EXHIBIT 5
 
                       [LETTERHEAD OF MARGARET M. FORAN]
 
September 25, 1997
 
Pfizer Inc.
235 East 42nd Street
New York, New York 10017-5755
 
Pfizer Inc.:
 
  In connection with the Registration Statement on Form S-8 relating to 50,000
shares of Common Stock of Pfizer Inc. under the Pfizer Canada Inc. Savings and
Investment Plan, it is my opinion that:
 
  All necessary corporate proceedings have been taken to authorize the
issuance of the shares under the Plan, and all such shares, upon issuance in
accordance with the Plan and upon full payment in cash for such shares issued,
will be validly issued and outstanding and fully paid and non-assessable.
 
  In preparing this opinion, I have examined certificates of public officials,
certificates of officers and copies certified to my satisfaction of such
corporate documents and records of the Company and such other papers as I have
thought relevant and necessary as a basis for my opinion. I have relied on
such certificates in connection with the accuracy of actual matters contained
in such documents which were not independently established.
 
  I consent to the use of this opinion in the Registration Statement and to
the reference to my name under the heading "Legal Opinion" in the Prospectus.
In giving such consent, I do not admit that I come within the category of
persons whose consent is required under Section 7 of the Securities Act of
1933, or the Rules and Regulations of the Securities and Exchange Commission.
 
Very truly yours,
 
        /s/ Margaret M. Foran
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          MARGARET M. FORAN