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 1-11757

                            THERMO OPTEK CORPORATION
            (Exact name of Registrant as specified in its character)

Delaware                                                              04-3283973
(State or other jurisdiction of                                 (I.R.S. Employer
incorporation or organization)                               Identification No.)

8 E. Forge Parkway
Franklin, Massachusetts                                                    02038
(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, $.01 par value                             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 $33,654,000.

As of January 28, 2000, the  Registrant  had  51,055,798  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 & 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 Stock and of
the common stock of its parent company,  Thermo Instrument Systems Inc. ("Thermo
Instrument"),  a manufacturer  of  measurement  and detection  instruments,  and
Thermo  Instrument's  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.

--------------------------------------------------------------------------------
Barry S. Howe           Mr. Howe,  44, has been a director,  president and chief
                        executive officer of the Corporation since October 1999.
                        Mr. Howe has been a vice president of Thermo  Instrument
                        since 1994 and has been  president  and chief  executive
                        officer of  ThermoSpectra  Corporation,  a  wholly-owned
                        subsidiary of the  Corporation  that supplies  precision
                        imaging,  inspection,  temperature  control and test and
                        measurement  instruments,   since  March  1998.  He  was
                        president   and  chief   executive   officer  of  Thermo
                        BioAnalysis  Corporation,  a wholly owned  subsidiary of
                        the Corporation from February 1995 to March 1998. Thermo
                        BioAnalysis  Corporation  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.   From  September  1989  to
                        December  1995,  he  served as the  president  of Thermo
                        Separation   Products  Inc.  and  its   predecessor,   a
                        manufacturer   of   chromatography   instruments  and  a
                        subsidiary of  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.
--------------------------------------------------------------------------------
Stephen R. Levy         Mr.  Levy,  59, has been a director  of the  Corporation
                        since November  1995.  Since November 1995, Mr. Levy has
                        been  president of The Apogee Group,  Inc., a company he
                        founded  that  provides   consulting  services  in  high
                        technology.  Mr. Levy served as chief executive  officer
                        of BBN Corporation, a high-technology company, from 1976
                        to 1994 and chairman of the board form 1983 to 1995.  He
                        retired from BBN Corporation in 1995.
--------------------------------------------------------------------------------



<PAGE>



--------------------------------------------------------------------------------
Earl R. Lewis           Mr.  Lewis,  56, has been a director of the  Corporation
                        since its  inception in August  1995.  He also served as
                        the  Corporation's  president  from August 1995 to April
                        1997.  He served as the chief  executive  officer of the
                        Corporation  from August 1995 through  January 1998. Mr.
                        Lewis has been president and chief executive  officer of
                        Thermo  Instrument  since March 1997 and  January  1998,
                        respectively,  and was chief operating officer of Thermo
                        Instrument  from January 1996 to January 1998.  Prior to
                        that time,  he was  executive  vice  president of Thermo
                        Instrument  from  January  1996 to March 1997 and senior
                        vice president of Thermo Instrument from January 1994 to
                        January  1996.  Mr.  Lewis  has  been  chief   operating
                        officer,  measurement and detection,  of Thermo Electron
                        since September 1998.  Prior to his appointment as chief
                        operating officer,  measurement and detection, Mr. Lewis
                        served as senior vice president of Thermo  Electron from
                        June 1998 to September  1998 and a vice  president  from
                        June 1996 to June 1998.  Mr. Lewis is a director of FLIR
                        Systems    Inc.,     Metrika    Systems     Corporation,
                        Spectra-Physics   Lasers,  Inc.,  SpectRx  Inc.,  Thermo
                        Instrument and ThermoQuest Corporation.
--------------------------------------------------------------------------------
Robert A. McCabe        Mr. McCabe,  65, has been a director of the  Corporation
                        since  March  1996.  He has been the  chairman  of Pilot
                        Capital   Corporation,   which  is  engaged  in  private
                        investments, since 1998. Mr. McCabe was the president of
                        Pilot Capital  Corporation from 1987 to 1998. Mr. McCabe
                        is also a director  of  Atlantic  Bank & Trust  Company,
                        Borg-Warner  Security   Corporation,   Church  &  Dwight
                        Company and Thermo Electron.
--------------------------------------------------------------------------------

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  present  members  of  the  audit
committee are Mr. Levy (Chairman) and Mr. McCabe.  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 present members of the human resources committee are Mr.
Levy and Mr.  McCabe  (Chairman).  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 five times, the audit committee met twice
and the human  resources  committee  met five 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.

