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

                                                FORM 10-K

(mark one)
[ X ] Annual Report Pursuant to Section 13 or 15(d) of the Securities
      Exchange Act of 1934 for the fiscal year ended January 1, 2000.

[   ] 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 charter)

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

8E 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:

       Title of each class         Name of each exchange 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 (or for such shorter period that the Registrant was
required to file such reports), and (2) has been subject to the filing
requirements for at least the past 90 days. Yes [ 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 year ended
January 1, 2000, are incorporated by reference into Parts I and II.

The information required by Part III of Form 10-K will be filed as part of an
amendment of this Form 10-K no later than 120 days after January 1, 2000, and
such information is incorporated by reference from such filing.

<PAGE>


                                 PART I

Item 1.  Business

(a)   General Development of Business

      Thermo Optek Corporation (the Company or the Registrant) is a worldwide
leader in spectroscopy instrumentation for molecular and elemental analysis
based upon energy and light measurements, as well as systems for materials
science, including surface analysis, characterization, preparation, and
physical-properties analysis. Thermo Optek provides industry, government, and
academia with complete solutions to specific analytical problems, moving
sophisticated analytical technology outside the laboratory. The Company's
instruments are used in virtually every industry for research and development,
manufacturing, and quality control. The businesses of the Company operate in two
segments: Spectroscopy (molecular and elemental analysis) and Materials Science
(surface analysis, characterization, and preparation and physical-properties
analysis).

      An element of the Company's strategy is to acquire products and
technologies that complement those of existing Thermo Optek companies. In August
1998, the Company acquired Gebruder Haake GmbH (Haake) from Thermo Instrument.
This business was originally part of the Scientific Instruments Division of
Fisons plc (Fisons), a wholly owned subsidiary of Rhone-Pulenc Rorer, Inc. In
addition to Haake, Thermo Optek has acquired three other Fisons companies from
Thermo Instrument - ARL Applied Research Laboratories (ARL) and VG Elemental, in
November 1996 and VG Systems in July 1997. Because Thermo Optek, Haake, ARL, VG
Elemental, and VG Systems were deemed for accounting purposes to be under
control of Thermo Instrument, their common majority owner, the transactions have
been accounted for in a manner similar to a pooling of interests. This means
that the effective date for all four acquisitions is March 29, 1996 - the date
that the businesses were acquired by Thermo Instrument.

      Haake is a supplier of viscometry and rheometry systems used by a wide
variety of manufacturers to measure the physical properties of liquid
substances. ARL is a manufacturer of Arc/Spark spectrometers used to analyze
solids, such as metals, and X-ray fluorescence instruments, used to analyze
nonmetallic solids, such as ceramics. VG Elemental is a manufacturer of
inductively coupled plasma (ICP) and mass spectroscopy instruments used to
analyze elemental liquids, particularly in high-sensitivity applications, such
as the evaluation of nutrition content of baby formulas. VG Systems manufactures
instrumentation and equipment for material and surface science analysis.

      On December 15, 1997, the Company distributed 100% of Thermo Vision's
outstanding capital stock in the form of a dividend to the Company's
shareholders. Following the distribution, Thermo Vision, which is in the
photonics business, was a publicly traded, majority-owned subsidiary of Thermo
Instrument Systems Inc. In January 2000, the shareholders of Thermo Vision voted
to merge Thermo Vision into Thermo Instrument for cash.

      As of January 1, 2000, Thermo Instrument owned 47,564,689 shares of the
Company's common stock, representing 93% of such stock outstanding. Thermo
Instrument is an 88%-owned subsidiary of Thermo Electron Corporation. As of
January 1, 2000, Thermo Electron owned 1,028,860 shares of the Company's common
stock, representing 2% of such stock outstanding. Thermo Instrument and Thermo
Electron develop, manufacture, and sell measurement and detection instruments
used in virtually every industry to monitor, collect, and analyze data that
provide knowledge for the user. For example, Thermo Instrument's and Thermo
Electron's powerful analysis technologies help researchers sift through data to
unlock the mysteries of DNA or develop new drugs; allow manufacturers to
fabricate ever-smaller components required to carry greater amounts of
information, faster; or monitor and control industrial processes on-line to
ensure that critical quality standards are met efficiently.

