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                                                                     EXHIBIT 5.1
 
June 28, 1996
 
Aetna Life and Casualty Company
151 Farmington Avenue
Hartford, Connecticut 06156
 
Aetna Inc.
151 Farmington Avenue
Hartford, Connecticut 06156
 
Ladies and Gentlemen:
 
     I have acted as counsel to Aetna Life and Casualty Company (to be renamed
Aetna Services, Inc.), a Connecticut corporation (the "Company") and Aetna Inc.,
a Connecticut corporation ("Aetna"), in connection with the registration under
the Securities Act of 1933, as amended (the "Securities Act"), of up to
$2,000,000,000 of senior or subordinated debt securities of the Company (the
"Debt Securities") and senior or subordinated guarantees (the "Guarantees") of
Aetna of the Debt Securities. I have examined or caused to be examined necessary
or appropriate corporate records, certificates and other documents, and
questions of law for the purposes of this opinion.
 
     Upon the basis of such examination and assuming that the Mergers referred
to in the registration statement have been duly consummated, I advise you that,
in my opinion:
 
          1. The Debt Securities will constitute valid and legally binding
     obligations of the Company subject to (a) bankruptcy, insolvency,
     reorganization, fraudulent transfer, moratorium and other similar laws now
     or hereafter in effect relating to or affecting creditors' rights generally
     and the rights of creditors of insurance companies generally, and (b)
     general principles of equity (regardless of whether considered in a
     proceeding at law or in equity) when the following conditions are met: (i)
     the registration statement has become effective under the Securities Act;
     (ii) the indenture relating to the Debt Securities and the Guarantees has
     been duly executed and delivered; (iii) the terms of the Debt Securities
     and of their issuance and sale have been duly established in conformity
     with the indenture relating to the Debt Securities so as not to violate any
     applicable law or result in a default under or breach of any agreement or
     instrument binding upon the Company and so as to comply with any
     requirement or restriction imposed by any court or governmental body having
     jurisdiction over the Company; and (iv) the Debt Securities have been duly
     executed and authenticated in accordance with the indenture relating to the
     Debt Securities, and duly issued and sold as contemplated by the
     registration statement and any prospectus supplement relating thereto.
 
          2. The Guarantees will constitute valid and legally binding
     obligations of Aetna subject to (a) bankruptcy, insolvency, reorganization,
     fraudulent transfer, moratorium and other similar laws now or hereafter in
     effect relating to or affecting creditors' rights generally and the rights
     of creditors of insurance companies generally, and (b) general principles
     of equity (regardless of whether considered in a proceeding at law or in
     equity) when the following conditions are met: (i) the registration
     statement has become effective under the Securities Act; (ii) the indenture
     relating to the Debt Securities and the Guarantees has been duly executed
     and delivered; (iii) the terms of the Debt Securities and the Guarantees to
     be endorsed thereon and of their issuance and sale have been duly
     established in conformity with the indenture relating to the Debt
     Securities and the Guarantees so as not to violate any applicable law or
     result in a default under or breach of any agreement or instrument binding
     upon Aetna and so as to comply with any requirement or restriction imposed
     by any court or governmental body having jurisdiction over Aetna; (iv) the
     Guarantees to be endorsed on the Debt Securities have been duly executed in
     accordance with the indenture relating to such Debt Securities and
     Guarantees; and (v) the Debt Securities have been duly executed and
     authenticated in accordance with the indenture relating to the Debt
     Securities, and duly issued and sold as contemplated by the registration
     statement and any prospectus supplement relating thereto.
 
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     I note that, as of the date of this opinion, a judgment for money in an
action based on a Debt Security denominated in a foreign currency, currency unit
or composite currency or on a Guarantee in respect of any such Debt Security in
a Federal court in the United States ordinarily would be enforced only in United
States dollars. I also note that, as of the date of this opinion, a state court
in the State of Connecticut rendering a judgment on a Debt Security denominated
in a foreign currency, currency unit or composite currency or on a Guarantee in
respect of any such Debt Security may apply Section 50a-57 of the General
Statutes of Connecticut, and render such judgment in the foreign currency in
which the Debt Security or the Guarantee in respect thereof is denominated. Such
judgment then would be payable in that foreign currency or, at the option of the
judgment debtor, in the amount of U.S. dollars which will purchase that foreign
currency on the conversion date (as defined in such Statutes).
 
     I am admitted to the Bar of the State of Connecticut and the foregoing
opinion is limited to the laws of the State of Connecticut and the federal laws
of the United States of America.
 
     In my examination or the examination which I caused to be made, the legal
capacity of all natural persons, the genuineness of all signatures, the
authenticity of all documents submitted to me as originals, the conformity to
original documents of all documents submitted to me as certified or photostatic
copies and the authenticity of the originals of such latter documents were
assumed. As to any facts material to the opinions expressed herein which were
not independently established or verified, I have relied upon oral or written
statements and representations of officers and other representatives of the
Company, Aetna and others.
 
     I hereby consent to the filing of this opinion as Exhibit 5.1 to the
registration statement and to the reference made to me under the heading
"Validity of the Securities" in the prospectus. In giving such consent, I do not
thereby admit that I am in the category of persons whose consent is required
under Section 7 of the Securities Act.
 
                                          Very truly yours,
 
                                          /s/ Thomas J. Calvocoressi
 
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                                          Thomas J. Calvocoressi
 
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