares of Thermo Instrument common stock.

     Determination of Validity.  We will determine all questions as to the
validity, form, eligibility, including the time of receipt, and acceptance for
exchange of any tendered shares of Thermo Instrument common stock pursuant to
any of the procedures described above. We will make these determinations in our
sole discretion, and our determinations will be final and binding. We reserve
the absolute right to reject any and all tenders of shares of Thermo Instrument
common stock that we determine are not in proper form or for which the
acceptance of, or exchange for, may, in the opinion of our counsel, be unlawful.

     We also reserve the absolute right to waive any of the conditions of the
exchange offer or any defect or irregularities in the tender of any shares of
Thermo Instrument common stock, whether or not similar defects or irregularities
are waived in the case of any other shares of Thermo Instrument common stock. We
will not treat your tender of shares of Thermo Instrument common stock as
validly made until all defects and irregularities have been cured or waived.
Neither we nor any of our affiliates or assigns, the information agent, the
depositary or any other person will be under any duty to give notification of
any defects or irregularities in tenders or incur any liability for failure to
give any such notification. Our interpretations of the terms and conditions of
the exchange offer, including the letter of transmittal and the instructions to
the letter of transmittal, will be final and binding.

     OUR ACCEPTANCE FOR EXCHANGE OF YOUR SHARES OF THERMO INSTRUMENT COMMON
STOCK TENDERED PURSUANT TO THE PROCEDURES DESCRIBED ABOVE WILL BE A BINDING
AGREEMENT BETWEEN US AND YOU UPON THE TERMS AND CONDITIONS OF THIS EXCHANGE
OFFER.

                                       37
<PAGE>   41

WITHDRAWAL RIGHTS

     General.  Your tender of shares of Thermo Instrument common stock pursuant
to the exchange offer is irrevocable except as otherwise provided in this
section. You may withdraw shares of Thermo Instrument common stock that you
tender in the exchange offer at any time before the exchange offer expires and,
unless we have previously accepted these shares for exchange as provided in this
prospectus, at any time after June 22, 2000. If we elect to provide a subsequent
offering period under Exchange Act Rule 14d-11, you will not have the right to
withdraw shares of Thermo Instrument common stock that you tender in the
subsequent offering period.

     Extensions.  If we:

     - extend the exchange offer,

     - are delayed in, or delay, our acceptance for exchange or the actual
       exchange of shares of Thermo Instrument common stock, or

     - are unable for any reason to accept for exchange or exchange shares of
       Thermo Instrument common stock,

then, without prejudice to our other rights under the exchange offer, the
depositary, on our behalf, may nevertheless return your tendered shares of
Thermo Instrument common stock and you may not exercise withdrawal rights except
to the extent described in this section. We will extend the exchange offer to
the extent required by law in the event of any extension or delay.

     Effectiveness of Withdrawal.  For your withdrawal to be effective, the
depositary must receive from you a written, telegraphic or facsimile
transmission notice of withdrawal at one of its addresses set forth on the back
cover of this prospectus. Your notice of withdrawal must include:

     - your name;

     - the number of shares of Thermo Instrument common stock that you wish to
       withdraw; and

     - the name of the registered holder of the shares of Thermo Instrument
       common stock that you wish to withdraw, if different from that of the
       person who tendered the shares of Thermo Instrument common stock.

If you have delivered or otherwise identified your share certificates to the
depositary, then, before the physical release of the share certificates, you
must also submit the serial numbers shown on the share certificates to the
depositary and you must have the signatures on the notice of withdrawal
guaranteed by an eligible institution, unless the shares of Thermo Instrument
common stock have been tendered for the account of an eligible institution. If
you tendered shares of Thermo Instrument common stock pursuant to the procedures
for book-entry transfer, as set forth above under "-- Procedures For Accepting
The Offer And Tendering Shares," any notice of withdrawal must specify the name
and number of the account at The Depository Trust Company to be credited with
the withdrawn shares of Thermo Instrument common stock and must otherwise comply
with the procedures of The Depository Trust Company.

     Revocation of Withdrawal.  You may not revoke a withdrawal. We will treat
any shares of Thermo Instrument common stock properly withdrawn as not validly
tendered for purposes of the exchange offer. However, you may re-tender
withdrawn shares of Thermo Instrument common stock at any time before the
exchange offer expires by again following one of the procedures described above
under "-- Procedures For Accepting The Offer And Tendering Shares."

     Validity of Withdrawals.  We will determine all questions as to the form
and validity, including the time of receipt, of any notice of withdrawal in our
sole discretion, and our determination will be final and binding. Neither we nor
any of our affiliates or assigns, the information agent, the depositary or any
other person will be under any duty to notify you of any defects or
irregularities in any notice of withdrawal or incur any liability for failure to
give any such notification.

                                       38
<PAGE>   42

CONDITIONS OF THE OFFER

     We have the right to extend or amend the exchange offer in our sole
discretion at any time before the exchange offer expires. In addition, we:

     - are not required to accept for exchange or, subject to any applicable
       rules and regulations of the SEC, including Rule 14e-1(c) under the
       Exchange Act, relating to our obligation to return tendered shares of
       Thermo Instrument common stock promptly after termination or withdrawal
       of the exchange offer, exchange shares of our common stock for any
       tendered shares of Thermo Instrument common stock, and

     - may delay the acceptance for exchange of or, subject to the restriction
       referred to above, the exchange of, any tendered shares of Thermo
       Instrument common stock.

     Minimum Number of Shares.  We may amend or terminate the exchange offer if
we would not own at least 90% of the outstanding shares of Thermo Instrument
immediately following the closing of the exchange offer. As of March 31, 2000,
we owned approximately 88.6% of the outstanding shares of Thermo Instrument
common stock. Assuming that optionholders exercised all outstanding Thermo
Instrument stock options and debenture holders did not convert any of Thermo
Instrument's 4% convertible subordinated debentures or 4.5% senior convertible
debentures into Thermo Instrument common stock, we would have owned
approximately 84.8% of the outstanding shares of Thermo Instrument common stock
at that date.

     Other Conditions.  In addition, we may amend or terminate the exchange
offer at any time on or after April 24, 2000 and before the time of acceptance
of the shares of Thermo Instrument common stock for exchange in the exchange
offer if any of the following events shall occur:

     - any change occurs in the business, properties, assets, liabilities,
       capitalization, stockholders' equity, financial condition, cash flows,
       operations, licenses, franchises or results of operations of Thermo
       Instrument or its subsidiaries which has a material adverse effect on
       Thermo Instrument and its subsidiaries taken as a whole;

     - any "governmental entity," including a government or governmental
       authority or agency, whether domestic, foreign or supranational,
       institutes or threatens any action, proceeding, application, claim or
       counterclaim, seeks or obtains any judgment, order or injunction, or
       takes any other action, which:

       -- challenges the acquisition by us or any of our affiliates of any
          shares of Thermo Instrument common stock pursuant to the exchange
          offer or the merger, restrains, prohibits or materially delays the
          making or consummation of the exchange offer or the merger, prohibits
          the performance of any of the contracts or other arrangements entered
          into by us or any of our affiliates in connection with the acquisition
          of the shares of Thermo Instrument common stock or Thermo Instrument,
          seeks to obtain any material amount of damages, or otherwise directly
          or indirectly adversely affects the exchange offer or the merger;

       -- seeks to prohibit or limit materially the ownership or operation by
          us, any of our affiliates or Thermo Instrument of all or any material
          portion of our business or assets or the businesses or assets of our
          affiliates or of Thermo Instrument and its subsidiaries, or to compel
          us, any of our affiliates or Thermo Instrument to dispose of or to
          hold separate all or any material portion of our, any of our
          affiliate's or Thermo Instrument's or its subsidiaries' businesses or
          assets as a result of the transactions contemplated by the exchange
          offer or the merger;

       -- seeks to impose any material limitation on the ability of us, any of
          our affiliates or Thermo Instrument to conduct Thermo Instrument's or
          its subsidiaries' businesses or to own Thermo Instrument's or its
          subsidiaries' assets;

       -- seeks to impose or confirm any material limitation on the ability of
          us or any of our affiliates to acquire or hold, or to exercise full
          rights of ownership of, any shares of Thermo Instrument

                                       39
<PAGE>   43

          common stock, including the right to vote such shares of Thermo
          Instrument common stock on all matters properly presented to the
          stockholders of Thermo Instrument;

       -- seeks to require us or any of our affiliates to divest all or any of
          our shares of Thermo Instrument common stock; or

       -- otherwise has resulted in or has a reasonable likelihood of resulting
          in a material adverse effect on our, any of our affiliate's or Thermo
          Instrument's business, financial condition, results of operation or
          prospects;

     - any statute, rule or regulation is enacted, promulgated, entered,
       enforced or treated as applicable to the exchange offer or the merger, or
       any other action is taken by any governmental entity or court, that
       results in, directly or indirectly, any of the consequences referred to
       in first four sub-bullets of the preceding bullet;

     - any preliminary or permanent judgment, order, decree, ruling or
       injunction is entered or issued, or any other action is taken by any
       governmental entity or court, whether on its own initiative or the
       initiative of any other person, which:

       -- restrains, prohibits or materially delays the making or completing of
          the exchange offer or the merger, prohibits the performance of any of
          the contracts or other arrangements entered into by us or any of our
          affiliates in connection with the acquisition of the shares of Thermo
          Instrument common stock or Thermo Instrument or otherwise directly or
          indirectly materially adversely affects the exchange offer or the
          merger;

       -- prohibits or limits materially the ownership or operation by us, any
          of our affiliates or Thermo Instrument of all or any material portion
          of our business or assets or the businesses or assets of our
          affiliates or of Thermo Instrument and its subsidiaries, or compels
          us, any of our affiliates or Thermo Instrument to dispose of or to
          hold separate all or any material portion of our, any of our
          affiliate's or Thermo Instrument's or its subsidiaries' businesses or
          assets as a result of the transactions contemplated by the exchange
          offer or the merger;

       -- imposes any material limitation on the ability of us or any of our
          affiliates to conduct Thermo Instrument's or its subsidiaries'
          businesses or to own Thermo Instrument's or its subsidiaries' assets;

       -- imposes or confirms any material limitation on the ability of us or
          any of our affiliates to acquire or hold, or to exercise full rights
          of ownership of, any shares of Thermo Instrument common stock,
          including the right to vote such shares of Thermo Instrument common
          stock on all matters properly presented to the stockholders of Thermo
          Instrument;

       -- requires us or any of our affiliates to divest of all or any of our
          shares of Thermo Instrument common stock; or

       -- otherwise has resulted in or has a reasonable likelihood of resulting
          in a material adverse effect on our, any of our affiliate's or Thermo
          Instrument's business, financial condition, results of operation or
          prospects;

     - any action, proceeding, application, claim or counterclaim is instituted
       or pending before any governmental entity or court, or any judgment,
       order or injunction is sought or any other action is taken by any person
       or entity, other than a governmental entity, which:

       -- challenges the acquisition by us or any of our affiliates of any
          shares of Thermo Instrument common stock pursuant to the exchange
          offer or the merger, restrains, prohibits or materially delays the
          making or consummation of the exchange offer or the merger, prohibits
          the performance of any of the contracts or other arrangements entered
          into by us or any of our affiliates in connection with the acquisition
          of the shares of Thermo Instrument common stock, seeks to obtain any
          material amount of damages, or otherwise directly or indirectly
          adversely affects the exchange offer or the merger;
                                       40
<PAGE>   44

       -- seeks to prohibit or limit materially the ownership or operation by
          us, any of our affiliates or Thermo Instrument of all or any material
          portion of our business or assets or the businesses or assets of our
          affiliates or of Thermo Instrument and its subsidiaries, or to compel
          us, any of our affiliates or Thermo Instrument to dispose of or to
          hold separate all or any material portion of our, any of our
          affiliate's or Thermo Instrument's or its subsidiaries' businesses or
          assets as a result of the transactions contemplated by the exchange
          offer or the merger;

       -- seeks to impose any material limitation on the ability of us, any of
          our affiliates or Thermo Instrument to conduct Thermo Instrument's or
          its subsidiaries' businesses or to own Thermo Instrument's and its
          subsidiaries' assets;

       -- seeks to impose or confirm any material limitation on the ability of
          us or any of our affiliates to acquire or hold, or to exercise full
          rights of ownership of, any shares of Thermo Instrument common stock,
          including the right to vote such shares of Thermo Instrument common
          stock on all matters properly presented to the stockholders of Thermo
          Instrument;

       -- seeks to require us or any of our affiliates to divest of all or any
          of our shares of Thermo Instrument common stock; or

       -- otherwise has resulted in or, in our reasonable discretion, has a
          reasonable likelihood of resulting in a material adverse effect on
          our, any of our affiliates' or Thermo Instrument's business, financial
          condition, results of operation or prospects;

      and which in the case of the first five sub-bullets of this bullet is
      successful or we determine, in our reasonable discretion, has a reasonable
      likelihood of being successful;

     - the registration statement of which this prospectus is a part does not
       become effective under the Securities Act of 1933 or is the subject of
       any stop order or proceedings seeking a stop order;

     - the shares of our common stock issuable to Thermo Instrument stockholders
       in the exchange offer and the merger and the shares issuable upon the
       exercise of options to purchase shares of our common stock or the
       conversion of debentures convertible into our common stock are not
       approved for listing on the New York Stock Exchange, subject to official
       notice of issuance;

     - any general suspension of trading in, or limitation on prices for,
       securities occurs on the New York Stock Exchange or the American Stock
       Exchange or in the over-the-counter market, other than any temporary
       suspension pursuant to a circuit breaker procedure then in effect and
       lasting for not more than three trading hours;

     - any declaration of a banking moratorium by federal or New York
       authorities or general suspension of payments in respect of lenders that
       regularly participate in the U.S. market in loans occurs;

     - any material limitation by any federal, state or local government or any
       court, administrative or regulatory agency or commission or other
       governmental authority or agency in the United States occurs that
       materially affects the extension of credit generally by lenders that
       regularly participate in the U.S. market in loans;

     - any commencement of a war involving the United States or any commencement
       of armed hostilities or other national or international circumstance
       involving the United States occurs that has a material adverse effect on
       bank syndication or financial markets in the United States; or

     - in the case of any occurrence described in the previous four bullets that
       existed on or at the time of the commencement of the exchange offer, a
       material acceleration or worsening of that occurrence; which in our
       reasonable judgment, in any case and regardless of the circumstances
       giving rise to the condition, makes it inadvisable to proceed with the
       exchange offer or with acceptance of shares of Thermo Instrument common
       stock for exchange or exchanges of shares of our common stock for shares
       of Thermo Instrument common stock.

                                       41
<PAGE>   45

     Conditions Solely for Our Benefit.  The foregoing conditions are for our
sole benefit and we may assert them regardless of any circumstances giving rise
to any condition. We may waive these conditions in whole or in part, at any time
and from time to time before the exchange offer expires, in our reasonable
discretion. Our failure, or the failure of any of our affiliates, at any time to
exercise any of the foregoing rights will not constitute a waiver of any right.
We will treat each right as an ongoing right which may be asserted at any time
and from time to time before the exchange offer expires.

LEGAL MATTERS; REGULATORY APPROVALS

     General.  Except as described below, we are not aware of any license or
regulatory permit that appears to be material to the business of Thermo
Instrument and its subsidiaries and may be adversely affected by our acquisition
of shares of Thermo Instrument common stock in the exchange offer or the merger.

     Except as described in this section, we are not aware of any other material
filing, approval or other action by any federal or state governmental or
administrative authority that we must obtain in connection with our acquisition
of shares of Thermo Instrument common stock as contemplated in this prospectus.
Should any other similar approval or action be required, we currently
contemplate seeking that approval or action. We cannot assure you that we could
obtain any other approval or action, if needed, without substantial conditions
or costs or that adverse consequences would not result to our or Thermo
Instrument's business if we do not obtain any other required approvals or
actions. Our obligation under the exchange offer to accept for exchange and
exchange shares of Thermo Instrument common stock is subject to a number of
conditions, including conditions relating to the legal matters discussed in this
section. See "-- Conditions Of The Offer."

     Antitrust.  We believe that the exchange offer and the merger are exempt
from the reporting requirements contained in the Hart-Scott-Rodino Antitrust
Improvements Act of 1976. Nevertheless, we cannot assure that a challenge to the
exchange offer and the merger on antitrust grounds will not be made or, if such
challenge is made, what the result will be.

     Foreign Approvals.  Thermo Instrument conducts business in a number of
foreign countries and jurisdictions. In connection with our acquisition of
shares of Thermo Instrument common stock pursuant to the exchange offer or the
merger, we and/or Thermo Instrument may be required to file information with, or
obtain the approval or consent of, governmental authorities in those foreign
countries and jurisdictions. The governments in those countries and
jurisdictions might attempt to impose additional conditions on Thermo
Instrument's operations conducted in such countries and jurisdictions as a
result of our acquisition of the shares of Thermo Instrument common stock
pursuant to the exchange offer or the merger of Thermo Instrument into Thermo
Electron.

     If foreign approvals or consents are required, we intend to make the
appropriate filings and applications. We do not know if or when we will obtain
any required foreign approvals or consents for which we file or apply. In
addition, we may be unable to cause Thermo Instrument or its subsidiaries to
satisfy or comply with foreign laws. Noncompliance may have adverse consequences
for Thermo Instrument or its subsidiaries after the exchange of shares of our
common stock for shares of Thermo Instrument common stock pursuant to the
exchange offer or the merger.

     State Anti-Takeover Statutes.  Section 203 of the Delaware General
Corporation Law prohibits business combination transactions involving a Delaware
corporation, such as Thermo Instrument, and an "interested stockholder" for
three years following the time the person became an interested stockholder.
Section 203 defines an interested stockholder in general as any person that
directly or indirectly beneficially owns 15% or more of the outstanding voting
stock of the subject corporation. The prohibitions in Section 203 do not apply
if special requirements are met or exceptions apply, including that prior to the
time a person became an interested stockholder the board of directors of the
subject corporation approved either the business combination or the transaction
which resulted in such person being an interested stockholder. We believe that
neither the exchange offer nor the merger is prohibited by Section 203 of the
Delaware General Corporation Law.
                                       42
<PAGE>   46

     A number of other states have adopted laws and regulations applicable to
attempts to acquire securities of corporations which are incorporated, or have
substantial assets, stockholders, principal executive offices or principal
places of business, or whose business operations otherwise have substantial
economic effects, in such states. In 1982, in Edgar v. MITE Corp., the Supreme
Court of the United States invalidated on constitutional grounds the Illinois
Business Takeover Statute, which, as a matter of state securities law, made
takeovers of corporations meeting the statute's requirements more difficult.
However, in 1987 in CTS Corp. v. Dynamics Corp. of America, the Supreme Court
held that the State of Indiana may, as a matter of corporate law, and, in
particular, with respect to those aspects of corporate law concerning corporate
governance, constitutionally disqualify a potential acquiror from voting on the
affairs of a target corporation without the prior approval of the remaining
stockholders. The state law before the Supreme Court was by its terms applicable
only to corporations that had a substantial number of stockholders in that state
and were incorporated there.

     Thermo Instrument, directly or through its subsidiaries, conducts business
in a number of states throughout the United States, some of which have enacted
anti-takeover laws. We do not know whether any of these laws will, by their
terms, apply to the exchange offer or the merger, and we have not necessarily
complied with any such laws. Should any person seek to apply any state
anti-takeover law to the exchange offer or the merger, we will take such action
as then appears desirable, which may include challenging the validity or
applicability of any such statute in appropriate court proceedings. In the event
it is asserted that one or more state anti-takeover laws is applicable to the
exchange offer or the merger, and an appropriate court does not determine that
it is inapplicable or invalid as applied to the exchange offer or the merger, we
may be required to file information with, or receive approvals from, the
relevant state authorities. In addition, if enjoined, we may be unable to accept
for exchange any shares of Thermo Instrument common stock tendered pursuant to
the exchange offer, or be delayed in continuing or consummating the exchange
offer. In any such case, we may not be obligated to accept for exchange any
shares of Thermo Instrument common stock tendered. See "-- Conditions Of The
Offer."

DIVIDENDS AND DISTRIBUTIONS

     If, on or after April 24, 2000, Thermo Instrument should declare or pay any
dividend or other distribution, including without limitation the issuance of
additional shares of Thermo Instrument common stock pursuant to any stock
dividend or stock split or the issuance of rights for the purchase of any
securities, with respect to the shares of Thermo Instrument common stock, and
the dividend or distribution is payable or distributable to stockholders of
record on a date occurring before the transfer to our name or the name of our
nominees or transferees on Thermo Instrument's stock transfer records of the
shares of Thermo Instrument common stock acquired pursuant to the exchange
offer, then, without prejudice to our rights described in "-- Conditions Of The
Offer":

     - in the event of a cash dividend or distribution, the exchange ratio per
       share will be reduced by multiplying the exchange ratio by a fraction the
       numerator of which is $19.375, the closing market price of the Thermo
       Instrument common stock on March 7, 2000, minus the amount of the cash
       dividend or distribution and the denominator is $19.375; and

     - in the event of a non-cash dividend or distribution, you will be required
       to deliver promptly and transfer to the depositary for our account any
       non-cash dividend or distribution, including additional shares of Thermo
       Instrument common stock, together with appropriate documentation of
       transfer. Pending your remittance or appropriate assurance of your
       remittance, we will be entitled to all rights and privileges as owner of
       any such non-cash dividend, distribution or right, and may withhold all
       of the shares of our common stock issuable to you in the exchange offer
       or reduce the exchange ratio by multiplying the exchange ratio by a
       fraction, the numerator of which is $19.375, the closing price of the
       Thermo Instrument common stock on March 7, 2000 minus the value of such
       non-cash dividend, distribution or right, as determined by us in our sole
       discretion, and the denominator of which is $19.375.

                                       43
<PAGE>   47

     If, on or after April 24, 2000, Thermo Instrument should split the shares
of its common stock or combine or otherwise change the shares of its common
stock or its capitalization, then, without prejudice to our rights described in
"-- Conditions Of The Offer," we may make appropriate adjustments to reflect
such split, combination or change in the exchange ratio and other terms of the
exchange offer, including without limitation the number or type of securities we
are offering in exchange for Thermo Instrument common stock.

FEES AND EXPENSES

     J.P. Morgan and The Beacon Group are acting as our financial advisors in
connection with the exchange offer and the merger involving Thermo Instrument
described in this prospectus.

     In October 1999, we engaged The Beacon Group as our financial advisor in
connection with our proposed acquisition of the outstanding shares held by
public stockholders in certain of our subsidiaries. We paid The Beacon Group
$500,000 in fees for services that The Beacon Group rendered pursuant to that
engagement in connection with our acquisition of the outstanding publicly-held
shares of common stock of ThermoTrex Corporation and ThermoLase Corporation.

     Pursuant to our letter agreement with J.P. Morgan and The Beacon Group,
dated January 17, 2000, we agreed to pay each of J.P. Morgan and The Beacon
Group a fee of $500,000 for its services in connection with the exchange offer
and the merger involving Thermo Instrument described in this prospectus. In
addition, we will reimburse J.P. Morgan and The Beacon Group for expenses
incurred in connection with these transactions. The letter agreement also
relates to our overall reorganization and provides for separate fees for
services with respect to other elements of our reorganization. These other fees
include a minimum retainer for each of J.P. Morgan and The Beacon Group of $1.25
million. The engagement letter provides for substantial additional compensation
if we complete some or all of the other elements of our reorganization. We have
agreed to indemnify J.P. Morgan and The Beacon Group and their affiliates
against certain liabilities, including liabilities under the federal securities
laws in connection with their engagement.

     We have retained D.F. King & Co., Inc. to act as the information agent and
American Stock Transfer & Trust Company to act as the depositary in connection
with the exchange offer. The information agent may contact holders of shares of
Thermo Instrument common stock by mail, telephone, telex, telecopy, telegraph
and personal interview and may request brokers, dealers, commercial banks, trust
companies and other nominees to forward the exchange offer material to
beneficial owners. Each of the information agent and the depositary will receive
reasonable and customary compensation for its services, will be reimbursed for
reasonable out-of-pocket expenses and will be indemnified against certain
liabilities and expenses in connection with the exchange offer, including
certain liabilities under U.S. federal securities laws.

     We will not pay any fees or commissions to any broker or dealer or any
other person for soliciting tenders of shares of Thermo Instrument common stock
in the exchange offer, other than to the information agent. We will, upon
request, reimburse brokers, dealers, commercial banks and trust companies for
customary mailing and handling expenses incurred by them in forwarding materials
to their customers.

                                       44
<PAGE>   48

     The following is an estimate of the fees and expenses that we expect to
incur in connection with the exchange offer and the merger:

<TABLE>
<CAPTION>

<S>                                                           <C>
Financial Advisors..........................................  $1,000,000
Legal.......................................................     250,000
Printing....................................................     100,000
Listing Fee.................................................      25,650
SEC Filing Fee..............................................     100,789
Depositary..................................................       7,500
Information Agent, including mailing........................      15,000
Miscellaneous...............................................      26,061
                                                              ----------
                                                              $1,525,000
                                                              ==========
</TABLE>

     We will pay these fees and expenses, including any cash paid for fractional
shares, out of cash that we currently hold. Thermo Instrument will not pay any
of the fees and expenses to be incurred by us in connection with the exchange
offer.

STOCK EXCHANGE LISTING

     Our common stock is listed on the New York Stock Exchange. We will make an
application as necessary to list on the New York Stock Exchange the common stock
that we will issue pursuant to the exchange offer and the merger. We will not
accept for exchange, or exchange for shares of our common stock, any shares of
common stock of Thermo Instrument or complete the merger unless the following
shares of our common stock are approved for listing on the New York Stock
Exchange, subject to official notice of issuance:

     - the shares issuable to Thermo Instrument stockholders in the exchange
       offer and the merger;

     - the shares issuable upon the exercise of options to purchase shares of
       Thermo Instrument common stock that we assume in connection with the
       exchange offer and the merger; and

     - shares issuable upon the conversion of the Thermo Instrument convertible
       debentures that we assume in connection with the exchange offer and the
       merger.

