<PAGE>

                                                Filed Pursuant to Rule 424(b)(5)


Registration Statement No. 333-76880

            PROSPECTUS SUPPLEMENT TO PROSPECTUS DATED APRIL 10, 2002

                               66,000,000 Shares

<Table>
<S>                      <C>
[CALPINE LOGO]           CALPINE CORPORATION
</Table>

                                  Common Stock
                               ------------------

     Our common stock is listed on The New York Stock Exchange under the trading
symbol "CPN." On April 24, 2002, the last sale price reported on The New York
Stock Exchange for our common stock was $11.80.

     The underwriters have a 30-day option to purchase a maximum of 9,900,000
additional shares to cover over-allotments of shares.

     INVESTING IN THE COMMON STOCK INVOLVES RISKS. SEE "RISK FACTORS" ON PAGE 7
IN THE ACCOMPANYING PROSPECTUS ABOUT FACTORS YOU SHOULD CONSIDER BEFORE
PURCHASING OUR COMMON STOCK.

<Table>
<Caption>
                                                                            UNDERWRITING
                                                           PRICE TO         DISCOUNTS AND       PROCEEDS TO
                                                            PUBLIC           COMMISSIONS          CALPINE
                                                       -----------------  -----------------  -----------------
<S>                                                    <C>                <C>                <C>
Per Share............................................  $11.50             $0.3738            $11.1262
Total................................................  $759,000,000       $24,670,800        $734,329,200
</Table>

     Delivery of the shares of common stock will be made on or about April 30,
2002.

     NEITHER THE SECURITIES AND EXCHANGE COMMISSION NOR ANY STATE SECURITIES
COMMISSION HAS APPROVED OR DISAPPROVED OF THESE SECURITIES OR DETERMINED IF THIS
PROSPECTUS SUPPLEMENT OR THE PROSPECTUS TO WHICH IT RELATES IS TRUTHFUL OR
COMPLETE. ANY REPRESENTATION TO THE CONTRARY IS A CRIMINAL OFFENSE.

                           Joint Bookrunning Managers
    CREDIT SUISSE FIRST BOSTON                          GOLDMAN, SACHS & CO.
           BANC OF AMERICA SECURITIES LLC
                           DEUTSCHE BANK SECURITIES

            The date of this prospectus supplement is April 24, 2002
<PAGE>

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

                               TABLE OF CONTENTS

                             PROSPECTUS SUPPLEMENT

<Table>
<Caption>
                                        PAGE
                                        ----
<S>                                     <C>
ABOUT THIS PROSPECTUS SUPPLEMENT......   S-1
THE OFFERING..........................   S-1
RECENT DEVELOPMENTS...................   S-1
DOCUMENTS INCORPORATED BY REFERENCE...   S-4
USE OF PROCEEDS.......................   S-4
CAPITALIZATION........................   S-5
</Table>

<Table>
<Caption>
                                        PAGE
                                        ----
<S>                                     <C>
PRICE RANGE OF COMMON STOCK...........   S-6
UNDERWRITING..........................   S-7
NOTICE TO CANADIAN RESIDENTS..........   S-9
LEGAL MATTERS.........................  S-10
EXPERTS...............................  S-10
</Table>

                                   PROSPECTUS

<Table>
<Caption>
                                        PAGE
                                        ----
<S>                                     <C>
ABOUT THIS PROSPECTUS.................    1
CALPINE CORPORATION...................    3
CALPINE CANADA ENERGY FINANCE ULC AND
  CALPINE CANADA ENERGY FINANCE II
  ULC.................................    5
CALPINE CAPITAL TRUST IV AND CALPINE
  CAPITAL TRUST V.....................    6
RISK FACTORS..........................    7
WHERE YOU CAN FIND MORE INFORMATION;
  DOCUMENTS INCORPORATED BY
  REFERENCE...........................    7
FORWARD-LOOKING STATEMENTS............    8
CALPINE CONSOLIDATED RATIO OF EARNINGS
  TO FIXED CHARGES....................    9
USE OF PROCEEDS.......................    9
PLAN OF DISTRIBUTION..................    9
</Table>

