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                                  UNITED STATES
                       SECURITIES AND EXCHANGE COMMISSION
                             Washington, D.C. 20549


                         SCHEDULE 13G - Amendment No. 1


                    Under the Securities Exchange Act of 1934


                              TransAlta Corporation
--------------------------------------------------------------------------------
                                (Name of Issuer)


                                  Common Shares
--------------------------------------------------------------------------------
                         (Title of Class of Securities)


                                    89346D107
                                 --------------
                                 (CUSIP Number)


                                December 31, 2004
--------------------------------------------------------------------------------
             (Date of Event Which Requires Filing of this Statement)


Check the appropriate box to designate the rule pursuant to which this Schedule
is filed:

|_|      Rule 13d-1(b)
|X|      Rule 13d-1(c)
|_|      Rule 13d-1(d)


----------
*The remainder of this cover page shall be filled out for a reporting person's
initial filing on this form with respect to the subject class of securities, and
for any subsequent amendment containing information which would alter the
disclosures provided in a prior cover page.

The information required in the remainder of this cover page shall not be deemed
to be "filed" for the purpose of Section 18 of the Securities Exchange Act of
1934 ("Act") or otherwise subject to the liabilities of that section of the Act
but shall be subject to all other provisions of the Act (however, see the
Notes).

Sec 1745 (6/01)



                                      -2-


---------------------------------------------
            CUSIP NO. 89346D107                                13G
---------------------------------------------

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

       Canada Pension Plan Investment Board / Not applicable

------------ -------------------------------------------------------------------
    2. CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (SEE INSTRUCTIONS)
                                                                         (a) |_|
       Not applicable                                                    (b) |_|

------------ -------------------------------------------------------------------
    3. SEC USE ONLY

------------ -------------------------------------------------------------------
    4. CITIZENSHIP OR PLACE OF ORGANIZATION

       Canada
------------ -------------------------------------------------------------------
                               5. SOLE VOTING POWER

                                               13,707,157
                            --------- ------------------------------------------
     NUMBER OF SHARES          6. SHARED VOTING POWER
  BENEFICIALLY OWNED BY
           EACH                                0
     REPORTING PERSON       --------- ------------------------------------------
           WITH                7. SOLE DISPOSITIVE POWER

                                               13,707,157
                            --------- ------------------------------------------
                               8. SHARED DISPOSITIVE POWER

                                               0
--------------------------- --------- ------------------------------------------
    9. AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

       13,707,157
------------ -------------------------------------------------------------------
   10. CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES
       (SEE INSTRUCTIONS)                                                    |_|

------------ -------------------------------------------------------------------
   11. PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW 9

       7.06%
------------ -------------------------------------------------------------------
   12. TYPE OF REPORTING PERSON (SEE INSTRUCTIONS)

       CO
------------ -------------------------------------------------------------------



                                      -3-


Item 1(a).        Name of Issuer

                  The name of the issuer is TransAlta Corporation (the
"Company").


Item 1(b).        Address of Issuer's Principal Executive Offices

                  The principal executive offices of the Company are located at
110 12th Avenue S.W., Calgary, Alberta T2R 0G7, Canada.


Item 2(a).        Name of Person Filing

                  This statement is being filed by Canada Pension Plan
Investment Board ("CPP Investment Board").


Item 2(b).        Address of Principal Business Office or, if none, Residence

                  The address of the principal business office of the reporting
person is One Queen Street East, Suite 2700, Toronto, Ontario M5C 2W5, Canada.


Item 2(c).        Citizenship

                  Canada.


Item 2(d).        Title of Class of Securities

                  The securities to which this statement relates are Common
Shares (the "Shares") of the Company.


Item 2(e).        CUSIP Number

                  The CUSIP number of the Shares is 89346D107.


Item 3.           If this statement is filed pursuant to ss.ss. 240.13d-1(b) or
                  240.13d-2(b) or (c), check whether the person filing is a:

                  Not applicable.



                                      -4-


Item 4.          Ownership

                         (a) As of December 31, 2004, CPP Investment Board
                 directly owned 13,707,157 Shares.

                         (b) The Shares directly owned by CPP Investment Board
                 represented approximately 7.06% of the issued and outstanding
                 Shares as of December 31, 2004.

                         (c) As of December 31, 2004, CPP Investment Board had
                 the sole power to vote or to direct the voting of the Shares
                 and had the sole power to dispose of or to direct the
                 disposition of the Shares.

Item 5.          Ownership of Five Percent or Less of a Class

                 Not applicable.


Item 6.          Ownership of More than Five Percent on Behalf of Another Person

                 Not applicable.


Item 7.          Identification and Classification of the Subsidiary Which
                 Acquired the Security Being Reported on by the Parent Holding
                 Company

                 Not applicable.


Item 8.          Identification and Classification of Members of the Group

                 Not applicable.


Item 9.          Notice of Dissolution of Group

                 Not applicable.


Item 10.         Certification

                    By signing below I certify that, to the best of my
                 knowledge and belief, the securities referred to above were
                 not acquired and are not held for the purpose of or with the
                 effect of changing or influencing the control of the issuer of
                 the securities and were not acquired and are not held in
                 connection with or as a participant in any transaction having
                 that purpose or effect.



                                      -5-


                                   Signature


                  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.
As of December 31, 2004


                                        Canada Pension Plan Investment Board


                                        By:     /s/ J. H. Butler
                                                -------------------------------
                                        Name:   J. H. Butler
                                        Title:  Vice President - General Counsel
                                                and Corporate Secretary