SECURITIES AND EXCHANGE COMMISSION
                             WASHINGTON, D.C. 20549

                                    FORM 8-A

                FOR REGISTRATION OF CERTAIN CLASSES OF SECURITIES
                    PURSUANT TO SECTION 12(b) OR 12(g) OF THE
                         SECURITIES EXCHANGE ACT OF 1934


                           Thermo Electron Corporation
             (Exact Name of Registrant as Specified in its Charter)


Delaware                                                         04-2209186
- --------                                                         ----------
(State of Incorporation or Organization)    (I.R.S. Employer Identification No.)

81 Wyman Street, Waltham, Massachusetts                          02454-9046
- ---------------------------------------                          ----------
(Address of Principal Executive Offices)                         (Zip Code)

If this form relates to the  registration  of a class of securities  pursuant to
Section  12(b)  of  the  Exchange  Act  and is  effective  pursuant  to  General
Instruction A.(c), please check the following box. [X]

If this form relates to the  registration  of a class of securities  pursuant to
Section  12(g)  of  the  Exchange  Act  and is  effective  pursuant  to  General
Instruction A.(d), please check the following box. [ ]

Securities  Act  registration  statement file number to which this form relates:
- ---------- (If applicable)

Securities to be registered pursuant to Section 12(b) of the Act:

     Title of Each Class                       Name of Each Exchange on Which
     To be so Registered                       Each Class is to be Registered
     -------------------                       -------------------------------

3-1/4% Convertible Subordinated Debentures      American Stock Exchange, Inc.
due 2007


Securities to be registered pursuant to Section 12(g) of the Act:

                                      None
                                      ----
                                (Title of Class)







                    INFORMATION REQUIRED IN REGISTRATION STATEMENT

ITEM 1. DESCRIPTION OF REGISTRANT'S SECURITIES TO BE REGISTERED.

      This Form 8-A is being filed by Thermo Electron Corporation to reflect the
fact that it has assumed the  obligations  of ThermoTrex  Corporation  under its
3-1/4%  Convertible  Subordinated  Debentures due 2007 (the  "Debentures")  as a
result of the merger,  effective  August 14, 2000, of  ThermoTrex  with and into
Thermo Electron.  Information  concerning the Debentures registered hereunder is
included  in the  sections  captioned  "Description  of Debt  Securities  of the
Company and the  Guarantees"  in the  prospectus  dated  September  11, 1997 and
"Description  of Debentures and the  Guarantees"  in the  prospectus  supplement
dated October 28, 1997,  which  prospectus and prospectus  supplement were filed
with  the  Commission  under  Rule  424 as a part of  ThermoTrex's  Registration
Statement on Form S-3 [File No. 333-34909 and  333-34909-01],  which information
is incorporated by reference herein. In addition,  as a result of the merger, in
which holders of ThermoTrex  common stock (other than Thermo Electron)  received
0.5503 shares of common stock of Thermo Electron in exchange for each ThermoTrex
share, the Debentures are now convertible into Thermo Electron common stock at a
conversion price of $49.06 per share.






                                    SIGNATURE

      Pursuant to the requirements of Section 12 of the Securities  Exchange Act
of 1934, the registrant has duly caused this registration statement to be signed
on its behalf by the undersigned, thereto duly authorized.

                                    THERMO ELECTRON CORPORATION



                                    By: /s/ Theo Melas-Kyriazi
                                        ---------------------------------------
                                        Theo Melas-Kyriazi
                                        Vice President and Chief
                                        Financial Officer

Date: August 14, 2000