<Table>
<Caption>
                                        PAGE
                                        ----
<S>                                     <C>
DESCRIPTION OF CAPITAL STOCK..........   12
DESCRIPTION OF DEPOSITARY SHARES......   16
DESCRIPTION OF THE DEBT SECURITIES....   19
DESCRIPTION OF PURCHASE CONTRACTS.....   35
DESCRIPTION OF UNITS..................   35
DESCRIPTION OF WARRANTS...............   36
DESCRIPTION OF TRUST PREFERRED
  SECURITIES..........................   37
CERTAIN UNITED STATES FEDERAL INCOME
  TAX CONSEQUENCES....................   43
CERTAIN CANADIAN FEDERAL INCOME TAX
  CONSIDERATIONS......................   58
LEGAL MATTERS.........................   59
EXPERTS...............................   59
</Table>

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

     YOU SHOULD RELY ONLY ON THE INFORMATION CONTAINED IN THIS PROSPECTUS
SUPPLEMENT, THE PROSPECTUS TO WHICH IT RELATES OR TO WHICH WE HAVE REFERRED YOU.
WE HAVE NOT AUTHORIZED ANYONE TO PROVIDE YOU WITH INFORMATION THAT IS DIFFERENT.
THIS DOCUMENT MAY ONLY BE USED WHERE IT IS LEGAL TO SELL THESE SECURITIES. THE
INFORMATION IN THIS PROSPECTUS SUPPLEMENT MAY ONLY BE ACCURATE ON THE DATE OF
THIS PROSPECTUS SUPPLEMENT.

                                        i
<PAGE>

                        ABOUT THIS PROSPECTUS SUPPLEMENT

     This document is in two parts. The first is this prospectus supplement,
which describes the specific terms of the common stock being offered by the
Calpine Corporation. The second part, the accompanying prospectus, gives more
general information, some of which may not apply to this offering.

     If the description of the offering varies between this prospectus
supplement and the accompanying prospectus, you should rely on the information
in this prospectus supplement.

     Unless we have indicated otherwise, references in this prospectus to
"Calpine," "we," "us" and "our" or similar terms are to Calpine Corporation and
its consolidated subsidiaries, excluding Calpine Capital Trust V, Calpine
Capital Trust IV, Calpine Capital Trust III, Calpine Capital Trust II and
Calpine Capital Trust. Unless we have indicated otherwise, references hereafter
in this prospectus to "$" or "dollar" are to the lawful currency of the United
States.

     On April 19, 2001, we acquired Encal Energy Ltd. ("Encal") in a merger
transaction that was accounted for as a pooling-of-interests under United States
generally accepted accounting principles, or U.S. GAAP. All financial
information contained in this prospectus supplement has been restated for all
historical periods presented as if Encal and Calpine had always been combined.
As used in this prospectus supplement, "EBITDA, as adjusted" is defined as net
income less income from unconsolidated investments, plus cash received from
unconsolidated investments, plus provision for tax, plus interest expense, plus
one-third of operating lease expense, plus depreciation, depletion and
amortization, plus distributions on our company-obligated mandatorily redeemable
convertible preferred securities of subsidiary trusts. This non-GAAP measure is
presented not as a measure of operating results, but rather as a measure of our
ability to service debt. EBITDA, as adjusted should not be construed as an
alternative to either (i) income from operations (determined in accordance with
U.S. GAAP) or (ii) cash flows from operating activities (determined in
accordance with U.S. GAAP). Prior to 2000, EBITDA, as adjusted had been
calculated according to an indenture definition. EBITDA, as adjusted has been
restated to conform to the definition set forth above for all periods presented.

                                  THE OFFERING

<Table>
<S>                                                           <C>
Common stock offered by Calpine.............................  66,000,000 shares
Common stock to be outstanding after the offering...........  373,762,616 shares
New York Stock Exchange Symbol..............................  CPN
</Table>

     The underwriters have a 30-day option to purchase a maximum of 9,900,000
additional shares to cover over-allotments of shares. This option is not
included in the number of shares of common stock to be outstanding after the
offering above, as it has not been exercised and there is no certainty as to
whether it will be exercised.

                              RECENT DEVELOPMENTS

     In addition to the recent developments described below, please see the
recent developments described in our Annual Report on Form 10-K for the year
ended December 31, 2001, and our Current Reports on Form 8-K or Form 8-K/A filed
with the SEC on January 16, 2002, January 17, 2002, February 8, 2002, March 13,
2002, March 13, 2002, March 26, 2002 and April 8, 2002, each of which is
incorporated by reference herein.