                                       45
<PAGE>   49

                          MARKET PRICES AND DIVIDENDS

PRICE RANGE OF SHARES OF OUR COMMON STOCK AND OF THERMO INSTRUMENT COMMON STOCK

     Our common stock is listed on the New York Stock Exchange under the symbol
"TMO." Thermo Instrument common stock is listed on the American Stock Exchange
under the symbol "THI." The following table sets forth the high and low sales
prices per share of our common stock and of Thermo Instrument common stock, as
reported in publicly available sources for each of the periods indicated.

<TABLE>
<CAPTION>
                                                                                      THERMO
                                                            THERMO ELECTRON         INSTRUMENT
                                                            ----------------      --------------
                                                            HIGH        LOW       HIGH      LOW
                                                            -----      -----      ----      ----
<S>                                                         <C>        <C>        <C>       <C>
Fiscal Year Ended January 2, 1999:
  First Quarter.......................................       43 5/16    36 5/8     35 7/16   27 13/16
  Second Quarter......................................       41 15/16   30 3/4     34 1/2    25 7/8
  Third Quarter.......................................       35 3/16    14 3/16    26 1/2    10
  Fourth Quarter......................................       20 1/16    13 9/16    15 1/8     7 7/8
Fiscal Year Ended January 1, 2000:
  First Quarter.......................................       18 3/16    13 3/8     17 7/16   13 1/2
  Second Quarter......................................       20 1/4     12 1/2     16 7/8    12 3/16
  Third Quarter.......................................       19 11/16   13 1/8     17        10 3/8
  Fourth Quarter......................................       16 1/8     12 3/4     12 3/4     8 1/8
Fiscal Year Ending December 30, 2000:
  First Quarter.......................................       26 7/8     14         23        10 1/4
  Second Quarter, through April 20, 2000..............       21 7/16    17 3/4     21        18 3/4
</TABLE>

     As of April 20, 2000, there were 8,329 holders of record and in excess of
36,500 beneficial owners of the shares of our common stock. As of April 20,
2000, there were 2,821 holders of record and in excess of 6,700 beneficial
owners of shares of Thermo Instrument common stock.

     On January 28, 2000, the last full trading day prior to the public
announcement of our intention to commence the exchange offer, the closing sale
price per share of Thermo Instrument common stock, as reported on the American
Stock Exchange, was $15.6875. On March 7, 2000, the day prior to our
announcement of the exchange ratio, the closing sale price per share of Thermo
Instrument common stock, as reported on the American Stock Exchange, was
$19.9375.

     YOU SHOULD OBTAIN CURRENT MARKET QUOTATIONS FOR THE SHARES OF OUR COMMON
STOCK AND THERMO INSTRUMENT COMMON STOCK.

DIVIDENDS

     Neither we nor Thermo Instrument has ever declared or paid any cash
dividends in respect of our common stock.

                                       46
<PAGE>   50

                          THE MERGER; APPRAISAL RIGHTS

THE MERGER

     If we complete the exchange offer, we will cause Thermo Instrument to merge
with and into Thermo Electron in accordance with the Delaware General
Corporation Law. Upon the effective date of this merger, each share of Thermo
Instrument common stock issued and outstanding immediately prior to the
effective date of the merger, other than shares owned by us and shares held by
Thermo Instrument's public stockholders, if any, who are entitled to and who
properly exercise their dissenters' rights under the Delaware General
Corporation Law, as described below under "-- Appraisal Rights," will be
cancelled and converted into a right to receive 0.85 shares of our common stock
for each share of Thermo Instrument common stock. Thermo Instrument stockholders
will also be entitled to receive cash in lieu of the issuance of fractional
shares of our common stock in an amount equal to $19.1875 for each whole share
of our common stock. As a result of the merger, Thermo Instrument will cease to
exist as a separate legal entity, and we will own all of Thermo Instrument's
assets.

     Under the Delaware General Corporation Law, if we hold at least 90% of the
outstanding shares of Thermo Instrument common stock, we may effect the merger
without a vote of Thermo Instrument's board of directors or Thermo Instrument's
other stockholders. We intend to take all necessary and appropriate action to
cause the merger to become effective as promptly as practicable after we
complete the exchange offer, and without a meeting of the Thermo Instrument's
stockholders.

APPRAISAL RIGHTS

     The Delaware General Corporation Law does not entitle stockholders of
Thermo Instrument who tender their shares of Thermo Instrument common stock in
the exchange offer to appraisal rights. If we complete the merger, then
stockholders of Thermo Instrument who do not tender their shares of Thermo
Instrument common stock to us pursuant to the exchange offer would have the
right to demand an appraisal of the fair value of their shares of Thermo
Instrument common stock in accordance with the provisions of Section 262 of the
Delaware General Corporation Law, which sets forth the rights and obligations of
stockholders of Thermo Instrument demanding an appraisal and the procedures to
be followed.

     The Appraisal Statute.  Under Delaware law, record holders of shares of
Thermo Instrument common stock who follow the procedures set forth in Section
262 will be entitled to have their shares appraised by the Court of Chancery of
the State of Delaware and to receive payment of the fair value of their shares
together with a fair rate of interest, if any, as determined by such court. The
Delaware court does not consider benefits arising from the merger in determining
the value of the Thermo Instrument common stock. The following is a summary of
the provisions of Section 262 of the Delaware General Corporation Law and is
qualified in its entirety by reference to the full text of Section 262, a copy
of which is included with this prospectus as Annex C.

     Required Notice and Demand.  Within ten days following the consummation of
the merger, we would notify the Thermo Instrument stockholders of record of:

     - the effective date of the merger;

     - the approval and consummation of the merger; and

     - the availability of appraisal rights under Section 262.

Any Thermo Instrument stockholder entitled to appraisal rights would have the
right, within 20 days after the date of mailing of the required notice, to
demand in writing from us an appraisal of the stockholder's shares. Such demand
would be sufficient if it reasonably informs us of the identity of the
stockholder and that the stockholder intends to demand an appraisal of the fair
value of the stockholder's shares. Failure to make such a timely demand would
foreclose a Thermo Instrument stockholder's right to appraisal.

     Only a record holder of shares of Thermo Instrument common stock at the
time of the merger would be entitled to assert appraisal rights for the shares
registered in that holder's name. You should execute any demand for appraisal in
your name, as it appears on your stock certificates, if you are the holder of
record. If you are not the holder of record, you should have the holder of
record execute any demand for

                                       47
<PAGE>   51

appraisal. Holders of shares of Thermo Instrument common stock who hold their
shares in brokerage accounts or other nominee forms and wish to exercise
appraisal rights should consult with their brokers to determine the appropriate
procedures for the making of a demand for appraisal by such nominee. You should
send or deliver all written demands for appraisal to Sandra L. Lambert,
Secretary, Thermo Instrument Systems Inc., c/o Thermo Electron Corporation, 81
Wyman Street, P.O. Box 9046, Waltham, Massachusetts 02454-9046, so that we
receive the request within 20 days after our mailing of the notice of the merger
described above.

     If you own shares of Thermo Instrument common stock in a fiduciary
capacity, such as in a capacity as a trustee, guardian or custodian, you should
execute the demand in that capacity. If more than one person owns the shares, as
in a joint tenancy or tenancy in common, all of the joint owners should execute
the demand or you should execute the demand on behalf of all of the joint
owners.
An authorized agent, including one or more joint owners, may execute a demand
for appraisal on behalf of a holder of record; however, the agent must identify
the record owner or owners and expressly disclose the fact that, in executing
the demand, the agent is agent for such owner or owners.

     A record holder, such as a broker holding shares of Thermo Instrument
common stock as nominee for several beneficial owners, may exercise appraisal
rights with respect to the shares held for one or more beneficial owners while
not exercising such rights with respect to the shares held for other beneficial
owners. In such case, the written demand should set forth the number of shares
as to which appraisal is sought. Where no number of shares is expressly
mentioned, the demand will be presumed to cover all shares held in the name of
the record owner.

     Filing a Petition for Appraisal.  Within 120 calendar days after the
effective date of the merger, we or any stockholder entitled to appraisal rights
under Section 262 and who has complied with the foregoing procedures may file a
petition in the Delaware Court of Chancery demanding a determination of the fair
value of the shares of Thermo Instrument common stock of all such stockholders.
We are not under any obligation, and have no present intention, to file a
petition with respect to the appraisal of the fair value of the shares of Thermo
Instrument common stock. Accordingly, it is the obligation of the stockholders
to initiate all necessary action to perfect their appraisal rights within the
time prescribed in Section 262.

     Information We Will Provide.  Within 120 calendar days after the effective
date of the merger, any stockholder of record who has complied with the
requirements for exercise of appraisal rights will be entitled, upon written
request, to receive from us a statement setting forth the aggregate number of
shares of Thermo Instrument common stock with respect to which demands for
appraisal have been received and the aggregate number of holders of such shares.
We must mail this statement within 10 calendar days after we receive a written
request or within 10 calendar days after the expiration of the period for the
delivery of demands for appraisals, whichever is later.

     The Court's Determination.  If you file a petition for an appraisal on a
timely basis, then, after a hearing on the petition, the Delaware Court of
Chancery will determine the stockholders entitled to appraisal rights and will
appraise the fair value of the shares of Thermo Instrument common stock,
together with a fair rate of interest, if any, to be paid upon the amount
determined to be the fair value. If you are considering seeking appraisal, you
should be aware that the fair value of your shares as determined under Section
262 could be more than, the same as or less than the amount per share that you
would otherwise receive if you did not seek appraisal of your shares. The
Delaware Supreme Court has stated that "proof of value by any techniques or
methods that are generally considered acceptable in the financial community and
otherwise admissible in court" should be considered in appraisal proceedings. In
addition, Delaware courts have decided that the statutory appraisal remedy,
depending on factual circumstances, may or may not be a dissenter's exclusive
remedy.

     The Court will determine the amount of interest, if any, to be paid upon
the amounts to be received by persons whose shares have been appraised. The
Court may also determine the costs of the action and tax the parties as the
Court deems equitable. The Court may also order that all or a portion of the
expenses incurred by any holder of shares in connection with an appraisal,
including, without limitation, reasonable attorneys' fees and the fees and
expenses of experts used in the appraisal proceeding, be charged pro rata
against the value of all the shares entitled to appraisal.

                                       48
<PAGE>   52

     The Court may require stockholders who have demanded an appraisal and who
hold shares of Thermo Instrument common stock represented by certificates to
submit their certificates for shares to the Court for notation thereon of the
pendency of the appraisal proceedings. If any stockholder fails to comply with
such direction, the Court may dismiss the proceedings as to such stockholder.

     Consequences of a Demand for Appraisal.  Any stockholder who has duly
demanded an appraisal in compliance with Section 262 will not, after the
effective date of the merger, be entitled to vote the shares of Thermo
Instrument common stock subject to such demand for any purpose or to be entitled
to the payment of dividends or other distributions on those shares, except
dividends or other distributions payable to holders of record of shares as of a
date prior to the effective date of the merger.

     If any stockholder who demands appraisal of shares under Section 262 fails
to perfect, or effectively withdraws or loses, the right to appraisal, as
provided in the Delaware General Corporation Law, the shares of Thermo
Instrument common stock of such holder will be converted into the right to
receive 0.85 shares of our common stock for each share of Thermo Instrument
common stock plus cash in lieu of the issuance of fractional shares of our
common stock in an amount equal to $19.1875 per whole share, without interest. A
stockholder will fail to perfect, or effectively lose, the right to appraisal if
no petition is filed within 120 calendar days after the effective date of the
merger. A stockholder may withdraw a demand for appraisal by delivering to us a
written withdrawal of the demand for appraisal and acceptance of the merger,
except that any such attempt to withdraw made more than 60 calendar days after
the effective date of the merger will require our written approval. Once you
have filed a petition for appraisal, the appraisal proceeding may not be
dismissed as to any stockholder without the approval of the Court.

     For federal income tax purposes, stockholders who receive cash for their
shares of Thermo Instrument common stock upon exercise of dissenters' rights
will realize taxable gain or loss. See "Federal Income Tax Consequences."

     THE FOREGOING SUMMARY IS NOT A COMPLETE STATEMENT OF THE PROCEDURES THAT
YOU MUST FOLLOW TO EXERCISE YOUR DISSENTING APPRAISAL RIGHTS. THE FULL TEXT OF
THE DELAWARE APPRAISAL STATUTE IS ATTACHED TO THIS PROSPECTUS AS ANNEX C. YOU
SHOULD READ ANNEX C IN ITS ENTIRETY BECAUSE FAILING TO COMPLY WITH THE
PROCEDURES SET FORTH IN THE DELAWARE APPRAISAL STATUTE WILL RESULT IN THE LOSS
OF YOUR APPRAISAL RIGHTS.

                        FEDERAL INCOME TAX CONSEQUENCES

     This section summarizes the important federal income tax consequences of
the exchange offer and the merger to you. This summary is based on the current
Internal Revenue Code, Treasury regulations and administrative rulings and court
decisions, all of which can change. If there are any changes to the Internal
Revenue Code, those regulations or those rulings and decisions, the tax
consequences to you might change. Any changes could be retroactive.

     You should know that this summary does not deal with all federal income tax
considerations that may be relevant to you because of your particular
circumstances. Some examples of circumstances that would involve different
federal income tax consequences are if you:

     - were a dealer in securities;

     - were an insurance company or financial institution;

     - were a foreign person or entity;

     - do not hold your Thermo Instrument common stock as a capital asset; or

     - acquired your shares in connection with stock option or stock purchase
       plans or in other compensatory transactions.

     In addition, the following discussion does not address the tax consequences
of the exchange offer and the merger under foreign, state or local tax laws. WE
RECOMMEND THAT YOU CONSULT YOUR OWN TAX ADVISOR AS TO THE SPECIFIC TAX
CONSEQUENCES TO YOU OF THE EXCHANGE OFFER AND THE MERGER, INCLUDING THE
APPLICATION OF STATE, LOCAL, FOREIGN AND OTHER TAX LAWS.

     In connection with the exchange offer and merger, Hale and Dorr LLP, our
legal counsel, has rendered a tax opinion to Thermo Instrument that the exchange
offer and the merger of Thermo

                                       49
<PAGE>   53

Instrument into us should be treated as one integrated transaction that will
qualify as a "reorganization" within the meaning of Section 368(a) of the
Internal Revenue Code. We and Thermo Instrument gave Hale and Dorr information
about the exchange offer and the merger. Hale and Dorr based their tax opinion
on that information. In addition, Hale and Dorr assumed some facts in giving
their tax opinion, and their opinion contains various qualifications and
limitations. We have filed Hale and Dorr's tax opinion as an exhibit to the
registration statement of which this prospectus is a part. Subject to the
assumptions, limitations and qualifications in the tax opinion, Hale and Dorr is
of the opinion that the exchange offer and the merger should result in the
following federal income tax consequences:

     - You will not recognize any gain or loss solely upon the exchange of your
       shares of Thermo Instrument common stock for our common stock pursuant to
       the exchange offer or the merger, except for any cash you receive in lieu
       of fractional shares of our common stock.

     - Your aggregate tax basis in our common stock that you receive pursuant to
       the exchange offer or the merger will be the same as your aggregate tax
       basis in the Thermo Instrument common stock that you tendered, reduced by
       the amount of any tax basis attributable to any fractional shares that
       you do not actually receive.

     - Your holding period for our common stock that you receive pursuant to the
       exchange offer or the merger will include the period for which you held
       the Thermo Instrument common stock that you exchange for our common
       stock, if you held the Thermo Instrument common stock as a capital asset
       at the time of the exchange.

     - Cash payments that you receive in lieu of a fractional share will be
       treated as if that fractional share of our common stock had been issued
       pursuant to the exchange offer or the merger and then redeemed by us
       after the exchange offer or the merger. You generally will recognize gain
       or loss upon any cash you so receive measured by the difference, if any,
       between the amount of cash you receive and your basis in that fractional
       share.

     - Neither we nor Thermo Instrument will recognize gain or loss directly as
       a result of the exchange offer or the merger.

     We will not, and Thermo Instrument will not, request a ruling from the
Internal Revenue Service in connection with the exchange offer or the merger.
You should be aware that Hale and Dorr's tax opinion will not bind the Internal
Revenue Service. Hale and Dorr relied upon many factual representations by us in
rendering its tax opinion and, in particular, upon our representation that if
the exchange offer is successful, we will cause the merger of Thermo Instrument
with and into us to occur.

     Hale and Dorr's tax opinion does not address or consider the tax effect on
you of our proposed spin-offs of our business that serves the healthcare
industry with a range of medical products for diagnosis and monitoring and our
paper recycling and papermaking equipment business. In that regard, we have
requested a ruling from the Internal Revenue Service regarding the tax
consequences of the spin-offs. We expect to proceed with the spin-offs only if
we receive a ruling that the spin-offs will qualify under Section 355 of the
Internal Revenue Code. Accordingly, if the spin-offs occur, we anticipate that
the ruling we receive from the Internal Revenue Service will address the tax
consequences of the spin-offs to our stockholders, including those stockholders
who received their shares pursuant to the exchange offer or the merger. Any
ruling that we receive from the Internal Revenue Service may provide that the
spin-offs could be taxable to some or all of our stockholders, including the
prior stockholders of Thermo Instrument who received our common stock pursuant
to the exchange offer or the merger.

     A successful challenge by the Internal Revenue Service to the
reorganization status of the exchange offer and the merger would result in your
recognizing taxable gain or loss on each share of Thermo Instrument common stock
that you exchanged in the exchange offer or the merger. The amount of gain or
loss would be equal to the difference between your basis in that share and the
fair market value, as of the effective time of the exchange, of our common stock
that you received in exchange for that share. In such event, a stockholder's
aggregate basis in our common stock so received would equal its fair market
value as of the effective time of the exchange, and the stockholder's holding
period for such stock would begin the day after the exchange.

                                       50
<PAGE>   54

          COMPARISON OF THE RIGHTS OF HOLDERS OF OUR COMMON STOCK AND
            THE RIGHTS OF HOLDERS OF THERMO INSTRUMENT COMMON STOCK

     Upon completion of the exchange offer and the merger, stockholders of
Thermo Instrument will become stockholders of Thermo Electron, rather than
stockholders of Thermo Instrument. Thermo Electron's charter and bylaws will
govern your rights as a stockholder of Thermo Electron. Our charter and bylaws
differ in some important respects from Thermo Instrument's charter and bylaws.
Both Thermo Electron and Thermo Instrument are incorporated under the laws of
the State of Delaware. As Thermo Electron stockholders, the Delaware General
Corporation Law will continue to govern the rights of former Thermo Instrument
stockholders.

     The following is a comparison of:

     - the current rights of Thermo Instrument stockholders under Thermo
       Instrument's charter and bylaws; and

     - the rights Thermo Instrument stockholders would have as Thermo Electron
       stockholders under Thermo Electron's charter and bylaws after the
       completion of the offer and the merger.

The comparison summarizes the material differences but does not list all
differences between the rights of Thermo Electron stockholders and Thermo
Instrument stockholders.

<TABLE>
<CAPTION>
                                      THERMO ELECTRON                             THERMO INSTRUMENT
                          ---------------------------------------      ---------------------------------------
<S>                       <C>                                          <C>
BOARD OF DIRECTORS
Classified Board          Divided into three classes, as nearly        Consists of single class serving a
                          equal in number as possible, with each       one-year term.
                          class serving a staggered three-year
                          term.

Removal of Directors      Directors may be removed for cause           Directors may be removed, with or
                          only, at any special or annual meeting,      without cause, by the holders of a
                          by the affirmative vote of a majority        majority of the shares then entitled to
                          in number of shares of the stockholders      vote at an election of directors.
                          present in person or by proxy at such
                          meeting entitled to vote for the
                          election of such director.

Filling of Board          Vacancies on the board of directors may      Same.
Vacancies                 be filled by the vote of a majority of
                          the directors then in office.

Size of Board             The number of directors may be fixed by      The number of directors may be fixed by
                          resolution of the board, but may not be      resolution of the board but may not be
                          less than 3. The current number of           less than 2 nor more than 13. The
                          directors is 9.                              current number of directors is 2.

ANNUAL MEETING            Held on date fixed by the board.             Same.

CALLING A SPECIAL         Special meetings may be called only by       Special meetings may be called only by
MEETING                   the board of directors, the chairman of      the board of directors, the chairman of
                          the board of directors or the chief          the board of directors, the president
                          executive officer.                           or any vice president.
</TABLE>

                                       51
<PAGE>   55

<TABLE>
<CAPTION>
                                      THERMO ELECTRON                             THERMO INSTRUMENT
                          ---------------------------------------      ---------------------------------------
<S>                       <C>                                          <C>
QUORUM REQUIREMENTS       The presence in person or by proxy of        Same.
                          the holders of a majority of the shares
                          entitled to vote at the meeting
                          constitute a quorum for that meeting,
                          except as otherwise provided by the
                          Delaware General Corporation Law.

STOCKHOLDER ACTION BY     May take action by written consent of        May take action by written consent of
WRITTEN CONSENT           stockholders having no less than the         stockholders having not less than 50%
                          minimum number of votes that would be        of all of the stock entitled to vote on
                          necessary to take such action at a           the action if a meeting were held.
                          meeting at which all shares entitled to
                          vote on the matter were present and
                          voted.

ADVANCE NOTICE FOR        A stockholder must deliver notice of         No advance notice provisions.
STOCKHOLDER NOMINATIONS   stockholder nominations or proposals to
AND OTHER BUSINESS        be made at an annual stockholders
                          meeting to the secretary not less than
                          60 days nor more than 75 days before
                          the first anniversary of the date on
                          which proxy materials for the preceding
                          year's annual stockholders meeting were
                          first mailed. However, if the date of
                          the annual meeting is moved ahead more
                          than 30 days before or delayed by more
                          than 30 days after the anniversary of
                          the preceding year's annual stockholder
                          meeting, a stockholder must deliver
                          notice not later than the close of
                          business on the later of:
                          - the 90th day prior to such annual
                            meeting; or
                          - the 10th day following the day on
                            which public announcement of the date
                            of such meeting is made.

AMENDMENTS TO
ORGANIZATIONAL DOCUMENTS

Certificate of            The approval of both our board of            Same.
Incorporation             directors and the holders of a majority
                          of our outstanding shares entitled to
                          vote for the amendment is required for
                          an amendment to our Certificate of
                          Incorporation.
</TABLE>

                                       52
<PAGE>   56

<TABLE>
<CAPTION>
                                      THERMO ELECTRON                             THERMO INSTRUMENT
                          ---------------------------------------      ---------------------------------------
<S>                       <C>                                          <C>
Bylaws                    The board of directors may amend and         The board of directors may amend and
                          repeal bylaws. The holders of a              repeal bylaws. The holders of a
                          majority of the shares of capital stock      majority of the shares of capital stock
                          issued and outstanding and entitled to       issued and outstanding and entitled to
                          vote, voting together as a single            vote, voting together as a single
                          class, may also amend or repeal any          class, may also amend or repeal any
                          bylaw or may adopt a new bylaw, except       bylaw or may adopt a new bylaw.
                          that the affirmative vote of the
                          holders of at least two-thirds of the
                          shares of our capital stock issued and
                          outstanding and entitled to vote is
                          required to amend or repeal, or adopt
                          new bylaws inconsistent with, those
                          which relate to directors or amending
                          the bylaws.

CAPITALIZATION

Authorized Common Stock   350 million shares.                          250 million shares.

Authorized Preferred      50,000 shares of preferred stock;            None.
Stock                     40,000 shares of the preferred stock
                          designated as Series B junior
                          participating preferred stock, used in
                          the stockholder rights plan described
                          below. The board of directors may fix
                          the rights and preferences of any class
                          or series of the remaining 10,000
                          shares of preferred stock. The rights
                          of the holders of our common stock will
                          be subject to, and may be adversely
                          affected by, the rights of holders of
                          any preferred stock that may be issued
                          in the future.

RIGHTS PLAN               We have a rights agreement dated as of       None.
                          January 19, 1996, which is described
                          below. The rights agreement is
                          triggered by, among other things, the
                          acquisition by a third party of 15% or
                          more of our total outstanding common
                          stock without the approval of our board
                          of directors. The board of directors
                          may redeem rights at any time until ten
                          days after a triggering acquisition.
</TABLE>

                                       53
<PAGE>   57

<TABLE>
<CAPTION>
                                      THERMO ELECTRON                             THERMO INSTRUMENT
                          ---------------------------------------      ---------------------------------------
<S>                       <C>                                          <C>
EXCULPATION AND           Certificate of Incorporation provides        Bylaws provide indemnification to
INDEMNIFICATION OF        indemnification to persons that are or       persons that are or were directors,
DIRECTORS, OFFICER AND    were directors or officers of ours, or       officers, employees or agents of Thermo
EMPLOYEES                 are or were serving at our request as        Instrument, or are or were serving at
                          directors or officers of another             the request of Thermo Instrument as
                          corporation, partnership, joint              directors, officers, employees or
                          venture, trust or other enterprise, to       agents of another corporation,
                          the fullest extent permitted by              partnership, joint venture, trust or
                          Delaware law.                                other enterprise, to the fullest extent
                                                                       permitted by Delaware law.
                          In the case of any action or suit by us
                          to procure a judgment in our favor, we       In the case of any action or suit by
                          will indemnify those directors and           Thermo Instrument to procure a judgment
                          officers only for expenses, including        in its favor, Thermo Instrument will
                          attorneys' fees, relating to any claim,      indemnify those directors, officers,
                          issue or matter as to which the              employees and agents only for expenses,
                          director or officer has been judged to       including attorneys' fees, relating to
                          be liable to us, if and only to the          any claim, issue or matter as to which
                          extent that the court determines that,       the director or officer has been judged
                          despite the adjudication of liability        to be liable to Thermo Instrument, if
                          but in view of all of the circumstances      and only to the extent that the court
                          of the case, the director or officer is      determines that, despite the
                          entitled to indemnity for such expenses      adjudication of liability but in view
                          which the court finds proper.                of all of the circumstances of the
                                                                       case, the director or officer is
                                                                       entitled to indemnity for such expenses
                                                                       which the court finds proper.
</TABLE>

THERMO ELECTRON STOCKHOLDER RIGHTS PLAN

     Under Delaware law, every corporation may create and issue rights entitling
the holders of the rights to purchase from the corporation shares of its capital
stock of any class or classes, subject to any provisions of its certificate of
incorporation. The price and terms of the shares must be stated in the company's
certificate of incorporation or in a resolution adopted by the board of
directors for the creation or issuance of such rights.

