SECURITIES AND EXCHANGE COMMISSION
                              WASHINGTON, DC 20549

                                   -----------

                                  SCHEDULE 13D
                                 (Rule 13d-101)

             INFORMATION TO BE INCLUDED IN STATEMENTS FILED PURSUANT
             TO RULE 13d-l(a) AND AMENDMENTS THERETO FILED PURSUANT
                                TO RULE 13d-2(a)

                                (Amendment No. 2)

                              Thoratec Corporation

                                (Name of Issuer)

                      Common Stock, no par value per share

                         (Title of Class of Securities)

                                   885175 30 7

                                 (CUSIP Number)

                             Seth H. Hoogasian, Esq.
                                 General Counsel
                                 (781) 622-1000
                           Thermo Electron Corporation
                                 81 Wyman Street
                        Waltham, Massachusetts 02454-9046

                  (Name, Address and Telephone Number of Person
                Authorized to Receive Notices and Communications)

                                 August 22, 2001

             (Date of Event Which Requires Filing of This Statement)

     If the filing  person has  previously  filed a statement on Schedule 13G to
report the  acquisition  that is the subject of this Schedule 13D, and is filing
this  schedule  because  of Rule  13d-1(e),  13d-1(f)  or  13d-1(g),  check  the
following box [ ].

          Note.  Schedules filed in paper format shall include a signed original
     and five copies of the schedule,  including all exhibits. See Rule 13d-7(b)
     for other  parties to whom copies are to be sent.  (Continued  on following
     pages)






---------------------------                          --------------------------
  CUSIP NO. 885175 30 7               13D                Page 2 of 6 Pages
---------------------------                          --------------------------


-------------------------------------------------------------------------------
1.    NAMES OF REPORTING PERSONS
      I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (ENTITIES ONLY)

      Thermo Electron Corporation
      04-2209186
-------------------------------------------------------------------------------
2.    CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP*                 (a) [ ]
                                                                        (b) [ ]
-------------------------------------------------------------------------------
3.    SEC USE ONLY

-------------------------------------------------------------------------------
4.    SOURCE OF FUNDS*

      SC
-------------------------------------------------------------------------------
5.    CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT TO
      ITEM 2(d) or 2(e)                                                     [ ]

-------------------------------------------------------------------------------
6.    CITIZENSHIP OR PLACE OF ORGANIZATION
      State of Delaware
-------------------------------------------------------------------------------
 NUMBER OF SHARES  7.    SOLE VOTING POWER
   BENEFICIALLY               11,868,634
  OWNED BY EACH
 REPORTING PERSON
       WITH
                   ------------------------------------------------------------
                   8.    SHARED VOTING POWER
                              2,731,779
                   ------------------------------------------------------------
                   9.    SOLE DISPOSITIVE POWER
                              14,600,413
                   ------------------------------------------------------------
                   10.   SHARED DISPOSITIVE POWER
                              -0-
-------------------------------------------------------------------------------
11.    AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON
       14,600,413

-------------------------------------------------------------------------------
12.    CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES*
       [ ]

-------------------------------------------------------------------------------
13.    PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11)
       26.5%

-------------------------------------------------------------------------------
14.    TYPE OF REPORTING PERSON*

       CO
-------------------------------------------------------------------------------
                      *SEE INSTRUCTIONS BEFORE FILLING OUT!





     Thermo  Electron  Corporation,  a  Delaware  corporation  ("the  "Reporting
Person"),  hereby  amends its  statement  on Schedule 13D relating to the common
stock,  no par value per share (the  "Common  Stock"),  of Thoratec  Corporation
(formerly known as Thoratec Laboratories Corporation),  a California corporation
(the "Company").

ITEM 2.    Identity and Background.

     Item 2 is hereby amended and restated as follows:

     This  Amendment  is being filed by the  Reporting  Person  pursuant to Rule
13d-2 to reflect the change of information  previously  reported under Item 5 of
its Schedule 13D, as amended.

     The  principal  business  address  and  principal  office  address  of  the
Reporting Person is 81 Wyman Street, Waltham, Massachusetts 02454-9046.

     The Reporting  Person is a leading  provider of analytical  and  monitoring
instruments used in a broad range of applications,  from life sciences  research
to telecommunications to food, drug, and beverage production.

     Appendix A attached to hereto sets forth with respect to each executive
officer and director of the reporting Person the following information:

          (a)  name;
          (b)  business address;
          (c)  present   principal   occupation  or  employment  and  the  name,
               principal  business  and  address  of any  corporation  or  other
               organization in which such employment is conducted; and
          (d)  citizenship.

To the knowledge of the Reporting  Person,  there is no person who may be deemed
to be a controlling person of the Reporting Person.

     During the last five  years,  neither  the  Reporting  Person  nor,  to the
knowledge of the  Reporting  Person,  any  executive  officer or director of the
Reporting Person has been convicted in a criminal proceeding  (excluding traffic
violations or similar misdemeanors).

