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 2, 1999

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

                       Commission file number 1-12745

                         THERMEDICS DETECTION INC.
           (Exact name of Registrant as specified in its charter)

Massachusetts                                                    04-3106698
(State or other jurisdiction of incorporation or
organization)                                    (I.R.S. Employer
Identification No.)

220 Mill Road
Chelmsford, Massachusetts                                        01824-4178
(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 exchangeon which registered
Common Stock, $.10 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. 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 29, 1999, was approximately $18,356,000.

As of January 29, 1999, the Registrant had 19,316,684 shares of Common Stock
outstanding.

                    DOCUMENTS INCORPORATED BY REFERENCE

Portions of the Registrant's Annual Report to Shareholders for the year ended
January 2, 1999, are incorporated by reference into Parts I and II.

Portions of the Registrant's definitive Proxy Statement for the Annual Meeting
of Shareholders to be held on May 27, 1999, are incorporated by reference into
Part III.


<PAGE>


                                   PART I
                                     
Item 1. Business

(a) General Development of Business

    The businesses of Thermedics Detection Inc. (the Company or the Registrant)
operate in two segments: Detection Instruments and Laboratory Products. The
Company's Detection Instruments segment develops, manufactures, and markets
high-speed detection and measurement systems used for quality assurance and
security applications. The Company's quality-assurance systems use ultratrace
chemical detectors, high-speed gas chromatography, X-ray imaging, near-infrared
spectroscopy, and other technologies to ensure the quality and safety of
in-process and finished products, primarily in the food, beverage,
pharmaceutical, forest products, chemical, and other consumer products
industries. The Company's security instruments use simultaneous trace particle-
and vapor-detection techniques based on its proprietary chemiluminescence and
high-speed gas chromatography technologies. Customers use the Company's security
instruments to detect plastic and other explosives at airports and border
crossings, for other high-security screening applications, and for forensics and
search applications. Along with earning revenues from the sale of existing
products, the Company performs contract research and development services for
government and industry customers and earns service revenues through long-term
contracts.

    Historically, principal product lines in the Company's Detection Instruments
segment were quality-assurance and security systems, including ALEXUS(R)
systems, which detect trace amounts of substances that would affect product
quality in refillable plastic beverage containers, and EGIS(R) explosives
detectors. The Company expanded its product lines to include near-infrared
analyzers through its acquisition of Moisture Systems Corporation and Rutter &
Co. B.V. (collectively, Moisture Systems) in January 1996. Also in 1996, the
Company introduced its InScan(R) high-speed X-ray imaging system and
Flash-GC(TM) high-speed gas chromatography system. In 1998, the Company
introduced a new line of benchtop explosives detectors based on its EGIS
technology. Additionally, in 1998, the Company introduced an offshoot of its
Flash-GC technology, called EZ Flash(TM).

    In 1998, the Company acquired Orion Research, Inc., a leading manufacturer
of electrochemistry products, from its parent company, Thermedics Inc. Orion
constitutes the Laboratory Products segment. Orion's products determine the
quality of a wide variety of items, including food, water, and pharmaceuticals,
by measuring their pH, conductivity, dissolved oxygen, and specific ion
concentration. Orion also offers titration products that make the same
measurements, but in a more automated manner, and titration products that
measure the moisture content of raw, in-process, and finished products. In
addition, Orion manufactures on-line versions of its specific ion-measurement
systems that are used to monitor water quality in the power, semiconductor,
petrochemical, paper, pharmaceutical, and drinking water industries.

    The Company operated as a division of Thermedics until its incorporation as
a Massachusetts corporation in December 1990. In connection with the Company's
incorporation, Thermedics transferred to the Company its TEA Analyzer and
certain other trace detection technologies in exchange for 10,000,000 shares of
the Company's common stock. A publicly traded subsidiary of Thermo Electron,
Thermedics develops, manufactures, and markets diverse product lines, including
implantable heart-assist devices and other biomedical products, electronic-test
instruments, and equipment that assures the quality of a wide variety of
consumer products and bulk materials. As of January 2, 1999, Thermedics owned
16,185,945 shares of the Company's outstanding common stock, representing 84% of
such stock outstanding. As of January 2, 1999, Thermedics is a 74%-owned
subsidiary of Thermo Electron Corporation. As of January 2, 1999, Thermo
Electron owned 882,450 shares of the Company's outstanding common stock,
representing 5% of such stock outstanding. Thermo Electron and Thermedics may
purchase shares of the Company's common stock from time to time in the open
market, or in negotiated transactions. During 1998*, Thermedics purchased
161,500 shares of the Company's common stock for $1.6 million. During 1998,
Thermo Electron purchased 882,450 shares of the Company's common stock for $8.2
million. Thermo Electron is a world leader in monitoring, analytical, and
biomedical instrumentation; biomedical products including heart-assist devices,
respiratory-care
--------------------
* References to 1998, 1997, and 1996 herein are for the fiscal years ended
  January 2, 1999, January 3, 1998, and December 28, 1996, respectively.