     We entered into a rights agreement dated as of January 19, 1996 with
BankBoston, N.A. as rights agent. On January 19, 1996, our board declared a
dividend distribution of one right for each outstanding share of our common
stock to our stockholders. Each right entitles the registered holder to purchase
from us a unit consisting of one ten-thousandth of a share of Series B junior
participating preferred stock at a purchase price of $250.00 in cash per unit,
subject to adjustment.

     The following description is a summary of all the material terms of our
stockholder rights plan. It does not restate these terms in their entirety. We
urge you to read our stockholder rights plan because it, and not this
description, defines the terms and provisions of our plan. We have filed a copy
of the rights agreement that established our rights plan as an exhibit to our
Registration Statement on Form 8-A, which we filed with the SEC on January 26,
1996 and which we incorporate by reference into the registration statement which
includes this prospectus. You may obtain a copy of the rights agreement at no
charge by writing to us at the address listed below under the caption "Where You
Can Find More Information."

                                       54
<PAGE>   58

     Distribution of rights.  Initially, the rights attach to all of our
outstanding common stock certificates and we will not distribute separate rights
certificates. The rights will separate from our common stock, and a distribution
date will occur, upon the earlier of the following events:

     - 10 days after a public announcement that a person or group of affiliated
       or associated persons has acquired, or obtained the right to acquire,
       beneficial ownership of 15% or more of the outstanding shares of our
       common stock; and

     - 10 business days following the start of a tender offer or exchange offer
       that would result in a person or group beneficially owning 15% or more of
       the outstanding shares of our common stock.

Until the distribution date:

     - the rights will be evidenced by our common stock certificates and will be
       transferred only with our common stock certificates;

     - new common stock certificates of ours will incorporate the rights
       agreement by reference; and

     - the surrender for transfer of any certificates of our common stock will
       also transfer the rights associated with our common stock represented by
       the certificate.

     The rights are not exercisable until the distribution date and will expire
at the close of business on January 29, 2006, unless we redeem or exchange them
earlier as described below.

     Flip in event.  If a person becomes the beneficial owner of 15% or more of
the shares of our common stock, each holder of a right will thereafter have the
right to receive, upon exercise, a number of shares of our common stock, or, in
some circumstances, cash, property or other securities of ours, which equals the
exercise price of the right divided by one-half of the current market price of
our common stock on the date the acquisition occurs. However, following the
acquisition:

     - rights are not exercisable until the rights are no longer redeemable by
       us as set forth below; and

     - all rights that are, or were, under the circumstances specified in the
       rights agreement, beneficially owned by any acquiring person will be null
       and void.

The event set forth in this paragraph is referred to as a "section 11(a)(ii)
event." A section 11(a)(ii) event does not occur if there is an offer for all of
our outstanding shares of common stock that our board of directors determines is
fair to our stockholders and in their best interests.

     For example, at an exercise price of $250 per right, each right not owned
by an acquiring person, or by some related parties, following a section
11(a)(ii) event would entitle the holder to purchase for $250 the number of
shares of our common stock, or other consideration, as noted above, as equals
$250 divided by one-half of the current market price of our common stock.
Assuming that our common stock had a per share value of $50 at that time, the
holder of each valid right would be entitled to purchase ten shares of our
common stock for $250.

     Flip over event.  If at any time after a person has become an acquiring
person:

     - we are acquired in a merger or other business combination transaction in
       which we are not the surviving corporation, or our common stock is
       changed or exchanged, or

     - 50% or more of our assets or earning power is sold or transferred,

then each holder of a right, except rights which previously have been voided as
set forth above, shall thereafter have the right to receive, upon exercise, that
number of shares of common stock of the acquiring company which equals the
exercise price of the right divided by one-half of the current market price of
that company's common stock at the date of the occurrence of the event. This
exercise right does not arise if the merger or other transaction follows an
offer for all of our outstanding shares of common stock that our board of
directors determines is fair to our stockholders and in their best interests.

                                       55
<PAGE>   59

     For example, at an exercise price of $250 per right, each right following
an event described in the preceding paragraph would entitle the holder to
purchase for $250 the number of shares of common stock of the acquiring company
as equals $250 divided by one-half of the current market price of that company's
common stock. Assuming that the common stock had a per share value of $100 at
that time, the holder of each valid right would be entitled to purchase five
shares of common stock of the acquiring company for $250.

     Exchange of rights.  At any time after a section 11(a)(ii) event, our board
of directors may exchange the rights, other than rights owned by the acquiring
person that have become void, in whole or in part, at an exchange ratio of one
share of our common stock, or one ten-thousandth of a share of preferred stock,
or of a share of a class or series of our preferred stock having equivalent
rights, preferences and privileges, per right.

     Series B junior participating preferred stock.  Preferred stock purchasable
upon exercise of the rights will not be redeemable. Each share of preferred
stock will be entitled to a minimum preferential quarterly dividend payment of
$100 per share and will be entitled to an aggregate dividend of 10,000 times the
dividend declared per share of our common stock. In the event of liquidation,
the holders of the preferred stock will be entitled to a minimum preferential
liquidating payment of $100 per share and will be entitled to an aggregate
payment of 10,000 times the payment made per share of our common stock. Each
share of preferred stock will have 10,000 votes, voting together with our common
stock. Finally, in the event of any merger, consolidation or other transaction
in which our common stock is changed or exchanged, each share of preferred stock
will be entitled to receive 10,000 times the amount received per share of our
common stock.

     These rights are protected by customary antidilution provisions and, in
light of our stock dividend in 1996, currently provide for the following:

     - an aggregate dividend per share of preferred stock of 15,000 times the
       dividend declared per share of our common stock;

     - an aggregate payment per share of preferred stock, in the event of
       liquidation, of 15,000 times the payment made per share of our common
       stock; and

     - 15,000 votes per share of preferred stock, voting together with our
       common stock.

     Because of the nature of the preferred stock's dividend, liquidation and
voting rights, the value of one ten-thousandth of a share of preferred stock
purchasable upon exercise of each right should approximate the value of one
share of our common stock.

     Redemption of rights.  At any time until ten days following the stock
acquisition date, we may redeem the rights in whole, but not in part, at a price
of $.01 per right, payable in cash or stock. Immediately upon an action of our
board of directors ordering redemption of the rights, the rights will terminate
and the only right of the holders of rights will be to receive the $.01
redemption price.

     Status of rights holder and tax effects.  Until a right is exercised, the
holder of the right, as such, will have no rights as a stockholder of ours,
including the right to vote or to receive dividends. Although the distribution
of the rights is not taxable to stockholders or to us, stockholders may,
depending upon the circumstances, recognize taxable income in the event that the
rights become exercisable for our common stock, or other consideration, or for
common stock of the acquiring company as described above.

     Effects of the rights.  The rights are intended to have anti-takeover
effects. The rights will cause substantial dilution to a person or group that
attempts to acquire us without conditioning the offer on a substantial number of
rights being acquired. The rights, however, should not affect any prospective
offeror willing to make an offer at a fair price and otherwise in the best
interests of us and our stockholders, as determined by a majority of our board
of directors. The rights should not interfere with any merger or

                                       56
<PAGE>   60

other business combination approved by our board of directors because the board
of directors may, at its option, at any time prior to the close of business on
the earlier of:

     - the tenth day following the stock acquisition date, or

     - January 29, 2006,

and in other specified circumstances, redeem all of the then outstanding rights
at the redemption price.

DELAWARE ANTI-TAKEOVER STATUTE

     Both we and Thermo Instrument are subject to Section 203 of the Delaware
General Corporation Law which, under some circumstances, may make it more
difficult for a person who would be an "interested stockholder," as defined in
Section 203, in either company, to effect various business combinations with
that company for a three-year period after becoming an interested stockholder.
Under Delaware law, a corporation's certificate of incorporation or bylaws may
exclude a corporation from the restrictions imposed by Section 203. Neither our
nor Thermo Instrument's certificate of incorporation and bylaws exclude the
company from the restrictions imposed by Section 203.

                       TRANSACTIONS WITH RELATED PARTIES

PRIOR CONTACTS

     Except as set forth in, or incorporated by reference in, this prospectus,
since January 1, 1998, there have been no contacts, negotiations or transactions
between us, on the one hand, and Thermo Instrument or any of its officers,
directors or affiliates, on the other hand, concerning a merger, consolidation
or acquisition, a tender offer or other acquisition of securities, an election
of directors or a sale or other transfer of a material amount of assets.

PRIOR BUSINESS RELATIONSHIPS

     Except as set forth in, or incorporated by reference in, this prospectus,
we have not, since January 1, 1998, had any business relationships or
transactions with Thermo Instrument or any of its executive officers, directors
or affiliates that would require disclosure in this prospectus under the SEC's
rules.

                                 LEGAL MATTERS

     Seth H. Hoogasian, Esq., our General Counsel, will pass on the validity of
the shares of our common stock offered by this prospectus. Mr. Hoogasian is a
full-time employee and officer of Thermo Electron, is an officer of Thermo
Instrument and, as of April 20, 2000, owned or had the right to acquire 386,647
shares of our common stock and 132,700 shares of the common stock of our
subsidiaries.

                                    EXPERTS

     Our financial statements and those of Thermo Instrument that we incorporate
by reference in this prospectus and the financial statement schedules that we
incorporated by reference in the registration statement of which this prospectus
is a part have been audited by Arthur Andersen LLP, independent public
accountants, to the extent and for the periods as indicated in their reports
with respect thereto, and are incorporated by reference in reliance upon the
authority of said firm as experts in giving said reports.

                                       57
<PAGE>   61

                      WHERE YOU CAN FIND MORE INFORMATION

     THIS PROSPECTUS INCORPORATES DOCUMENTS BY REFERENCE, INCLUDING IMPORTANT
BUSINESS AND FINANCIAL INFORMATION, WHICH ARE NOT PRESENTED IN OR DELIVERED WITH
THIS PROSPECTUS.

     YOU SHOULD RELY ONLY ON THE INFORMATION CONTAINED IN THIS DOCUMENT OR IN
DOCUMENTS TO WHICH WE HAVE REFERRED YOU. WE HAVE NOT AUTHORIZED ANYONE TO
PROVIDE YOU WITH ANY INFORMATION THAT IS DIFFERENT.

THERMO INSTRUMENT

     We incorporate by reference into this prospectus the following documents,
filed by Thermo Instrument (File No. 1-9786) with the SEC:

     - Thermo Instrument's Annual Report on Form 10-K for the fiscal year ended
       January 1, 2000; and

     - Thermo Instrument's Current Reports on Forms 8-K dated February 1, 2000
       and April 7, 2000.

THERMO ELECTRON

     We incorporate by reference into this prospectus the following documents,
which we have filed (File No. 1-8002) with the SEC:

     - Our Annual Report on Form 10-K for the fiscal year ended January 1, 2000;

     - Our Current Report on Form 8-K dated February 1, 2000;

     - Our Proxy Statement dated April 19, 2000;

     - The description of our common stock which is contained in our
       registration statement on Form 8-A and the amendment to that registration
       statement, filed under the Exchange Act; and

     - The description of our preferred stock purchase rights which is contained
       in our registration statement on Form 8-A and the amendments to that
       registration statement, filed under the Exchange Act.

     All documents that we file or that Thermo Instrument files pursuant to
Sections 13(a), 13(c), 14 or 15(d) of the Exchange Act from the date of this
prospectus to the date that shares are accepted for exchange pursuant to our
offer, the date that our offer is terminated or the date that the merger is
closed will also be deemed to be incorporated in this prospectus by reference.

     The information incorporated by reference in this prospectus is deemed to
be a part of this prospectus, except for any information superseded by
information in this prospectus or in any subsequently filed document that we
incorporate by reference in this prospectus.

     We will provide a copy of any and all of the information that we
incorporate by reference in this prospectus to any person, without charge, upon
written or oral request. If we do not specifically incorporate by reference
exhibits to the documents that we incorporate by reference in this prospectus,
then we will not provide copies of those exhibits. TO OBTAIN TIMELY DELIVERY,
YOU MUST REQUEST THE INFORMATION NO LATER THAN MAY 12, 2000.

     You should direct requests for documents relating to Thermo Instrument or
to us to: Sandra L. Lambert, Corporate Secretary, Thermo Electron Corporation,
81 Wyman Street, Waltham, Massachusetts 02454 (telephone: 781-622-1000;
facsimile: 781-768-6620).

                                       58
<PAGE>   62

     We file reports, proxy statements and other information with the SEC. You
may inspect and copy our reports, proxy statements and other information at the
public reference facilities maintained by the SEC at:

<TABLE>
<S>                     <C>                      <C>
Judiciary Plaza         Citicorp Center          Seven World Trade Center
Room 1024               500 West Madison Street  13th Floor
450 Fifth Street, N.W.  Suite 1400               New York, New York 10048
Washington, D.C. 20549  Chicago, Illinois 60661
</TABLE>

     You can also inspect reports, proxy statements and other information
concerning Thermo Instrument at:

     The American Stock Exchange
     86 Trinity Place
     New York, New York 10006-1881

     You can also inspect reports, proxy statements and other information
concerning us at:

     The New York Stock Exchange
     20 Broad Street
     New York, New York 10005

     You can also obtain copies of these materials by mail at prescribed rates
from the Public Reference Room at the SEC, 450 Fifth Street, N.W., Washington,
D.C. 20549. You may obtain information on the operation of the Public Reference
Room by calling the SEC toll-free at l-800-SEC-0330. The SEC maintains an
Internet site that contains reports, proxy statements and other information
regarding Thermo Electron and Thermo Instrument. The address of the SEC website
is http://www.sec.gov.

     We have filed a registration statement on Form S-4 under the Securities Act
with the SEC with respect to our common stock we would issue to Thermo
Instrument stockholders in the exchange offer and the merger. This prospectus
constitutes our prospectus filed as part of the registration statement. This
prospectus does not contain all of the information set forth in the registration
statement because we have omitted some parts of the registration statement in
accordance with the SEC's rules. The registration statement and its exhibits are
available for inspection and copying as set forth above.

     We have also filed with the SEC a statement on Schedule TO pursuant to Rule
14d-3 under the Exchange Act furnishing certain information about the exchange
offer. You may read and copy the Schedule TO and any amendments thereto at the
SEC's public reference room in Washington, D.C. referred to above.

     If you have any questions about the exchange offer, you should call the
information agent, D.F. King & Co., Inc. If you are a banker or broker, call
collect at (212) 269-5550. All others should call toll-free at (800) 290-6433.

     THIS PROSPECTUS DOES NOT CONSTITUTE AN OFFER TO SELL, OR A SOLICITATION OF
AN OFFER TO PURCHASE, THE SECURITIES OFFERED BY THIS PROSPECTUS, IN ANY
JURISDICTION OR FROM ANY PERSON TO WHOM OR FROM WHOM IT IS UNLAWFUL TO MAKE SUCH
OFFER OR SOLICITATION OF AN OFFER IN SUCH JURISDICTION. NEITHER THE DELIVERY OF
THIS PROSPECTUS NOR ANY DISTRIBUTION OF SECURITIES PURSUANT TO THIS PROSPECTUS
SHALL, UNDER ANY CIRCUMSTANCES, CREATE ANY IMPLICATION THAT THERE HAS BEEN NO
CHANGE IN THE INFORMATION SET FORTH OR INCORPORATED INTO THIS PROSPECTUS BY
REFERENCE OR IN OUR AFFAIRS SINCE THE DATE OF THIS PROSPECTUS.

                                       59
<PAGE>   63

                      [This page intentionally left blank]
<PAGE>   64

                          THERMO ELECTRON CORPORATION

         INDEX TO PRO FORMA CONSOLIDATED CONDENSED FINANCIAL STATEMENTS
                                  (UNAUDITED)

<TABLE>
<CAPTION>
                                                              PAGE
<S>                                                           <C>
Pro Forma Consolidated Condensed Financial Information of
  Thermo Electron Corporation (Unaudited)...................  F-2
Pro Forma Consolidated Condensed Statement of Operations for
  the fiscal year ended January 1, 2000.....................  F-3
Pro Forma Consolidated Condensed Balance Sheet as of January
  1, 2000...................................................  F-4
Notes to Pro Forma Consolidated Condensed Financial
  Statements................................................  F-5
</TABLE>

                                       F-1
<PAGE>   65

                          THERMO ELECTRON CORPORATION

             PRO FORMA CONSOLIDATED CONDENSED FINANCIAL STATEMENTS
                                  (UNAUDITED)

     The following unaudited pro forma consolidated condensed statement of
operations sets forth our results of operations for the fiscal year ended
January 1, 2000, as if we had completed the exchange offer and the merger at the
beginning of fiscal 1999. The following unaudited pro forma consolidated
condensed balance sheet sets forth our financial position as of January 1, 2000,
as if we had completed the exchange offer and the merger on January 1, 2000. For
purposes of determining the number of shares of our common stock that we will
issue in the exchange offer and the merger, we have used the exchange ratio of
0.85 shares of our common stock for each share of Thermo Instrument common
stock. The pro forma results of operations are not necessarily indicative of
future operations or the actual results that would have occurred if we had
completed the exchange offer and the merger at the beginning of fiscal 1999.

                                       F-2
<PAGE>   66

                          THERMO ELECTRON CORPORATION

            PRO FORMA CONSOLIDATED CONDENSED STATEMENT OF OPERATIONS
                       FISCAL YEAR ENDED JANUARY 1, 2000
                                  (UNAUDITED)

<TABLE>
<CAPTION>
                                                                        PRO FORMA
                                                         HISTORICAL    ADJUSTMENTS    PRO FORMA
                                                         ----------    -----------    ----------
                                                         (IN THOUSANDS EXCEPT PER SHARE AMOUNTS)
<S>                                                      <C>           <C>            <C>
Revenues                                                 $2,471,193      $    --      $2,471,193
                                                         ----------      -------      ----------
Costs and Operating Expenses:
  Cost of revenues.....................................   1,378,494           --       1,378,494
  Selling, general and administrative expenses.........     673,004        4,324         677,328
  Research and development expenses....................     171,100           --         171,100
  Restructuring and other unusual costs, net...........     149,589           --         149,589
                                                         ----------      -------      ----------
                                                          2,372,187        4,324       2,376,511
                                                         ----------      -------      ----------
Operating Income.......................................      99,006       (4,324)         94,682
Other Expense, Net.....................................     (61,520)          --         (61,520)
                                                         ----------      -------      ----------
Income from Continuing Operations Before Income Taxes,
  Minority Interest and Extraordinary Items............      37,486       (4,324)         33,162
Income Tax Provision...................................      33,073           --          33,073
Minority Interest Expense..............................      18,993       11,332           7,661
                                                         ----------      -------      ----------
Loss from Continuing Operations Before Extraordinary
  Items................................................  $  (14,580)     $ 7,008      $   (7,572)
                                                         ==========      =======      ==========
Loss per Share from Continuing Operations Before
  Extraordinary Items:
  Basic................................................  $     (.09)                  $     (.04)
                                                         ==========                   ==========
  Diluted..............................................  $     (.11)                  $     (.06)
                                                         ==========                   ==========
Basic and Diluted Weighted Average Shares..............     157,987       12,545         170,532
                                                         ==========      =======      ==========
</TABLE>

                                       F-3
<PAGE>   67

                          THERMO ELECTRON CORPORATION

                 PRO FORMA CONSOLIDATED CONDENSED BALANCE SHEET
                                JANUARY 1, 2000
                                  (UNAUDITED)

<TABLE>
<CAPTION>
                                                                        PRO FORMA
                                                         HISTORICAL    ADJUSTMENTS    PRO FORMA
                                                         ----------    -----------    ----------
                                                                     (IN THOUSANDS)
<S>                                                      <C>           <C>            <C>
                        ASSETS
Current Assets:
  Cash and cash equivalents............................  $  281,760     $      --     $  281,760
  Short-term available-for-sale investments, at quoted
     market value......................................     555,501            --        555,501
  Accounts receivable, net.............................     574,126            --        574,126
  Other current assets.................................     588,470            --        588,470
  Net assets of discontinued operations................     517,350            --        517,350
                                                         ----------     ---------     ----------
                                                          2,517,207            --      2,517,207
                                                         ----------     ---------     ----------
Property, Plant and Equipment, at Cost, Net............     510,647            --        510,647
                                                         ----------     ---------     ----------
Other Assets...........................................     247,897            --        247,897
                                                         ----------     ---------     ----------
Cost in Excess of Net Assets of Acquired Companies.....   1,227,335       172,971      1,400,306
                                                         ----------     ---------     ----------
Long-term Net Assets of Discontinued Operations........     678,756            --        678,756
                                                         ----------     ---------     ----------
                                                         $5,181,842     $ 172,971     $5,354,813
                                                         ==========     =========     ==========

       LIABILITIES AND SHAREHOLDERS' INVESTMENT
Current Liabilities....................................  $1,066,349     $      --     $1,066,349
                                                         ----------     ---------     ----------
Deferred Income Taxes and Other Deferred Items.........     163,063            --        163,063
                                                         ----------     ---------     ----------
Long-term Obligations:
  Subordinated convertible obligations.................   1,209,305            --      1,209,305
  Other................................................     356,669            --        356,669
                                                         ----------     ---------     ----------
                                                          1,565,974            --      1,565,974
                                                         ----------     ---------     ----------
Minority Interest......................................     364,278      (119,898)       244,380
                                                         ----------     ---------     ----------
Common Stock of Subsidiary Subject to Redemption.......       7,692            --          7,692
                                                         ----------     ---------     ----------
Shareholders' Investment:
  Common stock.........................................     167,433        12,545        179,978
  Capital in excess of par value.......................   1,052,837       280,324      1,333,161
  Retained earnings....................................   1,041,968            --      1,041,968
  Treasury stock at cost...............................    (189,646)           --       (189,646)
  Deferred compensation................................      (3,190)           --         (3,190)
  Accumulated other comprehensive items................     (54,916)           --        (54,916)
                                                         ----------     ---------     ----------
                                                          2,014,486       292,869      2,307,355
                                                         ----------     ---------     ----------
                                                         $5,181,842     $ 172,971     $5,354,813
                                                         ==========     =========     ==========
</TABLE>

                                       F-4
<PAGE>   68

                          THERMO ELECTRON CORPORATION

         NOTES TO PRO FORMA CONSOLIDATED CONDENSED FINANCIAL STATEMENTS
                                  (UNAUDITED)

<TABLE>
NOTE 1 -- PRO FORMA ADJUSTMENTS TO PRO FORMA CONSOLIDATED
          CONDENSED STATEMENT OF OPERATIONS (IN THOUSANDS
          EXCEPT IN TEXT)
                                                               YEAR ENDED
                                                              JANUARY 1, 2000
                                                                 ---------
                                                              DEBIT (CREDIT)
<S>                                                           <C>
SELLING, GENERAL AND ADMINISTRATIVE EXPENSES
Amortization of cost in excess of net assets of acquired
  companies created by the acquisition of additional shares
  of Thermo Instrument......................................     $   4,324
                                                                 ---------
MINORITY INTEREST EXPENSE
Decrease in minority interest expense as a result of our
  increased ownership of Thermo Instrument..................     $ (11,332)
                                                                 ---------
WEIGHTED AVERAGE SHARES
Increase in weighted average shares outstanding due to the
  assumed issuance of 12,545,187 shares of our common stock
  for the acquisition of additional shares of Thermo
  Instrument as of the beginning of 1999....................        12,545
NOTE 2 -- PRO FORMA ADJUSTMENTS TO PRO FORMA CONSOLIDATED
          CONDENSED BALANCE SHEET (IN THOUSANDS EXCEPT IN
          TEXT)
                                                              JANUARY 1, 2000
                                                                 ---------
                                                              DEBIT (CREDIT)
COST IN EXCESS OF NET ASSETS OF ACQUIRED COMPANIES
Increase in cost in excess of net assets of acquired
  companies as a result of our increased ownership of Thermo
  Instrument................................................     $ 172,971
                                                                 ---------
MINORITY INTEREST
Decrease in minority interest as a result of our increased
  ownership of Thermo Instrument............................       119,898
                                                                 ---------
COMMON STOCK
Increase in common stock due to the assumed issuance of
  12,545,187 shares of our common stock for the acquisition
  of additional shares of Thermo Instrument.................       (12,545)
CAPITAL IN EXCESS OF PAR VALUE
Increase in capital in excess of par value as a result of
  our increased ownership of Thermo Instrument and the
  conversion of outstanding stock options of Thermo
  Instrument into our stock options.........................      (280,324)
                                                                 ---------
</TABLE>

                                       F-5
<PAGE>   69

                      [This page intentionally left blank]
<PAGE>   70

                                    ANNEX A

              DIRECTORS AND EXECUTIVE OFFICERS OF THERMO ELECTRON
                             AND THERMO INSTRUMENT

THERMO ELECTRON

     We have set forth in the following table:

     - the name, business address, position with Thermo Electron, present
       principal occupation or employment and five-year employment history of
       each of our directors and executive officers; and

     - the names, principal businesses and addresses of any corporations or
       other organizations in which those principal occupations are conducted.

     Unless otherwise indicated, each occupation listed in the table refers to
Thermo Electron, each individual is a United States citizen and each
individual's business address is 81 Wyman Street, Waltham, Massachusetts 02454.

     Unless otherwise indicated, to our knowledge, none of our directors or
executive officers beneficially owns any shares of our common stock or Thermo
Instrument common stock or rights to acquire shares of our common stock or
Thermo Instrument common stock. Unless otherwise indicated, to our knowledge,
none of our directors or executive officers has been convicted in a criminal
proceeding during the last five years, excluding traffic violations or similar
misdemeanors, and none of our directors or executive officers was a party to any
judicial or administrative proceeding during the last five years that resulted
in a judgement, decree or final order enjoining the person from future
violations of, or prohibiting activities subject to, federal or state securities
laws, or a finding of any violation of federal or state securities laws.

     Mr. John N. Hatsopoulos retired from our board of directors effective
February 21, 2000. Dr. George N. Hatsopoulos retired from our board of directors
effective March 31, 2000.