COMPENSATION OF DIRECTORS

         CASH COMPENSATION

         Outside  directors  receive an annual  retainer  of $4,000 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 and Mr. Howe are both employees of Thermo  Electron or its
subsidiaries and do not receive any cash  compensation  from the Corporation for
their services as directors.  Directors are also  reimbursed  for  out-of-pocket
expenses incurred in attending such meetings.

         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 of control or proposed change of
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

<PAGE>

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 75,000 shares of Common Stock has been reserved for issuance
under the Deferred  Compensation  Plan and deferred units equal to approximately
4,022 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 are automatically granted options to
purchase  1,000  shares of Common  Stock  annually,  commencing  with the annual
meeting of the  Stockholders to be held in 2000. The annual grant is made at the
close of business on the date of each Annual Meeting of the  Stockholders of the
Corporation to each outside  director then holding  office.  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  90,000  shares of Common Stock had
been granted to directors  and were  outstanding  under the  Directors  Plan, no
options to purchase  Common Stock had lapsed or been  exercised,  and options to
purchase 135,000 shares of Common Stock were available 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, its former 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.

<PAGE>

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 -
"Certain Relationships and Related Transactions." 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)
-------------------         ------   ------     ------      ---------       ------------       ----------------
Barry S. Howe (4)           1999      $88,594   $175,000    $50,064 (THI)      900 (TMO)          $31,750 (5)
  President and Chief                                                       25,000 (THI)
  Executive Officer
-------------------------------------------------------------------------------------------------------------------------
Frederic T. Walder (6)      1999     $143,006   $120,000    $26,408 (TOC)   50,000 (TOC)               $0
  Senior Vice President     1998     $115,000    $76,000         --         10,000 (TOC)           $5,000
-------------------------------------------------------------------------------------------------------------------------
Gerard Abraham (7)          1999     $148,000    $50,000    $15,845 (TOC)   40,000 (TOC)           $7,170
  Vice President            1998     $144,500    $36,000         --          5,000 (TOC)           $7,200
                                                                             2,200 (TMO)
-------------------------------------------------------------------------------------------------------------------------
G. Roger Herd (8)           1999     $124,667    $80,000    $21,126 (TOC)   40,000 (TOC)           $5,625
  Vice President                                                             2,700 (TMO)
                                                                            25,000 (THI)
                            1998     $132,500    $60,000         --          5,000 (TOC)           $5,842
                                                                             2,600 (TMO)
-------------------------------------------------------------------------------------------------------------------------
Roland Schultner (9)        1999     $152,816    $30,252         --         30,000 (TOC)          $12,287 (10)
  Vice President
-------------------------------------------------------------------------------------------------------------------------
Robert J. Rosenthal (11)    1999      $37,019         $0         --            -- --              $19,874 (12)
  Former President and      1998     $175,000   $110,000                   240,000 (TOC)          $17,927 (12)
  Chief Executive Officer                                                    7,998 (TMO)
                                                                             7,500 (MKA)
                                                                             7,500 (ONX)
                                                                             4,000 (RGI)
                                                                             2,000 (TDX)
                                                                            24,999 (THI)
                                                                             2,000 (TRIL)
                                                                             1,023 (TKN)
                            1997     $148,500   $135,000         --         10,100 (TMO)          $44,502 (12)
-------------------------------------------------------------------------------------------------------------------------
</TABLE>

(1)      In fiscal 1999,  Messrs.  Abraham,  Herd and Walder were awarded 1,500,
         2,000 and 2,500 shares, respectively, of restricted Common Stock of the
         Corporation with a value of $15,845, $21,126 and $26,408, respectively,
         on the grant date and Mr. Howe was awarded  3,000 shares of  restricted
         common stock of Thermo  Instrument with a value of $50,064 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, Messrs.  Abraham, Herd
         and Walder held 1,500, 2,000 and 2,500 restricted shares, respectively,
         with an aggregate value of $17,063, $22,750 and $28,438,  respectively,
         and Mr. Howe held 3,000  restricted  shares with an aggregate  value of
         $33,375.

