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

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


                             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 are
set forth  under the  heading  "Forward-looking  Statements"  in  Exhibit  13 to
ThermoTrex  Corporation's  Annual Report on Form 10-K for the year ended October
3,  1998,  as  amended.  These  include  risks and  uncertainties  relating  to:
development  and   commercialization  of  products  under  development,   market
acceptance,   difficulty  in  retaining  qualified   management  and  personnel,
dependence on capital  spending  policies,  government  contracts,  decreases in
military weapons spending,  compliance with government regulations, the need for
regulatory   approvals,   healthcare   reform   and   uncertainty   of   patient
reimbursement,  intense  competition,  ability  to retain  qualified  personnel,
dependence  on  patents  and  proprietary  rights,   dependence  on  significant
relationships,   potential   product   liability,   risks  associated  with  the
Registrant's  acquisition and spinout strategy,  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  stating that its
parent  corporation,   Thermo  Electron  Corporation  ("Thermo  Electron"),  has
proposed the merger of the Registrant into Thermo Electron. The Registrant would
become a wholly owned subsidiary of Thermo Electron.  Public shareholders of the
Registrant would receive shares of the common stock,  $1.00 par value per share,
of Thermo  Electron  in  exchange  for their  shares of the common  stock of the
Registrant.

      This proposal is subject to numerous conditions,  including  establishment
of a price and exchange ratio,  confirmation  of anticipated  tax  consequences,
approval by the board of directors of the Registrant  (including its independent
directors),   negotiation  and  execution  of  a  definitive  merger  agreement,
completion  of review by the  Securities  and  Exchange  Commission  of  certain
required filings regarding the proposed  transaction,  and receipt of a fairness
opinion from an investment banking firm.
<PAGE>

      The Registrant also announced that,  prior to the consummation of a merger
with Thermo Electron, it plans to sell, in a private transaction,  approximately
3.7 million newly issued shares of common stock to Thermo Electron.  Such shares
will be issued from the Registrant's authorized but unissued shares. The purpose
of this sale is to increase  Thermo  Electron's  ownership of the  Registrant to
more than 80 percent,  which will allow the  Registrant  and Thermo  Electron to
file consolidated tax returns. The price will be established at the time of sale
by a committee of the board of directors of the Registrant.

      In  addition,   the  Registrant  announced  that  it  will  record  pretax
restructuring  and  other  charges  totaling  approximately  $105  million.  The
majority of these  charges will be recorded in the third fiscal  quarter,  which
ends July 3, 1999, and primarily  relate to  restructuring  at the  Registrant's
ThermoLase   Corporation   ("ThermoLase")   subsidiary   and  its  Trex  Medical
Corporation  ("Trex Medical")  subsidiary.  The charges at ThermoLase consist of
write-offs  relating to the sale or closure of its spas,  write-offs relating to
lasers, and the termination of various international joint venture arrangements.
Restructuring  expenses at Trex Medical consist of charges relating primarily to
the  decision  to  close  two of  Trex  Medical's  four  domestic  manufacturing
facilities  after  relocating  these  operations,  as previously  announced.  In
addition,  the  Registrant  will record a write-off of goodwill  resulting  from
these and related actions.

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 25th day of May, 1999.



                                        THERMOTREX CORPORATION


                                        By:  /s/ Theo Melas-Kyriazi
                                             Theo Melas-Kyriazi
                                             Chief Financial Officer
[{"type": "8-K", "sequence": "1", "description": "FORM 8-K", "secsgml_size_bytes": 6069}]
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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):

                                  May 24, 1999

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

                             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 are
set forth  under the  heading  "Forward-looking  Statements"  in  Exhibit  13 to
ThermoTrex  Corporation's  Annual Report on Form 10-K for the year ended October
3,  1998,  as  amended.  These  include  risks and  uncertainties  relating  to:
development  and   commercialization  of  products  under  development,   market
acceptance,   difficulty  in  retaining  qualified   management  and  personnel,
dependence on capital  spending  policies,  government  contracts,  decreases in
military weapons spending,  compliance with government regulations, the need for
regulatory   approvals,   healthcare   reform   and   uncertainty   of   patient
reimbursement,  intense  competition,  ability  to retain  qualified  personnel,
dependence  on  patents  and  proprietary  rights,   dependence  on  significant
relationships,   potential   product   liability,   risks  associated  with  the
Registrant's  acquisition and spinout strategy,  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  stating that its
parent  corporation,   Thermo  Electron  Corporation  ("Thermo  Electron"),  has
proposed the merger of the Registrant into Thermo Electron. The Registrant would
become a wholly owned subsidiary of Thermo Electron.  Public shareholders of the
Registrant would receive shares of the common stock,  $1.00 par value per share,
of Thermo  Electron  in  exchange  for their  shares of the common  stock of the
Registrant.

      This proposal is subject to numerous conditions,  including  establishment
of a price and exchange ratio,  confirmation  of anticipated  tax  consequences,
approval by the board of directors of the Registrant  (including its independent
directors),   negotiation  and  execution  of  a  definitive  merger  agreement,
completion  of review by the  Securities  and  Exchange  Commission  of  certain
required filings regarding the proposed  transaction,  and receipt of a fairness
opinion from an investment banking firm.
The Registrant also announced that,  prior to the consummation of a merger
with Thermo Electron, it plans to sell, in a private transaction,  approximately
3.7 million newly issued shares of common stock to Thermo Electron.  Such shares
will be issued from the Registrant's authorized but unissued shares. The purpose
of this sale is to increase  Thermo  Electron's  ownership of the  Registrant to
more than 80 percent,  which will allow the  Registrant  and Thermo  Electron to
file consolidated tax returns. The price will be established at the time of sale
by a committee of the board of directors of the Registrant.

      In  addition,   the  Registrant  announced  that  it  will  record  pretax
restructuring  and  other  charges  totaling  approximately  $105  million.  The
majority of these  charges will be recorded in the third fiscal  quarter,  which
ends July 3, 1999, and primarily  relate to  restructuring  at the  Registrant's
ThermoLase   Corporation   ("ThermoLase")   subsidiary   and  its  Trex  Medical
Corporation  ("Trex Medical")  subsidiary.  The charges at ThermoLase consist of
write-offs  relating to the sale or closure of its spas,  write-offs relating to
lasers, and the termination of various international joint venture arrangements.
Restructuring  expenses at Trex Medical consist of charges relating primarily to
the  decision  to  close  two of  Trex  Medical's  four  domestic  manufacturing
facilities  after  relocating  these  operations,  as previously  announced.  In
addition,  the  Registrant  will record a write-off of goodwill  resulting  from
these and related actions.

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.

                                        THERMOTREX CORPORATION

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