SAMUEL W. BODMAN...................    Dr. Bodman, 61, has been a director of
                                       Thermo Electron since May 1999. Since
                                       1988, Dr. Bodman has served as the
                                       chairman and chief executive officer of
                                       Cabot Corporation, a manufacturer of
                                       specialty chemicals and materials located
                                       at 75 State Street, Boston, MA 02109. Dr.
                                       Bodman is also a director of Cabot
                                       Corporation, John Hancock Financial
                                       Services, Inc., Security Capital Group
                                       Incorporated and Westvaco Corporation.

PETER O. CRISP.....................    Mr. Crisp, 67, has been a director of
                                       Thermo Electron since 1974. Mr. Crisp was
                                       a general partner of Venrock Associates,
                                       a venture capital investment firm located
                                       at 30 Rockefeller Plaza, New York, NY
                                       10112, for more than five years until his
                                       retirement in September 1997. He has been
                                       the vice chairman of Rockefeller
                                       Financial Services, Inc. since December
                                       1997. Mr. Crisp is also a director of
                                       American Superconductor Corporation,
                                       Evans & Sutherland Computer Corporation,
                                       Thermedics Inc., ThermoTrex Corporation
                                       and United States Trust Corporation.

ELIAS P. GYFTOPOULOS...............    Dr. Gyftopoulos, 72, has been a director
                                       of Thermo Electron since 1976. Dr.
                                       Gyftopoulos is Professor Emeritus of the
                                       Massachusetts Institute of Technology,
                                       where he was the Ford Professor of
                                       Mechanical Engineering and of Nuclear
                                       Engineering for more than 20 years until

                                       A-1
<PAGE>   71

                                       his retirement in 1996. Dr. Gyftopoulos
                                       is also a director of Thermo
                                       Cardiosystems Inc., ThermoLase
                                       Corporation, ThermoRetec Corporation and
                                       Trex Medical Corporation.

FRANK JUNGERS......................    Mr. Jungers, 73, has been a director of
                                       Thermo Electron since 1978. Mr. Jungers
                                       has been a consultant on business and
                                       energy matters since 1977. His business
                                       address is 822 N.W. Murray Boulevard,
                                       Suite 242, Portland, OR 97229. Mr.
                                       Jungers is also a director of The AES
                                       Corporation, Donaldson, Lufkin &
                                       Jenrette, Inc., Statia Terminals Group
                                       N.V., Thermo Ecotek Corporation and
                                       ThermoQuest Corporation.

ROBERT A. MCCABE...................    Mr. McCabe, 65, has been a director of
                                       Thermo Electron since 1962. He has been
                                       the chairman of Pilot Capital Corporation
                                       located at 444 Madison Avenue, Suite
                                       2103, New York, NY 10022, which is
                                       engaged in private investments, since
                                       1998. Mr. McCabe was the president of
                                       Pilot Capital Corporation from 1987 to
                                       1998. Mr. McCabe is also a director of
                                       Atlantic Bank & Trust Company, Burns
                                       International Services Corporation,
                                       Church & Dwight Company and Thermo Optek
                                       Corporation.

HUTHAM S. OLAYAN...................    Ms. Olayan, 46, has been a director of
                                       Thermo Electron since 1987. She has
                                       served since 1995 as president and a
                                       director of Olayan America Corporation, a
                                       member of the Olayan Group, and as
                                       president and a director of Competrol
                                       Real Estate Limited, another member of
                                       the Olayan Group, from 1986 until its
                                       merger into Olayan America Corporation in
                                       1997. The surviving company which is
                                       located at 505 Park Avenue, Suite 1100,
                                       New York, NY 10022, is engaged in private
                                       investments, including real estate, and
                                       advisory services. Ms. Olayan is also a
                                       director of Trex Medical Corporation. Ms.
                                       Olayan is a citizen of Saudi Arabia.

ROBERT W. O'LEARY..................    Mr. O'Leary, 56, has been a director of
                                       Thermo Electron since June 1998. He has
                                       been the president and chairman of
                                       Premier, Inc., a strategic alliance of
                                       not-for-profit health care and hospital
                                       systems located at 12225 El Camino Real,
                                       San Diego, CA 92130, since 1995.

RICHARD F. SYRON...................    Dr. Syron, 56, has been a director of
                                       Thermo Electron since September 1997, its
                                       president and chief executive officer
                                       since June 1999 and chairman of the board
                                       since January 2000. From April 1994 until
                                       May 1999, Dr. Syron was the chairman and
                                       chief executive officer of the American
                                       Stock Exchange Inc. located at 86 Trinity
                                       Place, New York, NY 10006-1881. Dr. Syron
                                       is also a director of Dreyfus
                                       Corporation, John Hancock Financial
                                       Services, Inc., and Thermo Fibertek Inc.

                                       A-2
<PAGE>   72

ROGER D. WELLINGTON................    Mr. Wellington, 73, has been a director
                                       of Thermo Electron since 1986. Mr.
                                       Wellington serves as the president and
                                       chief executive officer of Wellington
                                       Consultants, Inc. and Wellington
                                       Associates Inc., international business
                                       consulting firms he founded in 1994 and
                                       1989, respectively, each of which is
                                       located at P.O. Box 8186, 5555 Gulf of
                                       Mexico Drive, Unit 302, Longboat Key, FL
                                       34228. Mr. Wellington is also a director
                                       of Photoelectron Corporation and Thermo
                                       Fibergen Inc.

BRIAN D. HOLT......................    Mr. Holt, 51, became the chief operating
                                       officer, energy and environment, of
                                       Thermo Electron in September 1998. Mr.
                                       Holt has been the president and chief
                                       executive officer of Thermo Ecotek
                                       Corporation, a majority-owned subsidiary
                                       of Thermo Electron located at 245 Winter
                                       Street, Waltham, MA 02451, that is
                                       involved in electric power generation
                                       since February 1994. From March 1996 to
                                       September 1998, he was a vice president
                                       of Thermo Electron. Mr. Holt is also a
                                       director of The Randers Killam Group,
                                       Inc., Thermo Ecotek Corporation,
                                       ThermoRetec Corporation and Thermo
                                       TerraTech Inc.

JOHN T. KEISER.....................    Mr. Keiser, 64, became chief operating
                                       officer, biomedical, of Thermo Electron
                                       in September 1998 and was a vice
                                       president from April 1997 until his
                                       promotion. Mr. Keiser has been the
                                       president and chief executive officer of
                                       Thermedics Inc., a manufacturer of
                                       biomedical products, product
                                       quality-assurance systems and security
                                       devices, since March 1998 and December
                                       1998, respectively, and served as a
                                       senior vice president of Thermedics Inc.
                                       from 1994 until his promotion to
                                       president. He has also been the president
                                       of Thermo Electron's wholly owned
                                       biomedical group, a manufacturer of
                                       medical equipment and instruments, since
                                       1994. Mr. Keiser is a director of Metrika
                                       Systems Corporation, Thermedics Inc.,
                                       Thermo Cardiosystems Inc., ThermoLase
                                       Corporation, ThermoTrex Corporation and
                                       Trex Medical Corporation.

EARL R. LEWIS......................    Mr. Lewis, 56, became chief operating
                                       officer, measurement and detection, of
                                       Thermo Electron in September 1998, and
                                       served as senior vice president of Thermo
                                       Electron from June 1998 to September 1998
                                       and vice president from September 1996 to
                                       June 1998. Mr. Lewis has been president
                                       and chief executive officer of Thermo
                                       Instrument since March 1997 and January
                                       1998, respectively, and was chief
                                       operating officer from January 1996 to
                                       January 1998. Prior to that time, he was
                                       executive vice president of Thermo
                                       Instrument from January 1996 to March
                                       1997 and senior vice president from
                                       January 1994 to January 1996. Mr. Lewis
                                       served as chief executive officer of
                                       Thermo Optek Corporation, a

                                       A-3
<PAGE>   73

                                       majority-owned subsidiary of Thermo
                                       Instrument and a manufacturer of
                                       analytical instruments that measure
                                       energy and light for purposes of
                                       materials analysis, characterization and
                                       preparation, from its inception in August
                                       1995 to January 1998. Mr. Lewis is a
                                       director of FLIR Systems Inc., Metrika
                                       Systems Corporation, SpectRx Inc.,
                                       Spectra-Physics Lasers, Inc., Thermo
                                       Optek Corporation and ThermoQuest
                                       Corporation.

THEO MELAS-KYRIAZI.................    Mr. Melas-Kyriazi, 40, has been a vice
                                       president, of Thermo Electron since March
                                       1998 and its chief financial officer
                                       since January 1999. Prior to his
                                       appointment as a vice president of Thermo
                                       Electron, Mr. Melas-Kyriazi served as
                                       president and chief executive officer of
                                       ThermoSpectra Corporation, a subsidiary
                                       of Thermo Instrument that develops,
                                       manufactures, and markets precision
                                       imaging, inspection, measurement, and
                                       temperature-control instrumentation, from
                                       its inception in August 1994 until March
                                       1998. Mr. Melas-Kyriazi is a director of
                                       ThermoRetec Corporation. Mr.
                                       Melas-Kyriazi is a citizen of Greece.

WILLIAM A. RAINVILLE...............    Mr. Rainville, 58, became chief operating
                                       officer, recycling and resource recovery,
                                       of Thermo Electron in September 1998. Mr.
                                       Rainville was a senior vice president of
                                       Thermo Electron from March 1993 to
                                       September 1998, and a vice president of
                                       Thermo Electron from 1986 to 1993. He has
                                       been president and chief executive
                                       officer of Thermo Fibertek Inc., a
                                       majority-owned subsidiary of Thermo
                                       Electron located at 245 Winter Street,
                                       Waltham, MA 02451 that develops and
                                       manufactures equipment and products for
                                       the papermaking and paper-recycling
                                       industries, since its inception in 1991.
                                       Mr. Rainville is also a director of
                                       Thermo Ecotek Corporation, Thermo
                                       Fibergen Inc., Thermo Fibertek Inc.,
                                       ThermoRetec Corporation and Thermo
                                       TerraTech Inc.

     Stock Ownership.  The following table sets forth the beneficial ownership
of common stock of Thermo Instrument and Thermo Electron, as of January 31,
2000, with respect to each of our directors and executive officers. Our
directors and executive officers disclaim beneficial ownership of the shares of
Thermo Instrument common stock beneficially owned by us.

<TABLE>
<CAPTION>
                                                                  THERMO           THERMO
                                                                 ELECTRON        INSTRUMENT
                          NAME(1)                             CORPORATION(2)   SYSTEMS INC.(3)
                          -------                             --------------   ---------------
<S>                                                           <C>              <C>
Samuel W. Bodman............................................       27,599                 0
Peter O. Crisp..............................................      121,767             3,009
Elias P. Gyftopoulos........................................       91,399            88,842
Brian D. Holt...............................................      322,941               999
Frank Jungers...............................................      171,021            26,412
John T. Keiser..............................................      331,636           155,211
Earl R. Lewis...............................................      215,477           436,499
Robert A. McCabe............................................       66,326            46,846
</TABLE>

                                       A-4
<PAGE>   74

<TABLE>
<CAPTION>
                                                                  THERMO           THERMO
                                                                 ELECTRON        INSTRUMENT
                          NAME(1)                             CORPORATION(2)   SYSTEMS INC.(3)
                          -------                             --------------   ---------------
<S>                                                           <C>              <C>
Theo Melas-Kyriazi..........................................      458,532           182,715
Hutham S. Olayan............................................       49,568             3,009
Robert W. O'Leary...........................................       43,830               666
William A. Rainville........................................      361,499            19,065
Richard F. Syron............................................    1,074,006                 0
Roger D. Wellington.........................................       55,795             6,759
All directors and current executive officers as a group (14
  persons)..................................................    3,391,396           970,032
</TABLE>

- ---------------
(1) Except as reflected in the footnotes to this table, shares beneficially
    owned consist of shares owned by the indicated person or by that person for
    the benefit of minor children, and all share ownership includes sole voting
    and investment power.

(2) Shares of the Common Stock of Thermo Electron beneficially owned by Dr.
    Bodman, Mr. Crisp, Dr. Gyftopoulos, Mr. Holt, Mr. Jungers, Mr. Keiser, Mr.
    Lewis, Mr. McCabe, Mr. Melas-Kyriazi, Ms. Olayan, Mr. O'Leary, Mr.
    Rainville, Dr. Syron, Mr. Wellington and all directors and current executive
    officers as a group include 26,000, 25,596, 27,442, 284,948, 24,673,
    263,230, 212,278, 27,442, 384,361, 27,442, 27,000, 294,630, 1,011,000,
    24,673 and 2,660,715 shares, respectively, that such person or members of
    the group have the right to acquire within 60 days of January 31, 2000
    through the exercise of stock options. Shares beneficially owned by Mr.
    Melas-Kyriazi and all directors and current executive officers as a group
    include 1,071 shares allocated to Mr. Melas-Kyriazi's account maintained
    pursuant to the Thermo Electron's employee stock ownership plan (the
    "ESOP"). Shares beneficially owned by Dr. Bodman, Mr. Crisp, Dr.
    Gyftopoulos, Mr. Jungers, Mr. McCabe, Ms. Olayan, Mr. O'Leary, Dr. Syron,
    Mr. Wellington and all directors and current executive officers as a group
    include 1,599, 49,277, 1,378, 80,427, 34,725, 19,876, 3,830, 2,506, 26,342
    and 219,960 shares, respectively, allocated to accounts maintained pursuant
    to Thermo Electron's deferred compensation plan for directors. Shares
    beneficially owned by Ms. Olayan do not include 6,150,000 shares owned by
    Crescent Holding GmbH, a member of the Olayan Group. Crescent Holding GmbH
    is indirectly controlled by Suliman S. Olayan, Ms. Olayan's father. Ms.
    Olayan disclaims beneficial ownership of the shares owned by Crescent
    Holding GmbH. No director or current executive officer beneficially owned
    more than 1% of the Thermo Electron common stock outstanding as of such
    date; all directors and current executive officers as a group beneficially
    owned 2.13% of the Thermo Electron common stock outstanding as of January
    31, 2000.

(3) Shares of the common stock of Thermo Instrument beneficially owned by Mr.
    Crisp, Dr. Gyftopoulos, Mr. Holt, Mr. Jungers, Mr. Keiser, Mr. Lewis, Mr.
    McCabe, Mr. Melas-Kyriazi, Ms. Olayan, Mr. O'Leary, Mr. Rainville, Mr.
    Wellington and all directors and current executive officers as a group
    include 3,009, 40,586, 999, 11,443, 71,311, 409,081, 7,925, 163,687, 3,009,
    666, 19,065, 3,009 and 733,790 shares, respectively, that such person or
    members of the group have the right to acquire within 60 days of January 31,
    2000 through the exercise of stock options. Shares beneficially owned by Mr.
    Melas-Kyriazi and all directors and current executive officers as a group
    include 468 shares allocated to Mr. Melas-Kyriazi's account maintained
    pursuant to the ESOP. Shares beneficially owned by Mr. Jungers, Mr. McCabe
    and all directors and current executive officers as a group include 13,563,
    8,908 and 22,471 shares, respectively, allocated to their respective
    accounts maintained pursuant to Thermo Instrument's deferred compensation
    plan for directors. Shares beneficially owned by Mr. Lewis include 2,987
    shares held by his spouse. No director or current executive officer
    beneficially owned more than 1% of the Thermo Instrument common stock
    outstanding as of January 31, 2000; all directors and current executive
    officers as a group beneficially owned less than 1% of the Thermo Instrument
    common stock outstanding as of January 31, 2000.

                                       A-5
<PAGE>   75

THERMO INSTRUMENT

     We have set forth in the following table:

     - the name, business address, position with Thermo Instrument, present
       principal occupation or employment and five-year employment history of
       each of the directors and executive officers of Thermo Instrument; and

     - the names, principal businesses and addresses of any corporations or
       other organizations in which those principal occupations are conducted.

     Unless otherwise indicated, each occupation listed in the table refers to
Thermo Instrument, each individual is a United States citizen and each
individual's business address is 81 Wyman Street, Waltham, Massachusetts 02454.

     Unless otherwise indicated, to our knowledge, no director or executive
officer of Thermo Instrument beneficially owns any shares of our common stock or
of Thermo Instrument common stock or rights to acquire shares of our common
stock or Thermo Instrument common stock. Unless otherwise indicated, to our
knowledge, no director or executive officer of Thermo Instrument has been
convicted in a criminal proceeding during the last five years, excluding traffic
violations or similar misdemeanors, and no director or executive officer of
Thermo Instrument was a party to any judicial or administrative proceeding
during the last five years that resulted in a judgement, decree or final order
enjoining the person from future violations of, or prohibiting activities
subject to, federal or state securities laws, or a finding of any violation of
federal or state securities laws.

     Arvin H. Smith, John N. Hatsopoulos and Richard F. Syron resigned from the
board of directors of Thermo Instrument effective February 15, 2000, February
21, 2000 and March 7, 2000, respectively. George N. Hatsopoulos retired from the
board of directors of Thermo Instrument effective March 31, 2000.

EARL R. LEWIS.......................     Mr. Lewis, 56, has been a director and
                                         the chief executive officer of Thermo
                                         Instrument since January 1998, and has
                                         been president of Thermo Instrument
                                         since March 1997. He was chief
                                         operating officer of Thermo Instrument
                                         from January 1996 to January 1998.
                                         Prior to that time, he was executive
                                         vice president of Thermo Instrument
                                         from January 1996 to March 1997 and
                                         senior vice president from January 1994
                                         to January 1996. Mr. Lewis has been the
                                         chief operating officer, measurement
                                         and detection, of Thermo Electron since
                                         September 1998. Prior to his
                                         appointment as chief operating officer,
                                         Mr. Lewis served as senior vice
                                         president of Thermo Electron from June
                                         1998 to September 1998 and vice
                                         president from September 1996 to June
                                         1998. Mr. Lewis served as chief
                                         executive officer of Thermo Optek
                                         Corporation from its inception in
                                         August 1995 to January 1998. Mr. Lewis
                                         is a director of FLIR Systems Inc.,
                                         Metrika Systems Corporation, SpectRx
                                         Inc., Spectra-Physics Lasers, Inc.,
                                         Thermo Optek Corporation and
                                         ThermoQuest Corporation.

POLYVIOS C. VINTIADIS...............     Mr. Vintiadis, 64, has been a director
                                         of Thermo Instrument since July 1993.
                                         Mr. Vintiadis has been the chairman and
                                         chief executive officer of Towermarc
                                         Corporation, a real estate development
                                         company located at Two Sound View
                                         Drive, Green-
                                       A-6
<PAGE>   76

                                         wich, CT 06830, since 1984. Mr.
                                         Vintiadis is also a director of
                                         Spectra-Physics Lasers, Inc. and Thermo
                                         TerraTech Inc.

RICHARD W.K. CHAPMAN................     Dr. Chapman, 54, has been senior vice
                                         president of Thermo Instrument since
                                         July 1998 and was a vice president of
                                         Thermo Instrument from 1992 until July
                                         1998. He has been the chief executive
                                         officer, president and a director of
                                         ThermoQuest Corporation, a majority
                                         owned subsidiary of Thermo Instrument
                                         since its inception in June 1995.
                                         ThermoQuest Corporation develops and
                                         distributes mass spectrometers, liquid
                                         chromatographs, gas chromatographs, and
                                         multi-instrument combinations of these
                                         products for the pharmaceutical,
                                         environmental, and industrial
                                         marketplaces and is located at 2215
                                         Grand Avenue Parkway, Austin, TX
                                         78728-3812.

DENIS A. HELM.......................     Mr. Helm, 61, has been executive vice
                                         president of Thermo Instrument since
                                         January 1999, and was a senior vice
                                         president from 1994 to 1998. From 1981
                                         to 1998, Mr. Helm served as president
                                         of Thermo Instrument's Thermo
                                         Environmental Instruments Inc.
                                         subsidiary, a manufacturer of
                                         instruments and systems for detecting
                                         and monitoring environmental
                                         pollutants. Mr. Helm also served as
                                         chief executive officer of Metrika
                                         Systems Corporation, a majority-owned
                                         subsidiary of Thermo Instrument that
                                         develops and manufactures process
                                         optimization systems for raw material
                                         analysis and finished materials quality
                                         control, from November 1996 until
                                         February 1998. Mr. Helm's business
                                         address is 8 East Forge Parkway,
                                         Franklin, MA 02038. Mr. Helm is also a
                                         director of Metrika Systems
                                         Corporation.

BARRY S. HOWE.......................     Mr. Howe, 44, has been a vice president
                                         of Thermo Instrument since 1994. He has
                                         been president and chief executive
                                         officer of ThermoSpectra Corporation, a
                                         subsidiary of Thermo Instrument that
                                         develops, manufactures, and markets
                                         precision imaging, inspection,
                                         measurement, and temperature-control
                                         instrumentation, since March 1998 and
                                         was appointed president, chief
                                         executive officer and a director of
                                         Thermo Optek Corporation, a
                                         majority-owned subsidiary of Thermo
                                         Instrument in October 1999. Thermo
                                         Optek is a manufacturer of analytical
                                         instruments that measure energy and
                                         light for purposes of materials
                                         analysis, characterization and
                                         preparation. Mr. Howe also served as
                                         president and chief executive officer
                                         of Thermo BioAnalysis Corporation,
                                         which develops and markets instruments,
                                         consumables, diagnostics and
                                         information measurement systems for
                                         biochemistry, healthcare and other
                                         applications, from February 1995 to
                                         March 1998. Mr. Howe's business

                                       A-7
<PAGE>   77

                                         address is 8 East Forge Parkway,
                                         Franklin, MA 02038.

THEO MELAS-KYRIAZI..................     Mr. Melas-Kyriazi, 40, has been the
                                         chief financial officer of Thermo
                                         Instrument since January 1999. He has
                                         been a vice president of Thermo
                                         Electron since March 1998 and its chief
                                         financial officer since January 1999.
                                         Prior to his appointment as a vice
                                         president at Thermo Electron, Mr.
                                         Melas-Kyriazi served as president and
                                         chief executive officer of
                                         ThermoSpectra Corporation, a subsidiary
                                         of Thermo Instrument that develops,
                                         manufactures, and markets precision
                                         imaging, inspection, measurement, and
                                         temperature-control instrumentation,
                                         from its inception until March 1998.
                                         Mr. Melas-Kyriazi is a director of
                                         ThermoRetec Corporation. Mr.
                                         Melas-Kyriazi is a citizen of Greece.

     Stock Ownership.  The following table sets forth the beneficial ownership
of common stock of Thermo Instrument and Thermo Electron, as of January 31,
2000, with respect to each director and executive officer of Thermo Instrument.
While some directors and executive officers of Thermo Instrument are also
directors and executive officers of Thermo Electron or its subsidiaries, all
such persons disclaim beneficial ownership of the shares of common stock
beneficially owned by us.

<TABLE>
<CAPTION>
                                                                   THERMO            THERMO
                                                                 INSTRUMENT         ELECTRON
                          NAME(1)                             SYSTEMS INC.(2)    CORPORATION(3)
                          -------                             ----------------   --------------
<S>                                                           <C>                <C>
Richard W.K. Chapman........................................       225,530            79,801
Denis A. Helm...............................................       278,638           167,163
Barry S. Howe...............................................       303,290            71,655
Earl R. Lewis...............................................       436,499           215,477
Theo Melas-Kyriazi..........................................       182,715           458,532
Polyvios C. Vintiadis.......................................        17,597             2,500
All directors and current executive officers as a group (6
  persons)..................................................     1,444,269           995,128
</TABLE>

- ---------------
(1) Except as reflected in the footnotes to this table, shares of the common
    stock beneficially owned consist of shares owned by the indicated person or
    by that person for the benefit of minor children, and all share ownership
    includes sole voting and investment power.

(2) Shares of the Thermo Instrument common stock beneficially owned by Dr.
    Chapman, Mr. Helm, Mr. Howe, Mr. Lewis, Mr. Melas-Kyriazi, Mr. Vintiadis and
    all directors and current executive officers as a group include 196,249,
    216,250, 273,156, 409,081, 163,687, 11,745 and 1,270,168 shares,
    respectively, that such person or group had the right to acquire within 60
    days of January 31, 2000, through the exercise of stock options. Shares
    beneficially owned by Mr. Melas-Kyriazi and all directors and current
    executive officers as a group include 468 shares, allocated through January
    31, 2000, to Mr. Melas-Kyriazi's account maintained pursuant to Thermo
    Electron's employee stock ownership plan (the "ESOP"). Shares beneficially
    owned by Mr. Vintiadis and all directors and current executive officers as a
    group include 5,590 shares, allocated through January 1, 2000, to Mr.
    Vintiadis' account maintained under Thermo Instrument's deferred
    compensation plan for directors. Shares beneficially owned by Mr. Helm
    include a total of 5,264 shares held in custodial accounts for the benefit
    of four minor children. Shares beneficially owned by Mr. Howe include 374
    shares held in custodial accounts for the benefit of his minor children.
    Shares beneficially owned by Mr. Lewis include 2,987 shares held by his
    spouse. No director or current executive officer beneficially owned more
    than 1% of the Thermo Instrument common stock outstanding as of January 31,
    2000; all directors and current executive officers as a group beneficially
    owned 1.1% of the Thermo Instrument common stock outstanding as of such
    date.

                                       A-8
<PAGE>   78

(3) Shares of the common stock of Thermo Electron beneficially owned by Dr.
    Chapman, Mr. Helm, Mr. Howe, Mr. Lewis, Mr. Melas-Kyriazi and all directors
    and current executive officers as a group include 76,428, 99,816, 64,141,
    212,278, 384,361 and 837,024 shares, respectively, that such person or group
    had the right to acquire within 60 days of January 31, 2000, through the
    exercise of stock options. Shares beneficially owned by Mr. Melas-Kyriazi
    and all directors and current executive officers as a group include 1,071
    shares, allocated through January 31, 2000, to Mr. Melas-Kyriazi's account
    maintained pursuant to the ESOP. Shares beneficially owned by Mr. Helm
    include 8,100 shares held in custodial accounts for the benefit of his minor
    children. Shares beneficially owned by Mr. Howe include 200 shares held in
    custodial accounts for the benefit of his minor children. No director or
    current executive officer beneficially owned more than 1% of the Thermo
    Electron common stock outstanding as of January 31, 2000; all directors and
    current executive officers as a group beneficially owned less than 1% of the
    Thermo Electron common stock outstanding as of such date.