                                       2
<PAGE>

equipment, and mammography systems; and paper recycling and papermaking
equipment. Thermo Electron also develops alternative-energy systems and clean
fuels, provides a range of services including industrial outsourcing and
environmental-liability management, and conducts research and development in
advanced imaging, laser, and electronic information-management technologies.

    During 1998, Thermo Electron announced a proposed reorganization involving
certain of Thermo Electron's subsidiaries, including the Company. Under this
plan, Thermedics' majority interest in the Company would be transferred to
Thermo Electron. The Company would then be taken private and become a wholly
owned subsidiary of Thermo Electron. Shareholders of the Company would receive
cash in exchange for their shares of common stock. The proposed transactions are
subject to a number of conditions, as outlined in Note 10 to Consolidated
Financial Statements in the Registrant's 1998 Annual Report to Shareholders,
which is incorporated herein by reference.

Forward-looking Statements

    Forward-looking statements, within the meaning of Section 21E of the
Securities and 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 1998 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 8 to Consolidated Financial Statements in the Registrant's 1998 Annual
Report to Shareholders, which information is incorporated herein by reference.

(c) Description of Business

    (i) Principal Products and Services

Detection  Instruments

Quality-assurance Systems

    The Company designs, manufactures, and markets high-speed measurement,
detection, and rejection equipment that uses ultratrace chemical detectors,
X-ray imaging, near-infrared spectroscopy, gas chromatography, and other
technologies for product quality and productivity applications.

    ALEXUS. The Company's ALEXUS systems detect trace amounts of constituents
that would affect product quality in refillable plastic containers of soft
drinks, water, and other beverages. The Company's ALEXUS systems, introduced in
1992, have been installed on more than 300 bottling lines in more than 30
countries throughout the world, primarily in Europe and Latin America, by The
Coca-Cola Company, Perrier, and other major beverage producers.

    During 1998, 1997, and 1996, the Company derived revenues of $11.1 million,
$19.2 million, and $14.9 million, respectively, from ALEXUS systems.


                                       3
<PAGE>

    InScan. The Company's InScan system uses high-speed X-ray imaging technology
to determine accurate fill volume, net volume, proper contents, and package
integrity of containers for the beverage, food, and other industries. InScan
uses a low-power X-ray to capture data. This data produces an instant, detailed
image of each container. InScan's proprietary software then automatically
compares the data to a predetermined profile used to generate mathematical
algorithms to determine whether the container is acceptable. InScan incorporates
a sophisticated, high-speed rejection system that automatically removes
unacceptable containers from the line. The Company shipped its first InScan
units in 1996. The Company's InScan systems are currently used by major beer and
soft drink companies in the U.S. and overseas, including Miller, Molson, Coors,
Guinness Brewing Company, and The Coca-Cola Company. The Company has also sold
systems to the household products industry, the cosmetics industry, the
personal-care products industry, and the food industry.

    Moisture Systems. The Company's Moisture Systems division, acquired in 1996,
designs, manufactures, and markets equipment that uses near-infrared (NIR)
spectroscopy to measure moisture and other product constituents, including fats,
proteins, oils, flavorings, solvents, adhesives, and coatings, in a variety of
products as they move along manufacturing lines. The Company's systems are used
across the food, pharmaceutical, chemical, petrochemical, tobacco, forest
products, paper converting, plastics, textiles, corrugating, and other
industries. In 1997, the Company introduced the Quadra Beam 6600T, a system that
combines an NIR sensor with a processor that displays ingredient information to
offer customers a less expensive, easy-to-install, and space-saving on-line
analyzer. In 1998, the Company introduced the Quadra Beam 6600L, an
explosion-proof analyzer designed specifically for the on-line monitoring of
volatile liquids and gases. Also in 1998, the Company launched its most powerful
and cost-effective analyzer to date, SPECTRA-QUAD, which can measure
continuously up to three constituents in products moving along product lines.