     New Working Capital Credit Agreement. In March 2002, we closed a new
secured credit agreement comprised of (a) a $1.0 billion revolving credit
facility expiring on May 24, 2003 and (b) a two-year term loan facility for up
to $600 million that will be available to us provided we have satisfied certain
conditions to borrowing on or before June 8, 2002, as more fully described
below. At the same time, we amended our existing $400 million revolving credit
facility to provide, among other things, security for borrowings under that
facility. The security for the revolving and term loan facilities currently
includes (i) a pledge of the capital stock of our subsidiary holding, directly
or indirectly, the interests in our natural gas properties,
                                       S-1
<PAGE>

(ii) a pledge by certain of our subsidiaries of a total of 65% of the capital
stock of Calpine Canada Energy Ltd., (iii) the Saltend power plant located in
the United Kingdom and (iv) our equity investment in nine U.S. power plants. As
of April 24, 2002, approximately $250.0 million in aggregate principal amount of
borrowings were outstanding under the revolving credit facilities and an
additional $495.4 million in aggregate principal face amount of letters of
credit were issued, which included and offset $231.0 million of letters of
credit which were previously issued under the $400 million revolving credit
facility and $162.2 million of cash which was previously posted as margin
deposits to counterparties.

     The conditions to borrowing the $600 million term loan under the new term
loan facility include the following:

     - the transfer of our domestic gas reserves from certain of our
       subsidiaries to us (which we have recently completed) and the provision
       of security interests in such domestic gas reserves to the lenders under
       the new secured credit agreement and the lenders under our $400 million
       revolving credit facility; and

     - confirmation that the loans outstanding under the revolving credit
       facility under the new credit agreement continue to be rated Ba3 or
       better by Moody's Investor Service, Inc. and BB- or better by Standard &
       Poor's Ratings Group.

Provided we have satisfied the conditions to the term loan borrowing, we may
make a draw upon the term loan facility upon the earlier of (a) the syndication
of the term loan facility and (b) June 8, 2002 (whether or not the term loan
facility has been syndicated).

     In connection with the syndication in the bank markets of the term loan and
revolving credit facilities under the new credit agreement, the respective lead
arrangers for such facilities have recommended that the new credit agreement be
amended to change the pricing, structure, security and certain other terms of
such facilities. We have come to an agreement in principle with those lead
arrangers to amend certain terms of the new credit agreement, including:

     - increasing the applicable margins on base rate and eurodollar rate loans
       under both the term loan and revolving credit facilities;

     - providing additional security (for borrowings under the term loan and
       revolving credit facilities under the new credit agreement and borrowings
       under the $400 million revolving credit facility) in the form of pledges
       of the capital stock of all of our domestic subsidiaries (other than
       Calpine Energy Services, LP); and

     - providing that we may use a portion of the net proceeds of an equity
       offering to repay other indebtedness.

The lead arrangers may recommend additional changes to the term loan and
revolving credit facilities. In certain circumstances, (a) the term loan
facility may be terminated or (b) the terms of the revolving credit facility set
forth in the new credit agreement may be amended without our consent, if such
facility has not been successfully syndicated and we have not agreed to amend
the new credit agreement to make changes determined by the lead arrangers to be
necessary to the syndication of such facility. In addition, prior to June 8,
2002, the term loan facility lead arrangers could elect to terminate the term
loan facility if it has not been syndicated and there has occurred a disruption
or adverse change in financial, banking or capital market conditions that they
in good faith determine could materially impair the syndication of the term loan
facility. A copy of our new credit agreement and our $400 million revolving
facility, as amended, are filed with the SEC as exhibits to our Annual Report on
Form 10-K for the year ended December 31, 2001. Please see such exhibits for a
complete description of the terms and conditions of the credit facilities.

     California Long-Term Supply Contracts. On April 22, 2002, we announced that
we had restructured our long-term power contracts with the California Department
of Water Resources ("CDWR"). The Office of the Governor, the California Public
Utilities Commission ("CPUC"), the Electricity Oversight Board ("EOB") and the
California Attorney General ("AG") have endorsed the restructured contracts
                                       S-2
<PAGE>

and have agreed to drop all pending claims against us, including withdrawing the
complaint under Section 206 of the Federal Power Act recently filed by the CPUC
and EOB with the Federal Energy Regulatory Commission ("FERC") and terminating
their efforts to seek refunds from us through FERC refund proceedings. In
connection with the restructuring, we have agreed to pay $6 million over three
years to the AG to resolve any and all claims against us brought by the AG.