      On January 31, 2000, the Company announced that Thermo Instrument will
acquire the publicly held shares of the Company's common stock for $15.00 per
share in cash, as outlined in Note 14 to Consolidated Financial Statements in
the Registrant's 1999* Annual Report to Shareholders, which statements are
incorporated herein by reference.  This action is part of a major reorganization
plan under which Thermo Electron will spin in, spin off, and sell various
businesses to focus solely on its core measurement and detection instrument
business.
--------------------
* References to 1999, 1998, and 1997 herein are for the fiscal years ended
  January 1, 2000, January 2, 1999, and January 3, 1998, respectively.

                                       2
<PAGE>
Forward-looking Statements

      Forward-looking statements, within the meaning of Section 21E of the
Securities Exchange Act of 1934, are made throughout this Annual Report on Form
10-K. For this purpose, any statements contained herein that are not statements
of historical fact may be deemed to be forward-looking statements. Without
limiting the foregoing, the words "believes," "anticipates," "plans," "expects,"
"seeks," "estimates," and similar expressions are intended to identify
forward-looking statements. There are a number of important factors that could
cause the results of the Company to differ materially from those indicated by
such forward-looking statements, including those detailed under the heading
"Forward-looking Statements" in the Registrant's 1999 Annual Report to
Shareholders, which statements are incorporated herein by reference.

(b)   Financial Information About Segments

      Financial information concerning the Company's segments is summarized in
Note 11 to Consolidated Financial Statements in the Registrant's 1999 Annual
Report to Shareholders, which information is incorporated herein by reference.

(c)   Description of Business

      (i)  Principal Products and Services

      Almost every element in the periodic table, and nearly all molecules,
provide a unique response when exposed to energy (usually light). The Company's
light-based instruments "look" at these distinctive signatures to determine the
elemental and molecular composition of solids, liquids, and gases. Because light
is nondestructive, the Company's technologies do not destroy the sample being
tested. The Company's instruments can be found in crime laboratories throughout
the world. They are also ideally suited for use in manufacturing, both on and
off the production line.

      The Company's lines of business include spectroscopy instruments for
molecular and elemental analysis, and systems for materials science. The
Company's goal is to design instruments that both analyze substances and
synthesize information. Instead of providing raw data that must be interpreted
by an expert user, the Company integrates information about the application with
a database in its instruments to provide the user with a specific answer
relevant to his or her task. For example, the airline industry uses the
Company's Fourier transform infrared (FT-IR) instruments to analyze jet engine
lubricants to determine when the oil needs to be changed, and uses the Company's
Arc/Spark products to identify and quantify metals present in the airplane's
engine oil. The Company's instruments use this information to pinpoint, for
airplane maintenance workers, when specific engine components need to be
serviced or replaced. In another example, automobile recyclers use the Company's
Arc/Spark instruments to sort metal components of automobiles. In addition, they
use the Company's FT-IR instruments to classify plastics which, to be
effectively recycled, cannot be mixed. The Company's instruments instantly
identify each of the plastics and indicate to plant workers how to sort the
components, without the necessity of interpreting complex data. Similarly,
commercial recyclers can use these instruments to assist in the sorting of
plastics collected through curbside recycling programs.

      The applications for the Company's products continue to grow as the
Company continues to develop increasingly sophisticated instruments that have
enormous analytical power, but are easy to use by operators with varying levels
of education and technical expertise. Examples of some of the uses for the
Company's products are as follows:

      Spectroscopy Products. Pharmaceutical and chemical manufacturers use the
Company's FT-IR and UV/Vis instruments to assess the quality of active
ingredients during the production process. They use FT-Raman instruments to
"look" through the plastic or glass container to ensure that the contents match
the label on the outside. Semiconductor manufacturers use FT-IR instruments in
quality control, and to monitor the air in production labs to ensure the safety
of their workers.

                                       3
<PAGE>
      The beverage industry uses the Company's UV/Vis instruments to ensure that
fruit juice concentrate formulations are blended consistently to specification,
and ICP instruments to validate the vitamin and mineral content for nutrition
labels.