    During 1998, 1997, and 1996, the Company derived revenues of $12.2 million,
$15.4 million, and $18.0 million, respectively, from Moisture Systems.

    Flash-GC Gas Chromatography Systems. The Company designs, manufactures, and
markets high-speed gas chromatography systems that can analyze chemical samples
at speeds 20 to 50 times faster than conventional gas chromatography. The
Company currently markets its systems under the trade name Flash-GC for near
on-line process and quality-control applications that require high-speed
results. The Company is also targeting certain other segments of the
conventional gas chromatography market in which access to high-speed analysis
would be advantageous. The Flash-GC has applications in the food, flavors,
fragrance, chemical, pharmaceutical, forensic, and automotive industries, as
well as in medical and environmental laboratories. The Company is targeting only
those sectors of the laboratory and process gas chromatography market that are
expected to place a premium on near-instant analysis. In 1998, the Company
introduced the EZ-Flash, which is an upgrade kit that can be added to virtually
any conventional gas chromatograph to conduct chemical analyses up to 30 times
faster. Environmental-analysis and chemical companies have been the primary
buyers of this new product.

Security Instruments

    The Company designs, manufactures, and markets security instruments that use
trace particle- and vapor-detection techniques for forensics and search and
screening applications under the direction of police, border police,
transportation authorities, and carriers.

    The Company's principal security instrument is the EGIS system, a highly
sensitive particle- and vapor-detection system for screening people, baggage,
packages, freight, and electronic equipment such as personal computers for the
presence of a wide range of explosives, including plastic explosives that have
proven difficult to detect using conventional methods. The EGIS system is
designed for stand-alone use in the detection of explosives in carry-on items
and on personnel, and can be used in conjunction with enhanced X-ray and other
advanced imaging systems to provide a comprehensive explosives-detection system
for checked luggage. The Company also has developed SecurScan(TM), a
walk-through explosives detector.

                                       4
<PAGE>

    The Company believes that EGIS system is the most accurate and most
sensitive high-speed trace explosives-detection system available today. EGIS
employs the same high-speed gas chromatography technology used in the Flash-GC,
combined with chemiluminescent detection techniques to detect ultratrace
quantities of certain explosives and taggants, and to indicate the concentration
and type of explosive detected. Because EGIS' chemiluminescent detector responds
only to compounds of certain structures in the sample, rather than to the
thousands of compounds that may be contained in the sample, EGIS is more
selective than competing trace-detection systems, with fewer false-positive
readings. A processor in EGIS compares the chemical profile of the sample to the
known profiles of various explosives, including TNT, nitroglycerin, PETN,
Semtex, and C-4. Within seconds of the introduction of the sample into EGIS, the
system determines whether explosives are present, and, if so, identifies the
type and amount.

    Initially developed with internal funds and contract funding from the U.S.
Federal Aviation Administration (FAA) and the U.S. Department of State, more
than 275 EGIS units have been deployed to date. The EGIS system is currently
operational in 26 countries and is in use for carry-on and checked-luggage
screening at more than 50 international airports. EGIS is also used in
government buildings and embassies, and at border crossings and other locations
where there is a high degree of concern for security. The EGIS system has
assisted in identifying explosives used in terrorist bombings, including those
in the Federal Building in Oklahoma City and the World Trade Center in New York,
as well as in Israel, Buenos Aires, and the United Kingdom. In March 1996, the
Company supplied the U.S. government with eight EGIS systems to provide
counter-terrorism support in Israel. The Bureau of Alcohol, Tobacco, and
Firearms and the Federal Bureau of Investigation used EGIS systems in their
attempt to identify the cause of the crash of TWA Flight 800.

    During 1998, 1997, and 1996, the Company derived revenues of $8.3 million,
$10.3 million, and $7.1 million, respectively, from EGIS systems.

Laboratory Products

Electrochemistry Products

    Through its Orion Research subsidiary, the Company manufactures a wide range
of electrochemistry products that determine the quality of many substances by
measuring their pH, specific ion concentration, dissolved oxygen, and
conductivity. These products include electrodes, which detect and communicate
measurements to meters, also supplied by Orion, which display the measurement
information in a convenient and useful format. Orion also provides a host of
reagents and standards. These products are used in the food, beverage,
pharmaceutical, chemical, environmental analysis, drinking water, wastewater
treatment, agricultural, biomedical research, and many other industries.