(2)      Options  granted  by the  Corporation  are  designated  in the table as
         "TOC." 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  (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),  Thermo

<PAGE>

         Instrument  (designated  in the table as THI),  ThermoTrex  Corporation
         (designated  in the  table  as  TKN)  and  Thermo  Trilogy  Corporation
         (designated in the table as TRIL).

(3)      Represents   the  amount  of   matching   contributions   made  by  the
         individual's   employer   on   behalf  of  named   executive   officers
         participating  in the  Thermo  Electron  401(k)  plan  or  the  Nicolet
         Retirement Savings Plan.

(4)      Mr.  Howe  was  appointed  interim  president  on  March  22,  1999 and
         president and chief executive officer of the Corporation on October 14,
         1999. Prior to his appointment,  Mr. Howe served as president and chief
         executive officer of ThermoSpectra  Corporation, a subsidiary of Thermo
         Instrument. The annual compensation reported for fiscal 1999 represents
         the amount of Mr. Howe's annual compensation (salary and bonus) paid by
         the Corporation as  compensation  in his capacity as the  Corporation's
         president and chief executive officer.  For fiscal 1999,  approximately
         56% of Mr. Howe's salary and all of his bonus earned in all  capacities
         throughout the Thermo Electron organization was paid by the Corporation
         for his  services as chief  executive  officer.  For fiscal  1999,  all
         options  to  purchase   common   stock  of  Thermo   Electron  and  its
         subsidiaries  granted to Mr. Howe in all  capacities  within the Thermo
         Electron   organization   have   been   included   under   "Long   Term
         Compensation."  Prior to fiscal 1999,  Mr. Howe was granted  options to
         purchase  shares of the common stock of Thermo  Electron and certain of
         its  subsidiaries  other than the  Corporation  by Thermo  Electron and
         certain of its  subsidiaries.  These  options are not  reported in this
         table as they were granted as compensation  for service to other Thermo
         Electron  companies  in  capacities  other than in his  capacity as the
         president and chief executive officer of the Corporation.

(5)      In addition to the matching  contribution  referred to in footnote (3),
         such  amount  includes a payment of $25,000  made to Mr. Howe in fiscal
         1999 in connection with his relocation to Franklin, Massachusetts.

(6)      Mr.  Walder was  appointed an officer of the  Corporation  on April 28,
         1998. The salary reported for fiscal 1998 represents  compensation  for
         the entire fiscal year.

(7)      Mr.  Abraham was appointed an officer of the  Corporation on January 4,
         1998. The salary reported for fiscal 1998 represents  compensation  for
         the entire fiscal year.

(8)      Mr.  Herd was  appointed  an officer of the  Corporation  on January 4,
         1998. The salary reported for fiscal 1998 represents  compensation  for
         the entire fiscal year.

(9)      Mr.  Schultner was appointed an officer of the  Corporation  on October
         14, 1999. The salary reported for fiscal 1999  represents  compensation
         for the entire fiscal year.

(10)     Represents the amount of compensation  attributable to the pension plan
         maintained  by Gebruder  Haake GmbH, a wholly owned  subsidiary  of the
         Corporation.

(11)     Dr. Rosenthal was appointed  president of the Corporation in April 1997
         and chief  executive  officer of the  Corporation  in January  1998. He
         resigned as president and chief executive officer on March 19, 1999.

