SECURITIES AND EXCHANGE COMMISSION
                              WASHINGTON, DC 20549
               ---------------------------------------------------

                         AMENDMENT NO. 1 ON FORM 10-K/A
                                  TO FORM 10-K

(mark one)


  X     Annual Report Pursuant to Section 13 or 15(d) of the Securities Exchange
-----   Act of 1934

-----   Transition Report Pursuant to Section 13 or 15(d)  of the Securities
        Exchange Act of 1934

                          Commission file number 1-9786

                         THERMO INSTRUMENT SYSTEMS INC.
            (Exact name of Registrant as specified in its character)

Delaware                                                              04-2925809
(State or other jurisdiction of                                 (I.R.S. Employer
incorporation or organization)                               Identification No.)

81 Wyman Street
P.O. Box 9046
Waltham, MA                                                                02454
(Address of principal executive offices)                              (zip code)

       Registrant's telephone number, including area code: (781) 622-1000

           Securities registered pursuant to Section 12(b) of the Act:

                                                         Name of each exchange
Title of each class                                      on which registered
-------------------                                      -----------------------
Common Stock, $.10 par value                             American Stock Exchange
4% Convertible Subordinated Debentures due 2005          American Stock Exchange

           Securities registered pursuant to section 12(g)of the Act:
                                      None

Indicate by check mark whether the Registrant (1) has filed all reports required
to be filed by Section 13 or 15(d) of the Securities Exchange Act of 1934 during
the preceding 12 months, and (2) has been subject to the filing requirements for
at least the past 90 days.  X   No    .
                           ----   ----
Indicate by check mark if disclosure of delinquent  filers  pursuant to Item 405
of Regulation  S-K is not contained  herein,  and will not be contained,  to the
best  of  the  Registrant's   knowledge,  in  definitive  proxy  or  information
statements  incorporated  by  reference  into  Part III of this Form 10-K or any
amendment to this Form 10-K. [ ]

The  aggregate  market  value of the voting stock held by  nonaffiliates  of the
Registrant as of January 28, 2000, was approximately $221,069,000.

As of January 28, 2000, the Registrant  had  118,851,664  shares of Common Stock
outstanding.

                       DOCUMENTS INCORPORATED BY REFERENCE

Portions of the  Registrant's  Annual Report to Shareholders for the fiscal year
ended January 1, 2000, are incorporated by reference into Parts I and II.

<PAGE>

Items 10, 11, 12 and 13 of Part III of the  Registrant's  Annual  Report on Form
10-K for the fiscal year ended  January 1, 2000 are hereby  amended and restated
in their entirety as follows:

                                    Part III

Item 10 - DIRECTORS AND EXECUTIVE OFFICERS OF THE REGISTRANT

DIRECTORS

         Set forth  below  are the names of the  directors,  their  ages,  their
offices in the Corporation, if any, their principal occupation or employment for
the past five years,  the length of their tenure as  directors  and the names of
other public  companies in which such  persons hold  directorships.  Information
regarding their beneficial  ownership of the Corporation's Common and the common
stock of its  subsidiaries and its parent company,  Thermo Electron  Corporation
("Thermo  Electron"),  a  provider  of  products  and  services  in  measurement
instrumentation,  medical  devices,  power  generation and resource  recovery is
reported  in Item 12 -  Security  Ownership  of  Certain  Beneficial  Owners and
Management.

--------------------------------------------------------------------------------
Earl R. Lewis           Mr.  Lewis,  56,  has  been a  director  and  the  chief
                        executive officer of The Corporation since January 1998,
                        and has been  president of The  Corporation  since March
                        1997. He was chief operating  officer of The Corporation
                        from January 1996 to January  1998.  Prior to that time,
                        he was executive vice president of The Corporation  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,  a  majority-owned
                        subsidiary   of  The   Corporation   that   manufactures
                        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.
--------------------------------------------------------------------------------
Polyvios C. Vintiadis   Mr.   Vintiadis,   64,  has  been  a  director   of  The
                        Corporation  since July 1993. Mr. Vintiadis has been the
                        chairman  and  chief  executive   officer  of  Towermarc
                        Corporation,  a real estate development  company,  since
                        1984.   Mr.    Vintiadis   is   also   a   director   of
                        Spectra-Physics Lasers, Inc. and Thermo TerraTech Inc.
--------------------------------------------------------------------------------

COMMITTEES OF THE BOARD OF DIRECTORS AND MEETINGS

         The board of directors has  established an audit  committee and a human
resources  committee,  each consisting solely of directors who are not employees
of the Corporation, of Thermo Electron or of any other companies affiliated with
Thermo Electron ("outside directors"). The sole member of the audit committee is
Mr.  Vintiadis.  The audit  committee  reviews  the scope of the audit  with the
Corporation's independent public accountants and meets with them for the purpose
of reviewing  the results of the audit  subsequent to its  completion.  The sole
member of the human resources  committee is Mr.  Vintiadis.  The human resources
committee  reviews the  performance of senior  members of  management,  approves
executive  compensation and administers the Corporation's stock option and other
stock-based  compensation  plans.  The  Corporation  does not have a  nominating
committee of the board of directors. The board of directors met eight times, the
audit committee met twice and the human resources committee met six times during
fiscal 1999. Each director attended at least 75% of all meetings of the board of
directors and committees on which he served that were held during fiscal 1999.

<PAGE>

         The board of directors  established a special  committee  (the "Special
Committee") consisting solely of outside directors for the purpose of evaluating
the merits of the  proposed  exchange  offer and  merger  with  Thermo  Electron
pursuant to which the Corporation  would be taken private and either  recommend,
reject or take no  position  with  respect to the  proposed  exchange  offer and
merger.  See Item 13 - "Certain  Relationships  and Related  Transactions."  The
member of the Special Committee is Mr. Vintiadis.

COMPENSATION OF DIRECTORS

         CASH COMPENSATION

         Outside  directors  receive an annual  retainer  of $8,000 and a fee of
$1,000 per meeting for attending  regular meetings of the board of directors and
$500 per meeting for participating in meetings of the board of directors held by
means of  conference  telephone  and for  participating  in certain  meetings of
committees  of the  board  of  directors.  Payment  of  directors'  fees is made
quarterly.  Mr. Lewis is an employee of Thermo Electron or its  subsidiaries and
does not receive any cash  compensation from the Corporation for his services as
a director. Directors are also reimbursed for out-of-pocket expenses incurred in
attending such meetings.

         In addition,  the member of the Special Committee  receives a quarterly
fee of $15,000 and a fee of $1,000 per day for attending regular meetings of the
Special  Committee and $500 per day for participating in meetings of the Special
Committee held by means of conference telephone.

         DEFERRED COMPENSATION PLAN

         Under the Corporation's  deferred  compensation plan for directors (the
"Deferred  Compensation Plan"), a director has the right to defer receipt of his
cash fees  until he  ceases to serve as a  director,  dies or  retires  from his
principal occupation.  In the event of a change in control or proposed change in
control  of the  Corporation  that is not  approved  by the board of  directors,
deferred amounts become payable immediately.  Any of the following are deemed to
be a change of control:  (i) the acquisition by any person of 40% or more of the
outstanding  common  stock or voting  securities  of Thermo  Electron;  (ii) the
failure of the  Thermo  Electron  board of  directors  to include a majority  of
directors  who are  "continuing  directors",  which  term is  defined to include
directors  who were  members of Thermo  Electron's  board on July 1, 1999 or who
subsequent to that date were nominated or elected by a majority of directors who
were  "continuing  directors" at the time of such nomination or election;  (iii)
the consummation of a merger, consolidation, reorganization, recapitalization or
statutory  share  exchange  involving  Thermo  Electron  or the  sale  or  other
disposition of all or substantially  all of the assets of Thermo Electron unless
immediately  after such  transaction  (a) all holders of Thermo  Electron common
stock immediately prior to such transaction own more than 60% of the outstanding
voting securities of the resulting or acquiring corporation in substantially the
same  proportions as their ownership  immediately  prior to such transaction and
(b) no person after the transaction  owns 40% or more of the outstanding  voting
securities  of the  resulting  or  acquiring  corporation;  or (iv)  approval by
stockholders  of a  complete  liquidation  or  dissolution  of Thermo  Electron.
Amounts deferred  pursuant to the Deferred  Compensation  Plan are valued at the
end of each quarter as units of Common Stock. When payable, amounts deferred may
be  disbursed  solely in shares of Common Stock  accumulated  under the Deferred
Compensation  Plan.  As of January 1, 2000, a total of 154,377  shares of Common
Stock has been reserved for issuance  under the Deferred  Compensation  Plan and
deferred  units  equal to  approximately  43,517  shares  of Common  Stock  were
accumulated under the Deferred Compensation Plan.

         DIRECTORS STOCK OPTION PLAN

         The Corporation's  directors stock option plan (the "Directors  Plan"),
provides  for the grant of stock  options to purchase  shares of Common Stock to
outside  directors as  additional  compensation  for their service as directors.
Under the Directors Plan,  outside  directors receive an annual grant of options
to purchase 1,000 shares of Common Stock at the close of business on the date of
each Annual Meeting of the Stockholders of the Corporation.  Options  evidencing
annual grants are  immediately  exercisable at any time from and after the grant
date of the option and generally  expire on the third  anniversary  of the grant
date.

         The exercise price for options  granted under the Directors Plan is the
average of the closing  prices of the Common  Stock as reported on the  American
Stock  Exchange  (or other  principal  market on which the Common  Stock is then
traded) for the five trading days  immediately  preceding and including the date
of grant,  or, if the  shares are not then  traded,  at the last price per share
paid by third parties in an arms-length  transaction  prior to the option grant.
As of January 31, 2000,  options to purchase  45,848 shares of Common Stock were
outstanding  under the  Directors  Plan,  options to purchase  93,043  shares of
Common Stock had been granted, options to

<PAGE>

purchase 41,183 shares of Common Stock had been  exercised,  options to purchase
6,012 shares of Common Stock had lapsed,  and options to purchase  88,750 shares
of Common Stock were reserved for future grant.