Titration Products

    Orion's titration products are also used to measure pH, specific ion
concentration, conductivity, and dissolved oxygen, but in a more automated
manner, as well as to measure the moisture content of raw, in-process, or
finished products.

    Orion designs, manufactures and markets automated potentiometric and Karl
Fischer volumetric and coulometric titrators for a variety of industries. The
target markets include the food and beverage, petrochemical, pharmaceutical,
chemical, water and wastewater, and paper industries. Orion titration systems
are designed specifically to analyze samples in either quality control or
research environments.

    Orion's potentiometric titrators have been used in a wide range of
applications such as determining the amount of Vitamin C in beverages, hardness
in water, fluoride in toothpaste, surfactants in shampoos, and total acid number
in petrochemicals. Orion's Karl Fischer Titrators analyze moisture levels from
the parts-per-million to percentage range. Orion's most innovative titration
instrument is the Model TURBO2(R) with its built-in high-speed blender that
homogenizes whole samples in a moisture-free environment.

                                       5
<PAGE>

Process Products

    Included in process products is a complete family of on-line water analyzers
designed to monitor concentrations of various chemicals and contaminants.
Targeted markets include the power, semiconductor, petrochemical, and paper
industries.

    Orion's 1700 series on-line analyzers measure chlorine and fluoride in
wastewater, while the 1800 series measures specific ions and dissolved oxygen
analysis in pure and potable water.

    Orion's on-line water analyzers are used in the power industry, in order to
read low levels of residual salts, ions, and dissolved oxygen in the ultrapure
water used in the steam cycle. Lower detection levels and extended government
regulations have made on-line measurements increasingly important.

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

Detection Instruments

    The Company maintains active programs for the development and introduction
of new products and improvements to existing products. The Company also seeks to
develop new applications for its existing products and technology. In 1998, the
Company evolved the InScan system into three distinct products. The InScan 100
Fill Level/Net Content System assures the proper fill level and net content of
containers. The InScan 200 Foreign Material Detection System detects metal,
stones, glass, and other objects in packages. The InScan 300 Package Integrity
Analysis System provides package integrity information for small packages,
including verifying the presence and location of various components in packages.
The Company also made progress in creating a wider and higher tunnel for all of
its InScan systems, which will allow larger containers to be examined.

    In addition, the Company has been exploring a number of improvements to its
security product line. In 1998, the Company introduced a new family of benchtop
explosives detectors - the EGIS II, the more sensitive EGIS III, and EGIS IV,
the Company's most sensitive explosives detector to date. With this family of
products, the Company believes it can better meet various customers' analytical
needs as well as budget. The Company also is working to extend the capabilities
of its SecurScan to not only detect traces of explosives, but also illicit drugs
and metal-based weapons. In addition, the Company plans to broaden its product
line to include a chemical and biological warfare detection system.

Laboratory Products

    Innovative new Orion laboratory products for 1999 include the SensorLink(R)
system for dissolved oxygen and WineMaster(TM) Analysis System. SensorLink
records dissolved oxygen measurements directly into custom computer software.
WineMaster incorporates special chemical testing for the wine industry into
turnkey measurements. Two process product introductions for on-line pH and
on-line silica monitors will allow unattended continuous measurement of these
critical parameters in ultrapure and other waters used in industrial facilities.

    Company-funded research and development expenses were $9.6 million in 1998
and 1997, and $8.1 million in 1996. Contract research and development revenues
were $3.0 million, $1.4 million, and $1.8 million in 1998, 1997, and 1996,
respectively.

    (iii) Raw Materials

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

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<PAGE>

    (iv) Patents, Licenses, and Trademarks

    The Company's policy is to protect its intellectual property rights by
appropriate means, including applying for patents. The Company also enters into
licensing agreements with other companies in which it grants or receives rights
to specific patents and technical know-how. The Company owns 34 U.S. patents,
and has filed applications for five additional United States patents. The
Company's U.S. patents, more than 60% of which were issued after 1990, have
expiration dates ranging from 1999 through 2015. The Company also owns
corresponding patents, or has filed corresponding applications, in a number of
jurisdictions throughout the world. In addition, the Company has an exclusive,
perpetual, royalty-free license under ten patents covering the use of
near-infrared and very near-infrared emitting diodes for on-line spectral
measurements. The Company owns several patents covering certain aspects of its
chemiluminescent analysis technology and high-speed gas chromatography
technology. The Company believes that these patents provide the Company with
competitive advantages in the markets for certain of its products. 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

    Sales to The Coca-Cola Company, included in the Detection Instruments
segment, accounted for 7%, 26%, and 24% of the Company's total revenues in 1998,
1997, and 1996, respectively. Sales to Fisher Scientific and VWR Scientific,
both included in the Laboratory Products segment, each accounted for 10% of
total revenues in 1998.

