EXHIBIT 5.1


                      [LETTERHEAD OF DAVIS POLK & WARDWELL]


                                 March 25, 1998



The AES Corporation
1001 North 19th Street
Arlington, Virginia 22209

AES Trust II
c/o The AES Corporation
1001 North 19th Street
Arlington, Virginia 22209

Dear Ladies and Gentlemen:

         We have acted as counsel for The AES  Corporation  (the  "Company") and
AES Trust II (the "Trust") in connection with the Registration Statement on Form
S-3 (the  "Registration  Statement") filed by the Company and the Trust with the
Securities and Exchange  Commission under the Securities Act of 1933, as amended
(the "Securities  Act"),  relating to the registration of the Trust's $2.75 Term
Convertible  Securities,  series B,  liquidation  amount $50 per  security  (the
"TECONS") to be sold by certain  holders of such TECONS.  The TECONS were issued
pursuant to the  provisions  of the Amended and  Restated  Declaration  of Trust
dated as of October 29, 1997 (the "Declaration")  among the Company, as sponsor,
First Chicago Delaware Inc., The First National Bank of Chicago,  sponsor, First
Chicago Delaware Inc., the First National Bank of Chicago,  William R. Luraschi,
Barry J. Sharp and  Willard  Hoagland as  trustees,  and are  guaranteed  by the
Company to the extent described in the Preferred  Securities Guarantee Agreement
dated  as  of  October  29,  1997  (the  Guarantee").  The  Trust  has  acquired
$309,278,400 aggregate principal amount of 5.50% Junior Subordinated Convertible
Debentures (the  "Debentures") with the proceeds from the sale of the TECONS and
the sale to the Company of the common  securities of the Trust.  The  Debentures
were issued pursuant to the provisions of the Subordinated indenture dated as of
March 1, 1997  between the Company and the First  National  Bank of Chicago,  as
trustee, as supplemented by a Second




The AES Corporation                     2                         March 25, 1998


Supplemental  Indenture  dated as of  October  29,  1997  (the  Indenture  as so
supplemented is hereinafter referred to as the "Indenture").

         We have examined originals or copies, certified or otherwise identified
to our  satisfaction,  of such  documents,  corporate  records,  certificates of
public officials and other  instruments as we have deemed necessary or advisable
for the purpose of rendering this opinion.

         Based upon the foregoing, we are of the opinion that:

               (i) the Debentures  have been duly authorized and, assuming  that
         they  have been  executed  and  authenticated  in  accordance  with the
         provisions of the Indenture and delivered to and paid for by the Trust,
         are valid and  binding  obligations  of the  Company,  entitled  to the
         benefits  of  the  Indenture,   enforceable   against  the  Company  in
         accordance with their terms, except that the enforcement thereof may be
         subject  to (i)  bankruptcy,  insolvency,  reorganization,  moratorium,
         fraudulent  conveyance or other similar laws now or hereafter in effect
         relating to creditors' rights generally and (ii) general  principles of
         equity,  regardless of whether enforcement is sought in a proceeding at
         law or in equity;

               (ii)  the  Guarantee  has  been  duly  authorized,  executed  and
         delivered by the Company and  (assuming) due  authorization,  execution
         and delivery threre of by the Guarantee  Trustee),  constitutes a valid
         and binding agreement of the Company enforceable against the Company in
         accordance with its terms,  except that the enforcement  thereof may be
         subject  to  (bankruptcy,   insolvency,   reorganization,   moratorium,
         fraudulent  conveyance or other similar laws now or hereafter in effect
         relating to creditors' rights generally and (ii) general  principles of
         equity,  regardless of whether enforcement is sought in a proceeding at
         law or in equity; and

               (iii) the shares of Common Stock issuable upon  conversion of the
         Securities  have  been  duly  authorized  by the  company  and  validly
         reserved  for  issuance  by the  Company  upon such  conversion  by all
         necessary corporate action and such Common Stock, when duly issued upon
         such   conversion,   will  be   validly   issued  and  fully  paid  and
         non-assessable;  no holder  thereof is subject  to  personal  liability
         solely by  reason of being




The AES Corporation                     3                         March 25, 1998


         such a  holder;  and the  issuance  of  such  Common  Stock  upon  such
         conversion is not subject to preemptive rights.

         We are  members  of the Bar of the State of New York and the  foregoing
opinion is limited to the laws of the State of New York, the federal laws of the
United  States  of  America  and the  General  Corporation  Law of the  State of
Delaware.

         We hereby  consent to the  filing of this  opinion as an exhibit to the
Registration Statement. In addition, we consent to the reference to us under the
caption  "Legal   Matters"  in  the  Prospectus   constituting  a  part  of  the
Registration Statement.

         This  opinion is rendered  solely to you in  connection  with the above
matter.  This  opinion  may not be relied  upon by you for any other  purpose or
relied  upon by or  furnished  to any other  person  without  our prior  written
consent.

                                                     Very truly yours,

                                                     /s/ Davis Polk & Wardwell
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