      The Company's portable UV/Vis spectrophotometers are available in many
home decorating stores, designed to take the frustration and guesswork out of
paint color matching. Customers can bring paint or fabric samples to the paint
store or can bring home a hand-held device, take a reading from a wall, drape,
rug, or whatever needs to be matched, and bring it back to the store where the
device is plugged into a computer. The dealer uses the formula from the samples
to create a color prescription and a paint-dispensing system automatically mixes
a matched can of paint.

      The Company's ICP and atomic absorption spectroscopy instruments are also
used by municipalities in environmental monitoring to ensure the quality of the
air we breathe and the water we drink.

      Police departments and forensic labs around the world use the Company's
UV/Vis instruments to identify the type and country-of-origin of illicit
substances and to analyze crime scene evidence.

      Materials Science Products. Semiconductor manufacturers rely on the
Company's Auger and ESCA instruments to help them in building the next
generation of processors, analyzing the surface properties of chips in R&D, and
in failure analysis. The Company's V-100 and V-150 molecular beam epitaxy
products are used in the high volume production of devices for
telecommunications equipment, such as mobile phones, high-speed networks, and
digital switches. These instruments are used to grow and measure the thin films,
with the precision of a single atomic layer, that are the heart of these
devices. The Company also produces diffraction gratings used for routing light
through fiber optic cable.

      The food and beverage industries are significant customers for the
Company's instruments for physical-properties analysis. For instance, consumers
can count on the famous smooth body of German beer to remain the same glass
after glass because many German beer manufacturers use Thermo Optek's
high-precision viscometers to maintain the quality and consistency of their
products. The Company's rheometers are key instruments when it comes to
controlling the texture of foods to ensure consumer satisfaction as well as
shelf life stability, particularly in emulsions such as mayonnaise or whipped
cream.

      The Company's strategy is to continue to develop products and
technologies, to acquire product lines and technologies through acquisitions,
and to provide its customers with quality support services and applications
expertise.

Sales and Marketing

      The Company markets its instruments internally through its own worldwide
sales force and through a network of dealers and distributors. In addition, the
Company sells certain components and instruments pursuant to original equipment
manufacturer arrangements under which third parties purchase and resell the
Company's products. The Company's sales force is supported throughout the world
by a customer support group which provides training, instrument servicing, and
parts replacement.

      (ii) and (xi) New Products; Research and Development

      The Company maintains active programs for the development of new
technologies and the enhancement of existing products. Research and development
expenses for the Company were $27.8 million in 1999, $25.0 million in 1998, and
$30.9 million in 1997.

                                       4
<PAGE>
      (iii) Raw Materials

      Raw materials, components, and supplies purchased by the Company are
either available from a number of different suppliers or from alternative
sources that could be developed without a material adverse effect on the
Company. To date, the Company has experienced no material difficulties in
obtaining these items.

      (iv)  Patents, Licenses, and Trademarks

      The Company's policy is to protect its intellectual property rights,
including applying for and obtaining patents when appropriate. The Company holds
patents relating to its technologies expiring at various dates, with additional
patents pending. The Company also enters into licensing agreements with other
companies pursuant to which it has obtained rights to specific patents and
technical know-how. The Company also considers technical know-how, trade
secrets, and trademarks to be important to its business.

      (v)   Seasonal Influences

      There are no significant seasonal influences on the Company's sales of its
products.

      (vi)  Working Capital Requirements

      There are no special inventory requirements or credit terms extended to
customers that would have a material adverse effect on the Company's working
capital.

      (vii) Dependency on a Single Customer

      No single customer accounted for more than 10% of the Company's total
revenues in any of the past three years.

      (viii)Backlog

      The Company's backlog of firm orders was as follows:
<TABLE>
<CAPTION>
<S>                                                                                        <C>       <C>
(In thousands)                                                                             1999      1998
------------------------------------------------------------------------------------- ---------- ---------

Spectroscopy                                                                            $65,518    $62,543
Materials Science                                                                        33,827     22,833
                                                                                        -------    -------

                                                                                        $99,345    $85,376
                                                                                        =======    =======
      The Company believes that substantially all of the backlog at January 1,
2000, will be shipped or completed during 2000. Certain of these orders are
subject to cancellation by the customer upon payment of a cancellation charge.
Because of the possibility of customer changes in delivery schedules,
cancellation of orders, and potential delays in product shipments, the Company's
backlog as of any particular date may not be representative of actual sales for
any succeeding period.