STOCK OWNERSHIP POLICY FOR DIRECTORS

         The  human   resources   committee  of  the  board  of  directors  (the
"Committee")  has  established a stock holding policy for  directors.  The stock
holding  policy  requires  each  director  to hold a minimum of 1,000  shares of
Common Stock.  Directors are requested to achieve this ownership  level within a
three-year period. The chief executive officer of the Corporation is required to
comply with a separate stock holding policy established by the Committee,  which
is described below.

EXECUTIVE OFFICERS

         Reference  is made to Item 1(e) of this Annual  Report on Form 10-K for
information regarding the Executive Officers of the Registrant.

Item 11 - EXECUTIVE COMPENSATION

SUMMARY COMPENSATION TABLE

         The  following  table  summarizes  compensation  during  the last three
fiscal  years for  services to the  Corporation  in all  capacities  awarded to,
earned  by or  paid  to the  Corporation's  chief  executive  officer,  and  its
executive  officers  whose  total  annual  salary and bonus,  as  determined  in
accordance with the rules of the Securities and Exchange Commission, was greater
than $100,000,  and who were employed by the Corporation as of the end of fiscal
1999. These officers are together referred to as the "named executive officers."

         The Corporation is required to appoint certain  executive  officers and
full-time employees of Thermo Electron as executive officers of the Corporation,
in accordance with the Thermo Electron Corporate  Charter.  The compensation for
these executive officers is determined and paid entirely by Thermo Electron. The
time and effort  devoted by these  individuals to the  Corporation's  affairs is
provided to the Corporation under the Corporate  Services  Agreement between the
Corporation and Thermo Electron.  See Item 13 - "Relationship  with Affiliates."
Accordingly,  the  compensation  for these  individuals  is not  reported in the
following table.

<TABLE>
<CAPTION>
<S>                          <C>       <C>       <C>           <C>              <C>                 <C>
                                              SUMMARY COMPENSATION TABLE
--------------------------------------------------------------------------------------------------------------------
                                                            Long Term Compensation
                                                             ---------------------
                               Annual Compensation         Restricted       Securities
    Name and                Fiscal                            Stock         Underlying            All Other
Principal Position           Year    Salary     Bonus       Award (1)       Options (2)        Compensation (3)
-------------------         ------   ------     ------      ---------       ------------       ----------------
Earl R. Lewis (4)             1999   $256,000     $204,000      $80,102 (THI)    150,000 (THI)        $14,868 (5)
  President and               1998   $224,000     $160,000           --           33,333 (ONX)        $15,939 (5)
  Chief Executive Officer     1997   $198,000     $225,000          --            79,166 (THI)        $16,710 (5)
                                                                                  20,000 (MKA)
                                                                                  75,000 (TMQ)
---------------------------------------------------------------------------------------------------------------------
Richard W. K. Chapman (6)     1999   $220,015     $175,000      $77,241 (TMQ) (7) 25,000 (THI)        $24,805 (8)
  Senior Vice President                                                              500 (TMO)
                              1998   $190,000     $110,000          --            24,999 (THI)        $26,873 (8)
                                                                                   8,299 (TMO)
                                                                                   7,500 (MKA)
                                                                                   7,500 (ONX)
                                                                                   4,000 (RGI)
                                                                                   2,000 (TDX)
                                                                                 100,000 (TMQ)
                                                                                   1,023 (TKN)
                                                                                   2,000 (TRIL)
                              1997   $180,000     $153,000          --               300 (TMO)        $22,309 (8)
---------------------------------------------------------------------------------------------------------------------
</TABLE>


<PAGE>


<TABLE>
<CAPTION>
<S>                          <C>       <C>       <C>           <C>              <C>                 <C>
                                              SUMMARY COMPENSATION TABLE
--------------------------------------------------------------------------------------------------------------------
                                                            Long Term Compensation
                                                             ---------------------
                                Annual Compensation        Restricted           Securities
    Name and                Fiscal                            Stock             Underlying            All Other
Principal Position           Year    Salary     Bonus       Award (1)           Options (2)        Compensation (3)
-------------------         ------   ------     ------      ---------           ------------       ----------------
Denis A. Helm (6)             1999   $180,000     $150,000      $75,096 (THI)     50,000 (THI)             $7,200
  Executive Vice President                                                         3,800 (TMO)
                              1998   $162,000    $  85,000         --             19,999 (THI)             $7,200
                                                                                  11,598 (TMO)
                                                                                   7,500 (ONX)
                                                                                   4,000  (RGI)
                                                                                   2,000 (TDX)
                                                                                   1,023 (TKN)
                                                                                   2,000 (TRIL)
                              1997   $155,000      $92,000         --              3,700 (TMO)             $7,125
                                                                                  25,000 (MKA)
---------------------------------------------------------------------------------------------------------------------
Barry S. Howe (6)             1999   $157,500     $175,000      $50,064 (THI)     25,000 (THI)        $44,934 (9)
  Vice President                                                                     900 (TMO)
                              1998   $157,500    $  75,000         --            165,658 (THI)        $12,683 (9)
                                                                                   1,798 (TMO)
                                                                                   7,500 (MKA)
                                                                                   7,500 (ONX)
                                                                                   4,000  (RGI)
                                                                                   2,000 (TDX)
                                                                                   1,023 (TKN)
                                                                                   2,000 (TRIL)
                              1997   $150,000    $ 110,000         --              1,100 (TMO)        $14,923 (9)
---------------------------------------------------------------------------------------------------------------------
</TABLE>

(1)      In fiscal 1999,  Mr. Lewis,  Mr. Helm and Mr. Howe were awarded  4,800,
         4,500 and 3,000 shares respectively,  of restricted Common Stock of the
         Corporation with a value of $80,102, $75,096 and $50,064, respectively,
         on the grant date. The  restricted  stock awards vest 100% on the third
         anniversary  of the grant date.  Any cash  dividends paid on restricted
         shares are entitled to be retained by the recipient  without  regard to
         vesting.  Any non-cash dividends paid on restricted shares are entitled
         to  be  retained  by  the   recipient   subject  to  the  same  vesting
         restrictions  as the underlying  stock.  At the end of fiscal 1999, Mr.
         Lewis,  Mr.  Helm and Mr. Howe held  4,800,  4,500 and 3,000  shares of
         restricted  stock,  respectively,  with an aggregate  value of $53,400,
         $50,063 and $33,375, respectively.

(2)      Options  granted  by  the  Corporation  are  designated  as  "THI."  In
         addition,  the named executive  officers have also been granted options
         to purchase  common stock of the following  Thermo  Electron  companies
         during the last three fiscal years as part of Thermo  Electron's  stock
         option program: Thermo Electron Corporation (designated in the table as
         TMO),  Metrika  Systems  Corporation  (designated in the table as MKA),
         ONIX Systems Inc.  (designated in the table as ONX), The Randers Killam
         Group Inc. (designated in the table as RGI),  Thermedics Detection Inc.
         (designated in the table as TDX), ThermoQuest  Corporation  (designated
         in the table as TMQ), ThermoTrex  Corporation  (designated in the table
         as TKN) and  Thermo  Trilogy  Corporation  (designated  in the table as
         TRIL).

(3)      Includes  the amount of  matching  contributions  made on behalf of the
         executive officers participating in the Thermo Electron 401(k) plan or,
         in the case of Dr.  Chapman,  the 401(k)  plan  maintained  by Finnigan
         Corporation, a subsidiary of the Corporation.

(4)      Mr.  Lewis  has  served  in  various  management   capacities  for  the
         Corporation  and has served as an officer of Thermo Electron during the
         three-year  period  reported.  A portion  of Mr.  Lewis's  annual  cash
         compensation  (salary  and bonus) has been paid by Thermo  Electron  in
         each of the fiscal years reported as compensation for services provided
         to Thermo  Electron.  The annual cash  compensation  (salary and bonus)
         reported in the table for Mr. Lewis  represents  the amount paid by the
         Corporation and its subsidiaries  solely for Mr. Lewis's services as an
         officer of the  Corporation  or its  subsidiaries.  For

<PAGE>

         1999, 1998 and 1997,  approximately  80%, 80% and 90% respectively,  of
         Mr. Lewis's annual cash  compensation  (salary and bonus) earned in all
         capacities  throughout the Thermo Electron organization was paid by the
         Corporation  and its  subsidiaries  for his services to the Corporation
         and its subsidiaries. From time to time, Mr. Lewis has been, and in the
         future may be,  granted  options  to  purchase  common  stock of Thermo
         Electron and certain of its subsidiaries other than the Corporation and
         its majority-owned subsidiaries. These options are not reported in this
         table as they were granted as compensation for services to other Thermo
         Electron  companies  in  capacities  other than in his  capacity  as an
         executive officer of the Corporation.

(5)      In addition to the matching  contribution  referred to in footnote (3),
         such amount includes  $7,668,  $8,739 and $9,585,  respectively,  which
         represents the amount of  compensation  in fiscal 1999,  1998 and 1997,
         respectively,  attributable  to an  interest-free  loan provided to Mr.
         Lewis  pursuant to the stock holding  assistance  plan of Thermo Optek.
         See Item 13 - "Certain  Relationships  and Related  Transactions--Stock
         Holding Assistance Plans."

(6)      In fiscal 1999, 1998 and 1997, of the annual cash compensation reported
         in the table,  100%,  90% and 90%,  respectively,  of Mr. Helm's annual
         cash  compensation  (salary and bonus) was paid by the  Corporation and
         0%, 10% and 10%,  respectively,  of his cash  compensation  was paid by
         Metrika  Systems   Corporation,   a  wholly  owned  subsidiary  of  the
         Corporation   that  develops,   manufactures,   and  markets   on-line,
         high-speed  process-optimization systems for raw materials analysis and
         finished  materials  quality control.  All of Dr. Chapman's annual cash
         compensation  was paid by  ThermoQuest  Corporation,  a majority  owned
         subsidiary  of the  Corporation  that  develops  and  distributes  mass
         spectrometers,   liquid   chromatographs,   gas   chromatographs,   and
         multi-instrument combinations of these products for the pharmaceutical,
         environmental,   and  industrial  marketplaces,   where  he  serves  as
         president  and chief  executive  officer.  In 1999,  44% of Mr.  Howe's
         annual  compensation  was paid by ThermoSpectra  Corporation,  a wholly
         owned subsidiary of the Corporation,  that supplies  precision imaging,
         inspection,  temperature control and test and measurement  instruments,
         where he served as president and chief executive  officer until October
         1999,  and 56% was paid by Thermo  Optek.  In 1998,  48% of Mr.  Howe's
         annual cash compensation was paid by Thermo BioAnalysis Corporation,  a
         wholly owned subsidiary of the Corporation that develops, manufactures,
         and  supplies  a  broad  range  of  products,   including  biomolecular
         instruments  and  consumables,   clinical   laboratory   equipment  and
         supplies,  rapid,  point-of-care  diagnostic  test kits, and laboratory
         information-management  systems that are used in biochemical  research,
         clinical diagnosis, and pharmaceutical production.,  where he served as
         president and chief  executive  officer  until March 1998,  and 52% was
         paid  by  ThermoSpectra  Corporation.   In  1997,  all  of  Mr.  Howe's
         compensation  was  paid by  Thermo  BioAnalysis  Corporation,  where he
         served as president and chief executive officer.