                                       A-9
<PAGE>   79

                      [This page intentionally left blank]
<PAGE>   80

                                    ANNEX B

                   INFORMATION CONCERNING TRANSACTIONS IN THE
                       COMMON STOCK OF THERMO INSTRUMENT

     Neither we nor, to our knowledge, any of our directors or executive
officers engaged in any transactions in Thermo Instrument common stock during
the 60-day period ended April 20, 2000, except for the option exercises
described below.

<TABLE>
<CAPTION>
                                                                                        NUMBER OF
                                                                                     SHARES RECEIVED    EXERCISE PRICE
NAME                                         RELATIONSHIP           EXERCISE DATE     UPON EXERCISE       PER SHARE
- ----                                   -------------------------    -------------    ---------------    --------------
<S>                                    <C>                          <C>              <C>                <C>
Dr. Elias P. Gyftopoulos.............  Director, Thermo Electron       3/10/00            1,406             $11.15
Robert A. McCabe.....................  Director, Thermo Electron       3/20/00            1,406             $11.15
</TABLE>

                                       B-1
<PAGE>   81

                      [This page intentionally left blank]
<PAGE>   82

                                    ANNEX C

              SECTION 262 OF THE DELAWARE GENERAL CORPORATION LAW

     (a) Any stockholder of a corporation of this State who holds shares of
stock on the date of the making of a demand pursuant to subsection (d) of this
section with respect to such shares, who continuously holds such shares through
the effective date of the merger or consolidation, who has otherwise complied
with subsection (d) of this section and who has neither voted in favor of the
merger or consolidation nor consented thereto in writing pursuant to sec.228 of
this title shall be entitled to an appraisal by the Court of Chancery of the
fair value of the stockholder's shares of stock under the circumstances
described in subsections (b) and (c) of this section. As used in this section,
the word "stockholder" means a holder of record of stock in a stock corporation
and also a member of record of a nonstock corporation; the words "stock" and
"share" mean and include what is ordinarily meant by those words and also
membership or membership interest of a member of a nonstock corporation; and the
words "depository receipt" mean a receipt or other instrument issued by a
depository representing an interest in one or more shares, or fractions thereof,
solely of stock of a corporation, which stock is deposited with the depository.

     (b) Appraisal rights shall be available for the shares of any class or
series of stock of a constituent corporation in a merger or consolidation to be
effected pursuant to sec.251 (other than a merger effected pursuant to
sec.251(g)of this title), sec.252, sec.254, sec.257, sec.258, sec.263 or sec.264
of this title:

          (1) Provided, however, that no appraisal rights under this section
     shall be available for the shares of any class or series of stock, which
     stock, or depository receipts in respect thereof, at the record date fixed
     to determine the stockholders entitled to receive notice of and to vote at
     the meeting of stockholders to act upon the agreement of merger or
     consolidation, were either (i) listed on a national securities exchange or
     designated as a national market system security on an interdealer quotation
     system by the National Association of Securities Dealers, Inc. or (ii) held
     of record by more than 2,000 holders; and further provided that no
     appraisal rights shall be available for any shares of stock of the
     constituent corporation surviving a merger if the merger did not require
     for its approval the vote of the stockholders of the surviving corporation
     as provided in subsection (f) of sec.251 of this title.

          (2) Notwithstanding paragraph (1) of this subsection, appraisal rights
     under this section shall be available for the shares of any class or series
     of stock of a constituent corporation if the holders thereof are required
     by the terms of an agreement of merger or consolidation pursuant to
     sec.sec.251, 252, 254, 257, 258, 263 and 264 of this title to accept for
     such stock anything except:

             a. Shares of stock of the corporation surviving or resulting from
        such merger or consolidation, or depository receipts in respect thereof;

             b. Shares of stock of any other corporation, or depository receipts
        in respect thereof, which shares of stock (or depository receipts in
        respect thereof) or depository receipts at the effective date of the
        merger or consolidation will be either listed on a national securities
        exchange or designated as a national market system security on an
        interdealer quotation system by the National Association of Securities
        Dealers, Inc. or held of record by more than 2,000 holders;

             c. Cash in lieu of fractional shares or fractional depository
        receipts described in the foregoing subparagraphs a. and b. of this
        paragraph; or

             d. Any combination of the shares of stock, depository receipts and
        cash in lieu of fractional shares or fractional depository receipts
        described in the foregoing subparagraphs a., b. and c. of this
        paragraph.

          (3) In the event all of the stock of a subsidiary Delaware corporation
     party to a merger effected under sec.253 of this title is not owned by the
     parent corporation immediately prior to the merger, appraisal rights shall
     be available for the shares of the subsidiary Delaware corporation.

                                       C-1
<PAGE>   83

     (c) Any corporation may provide in its certificate of incorporation that
appraisal rights under this section shall be available for the shares of any
class or series of its stock as a result of an amendment to its certificate of
incorporation, any merger or consolidation in which the corporation is a
constituent corporation or the sale of all or substantially all of the assets of
the corporation. If the certificate of incorporation contains such a provision,
the procedures of this section, including those set forth in subsections (d) and
(e) of this section, shall apply as nearly as is practicable.

     (d) Appraisal rights shall be perfected as follows:

          (1) If a proposed merger or consolidation for which appraisal rights
     are provided under this section is to be submitted for approval at a
     meeting of stockholders, the corporation, not less than 20 days prior to
     the meeting, shall notify each of its stockholders who was such on the
     record date for such meeting with respect to shares for which appraisal
     rights are available pursuant to subsections (b) or (c) hereof that
     appraisal rights are available for any or all of the shares of the
     constituent corporations, and shall include in such notice a copy of this
     section. Each stockholder electing to demand the appraisal of such
     stockholder's shares shall deliver to the corporation, before the taking of
     the vote on the merger or consolidation, a written demand for appraisal of
     such stockholder's shares. Such demand will be sufficient if it reasonably
     informs the corporation of the identity of the stockholder and that the
     stockholder intends thereby to demand the appraisal of such stockholder's
     shares. A proxy or vote against the merger or consolidation shall not
     constitute such a demand. A stockholder electing to take such action must
     do so by a separate written demand as herein provided. Within 10 days after
     the effective date of such merger or consolidation, the surviving or
     resulting corporation shall notify each stockholder of each constituent
     corporation who has complied with this subsection and has not voted in
     favor of or consented to the merger or consolidation of the date that the
     merger or consolidation has become effective; or

          (2) If the merger or consolidation was approved pursuant to sec.228 or
     sec.253 of this title, each constituent corporation, either before the
     effective date of the merger or consolidation or within ten days
     thereafter, shall notify each of the holders of any class or series of
     stock of such constituent corporation who are entitled to appraisal rights
     of the approval of the merger or consolidation and that appraisal rights
     are available for any or all shares of such class or series of stock of
     such constituent corporation, and shall include in such notice a copy of
     this section; provided that, if the notice is given on or after the
     effective date of the merger or consolidation, such notice shall be given
     by the surviving or resulting corporation to all such holders of any class
     or series of stock of a constituent corporation that are entitled to
     appraisal rights. Such notice may, and, if given on or after the effective
     date of the merger or consolidation, shall, also notify such stockholders
     of the effective date of the merger or consolidation. Any stockholder
     entitled to appraisal rights may, within 20 days after the date of mailing
     of such notice, demand in writing from the surviving or resulting
     corporation the appraisal of such holder's shares. Such demand will be
     sufficient if it reasonably informs the corporation of the identity of the
     stockholder and that the stockholder intends thereby to demand the
     appraisal of such holder's shares. If such notice did not notify
     stockholders of the effective date of the merger or consolidation, either
     (i) each such constituent corporation shall send a second notice before the
     effective date of the merger or consolidation notifying each of the holders
     of any class or series of stock of such constituent corporation that are
     entitled to appraisal rights of the effective date of the merger or
     consolidation or (ii) the surviving or resulting corporation shall send
     such a second notice to all such holders on or within 10 days after such
     effective date; provided, however, that if such second notice is sent more
     than 20 days following the sending of the first notice, such second notice
     need only be sent to each stockholder who is entitled to appraisal rights
     and who has demanded appraisal of such holder's shares in accordance with
     this subsection. An affidavit of the secretary or assistant secretary or of
     the transfer agent of the corporation that is required to give either
     notice that such notice has been given shall, in the absence of fraud, be
     prima facie evidence of the facts stated therein. For purposes of
     determining the stockholders entitled to receive either notice, each
     constituent corporation may fix, in advance, a record date that shall be
     not more than 10 days prior to the date the notice is given, provided, that
     if the notice is given on or after the effective date of the

                                       C-2
<PAGE>   84

     merger or consolidation, the record date shall be such effective date. If
     no record date is fixed and the notice is given prior to the effective
     date, the record date shall be the close of business on the day next
     preceding the day on which the notice is given.

     (e) Within 120 days after the effective date of the merger or
consolidation, the surviving or resulting corporation or any stockholder who has
complied with subsections (a) and (d) hereof and who is otherwise entitled to
appraisal rights, may file a petition in the Court of Chancery demanding a
determination of the value of the stock of all such stockholders.
Notwithstanding the foregoing, at any time within 60 days after the effective
date of the merger or consolidation, any stockholder shall have the right to
withdraw such stockholder's demand for appraisal and to accept the terms offered
upon the merger or consolidation. Within 120 days after the effective date of
the merger or consolidation, any stockholder who has complied with the
requirements of subsections (a) and (d) hereof, upon written request, shall be
entitled to receive from the corporation surviving the merger or resulting from
the consolidation a statement setting forth the aggregate number of shares not
voted in favor of the merger or consolidation and with respect to which demands
for appraisal have been received and the aggregate number of holders of such
shares. Such written statement shall be mailed to the stockholder within 10 days
after such stockholder's written request for such a statement is received by the
surviving or resulting corporation or within 10 days after expiration of the
period for delivery of demands for appraisal under subsection (d) hereof,
whichever is later.

     (f) Upon the filing of any such petition by a stockholder, service of a
copy thereof shall be made upon the surviving or resulting corporation, which
shall within 20 days after such service file in the office of the Register in
Chancery in which the petition was filed a duly verified list containing the
names and addresses of all stockholders who have demanded payment for their
shares and with whom agreements as to the value of their shares have not been
reached by the surviving or resulting corporation. If the petition shall be
filed, by the surviving or resulting corporation, the petition shall be
accompanied by such a duly verified list. The Register in Chancery, if so
ordered by the Court, shall give notice of the time and place fixed for the
hearing of such petition by registered or certified mail to the surviving or
resulting corporation and to the stockholders shown on the list at the addresses
therein stated. Such notice shall also be given by or more publications at least
week before the day of the hearing, in a newspaper of general circulation
published in the City of Wilmington, Delaware or such publication as the Court
deems advisable. The forms of the notices by mail and by publication shall be
approved by the Court, and the costs thereof shall be borne by the surviving or
resulting corporation.

     (g) At the hearing on such petition, the Court shall determine the
stockholders who have complied with this section and who have become entitled to
appraisal rights. The Court may require the stockholders who have demanded an
appraisal for their shares and who hold stock represented by certificates to
submit their certificates of stock to the Register in Chancery for notation
thereon of the pendency of the appraisal proceedings; and if any stockholder
fails to comply with such direction, the Court may dismiss the proceedings as to
such stockholder.

     (h) After determining the stockholders entitled to an appraisal, the Court
shall appraise the shares, determining their fair value exclusive of any element
of value arising from the accomplishment or expectation of the merger or
consolidation, together with a fair rate of interest, if any, to be paid upon
the amount determined to be the fair value. In determining such fair value, the
Court shall take into account all relevant factors. In determining the fair rate
of interest, the Court may consider all relevant factors, including the rate of
interest which the surviving or resulting corporation would have had to pay to
borrow money during the pendency of the proceeding. Upon application by the
surviving or resulting corporation or by any stockholder entitled to participate
in the appraisal proceeding, the Court may, in its discretion, permit discovery
or other pretrial proceedings and may proceed to trial upon the appraisal prior
to the final determination of the stockholder entitled to an appraisal. Any
stockholder whose name appears on the list filed by the surviving or resulting
corporation pursuant to subsection (f) of this section and who has submitted
such stockholder's certificates of stock to the Register in Chancery, if such is
required, may participate fully in all proceedings until it is finally
determined that such stockholder is not entitled to appraisal rights under this
section
                                       C-3
<PAGE>   85

     (i) The Court shall direct the payment of the fair value of the shares,
together with interest, if any, by the surviving or resulting corporation to the
stockholders entitled thereto. Interest may be simple or compound, as the Court
may direct. Payment shall be so made to each such stockholder, in the case of
holders of uncertificated stock forthwith, and the case of holders of shares
represented by certificates upon the surrender to the corporation of the
certificates representing such stock. The Court's decree may be enforced as
other decrees in the Court of Chancery may be enforced, whether such surviving
or resulting corporation be a corporation of this State or of any state.

     (j) The costs of the proceeding may be determined by the Court and taxed
upon the parties as the Court deems equitable in the circumstances. Upon
application of a stockholder, the Court may order all or a portion of the
expenses incurred by any stockholder in connection with the appraisal
proceeding, including, without limitation, reasonable attorney's fees and the
fees and expenses of experts, to be charged pro rata against the value of all
the shares entitled to an appraisal.

     (k) From and after the effective date of the merger or consolidation, no
stockholder who has demanded appraisal rights as provided in subsection (d) of
this section shall be entitled to vote such stock for any purpose or to receive
payment of dividends or other distributions on the stock (except dividends or
other distributions payable to stockholders of record at a date which is prior
to the effective date of the merger or consolidation); provided, however, that
if no petition for an appraisal shall be filed within the time provided in
subsection (e) of this section, or if such stockholder shall deliver to the
surviving or resulting corporation a written withdrawal of such stockholder's
demand for an appraisal and an acceptance of the merger or consolidation, either
within 60 days after the effective date of the merger or consolidation as
provided in subsection (e) of this section or thereafter with the written
approval of the corporation, then the right of such stockholder to an appraisal
shall cease. Notwithstanding the foregoing, no appraisal proceeding in the Court
of Chancery shall be dismissed as to any stockholder without the approval of the
Court, and such approval may be conditioned upon such terms as the Court deems
just.

     (l) The shares of the surviving or resulting corporation to which the
shares of such objecting stockholders would have been converted had they
assented to the merger or consolidation shall have the status of authorized and
unissued shares of the surviving or resulting corporation. (Last amended by Ch.
339, L. '98, eff. 7-1-98.)

                                       C-4
<PAGE>   86

                      [This page intentionally left blank]
<PAGE>   87

                      [This page intentionally left blank]
<PAGE>   88

                      [This page intentionally left blank]
<PAGE>   89

     You or your broker, dealer, commercial bank, trust company or other nominee
should deliver your letter of transmittal, certificates for Thermo Instrument
shares and any other required documents to the depositary at one of its address
set forth below.

                   The Depositary for the exchange offer is:

                    AMERICAN STOCK TRANSFER & TRUST COMPANY

<TABLE>
<S>                              <C>
           By Mail:                   By Hand or Overnight
        40 Wall Street                      Courier:
          46th Floor                     40 Wall Street
   New York, New York 10005                46th Floor
     Attn: Reorganization           New York, New York 10005
          Department                  Attn: Reorganization
                                           Department
</TABLE>

                           By Facsimile Transmission:
                                 (718) 234-5001

                             Confirm by Telephone:
                                 (718) 921-8200

     You should direct any questions or requests for assistance or additional
copies of the prospectus, the letter of transmittal and the notice of guaranteed
delivery to the Information Agent at its telephone numbers and location listed
below. You may also contact your local broker, commercial bank, trust company or
nominee for assistance concerning the exchange offer.

                The Information Agent for the exchange offer is:

                             D.F. KING & CO., INC.
                          77 Water Street, 20th Floor
                               New York, NY 10005
                Bankers and Brokers Call Collect (212) 269-5550
                    All Others Call Toll-Free (800) 290-6433
<PAGE>   90

                                    PART II

                     INFORMATION NOT REQUIRED IN PROSPECTUS

ITEM 20.  INDEMNIFICATION OF DIRECTORS AND OFFICERS.

     The Delaware General Corporation Law and Thermo Electron's Certificate of
Incorporation and Bylaws limit the monetary liability of directors to Thermo
Electron and to its stockholders and provide for indemnification of Thermo
Electron's officers and directors for liabilities and expenses that they may
incur in such capacities. In general, officers and directors are indemnified
with respect to actions taken in good faith in a manner reasonably believed to
be in, or not opposed to, the best interests of Thermo Electron and, with
respect to any criminal action or proceeding, actions that the indemnitee had no
reasonable cause to believe were unlawful. Thermo Electron also has
indemnification agreements with its directors and officers that provide for the
maximum indemnification allowed by law.

     Thermo Electron has an insurance policy which insures its directors and
officers against those liabilities set forth in the insurance policy which might
be incurred in connection with the performance of their duties.

ITEM 21.  EXHIBITS AND FINANCIAL STATEMENT SCHEDULES.

     (a) The following exhibits are filed herewith or incorporated herein by
         reference:

<TABLE>
<CAPTION>
EXHIBIT
NUMBER                      DESCRIPTION OF DOCUMENT
- -------                     -----------------------
<C>       <S>
  3.1     Amended and Restated Certificate of Incorporation of the
          Registrant (incorporated by reference to Exhibit 1 to the
          Registrant's Amendment No. 3 to Registration Statement on
          Form 8-A/A filed on September 9, 1999 (SEC File No.
          1-8002)).
  3.2     Bylaws of the Registrant (incorporated by reference to
          Exhibit 3 to the Registrant's Quarterly Report on Form 10-Q
          for the quarter ended July 3, 1999 (SEC File No. 1-8002)).
  4.1     Reference is made to Exhibits 3.1 and 3.2 above.
  4.2     Fiscal Agency Agreement dated as of January 3, 1996, between
          the Registrant and Chemical Bank pertaining to the
          Registrant's 4 1/4% Subordinated Convertible Debentures due
          2003 (incorporated by reference to Exhibit 4.1 to
          Registrant's Annual Report on Form 10-K for the fiscal year
          ended December 30, 1995 (SEC File No. 1-8002)). The
          Registrant agrees, pursuant to Item 601(b)(4)(iii)(A) of
          Regulation S-K, to furnish to the Commission upon request, a
          copy of each instrument with respect to other long-term debt
          of the Registrant or its consolidated subsidiaries.
  4.3     Rights Agreement, dated as of January 19, 1996, between the
          Registrant and the First National Bank of Boston, as Rights
          Agent, which includes as Exhibit A the Form of Certificate
          of Designations, as Exhibit B the Form of Rights Certificate
          and as Exhibit C the Summary of Rights to Purchase Preferred
          Stock (incorporated by reference to Exhibit 1 to the
          Registrant's Registration Statement on Form 8-A filed on
          January 26, 1996, as amended by Amendment No. 1 to
          Registration Statement on Form 8-A/A filed on May 30, 1997
          (SEC File No. 1-8002)).
  4.4     Amendment No. 1 to Rights Agreement, dated as of June 11,
          1999, between the Registrant and BankBoston, N.A. (formerly,
          The First National Bank of Boston), as Rights Agent, which
          includes as Exhibit B the amended and restated Form of
          Rights Certificate and as Exhibit C the amended and restated
          Summary of Rights to Purchase Preferred Stock (incorporated
          by reference to Exhibit 2 to the Registrant's Amendment No.
          2 to Registration Statement on Form 8-A/A filed on June 21,
          1999 (SEC File No. 1-8002)).
</TABLE>

                                      II-1
<PAGE>   91

<TABLE>
<CAPTION>
EXHIBIT
NUMBER                      DESCRIPTION OF DOCUMENT
- -------                     -----------------------
<C>       <S>
  4.5     Indenture dated as of October 29, 1998, by and between the
          Registrant and Bankers Trust Company, as Trustee, relating
          to the issuance of senior debt securities by the Registrant
          (incorporated by reference to Exhibit 4.1 to the
          Registrant's Current Report on Form 8-K dated October 29,
          1998, filed with the SEC on October 30, 1998 (SEC File No.
          1-8002)).
  4.6     First Supplemental Indenture dated as of October 29, 1998,
          by and between the Registrant and Bankers Trust Company, as
          Trustee, relating to the issuance by the Registrant of
          $150,000,000 aggregate principal amount of its 7.625% Notes
          due 2008 (incorporated by reference to Exhibit 4.2 to the
          Registrant's Current Report on Form 8-K dated October 29,
          1998, filed with the SEC on October 30, 1998 (SEC File No.
          1-8002)).
  5.1     Opinion and consent of Seth H. Hoogasian, Esq. as to the
          validity of the securities being issued.
  8.1     Opinion and consent of Hale and Dorr LLP as to the material
          United States federal income tax consequences of the
          exchange offer and the merger.
 10.1     Form of Indemnification Agreement between the Registrant and
          the directors and officers of its majority-owned
          subsidiaries (filed as Exhibit 10.1 to the Registrant's
          Registration Statement on Form S-4 [Reg. No. 333-90661] and
          incorporated herein by reference).
 10.2     Form of Amended and Restated Indemnification Agreement
          between the Registrant and its directors and officers (filed
          as Exhibit 10.2 to the Registrant's Registration Statement
          on Form S-4 [Reg. No. 333-90661] and incorporated herein by
          reference).
 12.1     Computation of Registrant's ratio of earnings to fixed
          charges.
 12.2     Computation of Thermo Instrument's ratio of earnings to
          fixed charges.
 21.1     Subsidiaries of the Registrant (incorporated by reference to
          Exhibit 21.1 to the Registrant's Annual Report on Form 10-K
          dated January 1, 2000, filed with the SEC on March 22, 2000
          (SEC File No. 1-8002)).
 23.1     Consent of Arthur Andersen LLP, independent accountants to
          the Registrant.
 23.2     Consent of Arthur Andersen LLP, independent accountants to
          Thermo Instrument Systems Inc.
 23.3     Consent of Seth H. Hoogasian, Esq. (included in Exhibit 5.1
          of this Registration Statement).
 23.4     Consent of Hale and Dorr LLP (included in Exhibit 8.1 of
          this Registration Statement).
 24.1     Powers of Attorney (included in the signature pages of this
          Registration Statement).
 99.1     Form of Letter of Transmittal.
 99.2     Form of Notice of Guaranteed Delivery.
 99.3     Form of Broker Dealer Letter.
 99.4     Form of Letter to Clients.
 99.5     Form of Guidelines for Certification of Taxpayer
          Identification Number on Substitute Form W-9.
</TABLE>

ITEM 22.  UNDERTAKINGS.

     The undersigned registrant hereby undertakes:

          (1) that, for purposes of determining any liability under the
     Securities Act of 1933, each filing of the registrant's annual report
     pursuant to Section 13(a) or Section 15(d) of the Securities Exchange Act
     of 1934 (and, where applicable, each filing of an employee benefit plan's
     annual report pursuant to Section 15(d) of the Securities Exchange Act of
     1934) that is incorporated by reference in this registration statement
     shall be deemed to be a new registration statement relating to the
     securities offered therein, and the offering of such securities at that
     time shall be deemed to be the initial bona fide offering thereof;

          (2) that before any public reoffering of the securities registered
     hereunder through use of a prospectus which is a part of this registration
     statement, by any person or party who is deemed to be

                                      II-2
<PAGE>   92

     an underwriter within the meaning of Rule 145(c), the issuer undertakes
     that such reoffering prospectus will contain the information called for by
     the applicable registration form with respect to reofferings by persons who
     may be deemed underwriters, in addition to the information called for by
     the other items of the applicable form;

          (3) that every prospectus (i) that is filed pursuant to paragraph (2)
     immediately preceding, or (ii) that purports to meet the requirements of
     Section 10(a)(3) of the Act and is used in connection with an offering of
     securities subject to Rule 415, will be filed as a part of an amendment to
     the registration statement and will not be used until such amendment is
     effective, and that, for purposes of determining any liability under the
     Securities Act of 1933, each such post-effective amendment shall be deemed
     to be a new registration statement relating to the securities offered
     therein, and the offering of such securities at that time shall be deemed
     to be the initial bona fide offering thereof;

          (4) to respond to requests for information that is incorporated by
     reference into the prospectus pursuant to Items 4, 10(b), 11, or 13 of this
     Form, within one business day of receipt of such request, and to send the
     incorporated documents by first class mail or other equally prompt means,
     including information contained in documents filed after the effective date
     of this registration statement through the date of responding to such
     request; and

          (5) to supply by means of a post-effective amendment all information
     concerning a transaction, and the company being acquired involved therein,
     that was not the subject of and included in this registration statement
     when it became effective.

     Insofar as indemnification for liabilities under the Securities Act of 1933
may be permitted to directors, officers and controlling persons of the
registrant pursuant to the provisions described in Item 20 above, or otherwise,
the registrant has been advised that in the opinion of the Securities and
Exchange Commission such indemnification is against public policy as expressed
in the Securities Act and is therefore unenforceable. If a claim for
indemnification against such liabilities (other than the payment by the
registrant of expenses incurred or paid by a director, officer or controlling
person of the registrant in the successful defense of any action, suit or
proceeding) is asserted by such director, officer, or controlling person in
connection with the securities being registered, the registrant will, unless in
the opinion of its counsel the matter has been settled by controlling precedent,
submit to a court of appropriate jurisdiction the question whether such
indemnification by it is against public policy as expressed in the Securities
Act and will be governed by the final adjudication of such issue.

                                      II-3
<PAGE>   93

                                   SIGNATURES

     Pursuant to the requirements of the Securities Act of 1933, the registrant
has duly caused this registration statement to be signed on its behalf by the
undersigned, thereunto duly authorized, in the City of Waltham, Commonwealth of
Massachusetts, on this 24th day of April, 2000.