(12)     In addition to the matching  contributions referred to in footnote (3),
         such amounts includes  $7,834,  $12,927 and $458,  respectively,  which
         represents the amount of  compensation  in fiscal 1999,  1998 and 1997,
         respectively,  attributable  to an  interest-free  loan provided to Dr.
         Rosenthal.   (See  Item  13  -  "Certain   Relationships   and  Related
         Transactions - Stock Holding  Assistance Plan"). In addition the amount
         reported for fiscal 1997 includes  $36,919 in expenses  associated with
         Dr.  Rosenthal's  relocation to Franklin,  Massachusetts and the amount
         reported for fiscal 1999 includes  $12,040 in accrued  vacation paid in
         connection with Dr. Rosenthal's resignation.

STOCK OPTIONS GRANTED DURING FISCAL 1999

         The following table sets forth information concerning individual grants
of stock  options  made  during  fiscal  1999 to the  Corporation's  then  chief
executive  officer and the other 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.



<PAGE>



<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%
----                          -----------         ------------      -----        ----              ---          ----
Barry S. Howe                     900 (TMO)            0.03% (3)     $14.81      09/22/04         $3,680         $8,138
                               25,000 (THI)             2.1%         $11.95      09/15/04        $82,540       $182,390
---------------------------------------------------------------------------------------------------------------------------
Fredric T. Walder              25,000 (TOC)             5.2%         $11.45      03/25/04        $79,080       $174,758
                               25,000 (TOC)             5.2%          $9.59      06/29/06        $97,600       $227,455
---------------------------------------------------------------------------------------------------------------------------
Gerard Abraham                 25,000 (TOC)             5.2%         $11.45      03/25/04        $79,080       $174,758
                               15,000 (TOC)             3.1%          $9.59      06/29/06        $58,560       $136,473
---------------------------------------------------------------------------------------------------------------------------
G. Roger Herd                  25,000 (TOC)             5.2%         $11.45      03/25/04        $79,080       $174,758
                               15,000 (TOC)             3.1%          $9.59      06/29/06        $58,560       $136,473
                                2,700 (TMO)             0.1% (3)     $14.81      09/22/04        $11,050        $24,413
                               25,000 (THI)             2.1%         $11.95      09/15/04        $82,540       $182,390
---------------------------------------------------------------------------------------------------------------------------
Roland Schultner               15,000 (TOC)             3.1%         $11.45      03/25/04        $47,450       $104,854
                               15,000 (TOC)             3.1%          $9.59      06/29/06        $58,560       $136,473
---------------------------------------------------------------------------------------------------------------------------
Robert J. Rosenthal                  --                  --           --           --              --             --
---------------------------------------------------------------------------------------------------------------------------
</TABLE>

(1)      All  of  the  options  granted  during  fiscal  1999  were  immediately
         exercisable  as of the  end  of  fiscal  1999.  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 another 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 the
         optionee  continues  to be employed  by the  company or another  Thermo
         Electron company. The granting company may permit the holder 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   Summary
         Compensation  Table  above for the company  abbreviations  used in this
         table.

(2)      The amounts shown in 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)      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
         Thermo Electron and its subsidiaries.

STOCK OPTIONS EXERCISED DURING FISCAL 1999 AND FISCAL YEAR-END 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  Corporation's  chief  executive  officer and the other 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 (2)         Exercise     Realized (1)    Unexercisable) (2)    Unexercisable)
        ----               -----------         --------     ------------    ------------------   --------------
Barry S. Howe (3)             (THI)                 --               --         25,000  /0--              $0  /0--
                              (TMO)                                                900  /0              $171  /--
----------------------------------------------------------------------------------------------------------------------------
Gerard Abraham                (TOC)                 --               --         57,000  /0           $55,590  /--
                              (TMO)                 --               --          2,200  /0                $0  /--
--------------------------------------------------------------------------------------------------------------------------
Fredric T. Walder             (TOC)                 --               --         71,750  /0           $72,134  /--
                              (THI)              1,125          $10,828          9,375  /0                $0  /--
                              (TMQ)                 --               --          5,000  /0                $0  /--
                              (THS)              1,000           $6,000             -- --                 -- --
----------------------------------------------------------------------------------------------------------------------------
G. Roger Herd                 (TOC)                 --               --         64,500  /0           $62,378  /--
                              (TMO)              5,062          $30,170         14,662  /0           $12,226  /--
                              (THI)                 --               --         59,375  /0                $0  /--
                              (TMQ)                 --               --          5,000  /0                $0  /--
----------------------------------------------------------------------------------------------------------------------------
Roland Schultner              (TOC)                 --               --         34,000  /0           $40,275  /--
                              (THI)                 --               --          2,750  /0                $0  /--
----------------------------------------------------------------------------------------------------------------------------
Robert J. Rosenthal           (TOC)                 --               --             --  /--               --  /--
                              (TBA)              1,200          $11,250             --  /--               --  /--
                              (THI)             36,269         $119,597              -- /--               $0  /--
----------------------------------------------------------------------------------------------------------------------------
</TABLE>