(7)      In fiscal 1999,  Dr.  Chapman was awarded  7,400  shares of  restricted
         common stock of ThermoQuest  Corporation with a value of $77,241 on the
         grant  date.  The  restricted  stock  award  vests  100%  on the  third
         anniversary  of the grant date.  Any cash  dividends paid on restricted
         shares are entitled to be retained by the recipient  without  regard to
         vesting.  Any non-cash dividends paid on restricted shares are entitled
         to  be  retained  by  the   recipient   subject  to  the  same  vesting
         restrictions  as the underlying  stock.  At the end of fiscal 1999, Dr.
         Chapman held 7,400 shares of restricted  stock with an aggregate  value
         of $76,316.

(8)      In addition to the matching  contribution  referred to in footnote (3),
         such amount includes $14,805, $16,873 and $18,154, respectively,  which
         represents the amount of  compensation  in fiscal 1999,  1998 and 1997,
         respectively,  attributable  to  interest-free  loans  provided  to Dr.
         Chapman  pursuant  to the  stock  holding  assistance  plans of  Thermo
         BioAnalysis  Corporation  and  ThermoQuest  Corporation.  See Item 13 -
         "Certain   Relationships  and  Related   Transactions  --Stock  Holding
         Assistance Plans."

(9)      In addition to the matching  contribution  referred to in footnote (3),
         such amount includes $13,184, $12,886 and $8,173,  respectively,  which
         represents the amount of  compensation  in fiscal 1999,  1998 and 1997,
         respectively,  attributable to interest-free loans provided to Mr. Howe
         pursuant to the stock holding  assistance  plans of  ThermoSpectra  and
         Thermo  BioAnalysis,  See Item 13 - "Certain  Relationships and Related
         Transactions--Stock Holding Assistance Plans," and a payment of $25,000
         made to Mr. Howe in fiscal 1999 in  connection  with his  relocation to
         Franklin, Massachusetts.

<PAGE>


STOCK OPTIONS GRANTED DURING FISCAL 1999

         The following table sets forth information concerning individual grants
of stock options made during fiscal 1999 to the named executive officers. It has
not been the  Corporation's  policy  in the  past to  grant  stock  appreciation
rights, and no such rights were granted during fiscal 1999.

<TABLE>
<CAPTION>
<S>                              <C>                 <C>             <C>         <C>           <C>           <C>
                                                 OPTION GRANTS IN FISCAL 1999
-------------------------------------------------------------------------------------------------------------------
                                                                                            Potential Realizable
                                                   Percent of                                 Value at Assumed
                         Number of Securities    Total Options                             Annual Rates of Stock
                           Underlying Options      Granted to      Exercise                 Price Appreciation for
                              Granted and        Employees in     Price Per   Expiration       Option Term (2)
Name                          Company (1)         Fiscal Year       Share        Date          5%           10%
----                          -----------         ------------      -----        ----          ---          ----
Earl R. Lewis (3)            150,000 (THI)         12.83%           $14.76     01/06/06    $901,320      $2,100,465
-------------------------------------------------------------------------------------------------------------------
Richard W. K. Chapman         25,000 (THI)          2.14%           $11.95     09/15/04     $82,540        $182,390
                                 500 (TMO)          0.02%  (4)      $14.81     09/22/04      $2,050          $4,521
-------------------------------------------------------------------------------------------------------------------
Denis A. Helm                 50,000 (THI)          4.28%           $11.95     09/15/04    $165,080        $364,780
                               3,800 (TMO)          0.13%  (4)      $14.81     09/22/04     $15,550         $34,358
-------------------------------------------------------------------------------------------------------------------
Barry S. Howe                 25,000 (THI)          2.14%           $11.95     09/15/04     $82,540        $182,390
                                 900 (TMO)          0.03%  (4)      $14.81     09/22/04      $3,680          $8,138
-------------------------------------------------------------------------------------------------------------------
</TABLE>

(1)      All of the  options  granted  during  the fiscal  year are  immediately
         exercisable  as of the end of the fiscal  year.  Generally,  the shares
         acquired  upon  exercise  are  subject to  repurchase  by the  granting
         company at the exercise price if the optionee  ceases to be employed by
         such company or any other Thermo Electron company. The granting company
         may  exercise  its  repurchase  rights  within  six  months  after  the
         termination  of  the  optionee's  employment.   The  repurchase  rights
         generally lapse ratably over a one- to five-year  period,  depending on
         the option term, which may vary from five to seven years, provided that
         the  optionee  continues  to be  employed  by the  granting  company or
         another Thermo Electron  company.  The granting  company may permit the
         holders of options to exercise  options and to satisfy tax  withholding
         obligations  by  surrendering  shares equal in fair market value to the
         exercise price or withholding obligation. Please see footnote (2) under
         the Summary  Compensation  Table for the company  abbreviations used in
         this table.

(2)      The amounts shown on this table represent hypothetical gains that could
         be achieved for the  respective  options if exercised at the end of the
         option  term.   These  gains  are  based  on  assumed  rates  of  stock
         appreciation  of 5% and 10%  compounded  annually  from  the  date  the
         respective  options were granted to their  expiration  date.  The gains
         shown  are  net of  the  option  exercise  price,  but  do not  include
         deductions  for taxes or other expenses  associated  with the exercise.
         Actual  gains,  if any, on stock  option  exercises  will depend on the
         future  performance  of the common stock of the granting  company,  the
         optionee's  continued employment through the option period and the date
         on which the options are exercised.

(3)      Since  September  1996,  Mr.  Lewis has  served as an officer of Thermo
         Electron,  most recently as chief  operating  officer,  measurement and
         detection.  From time to time since September 1996, he has been, and in
         the future he may be,  granted  options  to  purchase  common  stock of
         Thermo Electron and its other  subsidiaries for service in his capacity
         as an officer of Thermo Electron. These options are not reported in the
         table  as they  were  granted  as  compensation  for  service  to these
         companies  in a capacity  other than in his  capacity  as an  executive
         officer of the Corporation.

(4)      These  options were granted  under stock  option  plans  maintained  by
         Thermo Electron companies other than the Corporation and,  accordingly,
         are reported as a percentage of total  options  granted to employees of
         such companies.

STOCK OPTIONS EXERCISED DURING FISCAL 1999 AND FISCAL YEAR-END OPTION VALUES

         The following table reports certain information  regarding stock option
exercises  during fiscal 1999 and  outstanding  stock options held at the end of
fiscal 1999 by the named executive  officers.  No stock appreciation rights were
exercised or were outstanding during fiscal 1999.



<PAGE>

<TABLE>
<CAPTION>
<S>                           <C>                <C>            <C>               <C>                   <C>
                    AGGREGATED OPTION EXERCISES IN FISCAL 1999 AND FISCAL 1999 YEAR-END OPTION VALUES
----------------------------------------------------------------------------------------------------------------------
                                                                                                      Value of
                                                                               Number of           Unexercised
                                                                               Securities          In-the-Money
                                                                               Underlying           Options at
                                                                           Unexercised Options      Fiscal Year
                                                Shares                      at Fiscal Year-End         -End
                                             Acquired on        Value         (Exercisable/       (Exercisable/
        Name               Company (1)         Exercise     Realized (2)    Unexercisable) (1)    Unexercisable)
        ----               -----------         --------     ------------    ------------------   --------------
Earl R. Lewis (3)                 (THI)           --             --          409,081/0 (4)       $282,375/--
                                  (MKA)           --             --            20,000/0                $0/--
                                  (ONX)           --             --            33,333/0                $0/--
                                  (TBA)           --             --            50,000/0          $270,938/--
                                  (TOC)           --             --          225,000/0 (5)       $203,625/--
                                  (TMQ)           --             --           125,000/0           $15,650/--
---------------------------------------------------------------------------------------------------------------------
Richard W. K. Chapman             (THI)           --             --           196,249/0           $24,563/--
                                  (TMO)         8,436          $40,957        80,646/0 (6)         $5,167/--
                                  (MKA)           --             --            7,500/0 (7)             $0/--
                                  (ONX)           --             --            7,500/0 (7)             $0/--
                                  (RGI)           --             --             4,000/0            $1,000/--
                                  (TDX)           --             --             2,000/0                $0/--
                                  (TBA)           --             --            30,000/0          $251,250/--
                                  (TFG)           --             --             2,000/0            $4,376/--
                                  (TFT)         6,750          $32,063            --/--                --/--
                                  (TLZ)           --             --             5,000/0                $0/--
                                  (TLT)           --             --                 0/2,000            --/$0(8)
                                  (TOC)           --             --            15,000/0           $13,575/--
                                  (TMQ)           --             --           325,000/0           $87,300/--
                                  (TSR)           --             --             2,000/0            $1,000/--
                                  (TKN)           --             --             1,023/0            $56.27/--
                                  (TRIL)          --             --                 0/2,000            --/$0(8)
                                  (TXM)           --             --             4,000/0                $0/--
---------------------------------------------------------------------------------------------------------------------
Denis A. Helm                     (THI)           --             --            216,250/0          $24,563/--
                                  (TMO)         8,436          $43,066        103,034/0 (6)       $16,608/--
                                  (MKA)           --             --             25,000/0               $0/--
                                  (ONX)           --             --             7,500/0 (7)            $0/--
                                  (RGI)           --             --              4,000/0           $1,000/--
                                  (TDX)           --             --              2,000/0               $0/--
                                  (TBA)           --             --             15,000/0         $125,625/--
                                  (TFT)         6,750          $31,644             --/--               --/--
                                  (TOC)           --             --             15,000/0          $13,575/--
                                  (TMQ)           --             --             10,000/0               $0/--
                                  (TKN)           --             --              1,023/0              $56/--
                                  (TRIL)          --             --                 0/2,000            --/$0(8)
---------------------------------------------------------------------------------------------------------------------
Barry S. Howe                     (THI)           --             --             273,155/0        $459,509/--
                                  (TMO)         2,530            $3,643         66,671/0 (6)      $16,428/--
                                  (MKA)           --             --              7,500/0 (7)           $0/--
                                  (ONX)           --             --              7,500/0 (7)           $0/--
                                  (RGI)           --             --               4,000/0          $1,000/--
                                  (TMD)           --             --               4,000/0              $0/--
                                  (TDX)           --             --               2,000/0              $0/--
                                  (TBA)         17,530        $152,444           35,000/0        $293,125/--
                                  (TCK)           --             --               6,000/0              $0/--
                                  (TFG)           --             --               2,000/0          $4,376/--
                                  (TFT)         6,750           $31,644           9,000/0          $7,515/--
                                  (TLZ)           --             --               5,000/0              $0/--
                                  (TLT)           --             --                  0/2,000           --/$0(8)
                                  (TOC)           --             --              15,000/0        $ 13,575/--
                                  (THP)         2,000          $5,800               --/--              --/--
                                  (TMQ)           --             --            90,000/0  (9)           $0/--
                                  (TSR)           --             --               2,000/0          $1,000/--
                                  (THS)         12,000          $65,200             --/--               $0/0
                                  (TTT)           --             --               4,000/0              $0/--