    (viii) Backlog

      The Company's backlog of firm orders at year-end 1998 and 1997 was:

(In thousands)                                                1998      1997
---------------------------------------------------------- -------- ---------

Detection Instruments                                       $4,494   $ 6,922
Laboratory Products                                          1,571     2,452
                                                            ------   -------

                                                            $6,065   $ 9,374
                                                            ======   =======

    Certain of these orders are cancelable by the customer upon payment of a
cancellation charge. The Company believes that substantially all of the backlog
at January 2, 1999, will be shipped or completed during the next twelve months.
The decrease in the backlog for Detection Instruments primarily resulted from
the completion of an order for security systems in 1998. The Company does not
believe that the size of its backlog is necessarily indicative of intermediate
or long-term trends in its business.

    (ix) Government Contracts

    The Company's security instruments are subject to regulation by the FAA,
corresponding foreign governmental authorities, The International Civil Aviation
Organization, and the United Nations organization which are responsible for
establishing standard practices for the aviation industry on a worldwide basis.


                                       7
<PAGE>

Sales of the Company's security instruments for use in airports have been and
will continue to be dependent upon governmental initiatives to require or
support the screening of baggage, carry-on items, and people with advanced
explosives-detection equipment. Substantially all of such systems have been
installed at airports in countries in which the applicable government or
regulatory authority overseeing the operations of the airport has mandated such
screening. Such mandates are influenced by many factors outside of the control
of the Company, including political and budgetary concerns of governments,
airlines, and airports. To date, the FAA has not mandated the use of any
explosives-detection system.

    (x)  Competition

    The markets for the Company's products are highly competitive. Competitors
may develop superior products or products of similar quality for sale at the
same or lower prices. Moreover, there can be no assurance that the Company's
products will not be rendered obsolete by new industry standards or changing
technology. There can be no assurance that the Company will be able to compete
successfully with existing or new competitors. The Company employs a variety of
sales methods for its products and services that are designed to fit the needs
of particular customer groups.

Detection Instruments

Quality-assurance Systems

    The Company's quality assurance systems compete with detection systems
manufactured by numerous companies. The Company believes, however, that these
companies are generally focused on particular niches in the process detection
systems market, only in some of which the Company competes. The ALEXUS system
encounters competition throughout the world, but primarily in the
German-speaking areas of Europe, with products offered by Walter Grassle GmbH of
Germany and Sudtronics S.A. of Switzerland. InScan competes with gamma-based
beverage fill-height detectors offered by a number of companies, including
Industrial Dynamics Company, based in California, and Heuft Systemtechnik GmbH,
based in Germany. ALEXUS systems are also sold through Krones GmbH, a large
German turnkey plant contractor for new bottling lines. Competition in the
moisture-detection market is highly fragmented. The Company's principal
competitor in this market is Infrared Engineering Limited, based in England. The
Company sells and services both its InScan and moisture systems equipment
through a mix of direct sales, manufacturers' representatives, and original
equipment manufacturer relationships around the world. The Company also operates
factory service centers for these products. The Flash-GC and EZ Flash systems
are new technologies competing in the developing high-speed gas chromatography
market segment. The Company's Flash-GC and EZ Flash compete principally against
high-speed gas chromatographs offered by ChromFast, based in Michigan. The
Company's gas chromatography systems are sold through a direct sales and
services organization. The Company is currently attempting to recruit additional
direct sales representatives for certain regions of the United States.

    Competition in the markets for each of the Company's quality-assurance
systems is based primarily on performance, durability, service and, to a lesser
extent, price. The Company believes that its systems' performance and speed, as
well as the Company's reputation for developing superior new technologies and
for the innovative application of existing technologies to a variety of
high-speed production environments and product quality assurance problems, are
competitive advantages.

Security Instruments

    In the security instrument market, the Company competes with a small number
of companies, including other makers of chemical trace detection instruments,
and, to a lesser degree, makers of enhanced X-ray detectors. Competition in this
market is based primarily on performance, including speed, accuracy, and the
range of explosives that can be detected; ease of use; service; and price. The
Company's principal competitor in the trace detection market is Barringer
Technologies Inc., a Canadian firm that has placed several trace detectors in
airport applications.