     During the last five  years,  neither  the  Reporting  Person  nor,  to the
knowledge of the  Reporting  Person,  any  executive  officer of director of the
Reporting  Person  has  been a party  to a civil  proceeding  of a  judicial  or
administrative  body of  competent  jurisdiction  which  resulted in a judgment,
decree  or final  order  enjoining  future  violations  of,  or  prohibiting  or
mandating activities subject to, Federal or State securities laws or finding any
violation with respect to such laws.

ITEM 5.    Interest in Securities of the Issuer.

     Item 5 is hereby amended and restated in its entirety as follows:


     (a) As of the date of this Amendment,  the Reporting Person owns 14,600,413
shares of Common Stock which represents 26.5% of the outstanding Common Stock of
the Company,  based upon the total Common Stock  outstanding  as reported on the
Company's  Quarterly  Report on Form 10-Q for the period ended June 30, 2001. Of
the 14,600,413  shares of Common Stock currently owned by the Reporting  Person,
(i) 30,727  shares of Common Stock are subject to options to acquire such shares
granted by the  Reporting  Person  pursuant to its director  and employee  stock
option  plans,  and (ii) 39,869  shares of Common  Stock are  issuable  upon the
conversion by the Reporting Person of $1,500,000  principal amount of the 4 3/4%
Debentures held by it.  Information with respect to the beneficial  ownership of
the shares of Common Stock of the other  persons named in Item 2 is set forth in
Appendix  A.  Except as set forth in this Item 5, to the best  knowledge  of the
Reporting Person,  none of the parties named in Item 2 owns any of the Company's
Common Stock.

     (b) With  respect  to  2,731,779  shares  of  Common  Stock of the  Company
beneficially  owned by the Reporting  Person,  the  Reporting  Person shares the
power to vote all of such shares with the  Company  pursuant to the  Shareholder
Agreement,  as  more  fully  described  in Item 4  above.  With  respect  to the
remainder of the shares of Common Stock of the Company beneficially owned by the
Reporting  Person,  the  Reporting  Person  has the sole  power to vote all such
shares.  Subject  to the  terms  of the  Shareholder  Agreement,  as more  fully
described in Item 4 above, the Reporting Person has the sole power to dispose of
the shares of Common Stock  beneficially owned by it. With respect to the shares
of Common Stock of the Company  beneficially owned by the other persons named in
Item 2,  except as set forth in  Appendix A, each such person has the sole power
to vote all of such shares and the sole power to dispose of all of such shares.

     Item 1 sets forth the Company's name and state of incorporation  along with
the address of its  principal  business  and  principal  office.  The  Company's
principal business is the research, development,  manufacturing and marketing of
medical devices for circulatory support and vascular graft applications.  To the
best knowledge of the Reporting Person,  during the last five years, the Company
(i) has  not  been  convicted  in any  criminal  proceeding  (excluding  traffic
violations  or  similar  misdemeanors)  and  (ii)  was  not a  party  to a civil
proceeding of a judicial or  administrative  body of competent  jurisdiction  as
result  of which it was or is  subject  to a  judgment,  decree  or final  order
enjoining future violations of, or prohibiting or mandating  activities  subject
to,  Federal or State  securities  laws or finding any violation with respect to
such laws.

     (c) Except as  described  below in this Item 5 and in Item 4, which item is
incorporated  herein by  reference,  neither  the  Reporting  Person nor, to the
knowledge of the Reporting  Person,  any person named in Appendix A beneficially
has effected any transactions in Common Stock during the past 60 days.

     The  Reporting  Person has  affected the  following  open market sales with
respect to the Common Stock since the filing of Amendment  No. 1 to its Schedule
13D:


--------------------------------------------------------------------------------
           Date                       Amount                Price per Share
--------------------------------------------------------------------------------
         08/07/01                     10,000                    $18.00
--------------------------------------------------------------------------------
         08/17/01                    100,000                   $17.4423
--------------------------------------------------------------------------------
         08/20/01                    165,000                    $18.612
--------------------------------------------------------------------------------
         08/21/01                    200,000                   $18.6254
--------------------------------------------------------------------------------
         08/22/01                    250,000                    $18.514
--------------------------------------------------------------------------------
         08/23/01                    300,000                   $19.4427
--------------------------------------------------------------------------------
         08/24/01                    303,240                   $19.1652
--------------------------------------------------------------------------------

     In addition to the  foregoing,  on August 17, 2001,  the  Reporting  Person
transferred  4,175 shares of Common Stock to a former  employee of the Reporting
Person who exercised an option to purchase the shares from the Reporting  Person
at a price of $13.07 per share.

     (d)  None.

     (e)  Not applicable.





                                   SIGNATURES

     After  reasonable  inquiry and to the best of my  knowledge  and belief,  I
certify that the information  set forth in this statement is true,  complete and
correct.