      (ix)  Government Contracts

      Not applicable.

                                       5
<PAGE>

      (x)   Competition

      The Company competes in each of its markets primarily on product
performance, reliability, customer service, and price. In the Spectroscopy
segment, the Company competes primarily with the AI division of The Perkin-Elmer
Corporation, Varian Associates, Inc., Agilent Technologies Inc., Spectro
Analytical Instruments, Inc., the Digilab division of Bio-Rad Laboratories,
Inc., Bruker Instruments, Inc., and Shimadzu Corporation. In the Materials
Science segment, the Company competes primarily with Physical Electronics, Inc.,
Riber Instruments S.A., Kratos (a division of Shimadzu), Omnicron Associates,
Brookfield Engineering Laboratories, Inc., and TA Instruments, Inc. (a
subsidiary of Waters Corporation).

      (xii) Environmental Protection Regulations

      The Company believes that compliance by the Company with federal, state,
and local environmental protection regulations will not have a material adverse
effect on its capital expenditures, earnings, or competitive position.

      (xiii)
Number of Employees

      As of January 1, 2000, the Company employed approximately 2,400 people.

(d)   Financial Information About Geographic Areas

      Financial information about geographic areas is summarized in Note 11 to
Consolidated Financial Statements in the Registrant's 1999 Annual Report to
Shareholders and is incorporated herein by reference.
</TABLE>
(e)   Executive Officers of the Registrant
<TABLE>
<CAPTION>
<S>     <C>                 <C>   <C>
        Name                Age   Present Title (Fiscal Year First Became Executive Officer)
        ------------------  ---   ---------------------------------------------------------

        Barry S. Howe       44    President and Chief Executive Officer (1999)
        Gerard Abraham      52    Vice President (1998)
        G. Roger Herd       62    Vice President (1998)
        Roland Schultner    51    Vice President (1999)
        Fredric T. Walder   42    Senior Vice President (1998)
        Theo Melas-Kyriazi  40    Chief Financial Officer (1998)
        Paul F. Kelleher    57    Chief Accounting Officer (1995)

      Each executive officer serves until his successor is chosen or appointed
by the Board of Directors and qualified or until his earlier resignation, death,
or removal. Mr. Howe has been President and Chief Executive Officer of the
Company since March 1999 and has been President and Chief Executive Officer of
ThermoSpectra Corporation since March 1998. Prior to joining ThermoSpectra, Mr.
Howe was President and Chief Executive Officer of Thermo BioAnalysis
Corporation, a publicly traded, majority-owned subsidiary of Thermo Instrument,
from February 1995 to March 1998, and President of Thermo Instrument's Thermo
Separation Products Inc. subsidiary and its predecessor, a manufacturer of
liquid chromatography instruments, from September 1989 to December 1995. Mr.
Abraham has been Vice President since January 1998, and from 1993 to 1997, was
President of ARL. Mr. Herd has been Vice President since January 1998, and
Managing Director of VG Systems since April 1996. Mr. Herd was Manager of
International Business Development for Thermo Instrument from April 1994 to
April 1996, and prior to April 1994, was Managing Director of Thermo Instrument
Australia PTY Ltd. Mr. Schultner has been Vice President since October 1999 and
Managing Director of Haake since January 1993. Mr. Walder has been Senior Vice
President since April 1998, and President of Nicolet since December 1997. Mr.
Walder was General Manager of Nicolet from January 1997 to December 1997, Vice
President of Marketing and Sales from January 1996 to December 1996, Director of
Marketing