     The restructuring includes the shortening of the duration of the two
ten-year, baseload energy contracts by two years and of the 20-year peaker
contract by ten years. These changes reduce CDWR's long-term purchase
obligations. In addition, we agreed to reduce the energy price on one ten-year
baseload contract from $61.00 to $59.60 per megawatt-hour, and to convert the
energy portion of the peaker contract to gas index pricing from fixed energy
pricing. We have also agreed to deliver up to 12.2 million megawatt-hours of
additional energy pursuant to the baseload energy contracts in 2002 and 2003.

     In connection with the restructuring, we have also agreed with CDWR that it
will have the right to assume and complete four of our projects currently
planned for California and in the advanced development stage if we do not meet
certain milestones with respect to each project assumed, provided that CDWR
reimburses us for all construction costs and certain other costs incurred by us
to the date CDWR assumes the relevant project.

     Earnings Outlook. On April 23, 2002, we announced that we expect fully
diluted earnings per share for the quarter ended March 31, 2002 will be
approximately $0.10 per share, before deduction of non-recurring equipment
cancellation costs of approximately $168.5 million, or $0.35 per share, and
before extraordinary items. After equipment cancellation costs and before
extraordinary items, we expect a net loss for the quarter of approximately $0.25
per fully diluted share. EBITDA, as adjusted is estimated to be approximately
$1.9 billion to $2.0 billion for the year ending December 31, 2002. We also
estimate fully diluted earnings per share before non-recurring equipment
cancellation costs and extraordinary items for the year ending December 31, 2002
will be approximately $1.50 to $1.60 per fully diluted share, which includes
dilution from this offering. The current year-end estimate reflects continued
uncertainty over the timing of a domestic economic recovery and a return to more
normal weather, as well as a gradual improvement in pricing. We continue to
evaluate the North American power market and intend to refine our year-end
outlook when market and other conditions provide greater visibility into 2002
results.

                                       S-3
<PAGE>

                      DOCUMENTS INCORPORATED BY REFERENCE

     The SEC permits us to "incorporate by reference" into this prospectus
supplement the information in documents we file with it, which means that we can
disclose important information to you by referring you to those documents. The
information incorporated by reference is considered to be a part of this
prospectus supplement and later information that we file with the SEC will
automatically update and supersede this information. In addition to the
documents incorporated by reference in the prospectus, listed on page 7 in the
prospectus under "Where You Can Find More Information; Documents Incorporated by
Reference," we incorporate by reference the documents listed below and any
future filings made with the SEC under Sections 13(a), 13(c), 14 or 15(d) of the
Securities Exchange Act until we sell all of the securities being registered or
until this offering is otherwise terminated:

     - Calpine's Current Report on Form 8-K/A filed with the SEC on April 8,
       2002.

     If you request a copy of any or all of the documents incorporated by
reference, then we will send to you the copies you requested at no charge.
However, we will not send exhibits to such documents, unless such exhibits are
specifically incorporated by reference in such documents. You should direct
requests for such copies either by writing to Calpine Corporation, 50 West San
Fernando Street, San Jose, California 95113, attention: Lisa M. Bodensteiner,
Assistant Secretary, or by telephoning (408) 995-5115.

     We have filed with the SEC a joint registration statement on Form S-3 under
the Securities Act of 1933, as amended, covering the securities described in
this prospectus supplement. This prospectus supplement does not contain all of
the information included in the registration statement. Any statement made in
this prospectus supplement concerning the contents of any contract, agreement or
other document is only a summary of the actual contract, agreement or other
document. If we have filed any contract, agreement or other document as an
exhibit to the registration statement, you should read the exhibit for a more
complete understanding of the document or matter involved. Each statement
regarding a contract, agreement or other document is qualified in its entirety
by reference to the actual document. Copies of documents described herein are
available free of charge upon request as provided in the preceding paragraph.

