EXHIBIT 5

December 6, 2001


Alcoa Inc.
201 Isabella Street
Pittsburgh, Pennsylvania 15212-5858

Ladies and Gentlemen:

This opinion is being furnished in connection with:

(i)  the Registration Statement on Form S-3 (File No. 333-59044; 333-59044-01)
     (the "Registration Statement") filed by Alcoa Inc., a Pennsylvania
     corporation (the "Company"), and Alcoa Trust I, a Delaware business trust
     (the "Trust"), with the Securities and Exchange Commission (the
     "Commission") for the purpose of registering under the Securities Act of
     1933, as amended (the "Act"), up to $3,000,000,000 aggregate offering price
     of the Company's debt securities, warrants to purchase debt securities,
     Class B Serial Preferred Stock, $1.00 par value, and common stock, $1.00
     par value, and Trust Preferred Securities of the Trust and related
     guarantee of the Trust Preferred Securities by the Company (collectively,
     the "Securities"), to be offered from time to time by the Company or the
     Trust, as applicable, on terms to be determined at the time of the
     offering; and

(ii) the offering and sale by the Company of $500,000,000 principal amount of
     Floating Rate Notes Due 2004 and $1,000,000,000 principal amount of 6%
     Notes Due 2012 (together, the "Notes"), as described in the Prospectus
     Supplement dated November 29, 2001 (the "Prospectus Supplement") and the
     accompanying Prospectus dated April 26, 2001 (the "Prospectus").

As a Counsel of the Company, I am generally familiar with its legal affairs. In
addition, I have examined the Articles and By-Laws of the Company; the Indenture
dated as of September 30, 1993 (the "Indenture") between the Company and J. P.
Morgan Trust Company, National Association (formerly Chase Manhattan Trust
Company, National Association), as successor trustee to PNC Bank, National
Association, as Trustee, under which the Notes will be issued; the Registration
Statement; the resolutions adopted by the Board of Directors of the Company
relating to the filing of the Registration Statement and the issuance and sale
of the Securities; the Certificate of Designated Officer Establishing Terms of
Debt Securities dated November 29, 2001; and such other certificates of officers
of the Company and other documents and corporate records as I have considered
necessary for the purposes of this opinion.

On the basis of the foregoing, I advise you that, in my opinion, the Notes have
been duly and validly authorized by the Company, and, upon proper execution,
delivery and authentication in accordance with the provisions of the Indenture
against payment therefor, the Notes will be legally issued and will constitute
valid and binding obligations of the Company enforceable against the Company in
accordance with and subject to their respective terms and the terms of the
Indenture, except as enforceability may be limited by applicable bankruptcy,
insolvency, reorganization, fraudulent transfer, moratorium and similar laws of
general applicability relating to or affecting the enforcement of creditors'
rights and by general equitable principles, and except that no opinion is
expressed as to the availability of the remedy of specific performance.



I am a member of the bar of the Commonwealth of Pennsylvania and my opinion is
limited to the laws of the Commonwealth of Pennsylvania and the laws of the
United States of America.

I hereby consent to the filing of this opinion as an exhibit to the Current
Report on Form 8-K of the Company dated the date hereof and to the reference to
me under the heading "Legal Matters" in the Prospectus Supplement and under the
heading "Legal Matters" in the Prospectus. In giving my consent, I do not admit
that I come within the category of persons whose consent is required under
Section 7 of the Act or the rules and regulations of the Commission under the
Act.

Very truly yours,



/s/ Thomas F. Seligson

Thomas F. Seligson

                                        2