SECURITIES
AND EXCHANGE COMMISSION Washington, D.C. 20549  
  FORM 40-F  oREGISTRATION STATEMENT PURSUANT
TO SECTION 12(B) OR (G) OF THE SECURITIES EXCHANGE ACT OF 1934  OR  ýANNUAL REPORT PURSUANT TO SECTION 13
OR 15(D) OF THE SECURITIES EXCHANGE ACT OF 1934  FOR THE
  FISCAL YEAR ENDED DECEMBER 31, 2004
  
  COMMISSION
  FILE NUMBER 000-31815  
  HYDROGENICS
CORPORATION (Exact
name of Registrant as specified in its charter)  Canada (Province
or other jurisdiction of incorporation or organization)  3629 (Primary
Standard Industrial Classification Code Number (if applicable))  Not applicable (I.R.S.
Employer Identification Number (if applicable))  5985 McLaughlin Road, Mississauga, Ontario, Canada
L5R 1B8, (905) 361-3660 (Address and telephone number of Registrants
principal executive offices)  CT Corporation System, 111 Eighth Avenue, New York,
New York 10011, (212) 894-8400 (Name, address (including zip
code) and telephone number (including area
code) of agent for service in the United States)  Securities registered or to be registered
pursuant to Section 12(b) of the Act:         None.  Securities registered or to be registered
pursuant to Section 12(g) of the Act: Common shares  Securities for which there is a reporting
obligation pursuant to Section 15(d) of the Act:      None.  For annual reports, indicate by check mark
the information filed with this Form  ý            Annual
  information form
  
  ý            Audited annual financial
  information  Indicate the
number of outstanding shares of each of the issuers classes of capital or
common stock as of the close of the period covered by the annual report  At December 31, 2004, 64,626,989 common
shares were issued and outstanding  
  Indicate by
check mark whether the Registrant by filing the information contained in this Form is
also thereby furnishing the information to the Commission pursuant to Rule 12g3-2(b) under
the Securities Exchange Act of 1934 (the Exchange Act). If Yes is marked,
indicate the file number assigned to the Registrant in connection with such
Rule.  Yeso     No ý  Indicate by
check mark whether the registrant (1) has filed all reports required to be
filed by Section 13 or 15(d) of the Securities Exchange Act of 1934
during the preceding 12 months (or for such shorter period that the registrant
was required to file such reports), and (2) has been subject to such
filing requirements for the past 90 days.  Yesý     No o


EVALUATION OF DISCLOSURE CONTROLS AND
PROCEDURES  As of the end
of the period covered by this Annual Report on Form 40-F, an evaluation
was carried out by our management, under the supervision, and with the
participation, of our Chief Executive Officer (the CEO) and Chief Financial
Officer (the CFO), of the effectiveness of our disclosure controls and
procedures (as defined in Exchange Act Rules 13a-15(e) and 15d-15(e)).
Based on that evaluation, the CEO and CFO concluded that such disclosure
controls and procedures were effective and designed to ensure that material
information relating to us and our consolidated subsidiaries would be made
known to them by others within those entities.  CHANGES IN INTERNAL CONTROL OVER FINANCIAL
REPORTING  During the
year ended December 31, 2004, there were no changes in our internal
control over financial reporting that have materially affected, or are
reasonably likely to materially affect, our internal control over financial
reporting.  IDENTIFICATION OF THE AUDIT COMMITTEE  We have a
separately-designated audit committee established in accordance with section 3(a)(58)(A) of
the Securities Exchange Act of 1934.  Our
audit committee is comprised of four independent members: Wesley Twiss, Donald
J. Lowry, Norman M. Seagram and Andrew T.B. Stuart.  AUDIT COMMITTEE FINANCIAL EXPERT  Our board of
directors has determined that it has at least one audit committee financial
expert serving on its audit committee. 
Wesley Twiss has been determined to be an audit committee financial
expert and is independent, as that term is defined by the Nasdaq National
Markets listing standards. The U.S. Securities and Exchange Commission has
indicated that the designation of this individual as an audit committee
financial expert does not make him an expert for any purpose, or impose any
duties, obligations or liabilities that are greater than those imposed on
members of the audit committee and board of directors who do not carry this
designation or affect the duties, obligations or liabilities of any other
member of the audit committee or board of directors.  CODE OF ETHICS  We have
adopted a written Code of Business Conduct and Ethics (the Code) which
governs the behavior of our directors, officers, and employees.  The Code also includes provisions required by
the Sarbanes-Oxley Act of 2002 that are
applicable to our CEO, CFO and other senior financial officers.  The board, through the Nomination and
Corporate Governance Committee, oversees compliance with the Code.  Any amendments or regulations any deviations
from or amendments to the Code will be publicly disclosed.  The Code is accessible on our investor
relations web page at www.hydrogenics.com.  2


