SECURITIES AND EXCHANGE COMMISSION

                             Washington, D.C. 20549

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


                                    FORM 8-K


                                 CURRENT REPORT

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



                                 Date of Report
                       (Date of earliest event reported):

                                  April 6, 2000

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


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


Massachusetts                       1-9567                         04-2788806
(State or other                 (Commission                    (I.R.S. Employer
jurisdiction of                  File Number)             Identification Number)
incorporation or
organization)


470 Wildwood Street, P.O. Box 2999
Woburn, Massachusetts                                                     01888
(Address of principal executive offices)                              (Zip Code)


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









This Form 8-K contains forward-looking statements that involve a number of risks
and  uncertainties.  Important factors that could cause actual results to differ
materially from those indicated by such forward-looking statements are set forth
under the  heading  "Forward-looking  Statements"  in Exhibit  13 to  Thermedics
Inc.'s  Annual  Report on Form 10-K for the year ended  January  1, 2000.  These
include risks and uncertainties  relating to: government regulation and industry
standards,  competition and technological change,  intellectual property rights,
reimbursement by insurers for medical procedures,  medical community  acceptance
of medical devices, availability of materials and components, product liability,
international operations,  the company's acquisition strategy, and the company's
cash management arrangement with Thermo Electron.

Item 5.     Other Events

      On April 7, 2000, the Registrant  issued a press release,  attached hereto
as Exhibit 99, regarding its previously announced tender offer for the shares of
common stock, $.10 par value per share, of its subsidiary  Thermedics  Detection
Inc.

Item 7.     Financial Statements, Pro Forma Financial Information and Exhibits

      (a)   Financial Statements of Business Acquired: not applicable.

      (b)   Pro Forma Financial Information: not applicable.

      (c)   Exhibits

            99 Press Release dated April 7, 2000.






                                    SIGNATURE


      Pursuant to the  requirements 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, on this 7th day of April, 2000.



                                        THERMEDICS INC.



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







                                                                      Exhibit 99




Investor Contact: 781-622-1111
Media Contact: 781-622-1252

           Thermedics Completes Cash Tender Offer for Thermedics Detection

WOBURN,  Mass.,  April 7, 2000 - Thermedics  Inc.  (ASE-TMD),  a Thermo Electron
company,  announced  today that it has  successfully  completed  the cash tender
offer of $8.00 per share for any and all  outstanding  shares of its  Thermedics
Detection Inc. subsidiary.

      The offer and withdrawal rights expired at midnight on Thursday,  April 6,
2000. Based on the preliminary report of the depositary for the offer,  American
Stock Transfer & Trust Company,  approximately 1.9 million Thermedics  Detection
shares were tendered.  This brings  Thermedics' and Thermo  Electron's  combined
equity  ownership  in  Thermedics   Detection  to  approximately  98.8  percent.
Thermedics  expects to complete the spin-in of Thermedics  Detection by Tuesday,
April 11, through a short-form  merger.  The short-form  merger does not require
Thermedics Detection board or shareholder approval.

      Shareholders  who  tendered  their shares in the tender offer will receive
payment for their shares shortly.  Shareholders  who did not tender their shares
will  also  receive  $8.00  per  share  in the  short-form  merger.  Information
outlining what steps these Thermedics Detection shareholders must take to obtain
payment will be mailed within a week to 10 days.

      The complete terms and conditions of the tender offer are set forth in the
offer to purchase,  letter of transmittal,  and other related  materials,  which
were filed with the Securities and Exchange Commission on March 10, 2000.

      Thermedics Inc. develops, manufactures, and markets diverse product lines,
including  implantable  heart-assist  devices  and  other  biomedical  products,
security  instruments,  and equipment that assures the quality of a wide variety
of consumer  products and bulk materials.  Thermedics is a public  subsidiary of
Thermo Electron  Corporation.  More  information is available on the Internet at
http://www.thermo.com/subsid/tmd1.html.