<PAGE>

---------------------------------------------------------------------------------------------------------------------
Barry S. Howe                     (TKN)           --             --               5,023/0             $56/--
  cont'd                          (TRIL)          --             --               0/2,000              --/$0(8)
                                  (TXM)           --             --               4,000/0              $0/--
---------------------------------------------------------------------------------------------------------------------
</TABLE>

(1)      All of the options  reported  outstanding at the end of the fiscal year
         were immediately  exercisable as of fiscal year-end,  except options to
         purchase  shares of the  common  stock of  ThermoLyte  Corporation  and
         Thermo Trilogy Corporation, which are not exercisable until the earlier
         of (i) 90 days after the  effective  date of the  registration  of that
         company's  common  stock under  Section 12 of the  Exchange Act or (ii)
         nine years after the grant date.  Generally,  the shares  acquired upon
         exercise of the options reported in the table are subject to repurchase
         by the granting company at the exercise price if the optionee ceases to
         be employed  by, or ceases to serve as a director  of, such  company or
         any other Thermo Electron  company.  The granting  company may exercise
         its  repurchase  rights within six months after the  termination of the
         optionee's employment or the cessation of directorship, as the case may
         be. For  publicly-traded  companies,  the repurchase  rights  generally
         lapse ratably over a one- to ten-year  period,  depending on the option
         term,  which may vary from  three to twelve  years,  provided  that the
         optionee  continues  to be  employed  by or serve as a director  of the
         granting  company or another Thermo Electron  company.  Certain options
         have three-year terms and the repurchase rights lapse in their entirety
         on the second anniversary of the grant date. For companies whose shares
         are not publicly-traded,  the repurchase rights lapse in their entirety
         on the ninth  anniversary of the grant date.  The granting  company may
         permit the  holders of options to  exercise  options and to satisfy tax
         withholding  obligations  by  surrendering  shares equal in fair market
         value to the  exercise  price or  withholding  obligation.  Please  see
         footnote  (2)  under the  Summary  Compensation  Table for the  company
         abbreviations  used in this table as well as the  following  additional
         company abbreviations: Thermedics Inc (designated in the table as TMD),
         Thermo BioAnalysis Corporation (designated in the table as TBA), Thermo
         Ecotek  Corporation  (designated in the table as TCK),  Thermo Fibergen
         Inc.  (designated  in the table as TFG),  Thermo  Fibertek  Corporation
         (designated in the table as TFT), ThermoLase Corporation (designated in
         the table as TLZ), ThermoLyte  Corporation  (designated in the table as
         TLT),   Thermo   Sentron  Inc.   (designated  in  the  tabel  as  TSR),
         ThermoSpectra  Corporation  (designated  in the  table as THS),  Thermo
         TerraTech Corporation (designated in the table as TTT) and Trex Medical
         Corporation (designated in the table as TXM).

(2)      Amounts shown in this column do not necessarily  represent actual value
         realized  from the sale of the shares  acquired  upon  exercise  of the
         option  because in many cases the shares are not sold on  exercise  but
         continue to be held by the executive officer exercising the option. The
         amounts shown  represent  the  difference  between the option  exercise
         price and the market price on the date of exercise, which is the amount
         that would have been  realized if the shares had been sold  immediately
         upon exercise.

(3)      Since  September  1996,  Mr.  Lewis has  served as an officer of Thermo
         Electron,  most recently as chief  operating  officer,  measurement and
         detection.  From time to time since September 1996, he has been, and in
         the future he may be,  granted  options  to  purchase  common  stock of
         Thermo Electron and its other subsidiaries for services in his capacity
         as an officer of Thermo Electron. These options are not reported in the
         table as they  were  granted  as  compensation  for  service  to Thermo
         Electron  in a capacity  other  than in his  capacity  as an  executive
         officer of the Corporation.

(4)      Options to purchase  62,500 shares of Common Stock granted to Mr. Lewis
         are  subject  to the same terms as  described  in  footnote  (1) above,
         except that the repurchase  rights of the granting company generally do
         not lapse until the tenth  anniversary  of the grant date. In the event
         of the employee's death or involuntary  termination  prior to the tenth
         anniversary of the grant date,  the  repurchase  rights of the granting
         company shall be deemed to have lapsed  ratably over a five year period
         commencing with the fifth anniversary of the grant date.

(5)      Options to purchase  100,000 shares of the common stock of Thermo Optek
         granted to Mr.  Lewis are  subject to the same  terms as  described  in
         footnote  (1) above,  except that the  repurchase  rights lapse 20% per
         year commencing on the sixth anniversary of the grant date.

(6)      Options to  purchase  45,000,  45,000  and 22,500  shares of the common
         stock of Thermo Electron granted to Dr. Chapman, Mr. Helm and Mr. Howe,
         respectively,  are subject to the same terms as  described  in footnote
         (1) above,  except that the repurchase  rights of the granting  company
         generally do not lapse until the tenth  anniversary  of the grant date.
         In the event of the employee's death or involuntary  termination  prior
         to the tenth  anniversary of the grant date,  the repurchase  rights of
         the  granting

<PAGE>

         company shall be deemed to have lapsed ratably over a five-year  period
         commencing with the fifth anniversary of the grant date.

(7)      Options to purchase 7,500 shares of common stock of Metrika Systems and
         7,500  shares of common  stock of ONIX  Systems  granted to each of Dr.
         Chapman  and Mr.  Howe are  subject to the same terms as  described  in
         footnote  (1) above,  except that the  repurchase  rights lapse 20% per
         year commencing on the fifth anniversary of the grant date.  Options to
         purchase  7,500 shares of common  stock of ONIX Systems  granted to Mr.
         Helm are subject to the same terms as  described in footnote (1) above,
         except that the repurchase  rights lapse 20% per year commencing on the
         fifth anniversary of the grant date.

(8)      No public market existed for the shares  underlying these options as of
         January 31, 2000. Accordingly, no value in excess of the exercise price
         has been attributed to these options.

(9)      Mr. Howe has two  ThermoQuest  options granted on January 10, 1996 that
         have a 12-year term. The repurchase  rights are deemed to lapse 100% on
         the tenth  anniversary  for the first  option  for 40,000  shares.  The
         repurchase  rights  are  deemed to lapse  18% on the  first and  second
         anniversaries  of the grant  date and 8%  annually  starting  the third
         anniversary of the grant date for the second option for 50,000 shares.

EXECUTIVE RETENTION AGREEMENTS

         Thermo  Electron has entered  into  agreements  with certain  executive
officers and key employees of Thermo Electron and its subsidiaries  that provide
severance  benefits if there is a change in control of Thermo Electron and their
employment is terminated by Thermo Electron "without cause" or by the individual
for  "good  reason,"  as these  terms  are  defined  therein,  within  18 months
thereafter.  For purposes of these  agreements,  a change in control exists upon
(i) the acquisition by any person of 40% or more of the outstanding common stock
or voting securities of Thermo Electron; (ii) the failure of the Thermo Electron
board of  directors  to  include a majority  of  directors  who are  "continuing
directors",  which  term is defined to  include  directors  who were  members of
Thermo  Electron's  board on the date of the agreement or who  subsequent to the
date of the agreement  were  nominated or elected by a majority of directors who
were  "continuing  directors" at the time of such nomination or election;  (iii)
the consummation of a merger, consolidation, reorganization, recapitalization or
statutory  share  exchange  involving  Thermo  Electron  or the  sale  or  other
disposition of all or substantially  all of the assets of Thermo Electron unless
immediately  after such  transaction  (a) all holders of Thermo  Electron common
stock immediately prior to such transaction own more than 60% of the outstanding
voting securities of the resulting or acquiring corporation in substantially the
same  proportions as their ownership  immediately  prior to such transaction and
(b) no person after the transaction  owns 40% or more of the outstanding  voting
securities  of the  resulting  or  acquiring  corporation;  or (iv)  approval by
stockholders of a complete liquidation or dissolution of Thermo Electron.

