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):

                                  May 24, 1999

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


                                 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 the
Registrant's  Annual  Report on Form 10-K for the year  ended  January  2, 1999.
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 Registrant's spinout and acquisition
strategies,   and  the   potential   impact  of  the  year  2000  on  processing
date-sensitive information.

Item 5.     Other Events

      On May 24, 1999, the Registrant  issued a press release  regarding certain
pretax charges that will be taken by the Registrant.

     The press release  stated that the  Registrant  will record pretax  charges
totaling approximately $30 million primarily in its second fiscal quarter, which
ends  July  3,  1999.  These  charges  will  be  incurred  as a  result  of  the
Registrant's  decision to sell its power electronics and test equipment business
to an unrelated  third party. If the Registrant has not sold this business prior
to the consummation of the previously announced proposed transaction with Thermo
Electron Corporation  ("Thermo Electron"),  then as part of any such transaction
the business would be  transferred  to Thermo  Electron as part of that proposed
transaction  and would  subsequently  be sold by Thermo Electron to an unrelated
third party.

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: not applicable.


                                    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 25th day of May, 1999.



                                        THERMEDICS INC.


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