                                       6
<PAGE>
from April 1994 to December 1995, and prior to April 1994, was a Marketing/Product Manager.  Mr.
Melas-Kyriazi was appointed Chief Financial Officer of the Company and Thermo Electron on January 1,
1999.  Mr. Melas-Kyriazi joined Thermo Electron in 1986 as Assistant Treasurer, and became Treasurer in
1988.  He was named President and Chief Executive Officer of ThermoSpectra Corporation, then a public
subsidiary of Thermo Instrument, in 1994.  In 1998, he became Vice President of Corporate Strategy for
Thermo Electron.  Mr. Melas-Kyriazi remains a Vice President of Thermo Electron.  Mr. Kelleher has held
comparable positions for at least five years with Thermo Instrument or Thermo Electron.  Messrs.
Abraham, Herd, and Walder are full-time employees of the Company.  Mr. Howe is an employee of
ThermoSpectra and the Company, but devotes such time to the affairs of the Company as the Company's
needs reasonably require.  Messrs. Melas-Kyriazi and Kelleher are full-time employees of Thermo
Electron, but devote such time to the affairs of the Company as the Company's needs reasonably require.

Item 2.     Properties

      The location and general character of the Company's principal properties
by segment as of January 1, 2000, are as follows:

      The Company's Spectroscopy segment owns approximately 489,000 square feet
of office and manufacturing space, principally in Wisconsin, New York, Colorado,
Germany, the United Kingdom, and Switzerland; and leases an additional 434,000
square feet of office and manufacturing space under leases expiring from 2000
through 2017, principally in Massachusetts, Connecticut, and the United Kingdom.

      The Company's Materials Science segment owns approximately 110,000 square
feet of office and manufacturing space in Germany; and leases approximately
168,000 square feet of office and manufacturing space under leases expiring from
2000 through 2013, principally in the United Kingdom and New Jersey.

      In addition, the Company leases office space throughout the world for its
sales and service operations. The Company believes that its facilities are in
good condition and are suitable and adequate to meet current needs and that
suitable alternate space is readily available if any of such leases are not
extended.

Item 3.     Legal Proceedings

      Not applicable.

Item 4.     Submission of Matters to a Vote of Security Holders

      Not applicable.


                                       7
<PAGE>

                                     PART II
Item 5.     Market for Registrant's Common Equity and Related Stockholder
            Matters

      Information concerning the market and market price for the Registrant's
common stock, $.01 par value, and dividend policy is included under the sections
labeled "Common Stock Market Information" and "Dividend Policy" in the
Registrant's 1999 Annual Report to Shareholders and is incorporated herein by
reference.

Item 6.     Selected Financial Data

      The information required under this item is included under the sections
labeled "Selected Financial Information" and "Dividend Policy" in the
Registrant's 1999 Annual Report to Shareholders and is incorporated herein by
reference.

Item 7.     Management's Discussion and Analysis of Financial Condition and
            Results of Operations

      The information required under this item is included under the heading
"Management's Discussion and Analysis of Financial Condition and Results of
Operations" in the Registrant's 1999 Annual Report to Shareholders and is
incorporated herein by reference.

Item 7A.    Quantitative and Qualitative Disclosures About Market Risk

      The information required under this item is included under the heading
"Management's Discussion and Analysis of Financial Condition and Results of
Operations" in the Registrant's 1999 Annual Report to Shareholders and is
incorporated in this document by reference.

Item 8.     Financial Statements and Supplementary Data

      The Registrant's Consolidated Financial Statements as of January 1, 2000,
and Supplementary Data are included in the Registrant's 1999 Annual Report to
Shareholders and are incorporated herein by reference.

Item 9.     Changes in and Disagreements with Accountants on Accounting and
            Financial Disclosure

      Not applicable.


                               PART III

      The information required under Items 10, 11, 12, and 13 of Form 10-K will
be filed as part of an amendment to this Form 10-K no later than 120 days after
January 1, 2000, the end of the Registrant's fiscal year covered by this Form
10-K.


                                       8
<PAGE>

                              PART IV

Item 14.  Exhibits, Financial Statement Schedules, and Reports on Form 8-K

(a,d)  Financial Statements and Schedules

       (1) The consolidated financial statements set forth in the list below are
           filed as part of this Report.

       (2) The consolidated financial statement schedule set forth in the list
           below is filed as part of this Report.

       (3) Exhibits filed herewith or incorporated herein by reference are set
           forth in Item 14(c) below.