         In 1998, Thermo Electron  authorized an executive  retention  agreement
with each of Mr. Earl R. Lewis, Dr. Richard W. K. Chapman, Mr. Denis A. Helm and
Mr. Barry S. Howe. These  agreements  provide that in the event the individual's
employment is terminated under the circumstances described above, the individual
would be entitled  to a lump sum payment  equal to the sum of (a) in the case of
Mr. Lewis,  two times,  and in the case of Messrs.  Chapman,  Helm and Howe, one
times, the individual's highest annual base salary in any 12 month period during
the prior five-year period, plus (b) in the case of Mr. Lewis, two times, and in
the case of Messrs.  Chapman, Helm and Howe, one times, the individual's highest
annual  bonus in any 12 month  period  during  the prior  five-year  period.  In
addition, the individual would be provided benefits for a period of, in the case
of Mr. Lewis, two years, and in the case of Messrs.  Chapman,  Helm and Howe one
year, after such termination,  substantially  equivalent to the benefits package
the individual  would have been otherwise  entitled to receive if the individual
was not terminated.  Further,  all repurchase  rights of Thermo Electron and its
subsidiaries  shall  lapse in their  entirety  with  respect to all  options and
restricted   stock  that  the  individual  holds  in  Thermo  Electron  and  its
subsidiaries,  including  the  Corporation,  as of the  date  of the  change  in
control.  Finally,  the individual would be entitled to a cash payment equal to,
in the case of Mr. Lewis, $20,000, and in the case of Messrs.  Chapman, Helm and
Howe $15,000, to be used toward outplacement services. These executive retention
agreements  supersede and replace any and all prior severance  arrangements that
these individuals had with Thermo Electron.

         Assuming  that the  severance  benefits  would have been  payable as of
January 1, 2000,  the lump sum salary and bonus payment under such  agreement to
Messrs. Lewis, Chapman, Helm and Howe would have been approximately  $1,140,000,
$373,000, $272,000 and $280,000,  respectively. In the event that payments under

<PAGE>

these  agreements are deemed to be so called "excess  parachute  payments" under
the applicable  provisions of the Internal Revenue Code of 1986, as amended (the
"Internal  Revenue  Code"),  the  individuals  would be  entitled  to  receive a
gross-up  payment  equal  to the  amount  of any  excise  tax  payable  by  such
individual with respect to such payment, plus the amount of all other additional
taxes imposed on such  individual  attributable  to the receipt of such gross-up
payment.

STOCK OWNERSHIP POLICY

         The  Committee has  established  a stock  holding  policy for the chief
executive  officer of the Corporation that requires him to own a multiple of his
compensation in shares of the  Corporation's  Common Stock.  The multiple is one
times  his  base  salary  and  reference  bonus  for the  fiscal  year in  which
compliance  is achieved.  The chief  executive  officer has three years from the
adoption of the policy to achieve this ownership level.

         In order to assist the chief  executive  officer in complying  with the
policy,  the Committee also adopted a stock holding  assistance plan under which
the Corporation is authorized to make interest-free loans to the chief executive
officer to enable him to purchase shares of Common Stock in the open market. Any
loans  are  required  to be  repaid  upon the  earlier  of  demand  or the tenth
anniversary  of the  date  of  the  loan,  unless  otherwise  determined  by the
Committee.  No loans were outstanding  under this program in 1999. See Item 13 -
"Certain  Relationships  and Related  Transactions  - Stock  Holding  Assistance
Plan."

         Similar stock holding policies and stock holding  assistance plans have
been  adopted  by  each  of the  Corporation's  publicly-traded,  majority-owned
subsidiaries.  Certain  executive  officers  of the  Corporation  who are  chief
executive officers of these subsidiaries are required to comply with these stock
holding  policies in lieu of the  Corporation's  stock  holding  policy and have
outstanding loans under such  subsidiaries'  stock holding assistance plans. See
Item 13 -  "Certain  Relationships  and  Related  Transactions  - Stock  Holding
Assistance Plans."

Item 12. SECURITY OWNERSHIP OF CERTAIN BENEFICIAL OWNERS AND MANAGEMENT

         The  following  table sets  forth the  beneficial  ownership  of Common
Stock,  as well as the  common  stock of Thermo  Electron,  Thermo  Instrument's
parent company,  and each  majority-owned  subsidiary of the Corporation,  as of
January 31, 2000, with respect to (i) each director, (ii) each executive officer
named in the  summary  compensation  table set  forth  below  under the  heading
"Executive  Compensation"  ("named executive  officers") and (iii) all directors
and current executive officers as a group. In addition, the following table sets
forth the  beneficial  ownership of Common Stock,  as of January 31, 2000,  with
respect to each person who was known by the Corporation to own beneficially more
than 5% of the outstanding shares of Common Stock.

         While certain  directors and executive  officers of the Corporation are
also  directors and executive  officers of Thermo  Electron or its  subsidiaries
other than the Corporation,  all such persons disclaim  beneficial  ownership of
the shares of common stock beneficially owned by Thermo Electron.

<TABLE>
<CAPTION>
<S>                                                 <C>                <C>             <C>               <C>
                                                  Thermo             Thermo           Thermo            Thermo
                                                Instrument          Electron        BioAnalysis         Optek
Name(1)                                     Systems Inc. (2)    Corporation (3)   Corporation (4)  Corporation (5)
-------                                     ------------------  ---------------   ---------------  ---------------
Thermo Electron Corporation(10)...............  114,606,480              N/A              N/A               N/A
Richard W. K. Chapman.........................      225,530           79,801           40,500            15,500
Denis A. Helm.................................      278,638          167,163           15,000            15,200
Barry S. Howe.................................      303,290           71,655           37,884            25,000
Earl R. Lewis.................................      436,499          215,477           72,500           252,000
Polyvios C. Vintiadis.........................       17,597            2,500                0                 0
All directors and current executive
   officers as a group (6 persons)............    1,444,269          995,128          184,884           347,700
</TABLE>



<PAGE>


<TABLE>
<CAPTION>
<S>                                                <C>                <C>               <C>                   <C>
                                                                    Metrika
                                               ThermoQuest          Systems             ONIX        Spectra-Physics
Name(1)                                      Corporation (6)    Corporation (7)   Systems Inc. (8)  Lasers, Inc. (9)
-------                                      ---------------    ---------------   ------------ ---  ----------------
Thermo Electron Corporation(10)...............        N/A                N/A             N/A                N/A
Richard W. K. Chapman.........................    351,746              7,500           7,500                  0
Denis A. Helm.................................     10,000             26,000           7,500                  0
Barry S. Howe.................................     90,000              7,500           7,500                  0
Earl R. Lewis.................................    135,000             20,000          35,333                  0
Polyvios C. Vintiadis.........................          0                  0               0                  0
All directors and current executive
officers as a group (6 persons)...............    589,246             86,000          87,833                  0
</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 Common Stock beneficially owned by Dr. Chapman, Mr. Helm,
         Mr. Howe,  Mr.  Lewis,  Mr.  Vintiadis  and all  directors  and current
         executive  officers  as a  group  include  196,249,  216,250,  273,156,
         409,081, 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 all
         directors and current executive  officers as a group include 468 shares
         allocated  through  January  31,  2000,  to their  respective  accounts
         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 the Deferred  Compensation  Plan. Shares  beneficially
         owned by Mr. Helm  include a total of 5,264  shares  held in  custodial
         accounts  for the benefit of his 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 named executive
         officer beneficially owned more than 1% of the Common Stock outstanding
         as of January 31, 2000; all directors and current executive officers as
         a group  beneficially owned 1.21% of the Common Stock outstanding as of
         such date.

(3)      Shares of the common stock of Thermo Electron beneficially owned by Dr.
         Chapman,  Mr. Helm,  Mr. Howe,  Mr. Lewis and all directors and current
         executive officers as a group include 76,428,  99,816,  64,141, 212,278
         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 all directors
         and  current  executive  officers  as a  group  include  1,071  shares,
         respectively,  allocated  through January 31, 2000, to their respective
         accounts  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 named executive  officer  beneficially
         owned more than 1% of the common stock of Thermo  Electron  outstanding
         as of January 31, 2000; all directors and current executive officers as
         a  group   beneficially  owned  less  than  1%  of  such  common  stock
         outstanding as of such date.

(4)      Shares of the common stock of Thermo BioAnalysis  Corporation  ("Thermo
         BioAnalysis"),  beneficially owned by Dr. Chapman,  Mr. Helm, Mr. Howe,
         Mr. Lewis and all directors and current  executive  officers as a group
         include   30,000,   15,000,   35,000,   50,000  and   149,000   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. Howe  include 600 shares held by Mr.
         Howe in  custodial  accounts  for the  benefit  of his minor  children.
         Shares  beneficially owned by Mr. Lewis include 1000 shares held by his
         spouse. No director or named executive officer  beneficially owned more
         than 1% of the common  stock of Thermo  BioAnalysis  outstanding  as of
         January 31, 2000;  all  directors and current  executive  officers as a
         group  beneficially owned less than 1% of such common stock outstanding
         as of such date.

(5)      Shares  of  the   common   stock  of  Thermo   Optek   Corporation,   a
         majority-owned   subsidiary  of  the  Corporation   ("Thermo   Optek"),
         beneficially  owned by Dr.  Chapman,  Mr. Helm, Mr. Howe, Mr. Lewis

<PAGE>

         and all  directors  and current  executive  officers as a group include
         15,000, 15,000, 15,000, 225,000 and 310,000 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.  Lewis  include  2,500 shares held by his spouse and 1,000
         shares  held  by his  son.  No  director  or  named  executive  officer
         beneficially  owned  more than 1% of the common  stock of Thermo  Optek
         outstanding as of January 31, 2000; all directors and current executive
         officers  as a group  beneficially  owned  less than 1% of such  common
         stock outstanding as of such date.

(6)      Shares of the common stock of ThermoQuest Corporation, a majority-owned
         subsidiary of the Corporation  ("ThermoQuest"),  beneficially  owned by
         Dr.  Chapman,  Mr. Helm,  Mr. Howe,  Mr.  Lewis and all  directors  and
         current executive officers as a group include 325,000,  10,000, 90,000,
         125,000 and 552,500 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.  No director  or named  executive  officer
         beneficially  owned  more than 1% of the  common  stock of  ThermoQuest
         outstanding as of January 31, 2000; all directors and current executive
         officers  as a group  beneficially  owned  1.16% of such  common  stock
         outstanding as of such date.