                                USE OF PROCEEDS

     Our net proceeds from the sale of the 66,000,000 shares of our common stock
in this offering (after deducting underwriting discounts and commissions and
estimated offering expenses) will be approximately $734.0 million (approximately
$844.0 million if the underwriters' over-allotment option in this common stock
offering is exercised in full). We expect to use the net proceeds from the
offering for working capital and general corporate purposes, which may include
the repayment of our existing indebtedness. As of March 31, 2002, we had
approximately $12.6 billion of outstanding indebtedness at various interest
rates and maturities. For a description of our indebtedness, see the financial
statements and related notes included in our Annual Report on Form 10-K for the
year ended December 31, 2001, incorporated be reference herein. Pending such
uses, we expect to invest the net proceeds in short-term, interest bearing
securities.

                                       S-4
<PAGE>

                                 CAPITALIZATION

     The following table sets forth, as of December 31, 2001, (i) Calpine's
actual consolidated capitalization; and (ii) on an estimated basis for purposes
of this prospectus supplement, Calpine's consolidated capitalization as adjusted
to reflect the net effect of (a) the repayment on March 13, 2002 of a note
payable of $64.8 million assumed in connection with our acquisition of Michael
Petroleum Corporation, (b) the repurchase of $192.5 million of our Zero-Coupon
Convertible Debentures Due 2021, (c) the issuance of $100 million in aggregate
principal amount of 4% Convertible Senior Notes Due 2006, pursuant to the
partial exercise of the initial purchaser's $200 million option to purchase
additional Convertible Senior Notes, (d) the repayment on April 1, 2002 of a
note payable which was assumed as part of the acquisition of the Silverado
facility and (e) this offering. The adjustments do not reflect normal day-to-day
operations. This table should be read in conjunction with the consolidated
financial statements and related notes thereto and the unaudited consolidated
condensed financial statements and related notes thereto incorporated by
reference in this prospectus supplement. All non-dollar amounts are translated
into dollar amounts using recent exchange rates.

<Table>
<Caption>
                                                                  DECEMBER 31, 2001
                                                              -------------------------
                                                                ACTUAL      AS ADJUSTED
                                                              -----------   -----------
                                                                     (UNAUDITED)
                                                                   (IN THOUSANDS,
                                                                EXCEPT SHARE AMOUNTS)
<S>                                                           <C>           <C>
SHORT-TERM DEBT:
Notes payable and borrowings under lines of credit, current
  portion...................................................  $    23,238   $    23,238
Capital lease obligation, current portion...................        2,206         2,206
Zero-Coupon Convertible Debentures Due 2021.................      878,000       685,500
                                                              -----------   -----------
     Total short-term debt..................................      903,444       710,944
LONG-TERM DEBT:
Notes payable and borrowings under lines of credit, net of
  current portion...........................................       74,750            --
Capital lease obligation, net of current portion............      207,219       207,219
Construction/project financing, net of current portion......    3,393,410     3,393,410
Convertible Senior Notes Due 2006...........................    1,100,000     1,200,000
Senior notes................................................    7,049,038     7,049,038
                                                              -----------   -----------
     Total long-term debt...................................   11,824,417    11,849,667
                                                              -----------   -----------
Company-obligated mandatorily redeemable convertible
  preferred securities of subsidiary trusts.................    1,123,024     1,123,024
Minority interests..........................................       47,389        47,389
                                                              -----------   -----------
STOCKHOLDERS' EQUITY:
Preferred stock, $.001 par value:
  10,000,000 shares authorized; one share outstanding,
  actual and as adjusted....................................           --            --
                                                              -----------   -----------
Common stock, $.001 par value:
  1,000,000,000 shares authorized; 307,058,751 shares
  outstanding, actual; and 373,058,751 shares outstanding,
  as adjusted...............................................          307           373
Additional paid-in capital..................................    2,040,836     2,774,726
Retained earnings...........................................    1,196,000     1,196,000
Accumulated other comprehensive loss........................     (226,574)     (226,574)
                                                              -----------   -----------
     Total stockholders' equity.............................    3,010,569     3,744,525
                                                              -----------   -----------
     Total capitalization...................................  $16,908,843   $17,475,549
                                                              ===========   ===========
</Table>

                                       S-5
<PAGE>

                          PRICE RANGE OF COMMON STOCK

     Our common stock is traded on The New York Stock Exchange (the "NYSE")
under the symbol "CPN." Public trading of the common stock commenced on
September 20, 1996. Prior to that, there was no public market for the common
stock. The following table sets forth, for the periods indicated, the high and
low sales price per share of our common stock on the NYSE.