                                          THERMO ELECTRON CORPORATION

                                          By:          /s/ RICHARD F. SYRON
                                            ------------------------------------
                                                       Richard F. Syron
                                                       President, Chief
                                              Executive Officer and
                                                       Chairman of the Board

                        POWER OF ATTORNEY AND SIGNATURES

     Each of the undersigned Directors and Officers of Thermo Electron
Corporation hereby appoints Theo Melas-Kyriazi, Seth H. Hoogasian and Sandra L.
Lambert, and each of them, his true and lawful attorneys-in-fact and agents,
with full power of substitution, for him and in his name, place and stead, in
any and all capacities, to sign any and all amendments (including post-effective
amendments) to this Registration Statement, and to file the same, with all
exhibits thereto, and all documents in connection therewith, with the Securities
and Exchange Commission, granting unto said attorneys-in-fact and agents, and
each of them, full power and authority to do and perform each and every act and
thing requisite and necessary to be done in and about the premises, as fully to
all intents and purposes as he might or could do in person, hereby ratifying and
confirming all that said attorneys-in-fact and agents or any of them, or their
or his substitute or substitutes, may lawfully do or cause to be done by virtue
thereof.

     Pursuant to the requirements of the Securities Act of 1933, this
Registration Statement has been signed below by the following persons in the
capacities and on the dates indicated:

<TABLE>
<CAPTION>
  SIGNATURE                                                         TITLE                      DATE
  ---------                                                         -----                      ----
  <S>                                                  <C>                                <C>
           /s/ RICHARD F. SYRON                        President, Chief Executive         April 24, 2000
  ---------------------------------------------------    Officer and Chairman of the
           Richard F. Syron                              Board (Principal Executive
                                                         Officer)

           /s/ THEO MELAS-KYRIAZI                      Vice President and Chief           April 24, 2000
  ---------------------------------------------------    Financial Officer (Principal
           Theo Melas-Kyriazi                            Financial Officer and
                                                         Principal Accounting Officer)

           /s/ SAMUEL W. BODMAN                        Director                           April 24, 2000
  ---------------------------------------------------
           Samuel W. Bodman

           /s/ PETER O. CRISP                          Director                           April 24, 2000
  ---------------------------------------------------
           Peter O. Crisp

           /s/ ELIAS P. GYFTOPOULOS                    Director                           April 24, 2000
  ---------------------------------------------------
           Elias P. Gyftopoulos

           /s/ FRANK JUNGERS                           Director                           April 24, 2000
  ---------------------------------------------------
           Frank Jungers
</TABLE>

                                      II-4
<PAGE>   94

<TABLE>
<CAPTION>
  SIGNATURE                                                         TITLE                      DATE
  ---------                                                         -----                      ----
  <S>                                                  <C>                                <C>
           /s/ ROBERT A. MCCABE                        Director                           April 24, 2000
  ---------------------------------------------------
           Robert A. McCabe

           /s/ HUTHAM S. OLAYAN                        Director                           April 24, 2000
  ---------------------------------------------------
           Hutham S. Olayan

           /s/ ROBERT W. O'LEARY                       Director                           April 24, 2000
  ---------------------------------------------------
           Robert W. O'Leary

           /s/ ROGER D. WELLINGTON                     Director                           April 24, 2000
  ---------------------------------------------------
           Roger D. Wellington
</TABLE>

                                      II-5

<PAGE>   1
                                                                     EXHIBIT 5.1



                           Thermo Electron Corporation
                                 81 Wyman Street
                        Waltham, Massachusetts 02454-9046




                                                                  April 24, 2000

Thermo Electron Corporation
81 Wyman Street
Waltham, Massachusetts 02454-9046

Re:      Registration Statement on Form S-4
         Relating to Common Stock, $1.00 par value,
         of Thermo Electron Corporation

Dear Sirs:

         I am General Counsel to Thermo Electron Corporation, a Delaware
corporation (the "Company"), and have acted as its counsel in connection with
the exchange offer by the Company for all issued and outstanding shares of
Thermo Instrument Systems Inc., a majority-owned subsidiary of the Company
("Thermo Instrument"), and the filing of a Registration Statement on Form S-4
(the "Registration Statement") in order to register, under the Securities Act of
1933, as amended, the shares of the Company's Common Stock, $1.00 par value per
share (the "Shares"), to be issued in exchange for the issued and outstanding
shares of Thermo Instrument.

         I or a member of my legal staff have reviewed the corporate proceedings
taken by the Company with respect to the authorization of the issuance of the
Shares. I or a member of my legal staff have also examined and relied upon
originals or copies, certified or otherwise authenticated to my satisfaction, of
all corporate records, documents, agreements or other instruments of the Company
and have made all investigations of law and have discussed with the Company's
representatives all questions of fact that I have deemed necessary or
appropriate.

         Based upon and subject to the foregoing, I am of the opinion that:

         1. The Company is a corporation validly existing and in corporate good
standing under the laws of the State of Delaware.

         2. The issuance of the Shares as contemplated in the Registration
Statement has been duly authorized by the Company.
<PAGE>   2
         3. The Shares, when issued in accordance with the provisions of the
Merger Agreement, will be validly issued, fully paid and nonassessable.

         This opinion is limited to the applicable provisions of the Delaware
Constitution, the General Corporation Law of the State of Delaware ("Delaware
Law") and reported judicial decisions interpreting Delaware Law.

         I hereby consent to the filing of this opinion as Exhibit 5 to the
Registration Statement and to being named in the Registration Statement under
the caption "LEGAL MATTERS".

                                                  Very truly yours,

                                                  /s/ Seth H. Hoogasian

                                                  Seth H. Hoogasian
                                                  General Counsel

THI 16832

<PAGE>   1
                                                                     EXHIBIT 8.1

                         [HALE AND DORR LLP LETTERHEAD]



                                                  April 24, 2000


Thermo Instrument Systems Inc.
81 Wyman Street
Waltham, Massachusetts 02454


                         Re:      Merger of Thermo Instrument Systems Inc.
                                  into Thermo Electron Corporation Following
                                  Completion of Thermo Electron Corporation's
                                  Offer to Exchange Shares of Thermo Electron
                                  Corporation Common Stock for Outstanding
                                  Shares of Thermo Instrument Systems Inc.
                                  Common Stock

Ladies and Gentlemen:

      This opinion is being delivered to you in connection with the filing of a
registration statement (the "Registration Statement") on Form S-4, which
includes the Prospectus relating to the merger of Thermo Instrument Systems Inc.
("Target") with and into Thermo Electron Corporation ("Acquiror") in accordance
with the Delaware General Corporation Law (the "Merger") following consummation
of Acquiror's offer to exchange 0.85 shares of common stock of Acquiror for each
outstanding share of common stock of Target (the "Exchange Offer"). Except as
otherwise provided, capitalized terms not defined herein have the meanings set
forth in the letters delivered to Hale and Dorr LLP by Acquiror and Target
containing certain representations of Acquiror and Target relevant to this
opinion (the "Representation Letters"). All section references, unless otherwise
indicated, are to the United States Internal Revenue Code of 1986, as amended
(the "Code").

      In our capacity as counsel to Acquiror and Target in the Merger, and for
purposes of rendering this opinion, we have examined and relied upon the
Registration Statement and the exhibits thereto, the Representation Letters, and
such other documents as we considered relevant to our analysis. In our
examination of documents, we have assumed the authenticity of original
documents, the accuracy of copies, the genuineness of signatures, and the legal
capacity of signatories.

      We have assumed that all parties to all documents examined by us have
acted, and will act, in accordance with the terms of such documents and that the
Exchange Offer and the Merger will be consummated pursuant to the terms and
conditions set forth in the Registration Statement without the waiver or
modification of any such terms and conditions. Furthermore, we have assumed that
all representations contained in the Representation Letters, are, and at the
Effective Time will be, true and complete in all
<PAGE>   2
Thermo Instrument Systems Inc.
April 24, 2000
Page 2



material respects, and that any representation made in any of the documents
referred to herein "to the best of the knowledge and belief" or "to the best of
the belief" (or similar qualification) of any person or party is, and at the
Effective Time will be, correct without such qualification. We have also assumed
that as to all matters for which a person or entity has represented that such
person or entity is not a party to, does not have, or is not aware of, any plan,
intention, understanding, or agreement, there is no such plan, intention,
understanding, or agreement. We have not attempted to verify independently such
representations, but in the course of our representation, nothing has come to
our attention that would cause us to question the accuracy thereof.

      The conclusions expressed herein represent our judgment as to the proper
treatment of certain aspects of the Exchange Offer and the Merger under the
income tax laws of the United States based upon the Code, Treasury Regulations,
case law, and rulings and other pronouncements of the Internal Revenue Service
(the "IRS") as in effect on the date of this opinion. No assurances can be given
that such laws will not be amended or otherwise changed prior to the Effective
Time, or at any other time, or that such changes will not affect the conclusions
expressed herein. Nevertheless, we undertake no responsibility to advise you or
your shareholders of any developments after the Effective Time in the
application or interpretation of the income tax laws of the United States.

      Our opinion represents our best judgment of how a court would decide if
presented with the issues addressed herein and is not binding upon either the
IRS or any court. Thus, no assurances can be given that a position taken in
reliance on our opinion will not be challenged by the IRS or rejected by a
court.

      This opinion addresses only the specific United States federal income tax
consequences of the Exchange Offer and the Merger set forth below, and does not
address any other federal, state, local, or foreign income, estate, gift,
transfer, sales, use, or other tax consequences that may result from the
Exchange Offer or the Merger or any other transaction (including any transaction
undertaken in connection with the Exchange Offer or the Merger). We express no
opinion regarding the tax consequences of the Exchange Offer or the Merger to
shareholders of Target that are subject to special tax rules, and we express no
opinion regarding the tax consequences of the Exchange Offer or the Merger
arising in connection with the ownership of options or warrants for Target
stock.

      On the basis of, and subject to, the foregoing, and in reliance upon the
representations and assumptions described above, we are of the opinion that the
Exchange Offer and the Merger should be treated as one integrated transaction
that will qualify as a reorganization within the meaning of Section 368(a).
Subject to the additional qualifications set forth immediately following the
numbered paragraphs below, the Exchange Offer and the Merger should result in
the following federal income tax consequences:

1.   A Target shareholder will not recognize any gain or loss solely upon the
     exchange of his or her shares of Target stock for Acquiror stock pursuant
     to the Exchange Offer or the Merger, except with respect any cash the
     shareholder receives in lieu of fractional shares of Acquiror stock;
<PAGE>   3
Thermo Instrument Systems Inc.
April 24, 2000
Page 3



2.   A Target shareholder's aggregate tax basis in the Acquiror stock that the
     shareholder receives pursuant to the Exchange Offer or the Merger will be
     the same as the shareholder's aggregate tax basis in the Target stock
     tendered, reduced by the amount of any tax basis attributable to any
     fractional shares not actually received;

3.   A Target shareholder's holding period for the Acquiror stock that the
     shareholder receives pursuant to the Exchange Offer or the Merger will
     include the period for which the shareholder held the Target stock that he
     or she exchanged for the Acquiror stock, provided that the shareholder held
     the Target stock as a capital asset at the time of the exchange pursuant to
     the Exchange Offer or at the Effective Time, as the case may be;

4.   Cash payments that a Target shareholder receives in lieu of a fractional
     share will be treated as if that fractional share of Acquiror stock had
     been issued pursuant to the Exchange Offer or the Merger and then redeemed
     by Acquiror; and

5.   Neither Acquiror nor Target will recognize gain or loss directly as a
     result of the Exchange Offer or the Merger.

      No opinion is expressed as to any federal income tax consequence of the
Exchange Offer or the Merger except as specifically set forth herein, and this
opinion may not be relied upon except with respect to the consequences
specifically discussed herein. In particular, and without limiting the foregoing
sentence, no opinion is expressed as to any aspect or effect of Acquiror's
proposed spin-offs of its medical products business and paper recycling and
papermaking equipment business, and any associated transactions, as described in
Acquiror's Request for Ruling under Section 355 initially filed with the IRS on
April 7, 2000 (the "Spin-Offs"); and no opinion is expressed as to the tax
treatment of the shareholders of Target on their receipt of stock or other
property pursuant to the Spin-Offs.

      This opinion is intended solely for the purpose of inclusion as an exhibit
to the Registration Statement. It may not be relied upon for any other purpose
or by any other person or entity, and may not be made available to any other
person or entity without our prior written consent. We hereby consent to the
filing of this opinion as an exhibit to the Registration Statement and further
consent to the use of our name in the Registration Statement in connection with
references to this opinion and the tax consequences of the Exchange Offer and
the Merger. In giving this consent, however, we do not hereby admit that we are
in the category of persons whose consent is required under Section 7 of the
Securities Act of 1933, as amended.

                                        Very truly yours,

                                        /s/ Hale and Dorr LLP

                                        HALE AND DORR LLP




<PAGE>   1
                                                                    EXHIBIT 12.1



                           THERMO ELECTRON CORPORATION

                       RATIO OF EARNINGS TO FIXED CHARGES
                             (DOLLARS IN THOUSANDS)

<TABLE>
<CAPTION>
                                                                                        Pro Forma              Year Ended
                                                                                           1999           1999            1998
                                                                                       -----------     ----------     -----------
<S>                                                                                    <C>             <C>            <C>
Income from continuing operations before provision for income taxes, minority
 interest, and extraordinary item                                                      $    33,162     $   37,486     $   254,493
Less:
 Minority interest in earnings of consolidated subsidiaries                                 (7,661)       (18,993)        (35,246)
Add:
 Minority interest in consolidated subsidiaries with fixed charges                           7,661         18,993          35,246
 Interest on indebtedness and amortization of debt expense                                  96,992         96,992          90,329
 Portion of rents representative of the interest factor (1)                                 19,365         19,365          17,765
                                                                                       -----------     ----------     -----------

      Income as adjusted                                                               $   149,519     $  153,843     $   362,587
                                                                                       ===========     ==========     ===========

Fixed Charges:
 Interest on indebtedness and amortization of debt expense                             $    96,992     $   96,992     $    90,329
 Portion of rents representative of the interest factor (1)                                 19,365         19,365          17,765
                                                                                       -----------     ----------     -----------

      Fixed Charges                                                                    $   116,357     $  116,357     $   108,094
                                                                                       ===========     ==========     ===========

Ratio of Earnings to Fixed Charges                                                            1.29           1.32            3.35
                                                                                       ===========     ==========     ===========
</TABLE>

<PAGE>   1
                                                                    EXHIBIT 12.2

                         THERMO INSTRUMENT SYSTEMS INC.

                       RATIO OF EARNINGS TO FIXED CHARGES
                             (DOLLARS IN THOUSANDS)

<TABLE>
<CAPTION>
                                                                                            Year Ended
                                                                                    ---------------------------
                                                                                      1999             1998
                                                                                      ----             ----

Income from continuing operations before provision for income taxes, minority
<S>                                                                                 <C>              <C>
 interest, and extraordinary item                                                   $ 179,683        $ 193,916
Less:
 Minority interest in earnings of consolidated subsidiaries                           (16,447)         (15,677)
Add:
 Minority interest in consolidated subsidiaries with fixed charges                     16,447           15,677
 Interest on indebtedness and amortization of debt expense                             50,988           45,458
 Portion of rents representative of the interest factor (1)                            13,632           10,799
                                                                                    ---------        ---------

      Income as adjusted                                                            $ 244,303        $ 250,173
                                                                                    =========        =========

Fixed Charges:
 Interest on indebtedness and amortization of debt expense                          $  50,988        $  45,458
 Portion of rents representative of the interest factor (1)                            13,632           10,799
                                                                                    ---------        ---------

      Fixed Charges                                                                 $  64,620        $  56,257
                                                                                    =========        =========

Ratio of Earnings to Fixed Charges                                                       3.78             4.45
                                                                                    =========        =========
</TABLE>

(1) Portion of rents representative of the interest factor is 1/3 of total
    rents.



<PAGE>   1
                                                                    EXHIBIT 23.1



                    Consent of Independent Public Accountants

To Thermo Electron Corporation:

         As independent public accountants, we hereby consent to the
incorporation by reference in this Registration Statement and related Prospectus
of Thermo Electron Corporation on Form S-4 of our reports dated February 17,
2000 (except with respect to the matters discussed in Note 17, as to which the
date is March 7, 2000) included or incorporated by reference in Thermo Electron
Corporation's Annual Report on Form 10-K for the year ended January 1, 2000, and
to all references to our Firm included in this Registration Statement and
related Prospectus.



                                            /s/ Arthur Andersen LLP

                                            Arthur Andersen LLP



Boston, Massachusetts
April 20, 2000

<PAGE>   1
                                                                    EXHIBIT 23.2



                    Consent of Independent Public Accountants

To Thermo Instrument Systems Inc.:

         As independent public accountants, we hereby consent to the
incorporation by reference in this Registration Statement and related Prospectus
of Thermo Electron Corporation on Form S-4 of our reports dated February 15,
2000 (except with respect to the matters discussed in Note 18, as to which the
date is March 8, 2000) included or incorporated by reference in Thermo
Instrument Systems Inc.'s Annual Report on Form 10-K for the year ended January
1, 2000, and to all references to our Firm included in this Registration
Statement and related Prospectus.



                                            /s/ Arthur Andersen LLP

                                            Arthur Andersen LLP



Boston, Massachusetts
April 20, 2000

<PAGE>   1

                             LETTER OF TRANSMITTAL
                    TO EXCHANGE 0.85 SHARES OF COMMON STOCK

                                       OF

                          THERMO ELECTRON CORPORATION
                                      FOR

                     EACH OUTSTANDING SHARE OF COMMON STOCK

                                       OF

                         THERMO INSTRUMENT SYSTEMS INC.
                     AND CASH IN LIEU OF FRACTIONAL SHARES
                PURSUANT TO THE PROSPECTUS DATED APRIL 24, 2000

  THE OFFER AND WITHDRAWAL RIGHTS WILL EXPIRE AT 12:00 MIDNIGHT, NEW YORK CITY
          TIME, ON FRIDAY, MAY 19, 2000, UNLESS THE OFFER IS EXTENDED.

                        The Depositary for the Offer is:
                    AMERICAN STOCK TRANSFER & TRUST COMPANY

<TABLE>
<S>                                                        <C>
                 By Mail:                                         By Hand or Overnight Courier:
              40 Wall Street                                             40 Wall Street
                46th Floor                                                 46th Floor
            New York, NY 10005                                         New York, NY 10005
      Attn: Reorganization Department                            Attn: Reorganization Department
</TABLE>

                           By Facsimile Transmission:

                                 (718) 234-5001

                             Confirm by Telephone:

                                 (718) 921-8200

     DELIVERY OF THIS LETTER OF TRANSMITTAL TO AN ADDRESS OTHER THAN AS SET
FORTH ABOVE, OR TRANSMISSIONS OF INSTRUCTIONS VIA A FACSIMILE NUMBER OTHER THAN
AS SET FORTH ABOVE, WILL NOT CONSTITUTE A VALID DELIVERY. YOU MUST SIGN THIS
LETTER OF TRANSMITTAL IN THE APPROPRIATE SPACE PROVIDED THEREFOR AND COMPLETE
THE SUBSTITUTE FORM W-9 SET FORTH BELOW.

     THE INSTRUCTIONS ACCOMPANYING THIS LETTER OF TRANSMITTAL SHOULD BE READ
CAREFULLY BEFORE THIS LETTER OF TRANSMITTAL IS COMPLETED.

     This Letter of Transmittal is to be completed by holders of shares of
common stock, par value $0.10 per share, of Thermo Instrument Systems Inc. (the
"Shares") either if certificates evidencing Shares ("Share Certificates") are to
be forwarded herewith or, unless an Agent's Message (as such term is used in the
Prospectus) is utilized, if delivery of Shares is to be made by book-entry
transfer into the account of American Stock Transfer & Trust Company, as
Depositary (the "Depositary"), at The Depository Trust Company ("DTC") pursuant
to the procedures set forth in the section of the Prospectus dated April 24,
2000 (the "Prospectus") captioned "The Exchange Offer -- Procedures For
Accepting The Offer And Tendering Shares." Stockholders who tender Shares by
book-entry transfer are referred to herein as "Book-Entry Stockholders."

     Stockholders whose Share Certificates are not immediately available or who
cannot deliver their Share Certificates and all other documents required hereby
to the Depositary prior to the Expiration Date (as such term is used in the
section of the Prospectus captioned "The Exchange Offer -- Terms Of The Exchange
Offer; Expiration Of The Exchange Offer"), or who cannot complete the procedures
for delivery by book-entry transfer on a timely basis, may tender their Shares
according to the guaranteed delivery procedures set forth in the section of the
Prospectus captioned "The Exchange Offer -- Procedures For Accepting The Offer
And Tendering Shares." See Instruction 2. DELIVERY OF DOCUMENTS TO DTC IN
ACCORDANCE WITH DTC'S PROCEDURES DOES NOT CONSTITUTE DELIVERY TO THE DEPOSITARY.
<PAGE>   2
<TABLE>
<CAPTION>
- ------------------------------------------------------------------------------------------------------------------------------------
                                                       DESCRIPTION OF SHARES TENDERED
- ------------------------------------------------------------------------------------------------------------------------------------
    NAME(S) AND ADDRESS(ES) OF REGISTERED HOLDER(S)                              SHARE CERTIFICATE(S) AND SHARE(S) TENDERED
(PLEASE FILL IN, IF BLANK, EXACTLY AS NAME(S) APPEAR(S)                        (ATTACH ADDITIONAL SIGNED LIST, IF NECESSARY).
             ON SHARE CERTIFICATE(S))                                                       SEE INSTRUCTION 3.
- ------------------------------------------------------------------------------------------------------------------------------------
                                                                                               TOTAL NUMBER
                                                                                                 OF SHARES
                                                                               SHARE            REPRESENTED           NUMBER
                                                                            CERTIFICATE          BY SHARE            OF SHARES
                                                                            NUMBER(S)*        CERTIFICATE(S)*       TENDERED**
<S>                                                                     <C>                 <C>                 <C>
                                                                        ------------------------------------------------------------

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

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

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

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

                                                                          TOTAL SHARES
- ------------------------------------------------------------------------------------------------------------------------------------
 *  Need not be completed by Book-Entry Stockholders.
 ** Unless otherwise indicated, all Shares represented by Share Certificates delivered to the Depositary will be deemed to have
    been tendered. See Instruction 4.
 IF ANY SHARE CERTIFICATES HAVE BEEN LOST OR DESTROYED, SEE INSTRUCTION 11.
- ------------------------------------------------------------------------------------------------------------------------------------
</TABLE>

[ ] CHECK HERE IF SHARES ARE BEING DELIVERED BY BOOK-ENTRY TRANSFER MADE TO AN
    ACCOUNT MAINTAINED BY THE DEPOSITARY WITH DTC AND COMPLETE THE FOLLOWING
    (ONLY PARTICIPANTS IN DTC MAY DELIVER SHARES BY BOOK-ENTRY TRANSFER):

   Name of Tendering Institution:

   DTC Account Number:

   DTC Transaction Code Number:

[ ] CHECK HERE IF SHARES ARE BEING DELIVERED PURSUANT TO A NOTICE OF GUARANTEED
    DELIVERY PREVIOUSLY SENT TO THE DEPOSITARY AND COMPLETE THE FOLLOWING
    (PLEASE ENCLOSE A PHOTOCOPY OF SUCH NOTICE OF GUARANTEED DELIVERY):

   Name(s) of Registered Holder(s):

   Window Ticket Number (if any):

   Date of Execution of Notice of Guaranteed Delivery:

   Name of Institution that Guaranteed Delivery:

   If delivered by Book-Entry Transfer:

   DTC Account Number:

   DTC Transaction Code Number:

                    NOTE: SIGNATURES MUST BE PROVIDED BELOW.
              PLEASE READ THE ACCOMPANYING INSTRUCTIONS CAREFULLY.

Ladies and Gentlemen:

     The undersigned hereby tenders to Thermo Electron Corporation, a Delaware
corporation (the "Acquiror"), the above-described shares of common stock, par
value $0.10 per share (the "Shares"), of Thermo Instrument Systems Inc., a
Delaware corporation (the "Company"), pursuant to the Acquiror's offer to
exchange shares of Acquiror's common stock, par value $1.00 per share ("Thermo
Electron Shares"), for Shares at an exchange ratio of 0.85 Thermo Electron
Shares for each Share and cash in lieu of fractional Thermo Electron Shares,
upon the terms and subject to the conditions set forth in the Acquiror's
Prospectus dated April 24, 2000 (the "Prospectus") relating to its offer to
exchange Thermo Electron Shares for Shares and in this Letter of Transmittal
(which, together with any amendments or supplements thereto or hereto,
collectively constitute the "Offer"), receipt of each of which is hereby
acknowledged.

     Subject to, and effective upon, acceptance for exchange of the Shares
tendered herewith in accordance with the terms and subject to the conditions of
the Offer, including, if the Offer is extended or amended, the terms and
conditions of any such extension or amendment, the undersigned hereby sells,
assigns and transfers to, or upon the order of, the Acquiror all right, title
and interest in and to all of the Shares that are being tendered hereby and any
and all dividends and distributions, including, without limitation,
distributions of additional Shares or rights declared, paid or issued with
<PAGE>   3

respect to the tendered Shares on or after April 24, 2000 (collectively,
"Distributions"), and irrevocably constitutes and appoints the Depositary the
true and lawful agent and attorney-in-fact of the undersigned with respect to
such Shares and any Distributions with full power of substitution (such power of
attorney being deemed to be an irrevocable power coupled with an interest) to
(a) deliver such Share Certificates and any Distributions, or transfer ownership
of such Shares and any Distributions on the account books maintained by DTC,
together in either case with appropriate evidences of transfer and authenticity,
to, or upon the order of, the Acquiror, upon receipt by the Depositary, as the
undersigned's agent, of the Thermo Electron Shares to be issued in exchange for
the Shares evidenced by such Share Certificates, (b) present such Shares and any
Distributions for transfer on the books of the Company, and (c) receive all
benefits and otherwise exercise all rights of record and beneficial ownership of
such Shares and any Distributions, all in accordance with the terms and subject
to the conditions of the Offer.