(1)      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.

(2)      All of the options reported  outstanding at the end of fiscal 1999 were
         immediately  exercisable as of the end of fiscal 1999.  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 serve as a director of, such
         company or another Thermo Electron  company.  The granting  company may
         exercise its repurchase  rights within six months after the termination
         of the optionee's employment or 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. For companies that
         are not publicly-traded, the repurchase rights generally lapse in their
         entirety on the ninth  anniversary of the grant date.  Certain  options
         have three-year terms and the repurchase rights lapse in their entirety
         on the second  anniversary of the grant date. The granting  company may
         permit the holder 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  Summary  Compensation  Table above for the company
         abbreviations  used in this table in addition to the following  company
         abbreviations:  Thermo BioAnalysis Corporation (designated in the table
         as TBA), ThermoQuest  Corporation  (designated in the table as TMQ) and
         ThermoSpectra Corporation (designated in the table as THS).

(3)      Mr.  Howe  was  appointed  interim  president  on  March  22,  1999 and
         president and chief executive officer of the Corporation on October 14,
         1999. Prior to his appointment,  Mr. Howe served as president and chief
         executive officer of ThermoSpectra  Corporation, a subsidiary of Thermo
         Instrument. Mr. Howe holds other unexercised options to purchase common
         stock  of  Thermo  Electron  and  its   subsidiaries

<PAGE>

         other than the Corporation, which were granted prior to his appointment
         as president  and chief  executive  officer of the  Corporation.  These
         options are not reported here as they were granted as compensation  for
         service to other Thermo Electron  companies in capacities other than in
         his capacity as chief executive officer of the Corporation.

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 those  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 Mr. Howe. This agreement  provides that in the event Mr. Howe's  employment
is terminated under circumstances described above, Mr. Howe would be entitled to
a lump sum  payment  equal to the sum of (a) one times his  highest  annual base
salary in any 12 month period during the prior  five-year  period,  plus (b) one
times his highest annual bonus in any 12 month period during the prior five-year
period.  In  addition,  Mr. Howe would be provided  benefits for a period of one
year after such termination  substantially equivalent to the benefits package he
would have been otherwise entitled to receive if he was not terminated. Further,
all repurchase  rights of Thermo  Electron and its  subsidiaries  shall lapse in
their  entirety  with  respect  to all  options  that Mr.  Howe  holds in Thermo
Electron and its subsidiaries,  including the Corporation, as of the date of the
change in control.  Finally,  Mr. Howe would be entitled to a cash payment equal
to $15,000 to be used toward outplacement services.

         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
Mr.  Howe would have been  approximately  $280,000.  In the event that  payments
under this  agreement  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"),  Mr. Howe would be entitled to receive a gross-up
payment  equal to the amount of any excise  tax  payable by him with  respect to
such  payment  plus the  amount of all other  additional  taxes  imposed  on him
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.  In
1997, Dr. Rosenthal, the Corporation's then chief executive officer,  received a
loan in the  principal  amount of $229,616  under this plan,  of which  $158,577
remained  outstanding as of January 1, 2000. 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.   See  Item  13  -  "Certain
Relationships and Related Transactions - Stock Holding Assistance Plan."