<Table>
<Caption>
                                                               HIGH     LOW
                                                              ------   ------
<S>                                                           <C>      <C>
2000
  First Quarter.............................................  $30.75   $16.09
  Second Quarter............................................   35.22    18.13
  Third Quarter.............................................   52.25    32.25
  Fourth Quarter............................................   52.97    32.25
2001
  First Quarter.............................................  $58.04   $29.00
  Second Quarter............................................   57.35    36.20
  Third Quarter.............................................   46.00    18.90
  Fourth Quarter............................................   28.85    10.00
2002
  First Quarter.............................................  $17.28   $ 6.15
  Second Quarter (through April 24, 2002)...................   13.55    10.12
</Table>

     As of April 23, 2002, there were approximately 1,382 holders of record of
our Common Stock. On April 24, 2002, the last sale price reported on the NYSE
for our Common Stock was $11.80 per share.

                                       S-6
<PAGE>

                                  UNDERWRITING

     Under the terms and subject to the conditions contained in an underwriting
agreement dated April 24, 2002, we have agreed to sell to the underwriters named
below, for whom Credit Suisse First Boston Corporation and Goldman, Sachs & Co.
are acting as representatives, the following respective numbers of shares of
common stock:

<Table>
<Caption>
                                                                NUMBER
                        UNDERWRITER                           OF SHARES
                        -----------                           ----------
<S>                                                           <C>
Credit Suisse First Boston Corporation......................  29,700,000
Goldman, Sachs & Co. .......................................  29,700,000
Banc of America Securities LLC..............................   3,300,000
Deutsche Bank Securities Inc. ..............................   3,300,000
                                                              ----------
          Total.............................................  66,000,000
                                                              ==========
</Table>

     The underwriting agreement provides that the underwriters are obligated to
purchase all the shares of common stock in the offering if any are purchased,
other than those shares covered by the over-allotment option described below.
The underwriting agreement also provides that if an underwriter defaults, the
purchase commitments of non-defaulting underwriters may be increased or the
offering may be terminated.

     We have granted to the underwriters a 30-day option to purchase up to
9,900,000 additional shares at the initial public offering price less the
underwriting discounts and commissions. The option may be exercised only to
cover any over-allotments of common stock.

     The underwriters propose to offer the shares of common stock initially at
the public offering price on the cover page of this prospectus supplement at
that price less a concession of $0.224 per share. The underwriters may allow a
discount of $0.10 per share on sales to other broker/dealers. After the initial
public offering, the representatives may change the public offering price and
concession and discount to broker/dealers.

     The following table summarizes the compensation and estimated expenses we
will pay.

<Table>
<Caption>
                                                 PER SHARE                             TOTAL
                                      --------------------------------    --------------------------------
                                         WITHOUT             WITH            WITHOUT             WITH
                                          OVER-             OVER-             OVER-             OVER-
                                        ALLOTMENT         ALLOTMENT         ALLOTMENT         ALLOTMENT
                                      --------------    --------------    --------------    --------------
<S>                                   <C>               <C>               <C>               <C>
Underwriting Discounts and
  Commissions paid by us............     $0.3738           $0.3738         $24,670,800       $28,371,420
Expenses payable by us..............     $0.0057           $0.0057         $   373,428       $   429,442
</Table>

     In the ordinary course of business, the underwriters and their affiliates
have provided financial advisory, investment banking and general financing and
banking services for us and our affiliates for customary fees. We expect to use
the net proceeds from the offering for working capital and general corporate
purposes, which may include the repayment of our existing indebtedness,
including indebtedness under our credit facilities. Accordingly, it is possible
that more than 10% of the proceeds of this offering could be used to repay
indebtedness owed by us to various lenders, including affiliates of Credit
Suisse First Boston Corporation, Banc of America Securities LLC and Deutsche
Bank Securities Inc. Accordingly, the offering is being made in compliance with
the requirements of Rule 2710(c)(8) of the Conduct Rules of the National
Association of Securities Dealers, Inc.

