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):

                               September 29, 1998

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


                             THERMOTREX CORPORATION
             (Exact name of Registrant as specified in its charter)


Delaware                        1-10791                          52-1711436
(State or other               (Commission                    (I.R.S. Employer
jurisdiction of               File Number)               Identification Number) 
incorporation or
organization)


10455 Pacific Center Court
San Diego, California                                            92121 
(Address of principal executive offices)                       (Zip Code)


                                 (619) 646-5300
                         (Registrant's telephone number
                              including area code)



<PAGE>


      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
include  those  set forth  under the  heading  "Forward-looking  Statements"  in
Exhibit 13 to ThermoTrex  Corporation's  Annual Report for the fiscal year ended
September 27, 1997. These include risks and  uncertainties  relating to: product
development and commercialization,  market acceptance, government regulation and
healthcare reform,  patient  reimbursement,  competition,  management of growth,
ability  to  attract  qualified  personnel,  intellectual  property  rights  and
litigation,  product  liability,  dependence on significant  OEM  relationships,
risks associated with ThermoTrex's  acquisition and spinout strategies,  and the
potential impact of the year 2000 on processing date-sensitive information.

Item 5.     Other Events

      On September 29, 1998,  ThermoTrex  Corporation  ("ThermoTrex")  issued
a press release announcing that its ThermoLase Corporation  ("ThermoLase") 
subsidiary will record aftertax restructuring and other charges totaling
approximately $15 million in its fourth fiscal  quarter,  ending  October  3, 
1998.  ThermoLase  will incur a charge of approximately  $8.3  million as a
result of its  decision  to close three of its domestic  Spa  Thira  locations
along  with  the spa in  France.  In  addition, ThermoLase  will incur a charge
of $6.7 million to write off certain tax assets, primarily  loss  carryforwards.
These charges will reduce  fourth  quarter 1998 diluted  earnings per share by 
approximately  $.79.  ThermoTrex  estimates that these actions will result in 
fiscal 1999 operating  savings of  approximately $2 million.

      ThermoLase will close its spas in Miami and Palm Beach, Florida, and in La
Jolla,  California.  The  remaining  11  domestic  spas will be  converted  into
full-service, luxury day spas, under the Greenhouse name.

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.



<PAGE>




                                    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 29th day of September, 1998.



                                          THERMOTREX CORPORATION


                                          By:/s/ Kenneth J. Apicerno
                                             Kenneth J. Apicerno
                                             Treasurer
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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):

                               September 29, 1998

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

                             THERMOTREX CORPORATION
             (Exact name of Registrant as specified in its charter)

Delaware                        1-10791                          52-1711436
(State or other               (Commission                    (I.R.S. Employer
jurisdiction of               File Number)               Identification Number) 
incorporation or
organization)

10455 Pacific Center Court
San Diego, California                                            92121 
(Address of principal executive offices)                       (Zip Code)

                                 (619) 646-5300
                         (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
include  those  set forth  under the  heading  "Forward-looking  Statements"  in
Exhibit 13 to ThermoTrex  Corporation's  Annual Report for the fiscal year ended
September 27, 1997. These include risks and  uncertainties  relating to: product
development and commercialization,  market acceptance, government regulation and
healthcare reform,  patient  reimbursement,  competition,  management of growth,
ability  to  attract  qualified  personnel,  intellectual  property  rights  and
litigation,  product  liability,  dependence on significant  OEM  relationships,
risks associated with ThermoTrex's  acquisition and spinout strategies,  and the
potential impact of the year 2000 on processing date-sensitive information.

Item 5.     Other Events

      On September 29, 1998,  ThermoTrex  Corporation  ("ThermoTrex")  issued
a press release announcing that its ThermoLase Corporation  ("ThermoLase") 
subsidiary will record aftertax restructuring and other charges totaling
approximately $15 million in its fourth fiscal  quarter,  ending  October  3, 
1998.  ThermoLase  will incur a charge of approximately  $8.3  million as a
result of its  decision  to close three of its domestic  Spa  Thira  locations
along  with  the spa in  France.  In  addition, ThermoLase  will incur a charge
of $6.7 million to write off certain tax assets, primarily  loss  carryforwards.
These charges will reduce  fourth  quarter 1998 diluted  earnings per share by 
approximately  $.79.  ThermoTrex  estimates that these actions will result in 
fiscal 1999 operating  savings of  approximately $2 million.

      ThermoLase will close its spas in Miami and Palm Beach, Florida, and in La
Jolla,  California.  The  remaining  11  domestic  spas will be  converted  into
full-service, luxury day spas, under the Greenhouse name.

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 29th day of September, 1998.

                                          THERMOTREX CORPORATION

                                          By:/s/ Kenneth J. Apicerno
                                             Kenneth J. Apicerno
                                             Treasurer