<PAGE>


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  Instrument,  the  Corporation's
parent company,  and of Thermo Electron,  Thermo Instrument's parent company, as
of  January  31,  2000,  with  respect  to (i) each  director,  (ii) each  named
executive  officer 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 Optek       Thermo Instrument     Thermo Electron
             Name (1)                   Corporation (2)     Systems Inc. (3)      Corporation (4)
             --------                   ---------------     ----------------      ---------------

Thermo Electron Corporation (5)          49,198,752                   N/A                   N/A
Gerard Abraham......................         58,500                     0                 2,200
G. Roger Herd.......................         71,120               137,147                49,877
Barry S. Howe.......................         25,000               303,290                71,655
Stephen R. Levy.....................         50,232                     0                     0
Earl R. Lewis.......................        252,000               436,499               215,477
Robert A. McCabe....................         70,961                46,846                66,326
Robert  J. Rosenthal................              0                   688                   350
Roland Schultner....................         35,300                 2,750                     0
Fredric T. Walder...................         75,500                11,891                 1,151
All directors and current executive
    officers as a group (10 persons)        712,613             1,121,826               865,568
</TABLE>


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

(2)      Shares of Common Stock beneficially owned by Mr. Abraham, Mr. Herd, Mr.
         Howe, Mr. Levy, Mr. Lewis, Mr. McCabe,  Mr.  Schultner,  Mr. Walder and
         all directors and current executive officers as a group include 57,000,
         64,500,  15,000,  45,000,  225,000,  45,000, 34,000, 71,750 and 597,250
         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. Levy, Mr. McCabe and
         all directors and current executive  officers as a group include 3,232,
         790 and 4,022 shares, respectively,  allocated through January 1, 2000,
         to  their  respective  accounts  maintained  pursuant  to the  Deferred
         Compensation  Plan.  Shares of Common Stock  beneficially  owned by Mr.
         McCabe  include 7,171 shares that he had the right to acquire within 60
         days of January 31, 2000,  through the conversion of the 5% convertible
         debentures  of  the  Corporation  due  2000.  Shares  of  Common  Stock
         beneficially  owned by Mr.  Lewis  include  2,500  shares  owned by his
         spouse.  Shares of the Common Stock  beneficially  owned by Mr.  McCabe
         include  5,000  shares  held by a trust of which he and  members of his
         family  are   trustees.   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 1.39% of the Common Stock  outstanding as of
         such date.

(3)      Shares of the common stock of Thermo Instrument  beneficially  owned by
         Mr. Herd, Mr. Howe, Mr. Lewis, Mr. McCabe,  Mr.  Schultner,  Mr. Walder
         and all  directors  and current  executive  officers as a group include
         59,375,  273,156,  409,081,  7,925,  2,750,  9,375 and 952,349  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 of the common stock of Thermo Instrument  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. Howe include 374 shares
         held by him as custodian for his

<PAGE>

         minor children.  Shares  beneficially  owned by Mr. Lewis include 2,987
         shares  held by his spouse.  Shares  beneficially  owned by Mr.  Walder
         include 280 shares held by his spouse.  No director or named  executive
         officer  beneficially  owned more than 1% of the common stock of Thermo
         Instrument  outstanding  as of January  31,  2000;  all  directors  and
         current executive  officers as a group owned less than 1% of the common
         stock of Thermo Instrument outstanding as of such date.

(4)      Shares of the common stock of Thermo Electron beneficially owned by Mr.
         Abraham,  Mr. Herd, Mr. Howe,  Mr. Lewis,  Mr. McCabe and all directors
         and  current  executive  officers  as a group  include  2,200,  14,662,
         64,141, 212,278,  12,442, and 705,084 shares,  respectively,  that such
         person or group has the right to acquire  within 60 days of January 31,
         2000, through the exercise of stock options. Shares of the common stock
         of Thermo  Electron  beneficially  owned by all  directors  and current
         executive  officers as a group include 1,071 shares  allocated to their
         respective  accounts  maintained  pursuant  to the ESOP.  Shares of the
         common stock of Thermo  Electron  beneficially  owned by Mr. McCabe and
         all directors and current executive  officers as a group include 34,725
         shares  allocated  to Mr.  McCabe's  account  under  Thermo  Electron's
         deferred compensation plan for directors.  Shares beneficially owned by
         Mr.  Howe  include 200 shares  held by him as  custodian  for his minor
         children.  Shares  beneficially  owned by Mr. Walder include 258 shares
         held by his spouse. 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 the common stock of Thermo
         Electron outstanding as of such date.