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<PAGE>

    The Company's security instruments are sold to a few key decision-makers
around the world, primarily government agencies or private companies fulfilling
government regulations. Accordingly, sales are made by a small, specialized
direct sales force, supported by a broader service organization, from offices
shared with ALEXUS sales and service organizations.

Laboratory Products

    The Company's Laboratory Products segment competes with several
international companies. The Company competes on the basis of performance,
service, technology, and price. Competitors include Corning, Fisher Scientific,
Mettler-Toledo, and Beckman Coulter. The two major titration competitors are
Metrohm, distributed by Brinkmann in the United States, and Mettler Toledo.
Other competitors of titration products are Radiometer, Kyoto, ManTech, and
Denver Instruments. Ninety-five percent of the process market is the power
industry where Orion competes with manufacturers such as Hach, Waltron, and
Swan. Other competitors of process products are Foxboro, Polymetron, and
Honeywell.

    (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 2, 1999, the Company had approximately 520 full-time
employees.

(d) Financial Information About Geographic Areas

    Financial information about geographic areas is summarized in Note 8 to
Consolidated Financial Statements in the Registrant's 1998 Annual Report to
Shareholders and is incorporated herein by reference.

(e) Executive Officers of the Registrant

     Name                 Age  Present Title (Fiscal Year First
                               Became Executive Officer)
     -----------------------------------------------------------------

     James Barbookles      50  Chief Executive Officer and President (1997)
     Theo Melas-Kyriazi    39  Chief Financial Officer (1998)
     Paul F. Kelleher      56  Chief Accounting Officer (1990)

    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. Barbookles has been President and
Chief Executive Officer of the Company since November 1997.  Mr.
Barbookles joined Orion in 1989 as Vice President of Research,
Development, and Engineering and was promoted to President and Chief
Operating Officer in 1993.  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.  In 1994, he was named President and Chief
Executive Officer of ThermoSpectra Corporation, a public subsidiary of
Thermo Instrument Systems Inc.  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 Thermedics or Thermo Electron.  Messrs.
Melas-Kyriazi and Kelleher are full-time employees of Thermo Electron, but
devote such portions of their time to the Company's affairs as the
Company's needs reasonably require.

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<PAGE>

Item 2.    Properties

Detection Instruments

    The Detection Instruments segment operates from one principal facility, an
85,000-square foot office, research and development, and manufacturing facility
in Chelmsford, Massachusetts, occupied under a lease expiring in 2006, subject
to one five-year renewal option at the election of the Company. The Detection
Instruments segment also leases approximately 10,000 square feet in Enschede,
Holland, occupied under a lease expiring in 2000. In addition, the Detection
Instruments segment leases approximately 8,400 square feet of office space
throughout the world for its sales and service operations under leases expiring
at various dates until 2000.

Laboratory Products

    The Laboratory Products segment operates primarily from a 115,000-square
foot office, research and development, and manufacturing facility in Beverly,
Massachusetts, occupied under a lease expiring in 2005. In addition, the
Laboratory Products segment leases approximately 12,000 square feet of office
and manufacturing space in Mexico under a lease expiring in June 1999, and owns
a storage facility in Scotland.

    The Company believes that these facilities are adequate for its present
operations. The Company believes suitable alternate space is available for lease
on acceptable terms in the event the Company does not renew leases expiring in
the near future.

Item 3.  Legal Proceedings

    Not applicable.

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

    Not applicable.


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<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, $.10 par value, and dividend policy is included under the sections
labeled "Common Stock Market Information" and "Dividend Policy" in the
Registrant's 1998 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 1998 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 1998 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 1998 Annual Report to Shareholders and
is incorporated herein by reference.

Item 8.  Financial Statements and Supplementary Data

    The Registrant's Consolidated Financial Statements as of January 2, 1999,
and Supplementary Data are included in the Registrant's 1998 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.

                                       11
<PAGE>

                                  PART III
Item 10. Directors and Executive Officers of the Registrant

    The information concerning directors required under this item is
incorporated herein by reference from the material contained under the caption
"Election of Directors" in the Registrant's definitive proxy statement to be
filed with the Securities and Exchange Commission pursuant to Regulation 14A,
not later than 120 days after the close of the fiscal year. The information
concerning delinquent filers pursuant to Item 405 of Regulation S-K is
incorporated herein by reference from the material contained under the heading
"Section 16(a) Beneficial Ownership Reporting Compliance" under the caption
"Stock Ownership" in the Registrant's definitive proxy statement to be filed
with the Securities and Exchange Commission pursuant to Regulation 14A, not
later than 120 days after the close of the fiscal year.