PRINCIPAL ACCOUNTANTS FEES AND SERVICES  The following table sets
forth the total remuneration that was paid by us and our subsidiaries to our
independent accountants, PricewaterhouseCoopers LLC, in each of our previous
two fiscal years:  2003
  
  2004(in thousands) 
  (unaudited)Audit fees
  
  434,143
  
  570,073Audit-related fees
  
  96,987
  
  25,293Tax fees
  
  36,555
  
  69,962All other fees
  
  
  
  28,666Total
  
  567,685
  
  693,994  Audit
Fees  These fees include
professional services rendered by the external auditors for the review of
interim financial statements, statutory audits of annual financial statements,
the review of prospectuses, consultations about financial and reporting
standards and other regulatory audits and filings.  Audit-related
fees  These fees include
professional services that reasonably relate to the above services, including
non-statutory audits and consultations about prospective financial accounting
and reporting standards.  Tax
fees  These fees include
professional services for tax compliance, tax advice, tax planning and advisory
services relating to the preparation of corporate tax returns.  Other
fees  These
fees for 2004 include professional services related to our public equity
offering of common shares which closed in February 2004, and services
related to our acquisition of Stuart Energy Systems Corporation which closed in
January 2005.  These fees for 2003
include professional services related to our acquisition of Greenlight Power
Technologies, Inc. which closed in January 2003, and services
relating to our public equity offering of common shares which closed in February 2004.  Our
audit committee approved all audit and non-audit services provided to us and to
our subsidiaries during the periods listed above.  Our audit committee has adopted pre-approval
policies and procedures to ensure that all services provided by the auditor are
approved in advance by the audit committee or are approved by the chair of the
audit committee and subsequently reported to the committee as a whole at the
following meeting of the committee.  OFF-BALANCE
SHEET ARRANGEMENTS  The disclosure
provided under the heading Managements Discussion and Analysis of Financial
Condition and Results of Operations  Contractual Obligations - Contingent
off-balance sheet arrangements on page 18 of Exhibit 99.2 hereto
(Managements Discussion and Analysis of Financial Condition and Results of
Operations for the year ended December 31, 2004) is incorporated by
reference herein.  3


TABULAR
DISCLOSURE OF CONTRACTUAL OBLIGATIONS  The disclosure
provided under the heading Managements Discussion and Analysis of Financial
Condition and Results of Operations  Contractual Obligations on page 17
of Exhibit 99.2 hereto (Managements Discussion and Analysis of Financial
Condition and Results of Operations for the year ended December 31, 2004)
is incorporated by reference herein.  UNDERTAKING  The registrant
undertakes to make available, in person or by telephone, representatives to
respond to inquiries made by the Commission staff, and to furnish promptly,
when requested to do so by the Commission staff, information relating to: the
securities registered pursuant to Form 40-F; the securities in relation to
which the obligation to file an annual report on Form 40-F arises; or
transactions in said securities.  CONSENT TO SERVICE OF PROCESS  The
Company has previously filed a Form F-X in connection with the class of
securities in relation to which the obligation to file this report arises.  Any
change to the name or address of the agent for service of process of the
registrant shall be communicated promptly to the Securities and Exchange
Commission by an amendment to the Form F-X referencing the file number of
the registrant.  4


SIGNATURES  Pursuant
to the requirements of the Securities Exchange Act of 1934, the registrant
hereby certifies that it meets all of the requirements for filing on Form 40-F
and that it has duly caused and authorized the undersigned to sign this annual
report on its behalf.   HYDROGENICS
  CORPORATIONBy:
  /s/
  Pierre RivardPierre RivardPresident, Chief Executive Officer and DirectorDate:  March 31,
  2005


EXHIBITS  Exhibit
  
  Description99.1
  
  Consolidated Financial
  Statements for the Year Ended December 31, 2004.99.2
  
  Managements Discussion
  and Analysis for the year ended December 31, 2004.99.3
  
  Renewal Annual Information
  Form for the year ended December 31, 2004.99.4
  
  Consent of
  PricewaterhouseCoopers LLP.99.5
  
  Certification of Chief
  Executive Officer of the Registrant pursuant to Section 302 of the
  Sarbanes-Oxley Act of 2002.99.6
  
  Certification of Chief
  Financial Officer of the Registrant pursuant to Section 302 of the
  Sarbanes-Oxley Act of 2002.99.7
  
  Certification of Chief
  Executive Officer of the Registrant pursuant to Section 906 of the
  Sarbanes-Oxley Act of 2002.99.8
  
  Certification of Chief
  Financial Officer of the Registrant pursuant to Section 906 of the
  Sarbanes-Oxley Act of 2002.