(5)      As  of  January  31,  2000,  Thermo  Electron,  primarily  through  its
         majority-owned subsidiary Thermo Instrument,  beneficially owned 96.31%
         of  the   outstanding   Common  Stock.   Shares  of  the  Common  Stock
         beneficially  owned by Thermo  Electron  include  606,328  shares  that
         Thermo  Electron has the right to acquire within 60 days of January 31,
         2000  through the  conversion  of  $8,455,000  principal  amount of the
         Corporation's  5% convertible  debentures due 2000.  Thermo  Electron's
         address is 81 Wyman Street, Waltham,  Massachusetts  02454-9046.  As of
         January 31,  2000,  Thermo  Electron  had the power to elect all of the
         members of the Corporation's board of directors.

SECTION 16(A) BENEFICIAL OWNERSHIP REPORTING COMPLIANCE

         Section 16(a) of the  Securities  Exchange Act of 1934, as amended (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
Instrument and its parent company,  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 11  transactions  associated
with the  cancellation,  grant and lapse 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 certain
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  1999.  The annual fee will  remain at 0.8% 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
$3,631,000 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. During 1999, the Corporation was
billed an  additional  $34,000 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  member  of the  Thermo  Group  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

<PAGE>

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 which 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  outstanding  common  stock of Thermo
Instrument and Thermo  Instrument  owns at least 80% of the  outstanding  Common
Stock of the Corporation.  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
Instrument's  equity  ownership of the  Corporation  were to drop below 80%, the
Company would file its own tax returns.  In 1999, the  Corporation  was assessed
$11,350,000 by Thermo Electron Corporate under the Tax Allocation Agreement.  As
of January 1, 2000, the Corporation owed Thermo Electron  $9,450,000 for amounts
due under the Tax Allocation Agreement.

         The Corporation leases office and manufacturing  space to ThermoSpectra
Corporation  ("ThermoSpectra"),  a subsidiary of Thermo Instrument,  and Nicolet
Biomedical  Inc.  ("Nicolet  Biomedical"),  a wholly owned  subsidiary of Thermo
Electron,   pursuant  to  an  arrangement   whereby  the   Corporation   charges
ThermoSpectra  and Nicolet  Biomedical  their  allocated  share of the occupancy
expenses of the Corporation's  principal Wisconsin facility,  based on the space
ThermoSpectra and Nicolet Biomedical utilize. The Corporation recorded operating
income of $947,000 in 1999 from these  affiliates.  These  leases are  effective
until  December 31, 2001,  but may be  terminated by  ThermoSpectra  and Nicolet
Biomedical  upon 90  days'  and 30  days'  prior  notice,  respectively,  to the
Corporation.

         The  Corporation  purchases and sells products  and/or  services in the
ordinary course of business with other subsidiaries of Thermo Electron. In 1999,
the Corporation sold a total of $9,287,000 of products and/or services to Thermo
Electron  Subsidiaries  and purchased a total of  $1,531,000 of products  and/or
services from such companies.

         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
$23,254,000  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  $10,000,000  based
on an  exchange  rate of  $1.6171/GBP  1.00,  and a  negative  cash  balance  of
approximately $12,900,000 based on the same exchange rate. 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%.

         The Corporation, along with other European-based subsidiaries of Thermo
Electron,  participates in a cash management arrangement in the Netherlands with
a  wholly  owned  subsidiary  of  Thermo  Electron.   Under  this   arrangement,
participants'  balances are pooled for interest calculation  purposes.  Interest
under this arrangement is based on Euro market rates. The Corporation has access
to  a  $2,963,000  line  of  credit  under  this  arrangement.  Thermo  Electron
guarantees all of the obligations of each  participant in this  arrangement.  At
year-end 1999, the Corporation had $297,000 invested under this arrangement, and
had borrowed $973,000 under this arrangement.