(7)      Shares  of  the  common  stock  of  Metrika  Systems   Corporation,   a
         majority-owned  subsidiary  of  the  Corporation  ("Metrika  Systems"),
         beneficially  owned by Dr.  Chapman,  Mr. Helm, Mr. Howe, Mr. Lewis and
         all directors and current executive  officers as a group include 7,500,
         25,000, 7,500, 20,000 and 85,000 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.  No director or named  executive
         officer  beneficially owned more than 1% of the common stock of Metrika
         Systems  outstanding  as of January 31, 2000; all directors and current
         executive  officers as a group  beneficially owned 1.16% of such common
         stock outstanding as of such date.

(8)      Shares of the common  stock of ONIX  Systems  Inc.,  ("ONIX  Systems"),
         beneficially  owned by Dr.  Chapman,  Mr. Helm, Mr. Howe, Mr. Lewis and
         all directors and current executive  officers as a group include 7,500,
         7,500, 7,500, 33,333, and 85,833 shares, respectively, that each person
         or group had the right to acquire  within 60 days of January 31,  2000,
         through the exercise of stock options.  No director or named  executive
         officer  owned  more  than  1% of the  common  stock  of  ONIX  Systems
         outstanding as of January 31, 2000; all directors and current executive
         officers  as a group  beneficially  owned  less than 1% of such  common
         stock outstanding as of such date.

(9)      The directors,  named executive officers and current executive officers
         did  not  individually  or as a  group  beneficially  own  any  of  the
         Spectra-Physics Lasers, Inc. common stock outstanding as of January 31,
         2000.

(10)     Shares  beneficially owned by Thermo Electron include 10,334,620 shares
         of Common Stock  issuable upon the  conversion of a 3 3/4%  convertible
         debenture due in 2000. Thermo Electron beneficially owned approximately
         88.71% of the Common Stock  outstanding as of January 31, 2000.  Thermo
         Electron's   address  is  81  Wyman  Street,   Waltham,   Massachusetts
         02454-9046.

SECTION 16(A) BENEFICIAL OWNERSHIP REPORTING COMPLIANCE

         Section 16(a) of the Exchange Act requires the Corporation's  directors
and executive  officers,  and  beneficial  owners of more than 10% of the Common
Stock,  such as  Thermo  Electron,  to file  with the  Securities  and  Exchange
Commission  initial  reports of  ownership  and  periodic  reports of changes in
ownership of the Corporation's securities.  Based upon a review of such filings,
all Section 16(a) filing  requirements  applicable to such persons were complied
with during 1999,  except in the following  instance.  Thermo Electron filed one
Form 4 late,  reporting a total of 17  transactions,  including  two open market
purchases  of shares of Common  Stock and 15  transactions  associated  with the
cancellation  and grant of options to purchase Common Stock granted to employees
under its stock option program.

Item 13 -  CERTAIN RELATIONSHIPS AND RELATED TRANSACTIONS

         The  Corporation  and Thermo  Electron  have  entered  into a Corporate
Services  Agreement (the  "Services  Agreement")  under which Thermo  Electron's
corporate staff provides  certain  administrative  services,  including  certain
legal advice and services, risk management, employee benefit administration, tax
advice and preparation of tax returns, centralized cash management and financial
and other services to the  Corporation.  The  Corporation was assessed an annual
fee equal to 0.8% of the  Corporation's  revenues  for these  services in fiscal

<PAGE>

1999,  excluding the revenues of  Spectra-Physics  Lasers,  Inc., which does not
participate in the Services Agreement. The annual fee will remain at 0.8% of the
Corporation's  revenues for fiscal 2000. The fee is reviewed annually and may be
changed by mutual  agreement  of the  Corporation  and Thermo  Electron.  During
fiscal 1999,  Thermo  Electron  assessed the  Corporation  $15.7 million in fees
under the Services  Agreement.  Management  believes  that the charges under the
Services  Agreement are reasonable and that the terms of the Services  Agreement
are fair to the  Corporation.  In fiscal  1999,  the  Corporation  was billed an
additional  $125,000  by Thermo  Electron  for certain  administrative  services
required by the Corporation that were not covered by the Services Agreement. The
Services Agreement  automatically  renews for successive  one-year terms, unless
canceled  by the  Corporation  upon 30 days'  prior  notice.  In  addition,  the
Services Agreement terminates  automatically in the event the Corporation ceases
to be a Thermo  subsidiary or ceases to be a participant in the Thermo  Electron
Corporate Charter. In the event of a termination of the Services Agreement,  the
Corporation  will be required to pay a termination fee equal to the fee that was
paid by the  Corporation  for  services  under the  Services  Agreement  for the
nine-month period prior to termination.  Following termination,  Thermo Electron
may provide  certain  administrative  services on an  as-requested  basis by the
Corporation or as required in order to meet the Corporation's  obligations under
Thermo  Electron's  policies and  procedures.  Thermo  Electron  will charge the
Corporation  a fee equal to the  market  rate for  comparable  services  if such
services are provided to the Corporation following termination.

         The Corporation has entered into a Tax Allocation Agreement with Thermo
Electron that outlines the terms under which the Corporation will be included in
Thermo  Electron's  consolidated  Federal and state  income tax  returns.  Under
current  law,  the  Corporation  will be included in such tax returns so long as
Thermo Electron owns at least 80% of the Corporation's outstanding Common Stock.
In years in which the  Corporation  has  taxable  income,  it will pay to Thermo
Electron amounts  comparable to the taxes the Corporation  would have paid if it
had filed its own separate  company tax  returns.  If Thermo  Electron's  equity
ownership of the Corporation  were to drop below 80%, the Company would file its
own tax returns. In 1999, the Corporation paid Thermo Electron $34,800,000 under
the Tax Allocation Agreement. As of January 1, 2000, the Corporation owed Thermo
Electron $18,150,000 for amounts due under the Tax Allocation Agreement.

         The  Corporation  purchases and sells products  and/or  services in the
ordinary  course of  business to Thermo  Electron  and Thermo  Electron's  other
subsidiaries. In 1999, the Corporation sold a total of $1,240,000 of products to
Thermo Electron and its other  subsidiaries  and purchased a total of $1,642,000
of products and/or services from such companies.

         Thermo  Optek  leases  office  and   manufacturing   space  to  Nicolet
Biomedical  Inc.  ("Nicolet  Biomedical"),  a wholly owned  subsidiary of Thermo
Electron,  pursuant to an  arrangement  whereby  Thermo  Optek  charges  Nicolet
Biomedical  its  allocated  share of the  occupancy  expenses of Thermo  Optek's
principal  Wisconsin facility,  based on the space Nicolet Biomedical  utilizes.
Thermo Optek  recorded  operating  lease income of $714,000 in 1999 from Nicolet
Biomedical.  This  lease  is  effective  until  December  31,  2001  but  may be
terminated by Nicolet Biomedical upon 30 days' prior notice to Thermo Optek.

         As of January 1, 2000, the Corporation had outstanding  $140,000,000 of
indebtedness  to Thermo  Electron,  represented by a 3 3/4 % Senior  Convertible
Note due 2000.  In  February  2000,  Thermo  Electron  converted  this Note into
10,334,620  shares of the  Corporation's  Common Stock at a  conversion  rate of
$13.55 per share.

         As of January 1,  2000,  Thermo  Electron  owned  $8,455,000  principal
amount of Thermo Optek's 5%  subordinated  convertible  debentures due 2000. The
debentures are convertible  into shares of Thermo Optek common stock at $13.9446
per share.

         In March  1999,  the  Corporation  borrowed  $200,000,000  from  Thermo
Electron  to  partially  fund its  acquisition  of  Spectra-Physics  AB ("SPAB")
pursuant to the Corporation's  tender offer for all of the outstanding shares of
SPAB. In August 1999, the Corporation repaid $50,000,000 of the principal amount
outstanding  under the  promissory  note and  refinanced the balance of the note
through  borrowings  from Thermo  Electron due February  2000. In February 2000,
Thermo Electron  extended the note to August 2000. This note bears interest at a
rate equal to the 30-day  Dealer  Commercial  Paper Rate as reported in the Wall
Street  Journal  ("DCP Rate") plus 150 basis  points  provided the note shall be
reduced to the DCP Rate plus 50 basis points to the extent of any funds invested
by the Corporation's  majority-owned  subsidiaries in Thermo Electron's domestic
cash management arrangement. The rate at fiscal 1999 year end was 6.0%.

<PAGE>

         ONIX  Systems  leases  approximately  24,000  square feet of office and
manufacturing space in Winchester, England on a month-to-month basis from Thermo
Power.  ONIX Systems  pays Thermo Power rent in an amount that is  approximately
equal to the pro  rata  share  of  Thermo  Power's  occupancy  costs,  including
utilities and taxes, which payments in 1999 were approximately $258,000.

         In March 2000,  Thermo  Electron  agreed to loan the  Corporation up to
$400  million to finance the  acquisitions  by the  Corporation  of the minority
interests in certain of its majority-owned subsidiaries. The loan bears interest
at a rate equal to the 30-day Dealer Commercial Paper Rate (the "DCP Rate") plus
150  basis  points,  adjusted  at the  beginning  of each  fiscal  month  of the
Corporation.  The  interest  rate will be  reduced to the DCP Rate plus 50 basis
points to the extent of any funds invested by the  Corporation's  majority-owned
subsidiaries in Thermo Electron's cash management  arrangement.  As of April 29,
2000, approximately $103 million was outstanding under this loan arrangement.

         The Corporation, along with other U.K.-based Thermo Electron companies,
participates  in a notional pool  arrangement  in the U.K.  with Barclays  Bank,
which includes a $114,943,000  credit  facility.  The  Corporation has access to
$60,200,000  under  this  credit  facility.  Under  this  arrangement,  Barclays
notionally  combines  the  positive  and  negative  cash  balances  held  by the
participants  to calculate  the net interest  yield/expense  for the group.  The
benefit  derived  from this  arrangement  is then  allocated  based on  balances
attributable to the respective  participants.  Thermo Electron guarantees all of
the obligations of each participant in this arrangement.  As of January 1, 2000,
the Corporation had a positive cash balance of  approximately  $41,426,000 and a
negative cash balance of approximately  $41,403,000 based on an exchange rate of
$1.6171/GBP  1.00.  For 1999,  the average  annual  interest  rate earned on GBP
deposits by participants in this credit arrangement was approximately  5.44% and
the average annual interest rate paid on overdrafts was approximately 5.8025%.