       List of Financial Statements and Schedules Referenced in this Item 14

       Information incorporated by reference from Exhibit 13 filed herewith:

          Consolidated Statement of Income
          Consolidated Balance Sheet
          Consolidated Statement of Cash Flows
          Consolidated Statement of Comprehensive Income and Shareholders'
               Investment
          Notes to Consolidated Financial Statements
          Report of Independent Public Accountants

       Financial Statement Schedules filed herewith:

          Schedule II:  Valuation and Qualifying Accounts

       All other schedules are omitted because they are not applicable or not
       required, or because the required information is shown either in the
       financial statements or in the notes thereto.

(b)    Reports on Form 8-K

       None.

(c)    Exhibits

       See Exhibit Index on the page immediately preceding exhibits.


                                       9
<PAGE>

                                   SIGNATURES

      Pursuant to the requirements of Section 13 or 15(d) of the Securities
Exchange Act of 1934, the Registrant has duly caused this report to be signed on
its behalf by the undersigned, thereunto duly authorized.

Date:  March 16, 2000         THERMO OPTEK CORPORATION


                              By: /s/ Barry S. Howe
                                  Barry S. Howe
                                  President and Chief Executive Officer

      Pursuant to the requirements of the Securities Exchange Act of 1934, this
report has been signed below by the following persons on behalf of the
Registrant and in the capacities indicated below, as of March 16, 2000.

Signature                         Title


By:  /s/ Barry S. Howe            President, Chief Executive Officer, and Director
     Barry S. Howe


By:  /s/ Theo Melas-Kyriazi       Chief Financial Officer
     Theo Melas-Kyriazi


By:  /s/ Paul F. Kelleher         Chief Accounting Officer
     Paul F. Kelleher


By:  /s/ Stephen R. Levy          Director
     Stephen R. Levy


By:  /s/ Earl R. Lewis            Chairman of the Board and Director
     Earl R. Lewis


By:  /s/ Robert A. McCabe         Director
     Robert A. McCabe


                                       10
<PAGE>
                  Report of Independent Public Accountants

To the Shareholders and Board of Directors of Thermo Optek Corporation:

      We have audited, in accordance with generally accepted auditing standards,
the consolidated financial statements included in Thermo Optek Corporation's
Annual Report to Shareholders incorporated by reference in this Form 10-K, and
have issued our report thereon dated February 15, 2000 (except with respect to
the matter discussed in Note 14, as to which the date is March 6, 2000). Our
audits were made for the purpose of forming an opinion on those statements taken
as a whole. The schedule listed in Item 14 on page 9 is the responsibility of
the Company's management and is presented for purposes of complying with the
Securities and Exchange Commission's rules and is not part of the basic
consolidated financial statements. This schedule has been subjected to the
auditing procedures applied in the audits of the basic consolidated financial
statements and, in our opinion, fairly states in all material respects the
consolidated financial data required to be set forth therein in relation to the
basic consolidated financial statements taken as a whole.



                                  Arthur Andersen LLP



Boston, Massachusetts
February 15, 2000
</TABLE>
                                       11
<PAGE>

SCHEDULE II

                                         THERMO OPTEK CORPORATION
                                    Valuation and Qualifying Accounts
                                              (In thousands)
<TABLE>
<CAPTION>
<S>                                 <C>         <C>          <C>          <C>        <C>         <C>

Description                                      Provision    Accounts    Accounts   Other (a)   Balance
                                    Balance at  Charged to   Recovered     Written                at End
                                     Beginning     Expense                     Off               of Year
                                       of Year
----------------------------------- ----------- ----------- ----------- ----------- ----------- ---------

Allowance for Doubtful Accounts

Year Ended January 1, 2000             $ 4,960     $   175     $   155     $  (874)    $  (135)    $ 4,281

Year Ended January 2, 1999             $ 5,709     $   519     $   238     $(1,492)    $   (14)    $ 4,960

Year Ended January 3, 1998             $ 5,541     $   629     $    83     $(1,036)    $   492     $ 5,709


Description                             Balance at   Established        Cash      Other (c)      Balance
                                         Beginning    as Cost of     Payments                     at End
                                           of Year  Acquisitions                                 of Year
------------------------------------- ------------- ------------- ------------ ------------- ------------