     Other than the offering of common stock pursuant to this Prospectus
Supplement, we have agreed that we will not offer, sell, contract to sell,
pledge or otherwise dispose of, directly or indirectly, or file with the
Securities and Exchange Commission a registration statement under the Securities
Act of 1933 (the "Securities Act") relating to any shares of our common stock or
securities convertible into or exchangeable or exercisable for any shares of our
common stock, or publicly disclose the intention to make

                                       S-7
<PAGE>

any such offer, sale, pledge, disposition or filing, without the prior written
consent of the representatives for a period of 90 days after the date of this
prospectus supplement, except as previously consented to by the representatives.

     Our executive officers and directors have agreed that they will not offer,
sell, contract to sell, pledge or otherwise dispose of, directly or indirectly,
any shares of our common stock or securities convertible into or exchangeable or
exercisable for any shares of our common stock, enter into a transaction which
would have the same effect, or enter into any swap, hedge or other arrangement
that transfers, in whole or in part, any of the economic consequences of
ownership of our common stock, whether any such aforementioned transaction is to
be settled by delivery of our common stock or such other securities, in cash or
otherwise, or publicly disclose the intention to make any such offer, sale,
pledge or disposition, or to enter into any such transaction, swap, hedge or
other arrangement, without, in each case, the prior written consent of the
representatives for a period of 90 days after the date of this prospectus
supplement.

     We have agreed to indemnify the underwriters against liabilities under the
Securities Act, or contribute to payments which the underwriters may be required
to make in that respect.

     In connection with the offering the underwriters may engage in stabilizing
transactions, over-allotment transactions, syndicate covering transactions and
penalty bids in accordance with Regulation M under the Securities Exchange Act
of 1934.

     - Stabilizing transactions permit bids to purchase the underlying security
       so long as the stabilizing bids do not exceed a specified maximum.

     - Over-allotment involves sales by the underwriters of shares in excess of
       the number of shares the underwriters are obligated to purchase, which
       creates a syndicate short position. The short position may be either a
       covered short position or a naked short position. In a covered short
       position, the number of shares over-allotted by the underwriters is not
       greater than the number of shares that they may purchase in the
       over-allotment option. In a naked short position, the number of shares
       involved is greater than the number of shares in the over-allotment
       option. The underwriters may close out any short position by either
       exercising their over-allotment option and/or purchasing shares in the
       open market.

     - Syndicate covering transactions involve purchases of the common stock in
       the open market after the distribution has been completed in order to
       cover syndicate short positions. In determining the source of shares to
       close out the short position, the underwriters will consider, among other
       things, the price of shares available for purchase in the open market as
       compared to the price at which they may purchase shares through the
       over-allotment option. If the underwriters sell more shares than could be
       covered by the over-allotment option, a naked short position, the
       position can only be closed out by buying shares in the open market. A
       naked short position is more likely to be created if the underwriters are
       concerned that there could be downward pressure on the price of the
       shares in the open market after pricing that could adversely affect
       investors who purchase in the offering.

     - Penalty bids permit the representatives to reclaim a selling concession
       from a syndicate member when the common stock originally sold by the
       syndicate member is purchased in a stabilizing or syndicate covering
       transaction to cover syndicate short positions.

These stabilizing transactions, syndicate covering transactions and penalty bids
may have the effect of raising or maintaining the market price of the common
stock or preventing or retarding a decline in the market price of the common
stock. As a result the price of the common stock may be higher than the price
that might otherwise exist in the open market. These transactions may be
effected on The New York Stock Exchange or otherwise and, if commenced, may be
discontinued at any time.

     A prospectus in electronic format may be made available on the websites
maintained by the underwriters, if any, participating in this offering. The
representatives may agree to allocate a number of shares to the underwriters for
sale to their online brokerage account holders. Internet distributions will be
allocated by the underwriters that will make internet distributions on the same
basis as other allocations.

                                       S-8
<PAGE>

                          NOTICE TO CANADIAN RESIDENTS

RESALE RESTRICTIONS

     The distribution of the common stock in Canada is being made only on a
private placement basis exempt from the requirement that we prepare and file a
prospectus with the securities regulatory authorities in each province where
trades of common stock are made. Any resale of the common stock in Canada must
be made under applicable securities laws which will vary depending on the
relevant jurisdiction, and which may require resales to be made under available
statutory exemptions or under a discretionary exemption granted by the
applicable Canadian securities regulatory authority. Purchasers are advised to
seek legal advice prior to any resale of the common stock.