         At year-end 1998, $8,216,000 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 agree ment 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

<PAGE>

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  $49,305,000  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  $8,733,000  line of
credit under this arrangement, of which the Corporation had borrowed $102,000 at
year-end  1999. The  Corporation  also had a positive cash balance of $4,500,000
under this  arrangement  at year-end 1999.  Interest  under this  arrangement is
calculated  based on Euro market rates and was 3.95% on the negative  balance at
year-end 1999.

         As of January  1, 2000  Thermo  Electron  owned  $8,455,0000  principal
amount of the Corporation's 5% subordinated convertible debentures due 2000. The
debentures are convertible into shares of Common Stock at $13.9446 per share.

         As of January 1, 2000, Thermo Electron and its other  subsidiaries owed
the  Corporation an aggregate of $1,784,000  for amounts due in connection  with
the sales of products,  services, and miscellaneous items. This amount is net of
amounts owed by the  Corporation to Thermo  Electron and its other  subsidiaries
under the  Services  Agreement,  for  related  administrative  charges,  and for
products,  services,  and  miscellaneous  items.  The largest amount of such net
indebtedness  owed  by  Thermo  Electron  and  its  other  subsidiaries  to  the
Corporation  since  January 2, 1999 was  $1,896,000.  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.  In furtherance of this plan, Thermo
Instrument  expects  to  cause  the  Corporation  to merge  with a  wholly-owned
subsidiary of Thermo  Instrument and Thermo  Electron in a  "short-form"  merger
under  Delaware law on May 11, 2000. In the merger,  each  outstanding  share of
Common Stock of the  Corporation  (other than shares  owned by the  wholly-owned
subsidiary,  the  Corporation  and  stockholders of the Corporation who properly
exercise  appraisal rights under Delaware law) will be  automatically  converted
into the right to receive $15.00 in cash, without interest,  and the Corporation
will become a private company.

         Executive  officers and directors of the Corporation who hold shares of
Common Stock in the  Corporation  will also  receive  $15.00 per share of Common
Stock on the same terms as all the other  stockholders.  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  (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.  In the case of vested  options held by such persons,  the holders
will be given the opportunity to elect either to convert the options into vested
options  for  Thermo  Electron  common  stock or to  receive  cash at the $15.00
transaction  price less the  applicable  exercise  price.  Vested  and  unvested
options that are assumed by Thermo  Electron  will be converted as follows:  The
number of shares of Thermo Electron common stock  underlying each assumed option
will equal the number of shares of Common Stock underlying the option before the
transaction,  multiplied by the "cash exchange ratio" described  below,  rounded
down to the nearest whole number of shares of Thermo Electron common stock.  The
exercise  price for each  assumed  option will be  calculated  by  dividing  the
exercise price of the option before the transaction by the "cash exchange ratio"
set forth below, rounded up to the nearest whole cent. The "cash exchange ratio"
is a fraction,  the numerator of which is $15.00 and the denominator of which is
the closing  price of Thermo  Electron  common  stock on the day  preceding  the
effective date of the transaction.

         In addition to the ownership  information that appears in the Item 12 -
"Security  Ownership of Certain  Beneficial  Owners and Management"  table,  Mr.
Melas-Kyriazi  (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 such table) holds options to purchase
40,000 shares of Common Stock.

<PAGE>

         Additionally,   certain   directors   participate   in   the   Deferred
Compensation  Plan.  See Item 12 -  "Security  Ownership  of Certain  Beneficial
Owners and Management." On the effective date of the proposed  transaction,  the
Deferred Compensation Plan will terminate and the participants will receive cash
in an amount equal to the balance of such participant's  stock units credited to
his account under the Deferred Compensation Plan, multiplied by $15.00.

STOCK HOLDING ASSISTANCE PLAN

         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.  In 1997, Dr. Rosenthal,
the Corporation's then chief operating officer, received a loan in the principal
amount of $229,616 under this plan, of which $158,577 remained outstanding as of
January 1, 2000. The loans are repayable upon the earlier of demand or the tenth
anniversary  of the  date  of  the  loan,  unless  otherwise  determined  by the
Committee.

                                   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 OPTEK CORPORATION


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