Accrued Acquisition Expenses (b)

Year Ended January 1, 2000                 $   674       $     -       $ (599)      $   (28)      $    47

Year Ended January 2, 1999                 $ 2,843       $   843       $(2,065)     $  (947)      $   674

Year Ended January 3, 1998                 $10,420       $ 2,441       $(7,049)     $(2,969)      $ 2,843


Description                             Balance at    Provision                    Other (f)      Balance
                                         Beginning   Charged to   Cash Payments                    at End
                                           of Year  Expense (e)                                   of Year
------------------------------------- ------------- ------------ -------------- ------------- ------------

Accrued Restructuring Costs (d)

Year Ended January 1, 2000                 $ 4,943       $  989       $(4,834)       $  (229)      $   869

Year Ended January 2, 1999                 $     -       $7,422       $(2,663)       $   184       $ 4,943

(a) Includes allowance of businesses acquired during the year as described in
    Note 2 to Consolidated Financial Statements in the Registrant's 1999 Annual
    Report to Shareholders and the effect of foreign currency translation.
(b) The nature of activity in this account is described in Note 2 to
    Consolidated Financial Statements in the Registrant's 1999 Annual Report to
    Shareholders.
(c) Primarily represents reversal of accrued acquisition expenses and
    corresponding reduction of cost in excess of net assets of acquired
    companies resulting from finalization of restructuring plans and the effect
    of foreign currency translation.
(d) The nature of activity in this account is described in Note 9 to
    Consolidated Financial Statements in the Registrant's 1999 Annual Report to
    Shareholders.
(e) Excludes provision of $0.2 million for an asset write-down and $0.4 million
    for the loss on the sale of a division in 1998.
(f) Represents the effect of foreign currency translation.



                                       12
<PAGE>

                                              EXHIBIT INDEX
Exhibit
Number         Description of Exhibit

 2.1           Stock Purchase Agreement dated as of November 4, 1996, among
               Thermo Instrument, SID Instruments Inc., and ATI Acquisition
               Corp. (filed as Exhibit 2.1 to the Company's Quarterly Report on
               Form 10-Q for the quarter ended September 28, 1996 [File No.
               1-11757] and incorporated herein by reference).

 2.2           Stock Purchase Agreement dated as of November 4, 1996, between
               Thermo Instrument and the Company (filed as Exhibit 2.2 to the
               Company's Quarterly Report on Form 10-Q for the quarter ended
               September 28, 1996 [File No. 1-11757] and incorporated herein by
               reference).

 2.3           Share Purchase Agreement dated as of July 30, 1997, between the Company and Thermo
               Instrument (filed as Exhibit 2 to the Company's Quarterly Report on Form 10-Q for the
               quarter ended June 28, 1997 [File No. 1-11757] and incorporated herein by reference).

 2.4           Share Purchase Agreement dated as of August 10, 1998, between the
               Company and Thermo Instrument Systems Inc. Pursuant to Item
               601(b)(2) of Regulation S-K, schedules to this Agreement have
               been omitted. The Company hereby undertakes to furnish
               supplementally a copy of such schedules to the Commission upon
               request (filed as Exhibit 2 to the Company's Quarterly Report on
               Form 10-Q for the quarter ended October 3, 1998 [File No.
               1-11757] and incorporated herein by reference).

 3.1           Certificate of Incorporation, as amended, of the Company (filed as Exhibit 3.l to the
               Company's Registration Statement on Form S-1 [Reg. No. 333-03630] and incorporated herein
               by reference).

 3.2           By-laws of the Company (filed as Exhibit 3.2 to the Company's Registration Statement on
               Form S-1 [Reg. No. 333-03630] and incorporated herein by reference).

10.1           Corporate Services Agreement dated as of August 18, 1995, between
               Thermo Electron and the Company (filed as Exhibit 10.1 to the
               Company's Registration Statement on Form S-1 [Reg.
               No. 333-03630] and incorporated herein by reference).

10.2           Thermo Electron Corporate Charter, as amended and restated
               effective January 3, 1993 (filed as Exhibit 10.1 to Thermo
               Electron's Annual Report on Form 10-K for the fiscal year ended
               January 2, 1993 [File No. 1-8002] and incorporated herein by
               reference).