REPRESENTATIONS OF PURCHASERS

     By purchasing common stock in Canada and accepting a purchase confirmation
a purchaser is representing to us and the dealer from whom the purchase
confirmation is received that

     - the purchaser is entitled under applicable provincial securities laws to
       purchase the common stock without the benefit of a prospectus qualified
       under those securities laws,

     - where required by law, that the purchaser is purchasing as principal and
       not as agent, and

     - the purchaser has reviewed the text above under Resale Restrictions.

RIGHTS OF ACTION (ONTARIO PURCHASERS ONLY)

     Under Ontario securities legislation, a purchaser who purchases a security
offered by this prospectus during the period of distribution will have a
statutory right of action for damages, or while still the owner of the shares,
for rescission against us in the event that this prospectus contains a
misrepresentation. A purchaser will be deemed to have relied on the
misrepresentation. The right of action for damages is exercisable not later than
the earlier of 180 days from the date the purchaser first had knowledge of the
facts giving rise to the cause of action and three years from the date on which
payment is made for the shares. The right of action for rescission is
exercisable not later than 180 days from the date on which payment is made for
the shares. If a purchaser elects to exercise the right of action for
rescission, the purchaser will have no right of action for damages against us.
In no case will the amount recoverable in any action exceed the price at which
the shares were offered to the purchaser and if the purchaser is shown to have
purchased the securities with knowledge of the misrepresentation, we will have
no liability. In the case of an action for damages, we will not be liable for
all or any portion of the damages that are proven to not represent the
depreciation in value of the shares as a result of the misrepresentation relied
upon. These rights are in addition to, and without derogation from, any other
rights or remedies available at law to an Ontario purchaser. The foregoing is a
summary of the rights available to an Ontario purchaser. Ontario purchasers
should refer to the complete text of the relevant statutory provisions.

ENFORCEMENT OF LEGAL RIGHTS

     All of our directors and officers as well as the experts named herein may
be located outside of Canada and, as a result, it may not be possible for
Canadian purchasers to effect service of process within Canada upon the issuer
or such persons. All or a substantial portion of our assets and the assets of
those persons may be located outside of Canada and, as a result, it may not be
possible to satisfy a judgment against us or those persons in Canada or to
enforce a judgment obtained in Canadian courts against us or those persons
outside of Canada.

TAXATION AND ELIGIBILITY FOR INVESTMENT

     Canadian purchasers of common stock should consult their own legal and tax
advisors with respect to the tax consequences of an investment in the common
stock in their particular circumstances and about the eligibility of the common
stock for investment by the purchaser under relevant Canadian legislation.

                                       S-9
<PAGE>

RELATIONSHIP WITH AFFILIATES OF CERTAIN UNDERWRITERS

     We are in compliance with the terms of the indebtedness owed by us to
affiliates of Credit Suisse First Boston Corporation, Banc of America Securities
LLC and Deutsche Bank Securities Inc. The decision of Credit Suisse First Boston
Corporation to distribute our shares of common stock was not influenced by their
respective affiliates that are our lenders and those affiliates had no
involvement in determining whether or when to distribute our shares of common
stock under this offering or the terms of this offering. Credit Suisse First
Boston Corporation, Banc of America Securities LLC and Deutsche Bank Securities
Inc. will not receive any benefit from this offering other than the underwriting
discounts and commissions paid by us.

                                 LEGAL MATTERS

     The validity of the securities offered hereby will be passed upon for us by
Covington & Burling, New York, New York. The underwriters have been represented
by Skadden, Arps, Slate, Meagher & Flom LLP, New York, New York.

                                    EXPERTS

     The financial statements incorporated by reference in this prospectus
supplement and the accompanying prospectus have been audited by Arthur Andersen
LLP, independent public accountants, as indicated in their reports with respect
thereto, and are included herein in reliance upon the authority of said firm as
experts in giving said reports.

     The report of Ernst and Young LLP, independent public accountants, with
respect to the audited financial statements of Encal Energy Ltd., which is
incorporated in this prospectus supplement by reference to our Annual Report on
Form 10-K for the year ended December 31, 2001, is included herein in reliance
upon the authority of said firm as experts in giving said report.

                                       S-10

