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):

                                January 31, 2000

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


                            THERMO CARDIOSYSTEMS INC.
                     -------------------------------------
             (Exact name of Registrant as specified in its charter)


Massachusetts                     1-10114                             04-3027040
--------------------------------------------------------------------------------
(State or other                (Commission                      (I.R.S. Employer
jurisdiction of                File Number)               Identification Number)
incorporation or
organization)


470 Wildwood Street
Woburn, Massachusetts                                                      01888
--------------------------------------------------------------------------------
(Address of principal executive offices)                              (Zip Code)


                                 (781) 932-8668
                         (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 Thermo
Cardiosystems  Inc.'s  Annual  Report on Form 10-K for the year ended January 2,
1999. These include risks and uncertainties  relating to: regulatory  approvals,
reimbursement by insurers,  medical community acceptance,  technological change,
competition,   new  products,   availability   of  materials   and   components,
intellectual  property  rights,   limited  experience  in  commercializing  LVAS
products,  product  liability,  international  operations  and  sales,  and  the
potential impact of the year 2000 on processing date-sensitive information.

Item 5.  Other Events
         ------------

         On January 31, 2000, the Registrant issued a press release, attached
hereto as Exhibit 99, regarding certain corporate transactions affecting the
Registrant.

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 January 31, 2000.


<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 31st day of January, 2000.



                                                 THERMO CARDIOSYSTEMS INC.


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



<PAGE>


                                                                      Exhibit 99

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

              THERMO CADIOSYSTEMS ANNOUNCES THAT ITS PARENT PLANS
                        TO SEEK A BUYER FOR THE COMPANY

WOBURN, Mass., January 31, 2000 - Thermo Cardiosystems Inc. (ASE-TCA) announced
today that its parent company, Thermedics Inc. (ASE-TMD), plans to seek a buyer
for Thermo Cardiosystems. This action is part of a major reorganization plan
under which Thermo Cardiosystems' ultimate parent, Thermo Electron Corporation
(NYSE-TMO), will spin in, spin off, and sell various businesses to focus solely
on its core measurement and detection instruments business.

         "For more than 30 years, Thermo Electron has tenaciously pursued the
research, development, and commercialization of its LVAS technology, so that
today, Thermo Cardiosystems holds the dominant position in this market," said R.
Michael Kleine, chief executive officer of Thermo Cardiosystems. "We continue to
make important strides with our next-generation technologies, which have the
potential to bring hope to many more cardiac patients. This is a good
opportunity for us to become part of a strategically aligned company with a
strong commercial presence in the cardiovascular market to allow us to
aggressively pursue the next phase of our ambitious growth plans."

         Thermo Cardiosystems Inc. is a leader in the research, development, and
manufacture of implantable left ventricular-assist systems (LVAS). Its
air-driven and electric HeartMate heart-assist devices are implanted alongside
the natural heart and take over the pumping function of the left ventricle for
patients whose hearts are too damaged or diseased to produce adequate blood
flow. Both devices are approved for commercial sale in the United States,
Europe, and Canada. The company also supplies whole-blood coagulation testing
equipment and related disposables, as well as single-use skin-incision devices.
More information is available on the Internet at
http://www.thermo.com/subsid/tca1.html.

The following constitutes a "Safe Harbor" statement under the Private Securities
Litigation Reform Act of 1995: This press release 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 company's annual report on Form 10-K for the
year ended January 2, 1999. These include risks and uncertainties relating to:
regulatory approvals, reimbursement by insurers, medical community acceptance,
technological change, competition, new products, availability of materials and
components, intellectual property rights, limited experience in commercializing
LVAS products, product liability, international operations and sales, and the
potential impact of the year 2000 on processing date-sensitive information.
[{"type": "8-K", "sequence": "1", "description": "FORM 8-K", "secsgml_size_bytes": 6797}]
{"company-data": {"conformed-name": "THERMO CARDIOSYSTEMS INC", "cik": "0000841939", "assigned-sic": "3845", "irs-number": "043027040", "state-of-incorporation": "MA", "fiscal-year-end": "0102"}, "filing-values": {"form-type": "8-K", "act": "34", "file-number": "001-10114", "film-number": "519414"}, "business-address": {"street1": "470 WILDWOOD ST", "street2": "P O BOX 2697", "city": "WOBURN", "state": "MA", "zip": "01888-2697", "phone": "7819328668"}, "mail-address": {"street1": "470 WILDWOOD STREET", "street2": "P O BOX 2697", "city": "WOBURN", "state": "MA", "zip": "01888-2697"}}
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):