         At year-end 1998,  $392,000,000 of the  Corporation's  cash equivalents
were  invested  in a  repurchase  agreement  with  Thermo  Electron.  Under this
agreement,  the Corporation in effect lent excess cash to Thermo Electron, which
Thermo  Electron  collateralized  with  investments  principally  consisting  of
corporate notes, U.S.  government  agency  securities,  commercial paper,  money
market funds and other marketable securities,  in the amount of at least 103% of
such obligation.  The  Corporation's  funds subject to the repurchase  agreement
were readily convertible into cash by the Corporation.  The repurchase agreement
earned a rate based on the 90-day  Commercial Paper Composite Rate plus 25 basis
points, set at the beginning of each quarter.

         Effective June 1999, the Corporation and Thermo Electron  commenced use
of a new  domestic  cash  management  arrangement.  Under  the new  arrangement,
amounts  advanced  to Thermo  Electron  by the  Corporation  for  domestic  cash
management  purposes bear interest at the 30-day  Dealer  Commercial  Paper Rate
plus 50 basis  points,  set at the beginning of each month.  Thermo  Electron is
contractually  required to maintain cash, cash equivalents,  and/or  immediately
available bank lines of credit equal to at least 50% of all funds invested under
this cash management  arrangement by all Thermo Electron subsidiaries other than
wholly owned subsidiaries. The Corporation has the contractual right to withdraw
its  funds  invested  in the cash  management  arrangement  upon 30 days'  prior
notice. At year-end 1999, the Corporation had invested  $256,522,000  under this
arrangement.   In  addition,   certain  of  the   Corporation's   European-based
subsidiaries  participate  in a new cash  management  arrangement  with a wholly
owned  subsidiary  of Thermo  Electron  on terms  similar to the  domestic  cash
management  arrangement.  The  Corporation  has access to a $43,300,000  line of
credit under this arrangement, of which the Corporation had invested $20,767,000
and had borrowed  $18,658,000 at year-end 1999.  Interest under this arrangement
is calculated  based on Euro market rates and was 3.25% on the positive  balance
and 3.95% on the negative balance at year-end 1999.

         The  Corporation,  along with certain  other Thermo  subsidiaries,  has
entered into a cash management  arrangement  with ABN AMRO. Only  European-based
Thermo  Subsidiaries  participate in this arrangement.  The new arrangement with
ABN AMRO consists of a zero balance  arrangement,  which  includes a $25,417,000
credit  facility.  The  Corporation  has access to $8,663,000  under this credit
facility.  Funds borrowed by the Corporation under this arrangement pay interest
at a rate set by  Thermo  Finance  B.V.,  a  wholly-owned  subsidiary  of Thermo
Electron,  at the beginning of each month,  based on  Netherlands  market rates.
Funds  invested  by the  Corporation  under the  arrangement  earn a rate set by
Thermo Finance B.V. at the beginning of each month,  based on Netherlands market
rates.  Such invested  funds are  collateralized  with  investments  principally
consisting of corporate notes,  U.S.  government-agency  securities,  commercial
paper, money market funds, and other marketable securities,  in the amount of at
least 103% of such obligation. Thermo Electron guarantees all of the obligations
of each participant in this arrangement.  As of January 1, 2000, the Corporation
had a positive cash

<PAGE>

balance of  approximately  $16,505 and a negative cash balance of  approximately
$5,502,000,  based on an exchange  rate of  $0.4554/NLG  1.00.  As of January 1,
2000, the average annual interest rate earned on NLG deposits by participants in
this credit arrangement was approximately  3.19% and the average annual interest
rate paid on overdrafts was approximately 3.74%.

         In  connection  with the  acquisition  of Park  Scientific  Instruments
Corporation  in March  1997,  ThermoSpectra  borrowed  $10,000,000  from  Thermo
Electron  pursuant  to a  promissory  note  that  was  paid in  March  1999.  In
connection  with the  acquisition  of NESLAB  Instruments,  Inc. and its related
sales and service entity NESLAB Instruments  Europa BV in the Netherlands,  from
the Corporation in July 1997,  ThermoSpectra  borrowed  $45,000,000  from Thermo
Electron,  which was repaid in full in December  1999. To partially  finance the
acquisition of Sierra Research and Technology  Inc. in July 1997,  ThermoSpectra
borrowed  $5,000,000 from Thermo Electron which was repaid in full in July 1999.
These notes bore interest at the 90-day  Commercial Paper Composite Rate plus 25
basis points, set at the beginning of each quarter.

         At January 1, 2000, the Corporation  owed Thermo Electron and its other
subsidiaries  an  aggregate  of  $9,193,000  for amounts due under the  Services
Agreement and related  administrative  charges, for other products and services,
and for miscellaneous items, excluding loans described above and $18,150,000 due
to Thermo  Electron under the Tax Allocation  Agreement,  net of amounts owed to
the  Corporation  by Thermo  Electron and its other  subsidiaries  for products,
services  and  other  miscellaneous  items.  The  largest  amount  of  such  net
indebtedness   owed  by  the  Corporation  to  Thermo  Electron  and  its  other
subsidiaries  since January 2, 1999 was  $12,654,000.  These amounts do not bear
interest and are expected to be paid in the normal course of business.

THERMO ELECTRON CORPORATE REORGANIZATION

         Thermo  Electron has adopted a major  reorganization  plan under which,
among  other  things,  it is  acquiring  the  minority  interest  in most of its
subsidiaries that have minority investors. As part of this plan, Thermo Electron
has acquired or intends to acquire the minority  interest in the Corporation and
certain of its subsidiaries  listed below. The consideration  paid or to be paid
to the  stockholders in each of these  completed or proposed  transactions is as
follows:

COMPLETED TRANSACTIONS

Subsidiary                                  Per Share Cash Payment
-----------                                 ----------------------

ThermoSpectra Corporation                           $16.00

Thermo Vision Corporation                            $7.00

ONIX Systems Inc.                                    $9.00

Thermo BioAnalysis Corporation                      $28.00



PROPOSED TRANSACTIONS

Cash Transactions
-----------------
Subsidiary                                  Per Share Cash Payment
----------                                  ----------------------
Metrika Systems Corporation                          $9.00

ThermoQuest Corporation                             $17.00

Thermo Optek Corporation                            $15.00



Stock Transactions
------------------
Subsidiary                                  Exchange Ratio*
----------                                  ---------------
Thermo Instrument Systems Inc.                   0.85

*The Exchange Ratio represents the number of shares of common stock that will be
exchanged for each share of the Corporation's common stock.

<PAGE>


EXECUTIVE OFFICER AND DIRECTOR PARTICIPATION IN COMPLETED TRANSACTIONS

         Executive  officers and directors of the Corporation who held shares of
common stock in the  subsidiaries  listed above under  "Completed  Transactions"
received the same cash  consideration per share of subsidiary stock as all other
stockholders of such subsidiaries.

         In addition,  the executive officers' and directors' options to acquire
shares of such subsidiaries' common stock, for which the granting  corporation's
repurchase  rights  had not  lapsed  ("unvested  options"),  were  automatically
assumed  by either  the  Corporation  or Thermo  Electron,  as  applicable,  and
converted into options to purchase shares of the  Corporation's  common stock or
Thermo  Electron's  common stock on the same terms as were applicable to all the
other holders of such subsidiary's  options,  as described below. In the case of
options to acquire  shares of such  subsidiaries'  common  stock,  for which the
granting  corporation's  repurchase  rights had lapsed ("vested  options"),  the
holders were given the  opportunity  to elect either to convert the options into
vested  options to acquire  shares of the  Corporation's  common stock or Thermo
Electron's  common stock,  as  applicable,  or to receive cash at the applicable
cash transaction price less the applicable  exercise price, on the same terms as
were applicable to all the other holders of such subsidiary's options.

         Vested and unvested  options that were  assumed by the  Corporation  or
Thermo  Electron in these  completed  transactions  generally  were converted as
follows:  The  number  of  shares of the  Corporation's  common  stock or Thermo
Electron's  common stock  underlying  each assumed  option equaled the number of
shares of subsidiary  common stock underlying the option before the transaction,
multiplied by the applicable "cash exchange ratio" described below, rounded down
to the  nearest  whole  number of shares of the  Corporation's  common  stock or
Thermo  Electron's  common stock. The exercise price for each assumed option was
calculated by dividing the exercise price of the subsidiary  stock option before
the transaction by the applicable "cash exchange ratio" described below, rounded
up to the nearest whole cent.  The  applicable  "cash  exchange  ratio" for each
transaction was a fraction,  the numerator of which was the cash price listed in
the chart at the beginning of this  subsection (the "Chart") and the denominator
of which  was the  closing  price of the  Corporation's  common  stock or Thermo
Electron's common stock, as applicable,  on the day preceding the effective date
of the transaction.

         Additionally,   certain   directors   participated   in  the   deferred
compensation plans of the various subsidiaries. On the effective date of each of
the completed cash transactions listed above, each of the affected subsidiaries'
deferred  compensation plans terminated and the participants received cash in an
amount equal to the balance of such participant's stock units credited to his or
her account under the respective deferred  compensation plan,  multiplied by the
cash price  listed in the  Chart.  Any such stock  units held by  directors  are
included in their stock ownership information described below.

         In the ThermoSpectra  Corporation transaction,  Mr. Howe, Mr. Lewis and
Mr. Melas-Kyriazi (the Corporation's Chief Financial Officer, who is not a named
executive  officer of the  Corporation  for purposes of Securities  and Exchange
Commission  regulations,  and whose  ownership  information  therefore  does not
appear in the "Stock  Ownership"  table)  received a cash  payment of $16.00 per
share for  15,010,  5,000 and  13,600  shares of common  stock of  ThermoSpectra
Corporation held by such individuals,  respectively.  Additionally, Dr, Chapman,
Mr. Helm, Mr. Howe, Mr. Lewis, Mr.  Melas-Kyriazi and Mr. Vintiadis held options
to  acquire  4,000,  4,000,   92,000,   50,000,   64,200  and  1,500  shares  of
ThermoSpectra Corporation common stock,  respectively,  that were converted into
options to acquire shares of common stock of Thermo Instrument  Systems Inc., as
described  above.  Additionally,  Mr. Howe elected to receive cash payments,  as
described  above,  for  options  to  purchase  an  additional  12,000  shares of
ThermoSpectra  Corporation  common stock, and received payments of $65,200,  for
such options.