Item 11. Executive Compensation

    The information required under this item is incorporated herein by reference
from the material contained under the caption "Executive Compensation" in the
Registrant's definitive proxy statement to be filed with the Securities and
Exchange Commission pursuant to Regulation 14A, not later than 120 days after
the close of the fiscal year.

Item 12. Security Ownership of Certain Beneficial Owners and Management

    The information required under this item is incorporated herein by reference
from the material contained under the caption "Stock Ownership" in the
Registrant's definitive proxy statement to be filed with the Securities and
Exchange Commission pursuant to Regulation 14A, not later than 120 days after
the close of the fiscal year.

Item 13. Certain Relationships and Related Transactions

    The information required under this item is incorporated herein by reference
from the material contained under the caption "Relationship with Affiliates" in
the Registrant's definitive proxy statement to be filed with the Securities and
Exchange Commission pursuant to Regulation 14A, not later than 120 days after
the close of the fiscal year.

                                       12
<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
       Reports of Independent Public Accountants

    Financial Statement Schedule 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

    On December 10, 1998, the Company filed a Current Report on Form 8-K dated
    December 10, 1998, the purpose of which was to provide an update to a
    proposed corporate reorganization by Thermo Electron involving certain of
    Thermo Electron's subsidiaries, including the Company.

(c) Exhibits

    See Exhibit Index on the page immediately preceding exhibits.

                                       13
<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 15, 1999               THERMEDICS DETECTION INC.


                                    By: /s/ James Barbookles
                                        James Barbookles
                                        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, as of March 15, 1999.

Signature                           Title


By: /s/ James Barbookles            President, Chief Executive Officer, 
    James Barbookles                 and Director


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


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


By: /s/ Morton Collins              Director
    Morton Collins


By: /s/ John T. Keiser              Chairman of the Board and Director
    John T. Keiser


By: /s/ Matthew C. Weisman          Director
    Matthew C. Weisman





                                       14
<PAGE>

                  Report of Independent Public Accountants 

To the Shareholders and Board of Directors of Thermedics Detection Inc.:

    We have audited, in accordance with generally accepted auditing standards,
the consolidated financial statements included in Thermedics Detection Inc.'s
Annual Report to Shareholders incorporated by reference in this Form 10-K, and
have issued our report thereon dated February 11, 1999. 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 13 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 11, 1999

                                       15
<PAGE>

<TABLE>
<CAPTION>

SCHEDULE II

                            THERMEDICS DETECTION INC.
                        Valuation and Qualifying Accounts
                                 (In thousands)

<S>                                 <C>         <C>         <C>         <C>         <C>         <C>   

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

Allowance for Doubtful Accounts

Year Ended January 2, 1999              $1,127      $  301      $    1      $ (395)     $  115      $1,149

Year Ended January 3, 1998              $1,455      $  200      $    8      $ (530)     $   (6)     $1,127

Year Ended December 28, 1996            $  828      $  642      $  203      $ (340)     $  122      $1,455
</TABLE>
<TABLE>
<CAPTION>

<S>                                       <C>          <C>           <C>          <C>               

Description                                Balance at   Established     Activity    Other (c)     Balance
                                            Beginning    as Cost of   Charged to                   at End
                                                   of  Acquisitions      Reserve                  of Year
                                                 Year
----------------------------------------- ------------ ------------- ------------ ----------- ------------

Accrued Acquisition Expenses (b)

Year Ended January 2, 1999                     $    -       $     -       $    -       $           $    -

Year Ended January 3, 1998                     $  580       $     -       $ (476)      $(104)      $    -

Year Ended December 28, 1996                   $  691       $   545       $ (620)      $ (36)      $  580

(a) Includes allowances of businesses acquired during the year as described in
    Note 2 to Consolidated Financial Statements in the Registrant's 1998 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 1998 Annual Report to
    Shareholders.
(c) Represents reduction of cost in excess of net assets of acquired companies
    for accrued acquisition expenses no longer necessary after finalization of
    restructuring plan.
</TABLE>



                                       16
<PAGE>

                               EXHIBIT INDEX
Exhibit
Number     Description of Exhibit

  2.1*     Asset Purchase Agreement dated as of January 25, 1996, among the
           Registrant, Moisture Systems Corporation, and certain Affiliates of
           Moisture Systems Corporation. Pursuant to Item 601(b)(2) of
           Regulation S-K, schedules to this Agreement have been omitted. The
           Registrant hereby undertakes to furnish supplementally a copy of such
           schedules to the Commission upon request.