10.3           Tax Allocation Agreement dated as of August 18, 1995, between
               Thermo Electron and the Company (filed as Exhibit 10.3 to the
               Company's Registration Statement on Form S-1 [Reg.
               No. 333-03630] and incorporated herein by reference).

10.4           Amended and Restated Master Guarantee Reimbursement and Loan Agreement dated as of
               December 5, 1997, between Thermo Instrument and the Company (filed as Exhibit 10.6 to the
               Company's Annual Report on Form 10-K for the fiscal year ended January 3, 1998 [File No.
               1-11757] and incorporated herein by reference).

10.5           Form of Indemnification Agreement for Officers and Directors (filed as Exhibit 10.9 to
               the Company's Registration Statement on Form S-1 [Reg. No. 333-03630] and incorporated
               herein by reference).

                                       13
<PAGE>

Exhibit
Number         Description of Exhibit

10.6           Fiscal Agency Agreement dated as of October 12, 1995, between the
               Company and The Chase Manhattan Bank (formerly Chemical Bank)
               (filed as Exhibit 10.10 to the Company's Registration Statement
               on Form S-1 [Reg. No. 333-03630] and incorporated herein by
               reference).

10.7           Stock Purchase Agreement dated as of April 11, 1996, between the Company and Thermo
               Instrument (filed as Exhibit 10.11 to the Company's Registration Statement on Form S-1
               [Reg. No. 333-03630] and incorporated herein by reference).

10.8           Asset Transfer Agreement dated as of December 31, 1995, by and among the Company, Nicolet
               Instrument Corporation, and Thermo Instrument (filed as Exhibit 10.12 to the Company's
               Registration Statement on Form S-1 [Reg. No. 333-03630] and incorporated herein by
               reference).

10.9           Indemnification Agreement dated as of November 4, 1996, between
               Thermo Instrument and the Company (filed as Exhibit 10.1 to the
               Company's Quarterly Report on Form 10-Q for the quarter ended
               September 28, 1996 [File No. 1-11757] and incorporated herein by
               reference).

10.10          Restated Stock Holdings Assistance Plan and Form of Promissory
               Note (filed as Exhibit 10.15 to the Company's Annual Report on
               Form 10-K for the fiscal year ended December 28, 1996 [File No.
               1-11757] and incorporated herein by reference).

10.11          Master Cash Management, Guarantee Reimbursement, and Loan Agreement dated as of June 1,
               1999, by and between the Registrant and Thermo Electron Corporation (filed as Exhibit
               10.1 to the Company's Quarterly Report on Form 10-Q for the quarter ended July 3, 1999
               [File No. 1-11757] and incorporated herein by reference).

10.12          Amended and Restated Equity Incentive Plan of the Registrant
               (filed as Exhibit 10.2 to the Company's Quarterly Report on Form
               10-Q for the quarter ended July 3, 1999 [File No.
               1-11757] and incorporated herein by reference).

10.13          Amended and Restated Deferred Compensation Plan for Directors of the Registrant (filed as
               Exhibit 10.3 to the Company's Quarterly Report on Form 10-Q for the quarter ended July 3,
               1999 [File No. 1-11757] and incorporated herein by reference).

10.14          Amended and Restated Directors Stock Option Plan of the Registrant (filed as Exhibit 10.4
               to the Company's Quarterly Report on Form 10-Q for the quarter ended July 3, 1999 [File
               No. 1-11757] and incorporated herein by reference).

               In addition to the stock-based compensation plans of the
               Registrant, the executive officers of the Registrant may be
               granted awards under stock-based compensation plans of Thermo
               Electron and Thermo Instrument for services rendered to the
               Registrant or such affiliated corporations. The terms of such
               plans are substantially the same as those of the Company's Equity
               Incentive Plan.

  13           Annual Report to Shareholders for the Year Ended January 1, 2000
               (only those portions incorporated herein by reference).

  21           Subsidiaries of the Registrant.

  23           Consent of Arthur Andersen LLP.

  27           Financial Data Schedule.
</TABLE>