                                        Dated:  August 24, 2001

                                        THERMO ELECTRON CORPORATION


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





                                   APPENDIX A

Thermo Electron Corporation

     The  name,  present  principal  occupation  or  employment  and  beneficial
ownership of shares of common stock of Thoratec  Corporation  (the "Company") of
each  director and executive  officer of Thermo  Electron  Corporation  ("Thermo
Electron") is set forth below.  Unless otherwise noted, all such individuals are
citizens of the United States.  Unless  otherwise noted, the business address of
each  executive  officer  and  director of Thermo  Electron is 81 Wyman  Street,
Waltham, Massachusetts 02454-9046.

Directors


                                                                            

-------------------------------------------------------------------------------------------------------------------
                                                            Beneficial Ownership of Shares of the Company
                                                                                Common Stock
                                                     --------------------------------------------------------------
                                                                                Shares Underlying
                                                                                     Options             Total
Name/Present Principal                               Shares Held                Exercisable Prior        Beneficial
Occupation or Employment       Business Address       Outright                  to August 24, 2001       Ownership
-------------------------------------------------------------------------------------------------------------------
Peter O. Crisp
Vice Chairman of Rockefeller                                0                              0                 0
Financial Services Inc.
-------------------------------------------------------------------------------------------------------------------
Frank Jungers                 822 NW Murrray
Private consultant on         Suite 242
business and energy           Portland, Oregon 97229        0                            835               835
matters.
-------------------------------------------------------------------------------------------------------------------
Jim P. Manzi
Currently involved in a
number of technology
startup ventures,                                           0                              0                 0
primarily relating to the Internet.
-------------------------------------------------------------------------------------------------------------------
Robert A. McCabe              Pilot Capital Corporation
Chairman of Pilot             444 Madison Avenue
Capital Corporation.          Suite 2103                 9,393                           835            10,228
                              New York, New York 10022
-------------------------------------------------------------------------------------------------------------------
Robert W. O'Leary
Chairman and Chief Executive
Officer of The Sagamore Group.                               0                             0                 0
-------------------------------------------------------------------------------------------------------------------
Hutham S. Olayan              Suite 1100
President and a director      505 Park Avenue
of Olayan America             New York, New York 10022   9,393                           835            10,228
Corporation.
-------------------------------------------------------------------------------------------------------------------
Michael E. Porter
Bishop William Lawrence
University Professor at                                      0                             0                 0
Harvard Business School.
-------------------------------------------------------------------------------------------------------------------
Elaine S. Ullian
President and Chief Executive                                0                             0                 0
Officer of Boston
Medical Center.
-------------------------------------------------------------------------------------------------------------------
Richard F. Syron
Chief Executive Officer
and Chairman of the                                          0                             0                 0
Board of Thermo Electron
-------------------------------------------------------------------------------------------------------------------
Marijn E. Dekkers(1)
President, Chief Operating Officer                           0                             0                 0
and Director of Thermo Electron
-------------------------------------------------------------------------------------------------------------------


(1) Mr. Dekkers is a citizen of The Netherlands






Executive Officers Who are Not Directors

      No person is a controlling stockholder of Thermo Electron.


                                                                                                

                                                            Beneficial Ownership of Shares of the Company
                                                                                Common Stock
                                                     --------------------------------------------------------------
                                                                                Shares Underlying
                                                                                     Options             Total
Name/Present Principal                               Shares Held                Exercisable Prior        Beneficial
Occupation or Employment       Business Address       Outright                  to August 24, 2001       Ownership
--------------------------------------------------------------------------------------------------------------------
Theo Melas-Kyriazi(2)                                    2,960                        16,700            19,660
Vice President and Chief
Financial Officer of
Thermo Electron
--------------------------------------------------------------------------------------------------------------------
Guy Broadbent(3)                                             0                             0                 0
Vice President of Thermo
Electron, President,
Optical Technologies
--------------------------------------------------------------------------------------------------------------------
Barry S. Howe                                                0                             0                 0
Vice President of Thermo
Electron, President,
Measurement and Control
--------------------------------------------------------------------------------------------------------------------
Colin Maddix                                                 0                             0                 0
Vice President of Thermo
Electron, President,
Life Sciences
--------------------------------------------------------------------------------------------------------------------
Seth H. Hoogasian                                            0                             0                 0
Vice President, General
Counsel and Secretary of
Thermo Electron
---------------------------------------------------------------------------------------------------------------------
Peter E. Hornstra                                            0                             0                 0
Corporate Controller and
Chief Accounting Officer
of Thermo Electron
----------------------------------------------------------------------------------------------------------------------
All directors and current executive officers as a       21,746                        19,205            40,951
group

(2) Mr. Melas-Kyriazi is a citizen of Greece.

(3) Mr. Broadbent is a citizen of the United Kingdom.