     The undersigned hereby irrevocably appoints Theo Melas-Kyriazi, Sandra L.
Lambert and Seth H. Hoogasian in their respective capacities as officers of the
Acquiror or one of its affiliates, and any individuals who shall hereafter
succeed to any such office of the Acquiror or one of its affiliates, and each of
them or any other designees of the Acquiror, as attorneys-in-fact and proxies of
the undersigned, each with full power of substitution, to the full extent of the
undersigned's rights with respect to any Distributions and the Shares tendered
by the undersigned and accepted for exchange and as to which the Acquiror issues
Thermo Electron Shares in exchange therefor. This power of attorney and proxy
shall be considered irrevocable and coupled with an interest in the tendered
Shares. Such appointment will be effective when, and only to the extent that,
the Acquiror accepts such Shares for exchange and deposits the Thermo Electron
Shares to be issued in respect thereof with the Depositary. Upon such deposit,
all prior powers of attorney and proxies given by the undersigned at any time
with respect to such Shares and any Distributions will, without further action,
be revoked, and no subsequent powers of attorney or proxies may be given nor any
subsequent written consents executed by the undersigned (and, if given or
executed, will not be deemed effective). Upon such deposit by the Acquiror, the
designees of the Acquiror will, with respect to such Shares and any
Distributions, be empowered to exercise all voting and other rights of the
undersigned as they in their sole discretion may deem proper at any annual or
special meeting of the Company's stockholders, or any adjournment or
postponement thereof, by written consent in lieu of any such meeting or
otherwise. The Acquiror reserves the right to require that, in order for Shares
to be deemed validly tendered, immediately upon the Acquiror's issuance of
Thermo Electron Shares in exchange for such Shares, the Acquiror must be able to
exercise full voting rights and other rights of a record and beneficial owner
with respect to such Shares and any Distributions, including, without
limitation, voting at any meeting of stockholders or by written consent in lieu
of any such meeting.

     The undersigned hereby represents and warrants that (a) the undersigned has
full power and authority to tender, sell, assign and transfer the Shares
tendered hereby and any Distributions and (b) when the Shares are accepted for
exchange by the Acquiror, the Acquiror will acquire good, marketable and
unencumbered title to the Shares and any Distributions, free and clear of all
liens, restrictions, charges and encumbrances, and the same will not be subject
to any adverse claim. The undersigned, upon request, shall execute and deliver
any additional documents deemed by the Depositary or the Acquiror to be
necessary or desirable to complete the sale, assignment and transfer of the
Shares tendered hereby and any Distributions. In addition, the undersigned shall
promptly remit and transfer to the Depositary for the account of the Acquiror
any Distribution in respect of the Shares tendered hereby, accompanied by
appropriate documentation of transfer, and, pending such remittance or
appropriate assurance thereof, the Acquiror shall be, subject to applicable law,
entitled to all rights and privileges as record and beneficial owner of any such
Distribution and may withhold shares of Thermo Electron Shares or reduce the
number of Thermo Electron Shares to be issued to the undersigned pursuant to the
Offer as provided in the Prospectus.

     No authority herein conferred or agreed to be conferred shall be affected
by, and all authority herein conferred or agreed to be conferred shall survive,
the death or incapacity of the undersigned and any obligation of the undersigned
hereunder shall be binding upon the heirs, personal representatives, successors
and assigns of the undersigned.

     Except as otherwise provided in the Prospectus, tenders of Shares made
pursuant to the Offer are irrevocable. Shares tendered pursuant to the Offer may
be withdrawn at any time prior to the Expiration Date (as such term is used in
the Prospectus) and, unless theretofore accepted for payment by the Acquiror
pursuant to the Offer, may also be withdrawn at any time after June 22, 2000.
See the section of the Prospectus captioned "The Exchange Offer -- Withdrawal
Rights."

     The undersigned understands that tenders of Shares pursuant to any of the
procedures described in the section of the Prospectus captioned "The Exchange
Offer -- Procedures For Accepting The Offer And Tendering Shares" and in the
Instructions hereto will constitute the undersigned's acceptance of the terms
and conditions of the Offer. The Acquiror's acceptance of such Shares for
exchange will constitute a binding agreement between the undersigned and the
Acquiror upon the terms and subject to the conditions set forth in the Offer.

     The undersigned understands that the Offer is conditioned upon, among other
things set forth in the Prospectus, there being validly tendered and not
withdrawn prior to the expiration of the Offer that number of Shares which,
together
<PAGE>   4

with the Shares held by the Acquiror, constitutes at least ninety percent (90%)
of the Shares outstanding on the Expiration Date.

     The undersigned understands that, under certain circumstances set forth in
the Prospectus, the Acquiror may terminate or amend the Offer or may not be
required to accept for payment any of the Shares tendered herewith.

     Unless otherwise indicated herein under "Special Issuance Instructions,"
please issue the Thermo Electron Shares and check for any cash in lieu of
fractional shares and issue or return any Share Certificate(s) for Shares not
tendered or not exchanged in the name(s) of the registered holder(s) appearing
under "Description Of Shares Tendered." Similarly, unless otherwise indicated
herein under "Special Delivery Instructions," please mail the Thermo Electron
Shares and check for any cash in lieu of fractional shares and return any Share
Certificate(s) for Shares not tendered or not exchanged (and accompanying
documents, as appropriate) to the address of the registered holder(s) appearing
under "Description Of Shares Tendered." In the event that both the "Special
Delivery Instructions" and the "Special Issuance Instructions" boxes are
completed, please issue the Thermo Electron Shares and check for any cash in
lieu of fractional shares and return any Share Certificate(s) for Shares not
tendered or not exchanged in the name(s) of, and deliver such Thermo Electron
Shares and check for any cash in lieu of fractional shares and return such Share
Certificate(s) to, the person(s) so indicated. Please credit any Shares tendered
herewith by book-entry transfer that are not exchanged by crediting the DTC
account designated above. The undersigned recognizes that the Acquiror has no
obligation pursuant to the "Special Issuance Instructions" to transfer any
Shares from the name(s) of the registered holder(s) thereof if the Acquiror does
not accept for exchange any of the Shares tendered hereby.

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

                         SPECIAL ISSUANCE INSTRUCTIONS
                        (SEE INSTRUCTIONS 1, 5, 6 AND 7)

        To be completed ONLY if Share Certificate(s) evidencing Shares not
   tendered or not exchanged, Thermo Electron Shares issued pursuant to the
   Offer or the check for any cash in lieu of fractional shares accepted for
   exchange are to be issued in the name of someone other than the
   undersigned.

   Issue:  [ ] check     [ ] certificates to:

   Name:
   ----------------------------------------------------
                                    (PLEASE PRINT)

   Address:
   --------------------------------------------------

   ------------------------------------------------------------
                               (INCLUDE ZIP CODE)

   ------------------------------------------------------------
                  (TAX IDENTIFICATION OR SOCIAL SECURITY NO.)
                 (SEE SUBSTITUTE FORM W-9 ON THE REVERSE SIDE)
                    ------------------------------------------------------------
                    ------------------------------------------------------------

                         SPECIAL DELIVERY INSTRUCTIONS
                        (SEE INSTRUCTIONS 1, 5, 6 AND 7)

        To be completed ONLY if Share Certificate(s) evidencing Shares not
   tendered or not exchanged, Thermo Electron Shares issued pursuant to the
   Offer or the check for any cash in lieu of fractional shares accepted for
   exchange are to be sent to someone other than the undersigned or to the
   undersigned at an address other than that shown above.

   Mail:  [ ] check     [ ] certificates to:

   Name:
   ----------------------------------------------------
                                    (PLEASE PRINT)

   Address:
   --------------------------------------------------

          ------------------------------------------------------------
                               (INCLUDE ZIP CODE)

                    ------------------------------------------------------------
<PAGE>   5

                                          IMPORTANT
               SIGN HERE AND COMPLETE SUBSTITUTE FORM W-9 ON THE REVERSE SIDE
             X
             -------------------------------------------------------------------
             X
             -------------------------------------------------------------------
                                  SIGNATURE(S) OF HOLDER(S)

             Dated:
             -------------------------------------------------, 2000

             (Must be signed by the registered holder(s) exactly as name(s)
             appear(s) on Share Certificate(s) or on a security position listing
             or by person(s) authorized to become registered holder(s) by
             certificates and documents transmitted herewith. If signature is by
             a trustee, executor, administrator, guardian, attorney-in-fact,
             officer of a corporation or other acting in a fiduciary or
             representative capacity, please provide the following information.
             See Instruction 5.)

             Name(s):
             -------------------------------------------------------------------

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

             -------------------------------------------------------------------
                                       (PLEASE PRINT)

             Capacity (Full Title):
             -------------------------------------------------------------------

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

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

             Address:
             -------------------------------------------------------------------

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

             -------------------------------------------------------------------
                                     (INCLUDE ZIP CODE)

             Area Code and Telephone Number:
    ----------------------------------------------------------------------------

             Tax Identification or Social Security No.:
           ---------------------------------------------------------------------

             Dated:
             ----------------------------------, 2000

                                  GUARANTEE OF SIGNATURE(S)
                                 (SEE INSTRUCTIONS 1 AND 5)

             Authorized Signature:
             -------------------------------------------------------------------

             Name:
             -------------------------------------------------------------------
                                       (PLEASE PRINT)

             Title:
             -------------------------------------------------------------------

             Name of Firm:
             -------------------------------------------------------------------
                                       (PLEASE PRINT)

             Address:
             -------------------------------------------------------------------
                                     (INCLUDE ZIP CODE)

             Area Code and Telephone Number:
    ----------------------------------------------------------------------------
             Dated:
             ----------------------------------, 2000
<TABLE>
<S><C>             <C>
    SIGN
    HERE
    [ARROW]
    [ARROW]

<S><C>
    SIGN      SIGN
    HERE      HERE
    [ARROW]   [ARROW]
    [ARROW]   [ARROW]
</TABLE>
<PAGE>   6

                                  INSTRUCTIONS

             FORMING PART OF THE TERMS AND CONDITIONS OF THE OFFER

     1.  Guarantee of Signatures.  No signature guarantee is required on this
Letter of Transmittal (a) if this Letter of Transmittal is signed by the
registered holder(s) of Shares (which term, for purposes of this document, shall
include any DTC participant whose name appears on a security position listing as
the owner of Share(s)) tendered herewith, unless such holder(s) has (have)
completed either the box entitled "Special Issuance Instructions" or the box
entitled "Special Delivery Instructions," or (b) if such Share(s) are tendered
for the account of a firm which is a commercial bank, broker, dealer, credit
union, savings association or other entity which is a member in good standing of
the Securities Transfer Agents Medallion Program, the Stock Exchanges' Medallion
Program or the New York Stock Exchange, Inc. Medallion Signature Program (each
of the foregoing being referred to as an "Eligible Institution"). In all other
cases, all signatures on this Letter of Transmittal must be guaranteed by an
Eligible Institution. See Instruction 5.

     2.  Delivery of Letter of Transmittal and Certificates.  This Letter of
Transmittal is to be completed by stockholders either if Share Certificates are
to be forwarded herewith or, unless an Agent's Message is utilized, if delivery
of Shares is to be made by book-entry transfer pursuant to the procedures set
forth in the section of the Prospectus captioned "The Exchange
Offer -- Procedures For Accepting The Offer And Tendering Shares." In order for
Shares to be validly tendered pursuant to the Offer, this Letter of Transmittal
(or a facsimile hereof), properly completed and duly executed, together with any
required signature guarantees, or an Agent's Message in connection with a
book-entry delivery of Shares, and any other documents required by this Letter
of Transmittal, must be received by the Depositary at one of its addresses set
forth on the front cover hereof prior to the Expiration Date and either (i)
Share Certificates evidencing tendered Shares must be received by the Depositary
at such address or such Shares must be tendered by book-entry transfer and a
timely confirmation of such book-entry transfer (a "Book-Entry Confirmation")
must be received by the Depositary, in each case prior to the Expiration Date or
(ii) the guaranteed delivery procedures described in the following sentence must
be complied with. Stockholders whose Share Certificates are not immediately
available or who cannot deliver their Share Certificates and all other required
documents to the Depositary prior to the Expiration Date or who cannot complete
the procedure for delivery by book-entry transfer on a timely basis may tender
their Shares by properly completing and duly executing a Notice of Guaranteed
Delivery pursuant to the guaranteed delivery procedures set forth in the section
of the Prospectus captioned "The Exchange Offer -- Procedures For Accepting The
Offer And Tendering Shares." Pursuant to such procedures: (i) such tender must
be made by or through an Eligible Institution; (ii) a properly completed and
duly executed Notice of Guaranteed Delivery, substantially in the form made
available by the Acquiror, must be received by the Depositary prior to the
Expiration Date; and (iii) the Share Certificates (or a Book-Entry Confirmation)
evidencing all tendered Shares, in proper form for transfer, together with this
Letter of Transmittal (or a facsimile hereof), properly completed and duly
executed, with any required signature guarantees (or, in the case of a
book-entry delivery, an Agent's Message) and any other documents required by
this Letter of Transmittal, must be received by the Depositary within three
American Stock Exchange trading days after the date of execution of such Notice
of Guaranteed Delivery.

     THE METHOD OF DELIVERY OF THIS LETTER OF TRANSMITTAL, SHARE CERTIFICATES
AND ALL OTHER REQUIRED DOCUMENTS, INCLUDING DELIVERY THROUGH DTC, IS AT THE SOLE
OPTION AND RISK OF THE TENDERING STOCKHOLDER, AND THE DELIVERY WILL BE DEEMED
MADE ONLY WHEN ACTUALLY RECEIVED BY THE DEPOSITARY. IF DELIVERY IS BY MAIL,
REGISTERED MAIL WITH RETURN RECEIPT REQUESTED, PROPERLY INSURED, IS RECOMMENDED.
IN ALL CASES, SUFFICIENT TIME SHOULD BE ALLOWED TO ENSURE TIMELY DELIVERY.

     No alternative, conditional or contingent tenders will be accepted. All
tendering stockholders, by execution of this Letter of Transmittal (or a
facsimile hereof), waive any right to receive any notice of the acceptance of
their Shares for exchange.

     If Share Certificates are forwarded to the Depositary in multiple
deliveries, a properly completed and duly executed Letter of Transmittal must
accompany each such delivery.

     3.  Inadequate Space.  If the space provided herein is inadequate, the
Share Certificate numbers, the number of Shares and any other required
information should be listed on a separate signed schedule attached hereto and
referenced in the box entitled "Description Of Shares Tendered."

     4.  Partial Tenders.  (Not Applicable to Book-Entry Stockholders.)  If
fewer than all the Shares evidenced by any Share Certificate submitted to the
Depositary herewith are to be tendered, fill in the number of Shares which are
to be
<PAGE>   7

tendered in the box entitled "Number of Shares Tendered." In such cases, new
Share Certificate(s) evidencing the Shares that were evidenced by the Share
Certificate(s) delivered to the Depositary herewith, but which were not tendered
hereby, will be sent to the registered holder(s) shown above, unless otherwise
provided in the box entitled "Special Delivery Instructions," as soon as
practicable after the expiration or termination of the Offer. All Shares
represented by Share Certificates delivered to the Depositary will be deemed to
have been tendered unless otherwise indicated.

     5.  Signatures on Letter of Transmittal, Stock Powers and Endorsements.  If
this Letter of Transmittal is signed by the registered holder(s) of the Shares
tendered hereby, the signature(s) must correspond with the name(s) as written on
the face of the Share Certificate(s) without alteration, enlargement or any
change whatsoever.

     If any of the Shares tendered hereby are owned of record by two or more
persons, all such persons must sign this Letter of Transmittal.

     If any of the tendered Shares are registered in the names of different
holders, it will be necessary to complete, sign and submit as many separate
Letters of Transmittal as there are different registrations of Share
Certificates.

     If this Letter of Transmittal or any Share Certificate or stock power is
signed by a trustee, executor, administrator, guardian, attorney-in-fact,
officer of a corporation or other person acting in a fiduciary or representative
capacity, such person should so indicate when signing, and proper evidence
satisfactory to the Acquiror of such person's authority so to act must be
submitted.

     If this Letter of Transmittal is signed by the registered holder(s) of the
Shares listed and tendered hereby, no endorsements of Share Certificates or
separate stock powers are required, unless Thermo Electron Shares or Share
Certificates evidencing Shares not tendered or not exchanged are to be issued in
the name of, a person other than the registered holder(s), in which case the
Share Certificate(s) evidencing the Shares tendered hereby must be endorsed or
accompanied by appropriate stock powers signed exactly as the name(s) of the
registered holder(s) appear(s) on such Share Certificate(s). Signatures on such
Share Certificate(s) or stock powers must be guaranteed by an Eligible
Institution.

     If this Letter of Transmittal is signed by a person other than the
registered holder(s) of the Share Certificate(s) listed and tendered hereby, the
Share Certificate(s) must be endorsed or accompanied by appropriate stock
powers, in either case signed exactly as the name(s) of the registered holder(s)
appear on such Share Certificate(s). Signature(s) on such Share Certificate(s)
and stock powers must be guaranteed by an Eligible Institution.

     6.  Stock Transfer Taxes.  Except as set forth in this Instruction 6, the
Acquiror will pay or cause to be paid any stock transfer taxes with respect to
the transfer and sale of Shares to it or its order pursuant to the Offer. If,
however, delivery of Thermo Electron Shares in exchange for Shares accepted for
exchange is to be made to, or if Share Certificate(s) evidencing Shares not
tendered or not exchanged are to be issued in the name of, any person other than
the registered holder(s), or if tendered Share Certificates are registered in
the name of any person other than the person(s) signing this Letter of
Transmittal, then the tendering holder must provide satisfactory evidence of the
payment of any applicable transfer taxes, (whether imposed on the registered
holder or such person) payable on account of the transfer to such person prior
to the delivery of Thermo Electron Shares.

     EXCEPT AS SET FORTH IN THIS INSTRUCTION 6, IT WILL NOT BE NECESSARY FOR
TRANSFER TAX STAMPS TO BE AFFIXED TO THE SHARE CERTIFICATE(S) TENDERED HEREBY.

     7.  Special Payment and Delivery Instructions.  If delivery of Thermo
Electron Shares in exchange for Shares accepted for exchange is to be made to,
if a check for cash in lieu of fractional shares accepted for exchange is to be
issued in the name of, or Share Certificate(s) evidencing Shares not tendered or
not exchanged are to be issued or returned to, a person other than the signer of
this Letter of Transmittal or if a check or such Share Certificate(s) are to be
returned to a person other than the signer of this Letter of Transmittal or to
an address of the signer other than that shown in this Letter of Transmittal,
the appropriate boxes on this Letter of Transmittal must be completed.

     8.  Waiver of Conditions.  The conditions of the Offer may be waived by the
Acquiror, in whole or in part, at any time and from time to time prior to the
Expiration Date in its sole discretion.

     9.  Substitute Form W-9.  Under U.S. federal income tax law, a stockholder
whose tendered Shares are accepted for exchange is required to provide the
Depositary with such stockholder's correct taxpayer identification number
<PAGE>   8

("TIN") (e.g., social security number or employer identification number) on
Substitute Form W-9 below and to certify whether such stockholder is subject to
backup withholding of federal income tax. If a tendering stockholder has been
notified by the Internal Revenue Service (the "IRS") that such stockholder is
subject to backup withholding, such stockholder must cross out item 2 of the
Certification box (Part 2) of the Substitute Form W-9, unless such stockholder
has since been notified by the IRS that such stockholder is no longer subject to
backup withholding. Failure to provide the information on the Substitute Form
W-9 may subject the tendering stockholder to federal income tax withholding at
the rate of 31% on the payment of any cash in lieu of fractional shares. If the
Depositary is not provided with the correct TIN, the IRS may subject the
stockholder or other payee to a $50 penalty.

     Certain stockholders are not subject to these backup withholding and
reporting requirements. Exempt recipients, such as corporations, are also
requested to provide their TIN and check the "Exempt" box in Part 3. Foreign
individuals or entities must submit a Form W-8 or W-8BEN, signed under penalties
of perjury, attesting to their foreign status. A Form W-8 or W8-BEN can be
obtained from the Depositary. See the enclosed "Guidelines For Certification Of
Taxpayer Identification Number On Substitute Form W-9" for more instructions.

     IF BACKUP WITHHOLDING APPLIES, THE DEPOSITARY IS REQUIRED TO WITHHOLD 31%
OF ANY CASH PAYMENTS MADE TO THE STOCKHOLDER OR OTHER PAYEE. BACKUP WITHHOLDING
IS NOT AN ADDITIONAL TAX. RATHER, THE TAX LIABILITY OF PERSONS SUBJECT TO BACKUP
WITHHOLDING WILL BE REDUCED BY THE AMOUNT OF TAX WITHHELD. IF WITHHOLDING
RESULTS IN AN OVERPAYMENT OF TAXES, A REFUND MAY BE OBTAINED FROM THE IRS.

     The "Awaiting TIN" box in Part 3 of the Substitute Form W-9 may be checked
if the tendering stockholder has not been issued a TIN and has applied for a TIN
or intends to apply for a TIN in the near future. If the "Awaiting TIN" box in
Part 3 is checked, the stockholder or other payee must also complete the
"Certificate Of Awaiting Taxpayer Identification Number" below in order to avoid
backup withholding. If the "Awaiting TIN" box in Part 3 is checked and the
"Certificate Of Awaiting Taxpayer Identification Number" is completed, the
Depositary may withhold 31% of all reportable cash payments made unless a
properly certified TIN is provided to the Depositary within 60 days.

     The stockholder is required to give the Depositary the TIN of the record
owner of the Shares or of the last transferee appearing on the transfers
attached to, or endorsed on, the Shares. If the Shares are in more than one name
or are not in the name of the actual owner, consult the enclosed "Guidelines For
Certification Of Taxpayer Identification Number On Substitute Form W-9" for
additional guidance on which number to report.

     10.  Questions and Requests for Assistance or Additional Copies.  Questions
and requests for assistance may be directed to the Information Agent at its
address and telephone numbers set forth below. Additional copies of the
Prospectus, this Letter of Transmittal and all other tender offer materials may
be obtained from the Information Agent or from brokers, dealers, commercial
banks or trust companies at the Acquiror's expense.

     11.  Lost, Destroyed or Stolen Certificates.  If any Share Certificate has
been lost, destroyed or stolen, the stockholder should promptly notify the
Depositary. The stockholder will then be instructed as to the steps that must be
taken in order to replace such Share Certificate. This Letter of Transmittal and
related documents cannot be processed until the procedures for replacing lost,
destroyed or stolen Share Certificates have been followed.

     IMPORTANT: THIS LETTER OF TRANSMITTAL (OR A FACSIMILE HEREOF), PROPERLY
COMPLETED AND DULY EXECUTED, OR, IF APPROPRIATE, AN AGENT'S MESSAGE, TOGETHER
WITH SHARE CERTIFICATES OR CONFIRMATION OF BOOK-ENTRY TRANSFER AND ALL OTHER
REQUIRED DOCUMENTS, OR A PROPERLY COMPLETED AND DULY EXECUTED NOTICE OF
GUARANTEED DELIVERY, MUST BE RECEIVED BY THE DEPOSITARY PRIOR TO THE EXPIRATION
DATE.
<PAGE>   9

<TABLE>
<S>                                <C>                                                    <C>
- ----------------------------------------------------------------------------------------------------------------------------
PAYER'S NAME: AMERICAN STOCK TRANSFER & TRUST COMPANY
- ----------------------------------------------------------------------------------------------------------------------------
 SUBSTITUTE                         PART 1 -- PLEASE PROVIDE YOUR TIN IN THE BOX AT THE    -------------------------------
 FORM W-9                           RIGHT AND CERTIFY BY SIGNING AND DATING BELOW:              Social security number
 DEPARTMENT OF THE TREASURY,
 INTERNAL REVENUE SERVICE                                                                                 or
 PAYER'S REQUEST FOR                                                                       -------------------------------
 TAXPAYER IDENTIFICATION                                                                       Employer identification
 NUMBER ("TIN")                                                                                         number
                                                                                           (If awaiting TIN, write "Applied
                                                                                                         For")
                                   -----------------------------------------------------------------------------------------
                                    PART 2 -- CERTIFICATION -- Under penalties of                     PART 3 --
                                    perjury, I certify that:                                       [ ] Awaiting TIN
                                    (1) The number shown on this form is my correct                   [ ] Exempt
                                    Taxpayer Identification Number (or I am waiting for a
                                        number to be issued to me), and
                                    (2) I am not subject to backup withholding because:
                                        (a) I am exempt from backup withholding, or
                                        (b) I have not been notified by the Internal
                                    Revenue Service (the "IRS") that I am subject to
                                            backup withholding as a result of a failure
                                            to report all interest or dividends, or
                                        (c) the IRS has notified me that I am no longer
                                    subject to backup withholding.
                                   -----------------------------------------------------------------------------------------
                                    CERTIFICATION INSTRUCTIONS -- You must cross out Item (2) above if you have been
                                    notified by the IRS that you are currently subject to backup withholding because of
                                    underreporting interest or dividends on your tax return. However, if after being
                                    notified by the IRS that you were subject to backup withholding you received another
                                    notification from the IRS that you are no longer subject to backup withholding, do not
                                    cross out such Item (2).
- ----------------------------------------------------------------------------------------------------------------------------

          SIGN HERE                SIGNATURE
                                   --------------------------------------   DATE
                                   ---------------, 2000
- ----------------------------------------------------------------------------------------------------------------------------
</TABLE>

NOTE: FAILURE TO COMPLETE AND RETURN THIS FORM MAY RESULT IN BACKUP WITHHOLDING
      OF 31% OF ANY REPORTABLE CASH PAYMENTS MADE TO YOU PURSUANT TO THE OFFER.
      PLEASE REVIEW THE ENCLOSED GUIDELINES FOR CERTIFICATION OF TAXPAYER
      IDENTIFICATION NUMBER ON SUBSTITUTE FORM W-9 FOR ADDITIONAL DETAILS.
<PAGE>   10

               YOU MUST COMPLETE THE FOLLOWING CERTIFICATE IF YOU
        CHECKED THE "AWAITING TIN" BOX IN PART 3 OF SUBSTITUTE FORM W-9.

             CERTIFICATE OF AWAITING TAXPAYER IDENTIFICATION NUMBER

     I certify under penalties of perjury that a Taxpayer Identification Number
has not been issued to me, and either (1) I have mailed or delivered an
application to receive a Taxpayer Identification Number to the appropriate
Internal Revenue Service Center or Social Security Administration Office, or (2)
I intend to mail or deliver an application in the near future. I understand that
if I do not provide a Taxpayer Identification Number, 31% of all reportable cash
payments made to me may be withheld until I provide a Taxpayer Identification
Number with required certifications, which should be provided within 60 days.