  2.2*     Share Purchase Agreement dated as of January 25, 1996, among the
           Registrant, Rutter Holding B.V., and certain Affiliates of Rutter
           Holding B.V. Pursuant to Item 601(b)(2) of Regulation S-K, schedules
           to this Agreement have been omitted. The Registrant hereby undertakes
           to furnish supplementally a copy of such schedules to the Commission
           upon request.

  2.3      Agreement and Plan of Reorganization dated as of May 6, 1998, by and
           among the Registrant, Orion Acquisition Inc., Thermedics Inc., and
           Orion Research, Inc. Pursuant to Item 601(b)(2) of Regulation S-K,
           schedules to this Agreement have been omitted. The Registrant hereby
           undertakes to furnish supplementally a copy of such schedules to the
           Commission upon request (incorporated by reference herein from
           Exhibit 2.3 to the Registrant's Quarterly Report on Form 10-Q for the
           quarter ended April 4, 1998 [File No. 1-12745]).

  3.1*     Articles of Organization of the Registrant, as amended.

  3.2*     By-Laws of the Registrant.

  4.1*     Specimen Common Stock Certificate.

  4.2*     Specimen Rights Certificate.

 10.1*     Corporate Services Agreement dated as of March 20, 1996, between
           Thermo Electron Corporation and the Registrant.

 10.2      Thermo Electron Corporate Charter, as amended and restated effective
           January 3, 1993 (incorporated by reference herein from 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]).

 10.3*     Tax Allocation Agreement dated as of March 20, 1996, between
           Thermedics Inc. and the Registrant.

 10.4*     Master Repurchase Agreement dated as of March 20, 1996, between
           Thermo Electron and the Registrant.

 10.5      Amended and Restated Master Guarantee Reimbursement and Loan
           Agreement dated as of December 10, 1997, between Thermo Electron and
           the Registrant (incorporated by reference herein from Exhibit 10.5 to
           the Registrant's Annual Report on Form 10-K for the fiscal year ended
           January 3, 1998 [File No. 1-12745]).

 10.6      Amended and Restated Master Guarantee Reimbursement and Loan
           Agreement dated as of December 10, 1997, between Thermedics and the
           Registrant (incorporated by reference herein from Exhibit 10.6 to the
           Registrant's Annual Report on Form 10-K for the fiscal year ended
           January 3, 1998 [File No. 1-12745]).

                                       17
<PAGE>

Exhibit
Number     Description of Exhibit

 10.7*     Equity Incentive Plan of the Registrant.

 10.8*     Deferred Compensation Plan for Directors of the Registrant.

           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 Thermedics for
           services rendered to the Registrant or to such affiliated
           corporations. The terms of such plans are substantially the same as
           those of the Registrant's Equity Incentive Plan.

 10.9*     $21.2 Million Principal Amount Promissory Note due March 1998, issued
           by the Registrant to Thermedics.

 10.10*    Form of Indemnification Agreement for Officers and Directors.

 10.11*    Stock Purchase Agreement dated as of March 25, 1996, between David H.
           Fine and the Registrant.

 10.12     Stock Holdings Assistance Plan and Form of Promissory Note
           (incorporated by reference herein from Exhibit 10.12 to the
           Registrant's Annual Report on Form 10-K for the fiscal year ended
           January 3, 1998 [File No. 1-12745]).

 13        Annual Report to Shareholders for the year ended January 2, 1999
           (only those portions incorporated herein by reference).

 21        Subsidiaries of the Registrant.

 23        Consent of Arthur Andersen LLP.

 27        Financial Data Schedule for the year ended January 2, 1999.

 27.1      FinancialData Schedule for the year ended January 3, 1998 (restated 
           for the acquisition of Orion Research, Inc.).

 27.2     FinancialData Schedule for the year ended December 28, 1996 (restated 
          for the acquisition of Orion Research, Inc.).


Each exhibit above that is marked with an asterisk (*) is incorporated by
reference to the correspondingly numbered exhibit to the Company's Registration
Statement on Form S-1 [File No. 333-31987].


                                       18
<PAGE>