                                January 31, 2000

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

                            THERMO CARDIOSYSTEMS INC.
                     -------------------------------------
             (Exact name of Registrant as specified in its charter)

Massachusetts                     1-10114                             04-3027040
--------------------------------------------------------------------------------
(State or other                (Commission                      (I.R.S. Employer
jurisdiction of                File Number)               Identification Number)
incorporation or
organization)

470 Wildwood Street
Woburn, Massachusetts                                                      01888
--------------------------------------------------------------------------------
(Address of principal executive offices)                              (Zip Code)

                                 (781) 932-8668
                         (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 Thermo
Cardiosystems  Inc.'s  Annual  Report on Form 10-K for the year ended January 2,
1999. These include risks and uncertainties  relating to: regulatory  approvals,
reimbursement by insurers,  medical community acceptance,  technological change,
competition,   new  products,   availability   of  materials   and   components,
intellectual  property  rights,   limited  experience  in  commercializing  LVAS
products,  product  liability,  international  operations  and  sales,  and  the
potential impact of the year 2000 on processing date-sensitive information.

Item 5.  Other Events
         ------------

         On January 31, 2000, the Registrant issued a press release, attached
hereto as Exhibit 99, regarding certain corporate transactions affecting the
Registrant.

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 January 31, 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 31st day of January, 2000.

                                                 THERMO CARDIOSYSTEMS INC.

                                                 By:/s/ Theo Melas-Kyriazi
                                                    ----------------------------
                                                    Theo Melas-Kyriazi
                                                    Chief Financial Officer
Exhibit 99

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

              THERMO CADIOSYSTEMS ANNOUNCES THAT ITS PARENT PLANS
                        TO SEEK A BUYER FOR THE COMPANY

WOBURN, Mass., January 31, 2000 - Thermo Cardiosystems Inc. (ASE-TCA) announced
today that its parent company, Thermedics Inc. (ASE-TMD), plans to seek a buyer
for Thermo Cardiosystems. This action is part of a major reorganization plan
under which Thermo Cardiosystems' ultimate parent, Thermo Electron Corporation
(NYSE-TMO), will spin in, spin off, and sell various businesses to focus solely
on its core measurement and detection instruments business.

         "For more than 30 years, Thermo Electron has tenaciously pursued the
research, development, and commercialization of its LVAS technology, so that
today, Thermo Cardiosystems holds the dominant position in this market," said R.
Michael Kleine, chief executive officer of Thermo Cardiosystems. "We continue to
make important strides with our next-generation technologies, which have the
potential to bring hope to many more cardiac patients. This is a good
opportunity for us to become part of a strategically aligned company with a
strong commercial presence in the cardiovascular market to allow us to
aggressively pursue the next phase of our ambitious growth plans."

         Thermo Cardiosystems Inc. is a leader in the research, development, and
manufacture of implantable left ventricular-assist systems (LVAS). Its
air-driven and electric HeartMate heart-assist devices are implanted alongside
the natural heart and take over the pumping function of the left ventricle for
patients whose hearts are too damaged or diseased to produce adequate blood
flow. Both devices are approved for commercial sale in the United States,
Europe, and Canada. The company also supplies whole-blood coagulation testing
equipment and related disposables, as well as single-use skin-incision devices.
More information is available on the Internet at
http://www.thermo.com/subsid/tca1.html.

The following constitutes a "Safe Harbor" statement under the Private Securities
Litigation Reform Act of 1995: This press release 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 company's annual report on Form 10-K for the
year ended January 2, 1999. These include risks and uncertainties relating to:
regulatory approvals, reimbursement by insurers, medical community acceptance,
technological change, competition, new products, availability of materials and
components, intellectual property rights, limited experience in commercializing
LVAS products, product liability, international operations and sales, and the
potential impact of the year 2000 on processing date-sensitive information.