Signature:
- ---------------------------------------------------                       Dated:
- ------------------------------ , 2000
<PAGE>   11

                    The Information Agent for the Offer is:

                             D.F. KING & CO., INC.
                          77 Water Street, 20th Floor
                               New York, NY 10005
                Bankers and Brokers Call Collect (212) 269-5550
                    All Others Call Toll-Free (800) 290-6433

<PAGE>   1

                         NOTICE OF GUARANTEED DELIVERY
                                      FOR

                        TENDER OF SHARES OF COMMON STOCK
                                       OF

                         THERMO INSTRUMENT SYSTEMS INC.
                                       TO

                          THERMO ELECTRON CORPORATION

     As set forth in the section captioned "The Exchange Offer -- Procedures For
Accepting The Offer And Tendering Shares" in the Prospectus dated April 24, 2000
(the "Prospectus"), this Notice of Guaranteed Delivery or one substantially in
the form hereof must be used to tender shares of common stock, par value $0.10
per share (the "Shares"), of Thermo Instrument Systems Inc., a Delaware
corporation (the "Company"), pursuant to the Offer (as defined below) if
certificates evidencing Shares are not immediately available or the certificates
evidencing Shares and all other required documents cannot be delivered to
American Stock Transfer & Trust Company (the "Depositary") prior to the
Expiration Date (as such term is used in the Prospectus), or if the procedures
for delivery by book-entry transfer cannot be completed on a timely basis. This
instrument may be delivered by hand or transmitted by facsimile transmission,
overnight courier or mail to the Depositary.

                        The Depositary for the Offer is:

                    AMERICAN STOCK TRANSFER & TRUST COMPANY

<TABLE>
<S>                                            <C>
                   By Mail:                            By Hand or Overnight Courier:
                40 Wall Street                                 40 Wall Street
                  46th Floor                                     46th Floor
           New York, New York 10005                       New York, New York 10005
       Attn: Reorganization Department                Attn: Reorganization Department
</TABLE>

                           By Facsimile Transmission:
                                 (718) 234-5001

                             Confirm by Telephone:
                                 (718) 921-8200

     DELIVERY OF THIS NOTICE OF GUARANTEED DELIVERY TO AN ADDRESS OTHER THAN AS
SET FORTH ABOVE, OR TRANSMISSIONS OF INSTRUCTIONS VIA A FACSIMILE NUMBER OTHER
THAN AS SET FORTH ABOVE, WILL NOT CONSTITUTE A VALID DELIVERY.

     This Notice of Guaranteed Delivery is not to be used to guarantee
signatures. If a signature on a Letter of Transmittal is required to be
guaranteed by an Eligible Institution (as such term is used in the Prospectus)
under the instructions thereto, such signature guarantee must appear in the
applicable space provided in the signature box in the Letter of Transmittal.

              THE GUARANTEE ON THE REVERSE SIDE MUST BE COMPLETED
<PAGE>   2

Ladies and Gentlemen:

     The undersigned hereby tenders to Thermo Electron Corporation, a Delaware
corporation, upon the terms and subject to the conditions set forth in the
Prospectus and in the related Letter of Transmittal (which, together with any
amendments or supplements thereto, collectively constitute the "Offer"), receipt
of each of which is hereby acknowledged, the number of Shares indicated below
pursuant to the guaranteed delivery procedures set forth in the section of the
Prospectus captioned "The Exchange Offer -- Procedures For Accepting The Offer
And Tendering Shares."

 Signature(s):

 Name(s) of Record Holder(s):

                              Please Type or Print

 Number of Shares:

 Share Certificate No(s). (if available):

 Dated:, 2000
Address:

                                                                       Zip Code

Area Code and Tel. No.(s):

Check box if Shares will be tendered by book-entry transfer:  [ ]

DTC Account Number:

                                   GUARANTEE
                   (Not to be used for signature guarantees)

      The undersigned, a firm which is a commercial bank, broker, dealer,
 credit union, savings association or other entity which is a member in good
 standing of the Securities Transfer Agents Medallion Program, the Stock
 Exchanges' Medallion Program or the New York Stock Exchange, Inc. Medallion
 Signature Program, hereby guarantees to either deliver to the Depositary
 certificates evidencing all the Shares tendered hereby, in proper form for
 transfer, or to deliver such Shares pursuant to the procedure for book-entry
 transfer into the Depositary's account at The Depository Trust Company, in
 either case together with the Letter of Transmittal (or a facsimile thereof),
 properly completed and duly executed, with any required signature guarantees
 or an Agent's Message (as such term is used in the Prospectus) in the case of
 a book-entry transfer, and any other required documents, all within three
 American Stock Exchange trading days after the date hereof.

 Name of Firm:

 Address:
                                                                       Zip Code

 Area Code and Tel. No.:

 Authorized Signature:

 Name:

 Title:

 Dated: , 2000

     NOTE: DO NOT SEND CERTIFICATES WITH THIS NOTICE OF GUARANTEED DELIVERY.
         CERTIFICATES SHOULD BE SENT WITH YOUR LETTER OF TRANSMITTAL.

<PAGE>   1

                          THERMO ELECTRON CORPORATION

                               OFFER TO EXCHANGE
                          0.85 SHARES OF COMMON STOCK
                                       OF

                          THERMO ELECTRON CORPORATION
                                      FOR
                     EACH OUTSTANDING SHARE OF COMMON STOCK
                                       OF

                         THERMO INSTRUMENT SYSTEMS INC.

  THE OFFER AND WITHDRAWAL RIGHTS WILL EXPIRE AT 12:00 MIDNIGHT, NEW YORK CITY
          TIME, ON FRIDAY, MAY 19, 2000, UNLESS THE OFFER IS EXTENDED.

                                                                  April 24, 2000

To:  Brokers, Dealers, Commercial Banks,
     Trust Companies and Other Nominees:

     This letter relates to the offer by Thermo Electron Corporation, a Delaware
corporation (the "Acquiror"), to exchange shares of the Acquiror's common stock,
par value $1.00 per share (the "Thermo Electron Shares"), for shares of common
stock, value $0.10 per share (the "Shares"), of Thermo Instrument Systems Inc.,
a Delaware corporation (the "Company"), at an exchange ratio of 0.85 Thermo
Electron Shares for each Share (along with cash in lieu of fractional Thermo
Electron Shares), upon the terms and subject to the conditions set forth in the
Prospectus dated April 24, 2000 (the "Prospectus") and in the related Letter of
Transmittal (which, together with any amendments or supplements thereto,
collectively constitute the "Offer") enclosed herewith.

     THE OFFER IS CONDITIONED UPON, AMONG OTHER THINGS DESCRIBED IN THE
PROSPECTUS, THERE BEING VALIDLY TENDERED AND NOT WITHDRAWN PRIOR TO THE
EXPIRATION OF THE OFFER THAT NUMBER OF SHARES WHICH, TOGETHER WITH SHARES OWNED
BY THERMO ELECTRON, CONSTITUTES AT LEAST NINETY PERCENT (90%) OF THE OUTSTANDING
SHARES ON THE EXPIRATION DATE (AS SUCH TERM IS USED IN THE SECTION OF THE
PROSPECTUS CAPTIONED "THE EXCHANGE OFFER -- TERMS OF THE EXCHANGE OFFER;
EXPIRATION OF THE EXCHANGE OFFER"). THE OFFER IS ALSO SUBJECT TO OTHER IMPORTANT
TERMS AND CONDITIONS CONTAINED IN THE PROSPECTUS.

     Enclosed for your information and for forwarding to your clients for whose
accounts you hold Shares registered in your name or in the name of your nominees
are copies of the following documents:

        1. The Prospectus dated April 24, 2000.

        2. The green Letter of Transmittal to tender Shares (for your use and
           for the information of your clients), including Guidelines for
           Certification of Taxpayer Identification Number on Substitute Form
           W-9.

        3. The yellow Notice of Guaranteed Delivery for Shares (to be used to
           accept the Offer if Share certificates evidencing Shares ("Share
           Certificates") are not immediately available or if such Share
           Certificates and all other required documents cannot be delivered to
           American Stock Transfer & Trust Company (the "Depositary") prior to
           the Expiration Date or if the procedures for book-entry transfer
           cannot be completed on a timely basis).

        4. A gray printed form of letter which may be sent to your clients for
           whose accounts you hold Shares registered in your name or in the name
           of your nominees, with space provided for obtaining such clients'
           instructions with regard to the Offer.

        5. A return envelope addressed to the Depositary.

     YOUR PROMPT ACTION IS REQUESTED. WE URGE YOU TO CONTACT YOUR CLIENTS AS
PROMPTLY AS POSSIBLE. PLEASE NOTE THAT THE OFFER AND WITHDRAWAL RIGHTS WILL
EXPIRE AT 12:00 MIDNIGHT, NEW YORK CITY TIME, ON FRIDAY, MAY 19, 2000, UNLESS
THE OFFER IS EXTENDED.
<PAGE>   2

     In all cases, the delivery of Thermo Electron Shares for Shares tendered
and accepted for exchange pursuant to the Offer will be made only after timely
receipt by the Depositary of (i) certificates evidencing Shares ("Share
Certificates") or timely confirmation of a book-entry transfer of such Shares
into the Depositary's account at The Depositary Trust Company pursuant to the
procedures set forth in the section of the Prospectus captioned "The Exchange
Offer -- Procedures For Accepting The Offer And Tendering Shares," (ii) the
Letter of Transmittal (or a facsimile thereof), properly completed and duly
executed, with any required signature guarantees, or an Agent's Message (as such
term is used in the section of the Prospectus captioned "The Exchange
Offer -- Acceptance For Exchange And Exchange Of Shares") in connection with a
book-entry transfer, and (iii) any other documents required by the Letter of
Transmittal.

     If a stockholder desires to tender Shares pursuant to the Offer and such
stockholder's Share Certificates are not immediately available or such
stockholder cannot deliver the Share Certificates and all other required
documents to reach the Depositary prior to the Expiration Date, or such
stockholder cannot complete the procedure for delivery by book-entry transfer on
a timely basis, such Shares may nevertheless be tendered by following the
guaranteed delivery procedures specified in the section of the Prospectus
captioned "The Exchange Offer -- Procedures For Accepting The Offer And
Tendering Shares."

     No fees or commissions will be paid to brokers, dealers or any other
persons (other than to D.F. King & Co., Inc., the Information Agent, as
described in the Prospectus) for soliciting tenders of Shares pursuant to the
Offer. The Acquiror will, however, upon request, reimburse you for customary
mailing and handling expenses incurred by you in forwarding any of the enclosed
materials to your clients.

     The Acquiror will pay or cause to be paid any stock transfer taxes payable
on the transfer of Shares by the Acquiror pursuant to the Offer, except as
otherwise provided in Instruction 6 of the Letter of Transmittal.

     Questions and requests for assistance or for additional copies of the
enclosed materials may be directed to the Information Agent at its address and
telephone numbers set forth on the back cover of the Prospectus.

     NOTHING CONTAINED HEREIN OR IN THE ENCLOSED DOCUMENTS SHALL CONSTITUTE YOU
OR ANY OTHER PERSON THE AGENT OF THERMO ELECTRON CORPORATION OR ANY OF ITS
SUBSIDIARIES, THE COMPANY, THE DEPOSITARY OR THE INFORMATION AGENT, OR ANY
AFFILIATE OF ANY OF THEM, OR AUTHORIZE YOU OR ANY OTHER PERSON TO MAKE ANY
STATEMENT OR USE ANY DOCUMENT ON BEHALF OF ANY OF THEM IN CONNECTION WITH THE
OFFER OTHER THAN THE ENCLOSED DOCUMENTS AND THE STATEMENTS CONTAINED THEREIN.

<PAGE>   1

                          THERMO ELECTRON CORPORATION
                               OFFER TO EXCHANGE
                          0.85 SHARES OF COMMON STOCK

                                       OF

                          THERMO ELECTRON CORPORATION
                                      FOR

                     EACH OUTSTANDING SHARE OF COMMON STOCK

                                       OF

                         THERMO INSTRUMENT SYSTEMS INC.

  THE OFFER AND WITHDRAWAL RIGHTS WILL EXPIRE AT 12:00 MIDNIGHT, NEW YORK CITY
          TIME, ON FRIDAY, MAY 19, 2000, UNLESS THE OFFER IS EXTENDED.

To Our Clients:

     Enclosed for your consideration is a Prospectus dated April 24, 2000 (the
"Prospectus") and the related Letter of Transmittal (which, together with any
amendments or supplements thereto, collectively constitute the "Offer") relating
to an offer by Thermo Electron Corporation, a Delaware corporation (the
"Acquiror"), to exchange shares of common stock of the Acquiror, par value $1.00
per share (the "Thermo Electron Shares"), for shares of common stock, par value
$0.10 per share (the "Shares"), of Thermo Instrument Systems Inc., a Delaware
corporation (the "Company"), at an exchange ratio of 0.85 Thermo Electron Shares
for each Share (along with cash in lieu of fractional Thermo Electron Shares),
upon the terms and subject to the conditions set forth in the Offer.

     We are the holder of record of Shares held by us for your account. A TENDER
OF SUCH SHARES CAN BE MADE ONLY BY US AS THE HOLDER OF RECORD AND PURSUANT TO
YOUR INSTRUCTIONS. THE LETTER OF TRANSMITTAL IS FURNISHED TO YOU FOR YOUR
INFORMATION ONLY AND CANNOT BE USED BY YOU TO TENDER SHARES HELD BY US FOR YOUR
ACCOUNT.

     We request instructions as to whether you wish to have us tender on your
behalf any or all of the Shares held by us for your account, pursuant to the
terms and subject to the conditions set forth in the Offer.

     Your attention is directed to the following:

     - The exchange ratio of 0.85 Thermo Electron Shares for each Share (along
       with cash in lieu of fractional Thermo Electron Shares).

     - The Offer and withdrawal rights will expire at 12:00 midnight, New York
       City time, on Friday, May 19, 2000, unless the Offer is extended.

     - The Offer is made for all of the outstanding Shares not owned by Thermo
       Electron.

     - The Offer is conditioned upon, among other things described in the
       Prospectus, there being validly tendered and not withdrawn prior to the
       expiration of the Offer that number of Shares which, together with Shares
       owned by Thermo Electron, constitutes at least ninety percent (90%) of
       the outstanding Shares on the Expiration Date (as such term is used in
       the section of the Prospectus captioned "The Exchange Offer -- Terms Of
       The Exchange Offer; Expiration Of The Exchange Offer"). The Offer is also
       subject to other important terms and conditions contained in the
       Prospectus.
<PAGE>   2

     - Tendering stockholders will not be obligated to pay brokerage fees or
       commissions or, except as set forth in Instruction 6 of the Letter of
       Transmittal, stock transfer taxes on the transfer of Shares to the
       Acquiror pursuant to the Offer.

     - In all cases, the delivery of Thermo Electron Shares for Shares tendered
       and accepted for exchange pursuant to the Offer will be made only after
       timely receipt by American Stock Transfer & Trust Company (the
       "Depositary") of (i) certificates evidencing Shares or timely
       confirmation of a book-entry transfer of such Shares into the
       Depositary's account at The Depositary Trust Company pursuant to the
       procedures set forth in the section of the Prospectus captioned "The
       Exchange Offer -- Procedures For Accepting The Offer And Tendering
       Shares," (ii) the Letter of Transmittal (or a facsimile thereof),
       properly completed and duly executed, with any required signature
       guarantees, or an Agent's Message (as such term is used in the section of
       the Prospectus captioned "The Exchange Offer -- Acceptance For Exchange
       And Exchange Of Shares") in connection with a book-entry transfer and
       (iii) any other documents required by the Letter of Transmittal.

     The Offer is being made solely by the Prospectus and the related Letter of
Transmittal and is being made to all holders of Shares. The Offer is not being
made to (nor will tenders be accepted from or on behalf of) holders of Shares in
any jurisdiction in which the making of the Offer or the acceptance thereof
would not be in compliance with the laws of such jurisdiction. However, Thermo
Electron may, in its sole discretion, take such action as it may deem necessary
to make the Offer in any such jurisdiction and extend the Offer to holders of
Shares in such jurisdiction.

     If you wish to have us tender any or all of the Shares held by us for your
account, please instruct us by completing, executing and returning to us the
instruction form contained in this letter. If you authorize a tender of your
Shares, all such Shares will be tendered unless otherwise specified in such
instruction form. YOUR INSTRUCTIONS SHOULD BE FORWARDED TO US IN AMPLE TIME TO
PERMIT US TO SUBMIT A TENDER ON YOUR BEHALF PRIOR TO THE EXPIRATION OF THE
OFFER.
<PAGE>   3

                        INSTRUCTIONS WITH RESPECT TO THE
                               OFFER TO EXCHANGE
                          0.85 SHARES OF COMMON STOCK
                                       OF

                          THERMO ELECTRON CORPORATION
                                      FOR
                     EACH OUTSTANDING SHARE OF COMMON STOCK
                                       OF

                         THERMO INSTRUMENT SYSTEMS INC.

     The undersigned acknowledge(s) receipt of your letter and the enclosed
Prospectus dated April 24, 2000 (the "Prospectus") and the related Letter of
Transmittal (which, together with any amendments or supplements thereto,
collectively constitute the "Offer") relating to an offer by Thermo Electron
Corporation, a Delaware corporation, to exchange shares of common stock of
Thermo Electron, par value $1.00 share (the "Thermo Electron Shares"), for
shares of common stock, par value $0.10 per share (the "Shares"), of Thermo
Instrument Systems Inc., a Delaware corporation, at an exchange ratio of 0.85
Thermo Electron Shares for each Share (along with cash in lieu of fractional
Thermo Electron Shares), upon the terms and subject to the conditions of the
Offer.

     This will instruct you to tender the number of Shares indicated below (or,
if no number is indicated below, all Shares) that are held by you for the
account of the undersigned, upon the terms and subject to the conditions set
forth in the Offer.

<TABLE>
<CAPTION>
<S>  <C>                                                 <C>
     ------------------------------------------------
     Number of Shares to be
     Tendered(1):
     ------------------------------------------------
     Dated: ------------------------------, 2000

     SIGN HERE                                           x
                                                         ------------------------------------------------
                                                         Signature(s):
                                                         ------------------------------------------------
                                                         Please type or print name(s):
                                                         ------------------------------------------------
                                                         Address:
                                                         ------------------------------------------------
                                                         Area Code and Telephone Number:
                                                         ------------------------------------------------
                                                         Tax Identification or Social Security No.:

  (1) Unless otherwise indicated, it will be assumed that all of the Shares held by us for your account
      are to be tendered.
</TABLE>

<PAGE>   1

            GUIDELINES FOR CERTIFICATION OF TAXPAYER IDENTIFICATION
                         NUMBER ON SUBSTITUTE FORM W-9

GUIDELINES FOR DETERMINING THE PROPER IDENTIFICATION NUMBER TO GIVE THE PAYER.
Social Security numbers have nine digits separated by two hyphens: i.e.,
000-00-0000. Employer identification numbers have nine digits separated by only
one hyphen: i.e., 00-0000000. The table below will help determine the number to
give the Payer.

<TABLE>
<C>  <S>                                 <C>
- ------------------------------------------------------------
                                         GIVE THE
FOR THIS TYPE OF ACCOUNT:                SOCIAL SECURITY
                                         NUMBER OF:
- ------------------------------------------------------------

 1.  An individual's account             The individual
 2.  Two or more individuals (joint      The actual owner of
     account)                            the account or, if
                                         combined funds, the
                                         first individual on
                                         the account(1)
 3.  Husband and wife (joint account)    The actual owner of
                                         the account or, if
                                         joint funds, the
                                         first individual on
                                         the account(1)
 4.  Custodian account of a minor        The minor(2)
     (Uniform Gift to Minors Act)
 5.  Adult and minor (joint account)     The adult, or, if
                                         the minor is the
                                         only contributor,
                                         the minor(1)
 6.  Account in the name of guardian or  The ward, minor, or
     committee for a designated ward,    incompetent
     minor or incompetent person         person(3)
 7.  (a) The usual revocable savings     The grantor-
         trust account (grantor is also  trustee(1)
         trustee)
     (b) So-called trust account that    The actual owner(1)
         is not a legal or valid trust
         under State law
 8.  Sole proprietorship account         The owner(4)
- ------------------------------------------------------------
</TABLE>

<TABLE>
<C>  <S>                                 <C>
- ------------------------------------------------------------
                                         GIVE THE EMPLOYER
FOR THIS TYPE OF ACCOUNT:                IDENTIFICATION
                                         NUMBER OF:
- ------------------------------------------------------------

 9.  A valid trust, estate, or pension   The legal entity
     trust                               (Do not furnish the
                                         identifying number
                                         of the personal
                                         representative or
                                         trustee unless the
                                         legal entity itself
                                         is not designated
                                         in the account
                                         title.)(5)
10.  Corporate account                   The corporation
11.  Religious, charitable, or           The organization
     educational organization account
12.  Partnership account held in the     The partnership
     name of the business
13.  Association, club, or other tax-    The organization
     exempt organization
14.  A broker or registered nominee      The broker or
                                         nominee
15.  Account with the Department of      The public entity
     Agriculture in the name of a
     public entity (such as a State or
     local government, school district,
     or prison) that receives
     agricultural program payments
- ------------------------------------------------------------
</TABLE>

(1) List first and circle the name of the person whose number you furnish.
(2) Circle the minor's name and furnish the minor's social security number.
(3) Circle the ward's, minor's or incompetent person's name and furnish such
    person's social security number.
(4) Show the name of the owner.
(5) List first and circle the name of the legal trust, estate, or pension trust.

NOTE: If no name is circled when there is more than one name, the number will be
      considered to be that of the first name listed.
<PAGE>   2

               GUIDELINES FOR CERTIFICATION OF TAXPAYER IDENTIFICATION
                            NUMBER ON SUBSTITUTE FORM W-9

                                        PAGE 2

OBTAINING A NUMBER
If you don't have a taxpayer identification number or you don't know your
number, obtain Form SS-5, Application for a Social Security Number Card (for
individuals), or Form SS-4, Application for Employer Identification Number (for
businesses and all other entities), at the local office of the Social Security
Administration or the Internal Revenue Service and apply for a number.

PAYEES EXEMPT FROM BACKUP WITHHOLDING
Payees specifically exempted from backup withholding on ALL payments include the
following (Section references are to the Internal Revenue Code):
  - A corporation.
  - A financial institution.
  - An organization exempt from tax under section 501(a), or an individual
    retirement plan, or a custodial account under section 403(b)(7).
  - The United States or any agency or instrumentality thereof.
  - A State, the District of Columbia, a possession of the United States, or any
    subdivision or instrumentality thereof.
  - A foreign government, a political subdivision of a foreign government, or
    any agency or instrumentality thereof.
  - An international organization or any agency, or instrumentality thereof.
  - A registered dealer in securities or commodities registered in the U.S. or
    possession of the U.S.
  - A real estate investment trust.
  - A common trust fund operated by a bank under section 584(a).
  - An exempt charitable remainder trust, or a non-exempt trust described in
    section 4947(a)(1).
  - An entity registered at all times under the Investment Company Act of 1940.
  - A foreign central bank of issue.
Payments of dividends and patronage dividends not generally subject to backup
withholding include the following:
  - Payments to nonresident aliens subject to withholding under section 1441.
  - Payments to partnerships not engaged in a trade or business in the U.S. and
    which have at least one nonresident partner.
  - Payments of patronage dividends where the amount received is not paid in
    money.
  - Payments made by certain foreign organizations.
  - Payments made to a nominee.
Payments of interest not generally subject to backup withholding include the
following:
  - Payments of interest on obligations issued by individuals.

NOTE: You may be subject to backup withholding if this interest is $600 or more
and is paid in the course of the payer's trade or business and you have not
provided your correct taxpayer identification number to the payer.
  - Payments of tax-exempt interest (including exempt-interest dividends under
    section 852).
  - Payments described in section 6049(b)(5) to nonresident aliens.
  - Payments on tax-free government bonds under section 1451.
  - Payments made by certain foreign organizations.
  - Payments made to a nominee.
Exempt payees described above should file the Substitute Form W-9 to avoid
possible erroneous backup withholding. FILE THIS FORM WITH THE PAYER, FURNISH
YOUR TAXPAYER IDENTIFICATION NUMBER, WRITE "EXEMPT" ON THE FACE OF THE FORM,
SIGN AND DATE THE FORM AND RETURN IT TO THE PAYER.

Certain payments other than interest, dividends, and patronage dividends that
are not subject to information reporting are also not subject to backup
withholding. For details, see sections 6041, 6041A(a), 6042, 6044, 6045, 6049,
6050A and 6050N, and the regulations under those sections.

PRIVACY ACT NOTICE.  Section 6109 requires most recipients of dividend,
interest, or other payments to give taxpayer identification numbers to payers
who must report the payments to the IRS. The IRS uses the numbers for
identification purposes and to help verify the accuracy of tax returns. Payers
must be given the numbers whether or not recipients are required to file a tax
return. Payers must generally withhold 31% of taxable interest, dividend, and
certain other payments to a payee who does not furnish a taxpayer identification
number to a payer. Certain penalties may also apply.

PENALTIES
(1) PENALTY FOR FAILURE TO FURNISH TAXPAYER IDENTIFICATION NUMBER.  If you fail
to furnish your taxpayer identification number to a payer, you are subject to a
penalty of $50 for each such failure unless your failure is due to reasonable
cause and not to willful neglect.
(2) FAILURE TO REPORT CERTAIN DIVIDEND AND INTEREST PAYMENTS. If you fail to
include any portion of an includible payment for interest, dividends or
patronage dividends in gross income, such failure is strong evidence of
negligence. If negligence is shown, you will be subject to a penalty of 20% on
any portion of an underpayment attributable to that failure.
(3) CIVIL PENALTY FOR FALSE INFORMATION WITH RESPECT TO WITHHOLDING.  If you
make a false statement with no reasonable basis which results in no imposition
of backup withholding, you are subject to a penalty of $500.
(4) CRIMINAL PENALTY FOR FALSIFYING INFORMATION.  Willfully falsifying
certifications or affirmations may subject you to criminal penalties including
fines and/or imprisonment.

 FOR ADDITIONAL INFORMATION CONTACT YOUR TAX CONSULTANT OR THE INTERNAL REVENUE
                                    SERVICE.


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