         In the Thermo Vision Corporation transaction, Dr. Chapman, Mr. Helm and
Mr.  Lewis  received  a cash  payment  of $7.00 per share for 70, 28 and  17,720
shares of common stock of Thermo Vision  Corporation  held by such  individuals,
respectively.  Additionally,  Dr.  Chapman,  Mr. Helm, Mr. Howe, Mr. Lewis,  Mr.
Melas-Kyriazi  and Mr.  Vintiadis held options to acquire 7,500,  7,500,  7,500,
25,000,  70,000,  and 1,500 shares of Thermo  Vision  Corporation  common stock,
respectively, that were converted into options to acquire shares of common stock
of Thermo Instrument Systems Inc., as described above.

         In the ONIX Systems Inc. transaction, Mr. Lewis received a cash payment
of $9.00 per share for 2,000 shares of common stock of ONIX Systems Inc. held by
him.  Additionally,  Dr.  Chapman,  Mr.  Helm,  Mr.  Howe,  Mr.  Lewis  and  Mr.
Melas-Kyriazi  held options to acquire 7,500,  7,500,  7,500,  33,333 and 30,000
shares of

<PAGE>

ONIX Systems Inc. common stock,  respectively,  that were converted into options
to acquire shares of Thermo Electron common stock, as described above.

         In the Thermo BioAnalysis  Corporation  transaction,  Dr. Chapman,  Mr.
Howe and Mr. Lewis received a cash payment of $28.00 per share for 10,500, 2,884
and 22,500 shares of common stock of Thermo BioAnalysis Corporation held by such
individuals,  respectively.  Additionally,  Dr. Chapman, Mr. Helm, Mr. Howe, Mr.
Lewis and Mr.  Melas-Kyriazi  held  options to acquire  18,000,  9,000,  30,000,
34,250 and 19,000 shares of Thermo BioAnalysis common stock, respectively,  that
were converted into options to acquire shares of Thermo  Electron  common stock,
as described above. Additionally,  Dr. Chapman, Mr. Helm, Mr. Howe and Mr. Lewis
elected to receive cash payments, as described above, for options to purchase an
additional  12,000,  6,000, 5,000 and 15,750 shares of Thermo BioAnalysis common
stock, respectively,  and received a payment of $216,000,  $108,000, $90,000 and
$258,000, respectively, for such options.

EXECUTIVE OFFICER AND DIRECTOR PARTICIPATION IN PROPOSED TRANSACTIONS

         Executive  officers and directors of the Corporation who hold shares of
common stock in the subsidiaries listed above under "Proposed Transactions" will
receive  the same  consideration  per  share of  subsidiary  stock as all  other
stockholders of such subsidiaries.  See Item 12 - "Security Ownership of Certain
Beneficial Owners and Management."

         In  addition,   certain   executive   officers  and  directors  of  the
Corporation  hold options to acquire shares of common stock of the  subsidiaries
listed above (See Item 12 - "Security Ownership of Certain Beneficial Owners and
Management") which options will be treated in the same manner as options held by
other employees.  In general,  all unvested options held by such persons will be
assumed by Thermo  Electron  and  converted  into  options to acquire  shares of
Thermo  Electron's  common stock on the same terms as are  applicable to all the
other holders of such subsidiary's  options.  In the case of vested options held
by  such  persons  in  subsidiaries  that  are  the  subject  of  proposed  cash
transactions,  the  holders  will be given the  opportunity  to elect  either to
convert the options into vested options for Thermo  Electron's  common stock, as
described  below,  or to receive cash at the applicable cash  transaction  price
less the applicable  exercise price. In the case of options held by such persons
in  subsidiaries  that are the subject of the proposed  stock  transaction,  the
options will be converted into options for Thermo  Electron's  common stock,  as
described below.

         Vested and unvested  options that are being assumed by Thermo  Electron
in the proposed cash  transactions  referenced above generally will be converted
as follows:  The number of shares of Thermo  Electron's  common stock underlying
each assumed  option will equal the number of shares of subsidiary  common stock
underlying the option before the transaction, multiplied by the applicable "cash
exchange  ratio"  described  below,  rounded down to the nearest whole number of
shares of Thermo  Electron's  common stock.  The exercise price for each assumed
option will be calculated by dividing the exercise price of the subsidiary stock
option before the transaction by the applicable  "cash exchange ratio" set forth
below,  rounded up to the nearest  whole cent.  The  applicable  "cash  exchange
ratio" for each  transaction  is a fraction,  the numerator of which is the cash
price listed in the Chart and the  denominator  of which is the closing price of
Thermo  Electron's  common stock on the day preceding the effective  date of the
transaction.

         Vested and unvested  options that are being assumed by Thermo  Electron
in the proposed stock  transaction  referenced above will generally be converted
as follows:  The number of shares of Thermo  Electron's  common stock underlying
each assumed  option will equal the number of shares of subsidiary  common stock
underlying  the option  before the  transaction,  multiplied  by the  applicable
exchange ratio set forth in the Chart,  rounded down to the nearest whole number
of shares of Thermo Electron's common stock. The exercise price for each assumed
option will be calculated by dividing the exercise price of the subsidiary stock
option before the transaction by the applicable  exchange ratio set forth in the
Chart, rounded up to the nearest whole cent.

         In addition to the ownership  information that appears in the Item 12 -
"Security  Ownership of Certain  Beneficial  Owners and Management"  table,  Mr.
Melas-Kyriazi holds shares of, or options to purchase shares of, common stock of
the  subsidiaries  listed above under "Proposed  Transactions"  as follows.  Mr.
Melas-Kyriazi  owns 19,028  shares in the common stock of the  Corporation.  Mr.
Melas-Kyriazi owns options to purchase 25,000, 25,000, 40,000 and 163,687 shares
of  Metrika  Systems   Corporation,   ThermoQuest   Corporation,   Thermo  Optek
Corporation and the Corporation, respectively.

         Additionally,   certain   directors   participate   in   the   deferred
compensation  plans  of  the  various  subsidiaries.  See  Item  12 -  "Security
Ownership of Certain Beneficial Owners and Management." On the effective date of
each of the  proposed  cash  transactions  listed  above,  each of the  affected
subsidiaries'  deferred  compensation

<PAGE>

plans will terminate and the  participants  will receive cash in an amount equal
to the balance of such participant's  stock units credited to his or her account
under the respective  deferred  compensation plan,  multiplied by the cash price
listed in the Chart.  On the effective  date of the proposed  stock  transaction
listed above, the  Corporation's  deferred  compensation plan will be assumed by
Thermo  Electron,  and the stock units  credited to each  participant's  account
under the  deferred  compensation  plan will be  converted  into stock units for
Thermo Electron's common stock at the exchange ratio set forth in the Chart.



<PAGE>


STOCK HOLDING ASSISTANCE PLANS

         The human resources  committee of the Corporation's  board of directors
(the  "Committee")  established a stock  holding  policy that requires its chief
executive  officer  to  acquire  and hold a  minimum  number of shares of Common
Stock.  In order to assist the chief  executive  officer in  complying  with the
policy,  the Committee also adopted a stock holding  assistance plan under which
the Corporation may make interest-free  loans to the chief executive officer, to
enable him to purchase Common Stock in the open market.  Loans will be repayable
upon the  earlier  of demand or the tenth  anniversary  of the date of the loan,
unless otherwise determined by the Committee.  No such loans were outstanding in
1999.

         Each of the Corporation's publicly-traded,  majority-owned subsidiaries
have adopted similar stock holding policies and stock holding  assistance plans,
which were  applicable to their  executive  officers prior to their amendment to
make them applicable only to their chief executive  officers.  Certain executive
officers  of the  Corporation  are also the chief  executive  officers  of these
subsidiaries  and are  required to comply with the  subsidiary's  stock  holding
policies.  Mr. Earl R. Lewis,  the  Corporation's  president and chief executive
officer,  was also the chief executive  officer of Thermo Optek until January 4,
1998. Dr. Richard W. K. Chapman, a senior vice president of the Corporation,  is
also the chief executive officer of ThermoQuest and was chairman of the board of
Thermo  BioAnalysis  until June 26, 1997. Mr. Barry S. Howe, a vice president of
the  Corporation,  was also the chief  executive  officer of Thermo  BioAnalysis
until  March  11,  1998  and  is  currently  the  chief  executive   officer  of
ThermoSpectra.  In 1996,  Mr. Lewis  received a loan in the principal  amount of
$194,030 under the Thermo Optek stock holding assistance plan to purchase 15,000
shares of the common stock of Thermo  Optek,  of which amount  $155,224 is still
outstanding.  Dr.  Chapman  received  loans in 1996 in the principal  amounts of
$210,654 and $131,176,  under the stock holding  assistance plans of ThermoQuest
and Thermo  BioAnalysis,  respectively,  to purchase 15,000 shares of the common
stock  of  ThermoQuest   and  10,000  shares  of  the  common  stock  of  Thermo
BioAnalysis,  of which amounts  $168,523 and $131,176,  respectively,  are still
outstanding.  In 1996,  Mr.  Howe  received  loans in the  principal  amount  of
$164,376  under the stock  holding  assistance  plan of  Thermo  BioAnalysis  to
purchase 12,000 shares of Thermo BioAnalysis,  of which amount $131,500 is still
outstanding.  In 1998,  Mr.  Howe  received  a loan in the  principal  amount of
$141,992 to purchase 15,000 shares of ThermoSpectra, of which the entire is paid
in full.  Each of these  loans is  repayable  upon the  earlier of demand or the
tenth  anniversary of the date of the loan,  unless otherwise  determined by the
human resources committee of the board of directors of the applicable company.

                                   SIGNATURES

Pursuant to the  requirements of Section 13 or 15(d) of the Securities  Exchange
Act of 1934,  the Registrant has duly caused this Amendment No. 1 on Form 10-K/A
to be signed by the undersigned, duly authorized.



                                              THERMO INSTRUMENT SYSTEMS INC.

                                              By:  /s/  Sandra L. Lambert
                                                 ---------------------------
                                                  Sandra L. Lambert
                                                  Secretary