Exhibit 5

                                          October 6, 1999

Indiana Michigan Power Company
One Summit Square
Fort Wayne, Indiana 46801

Ladies and Gentlemen:

                  We have acted as counsel to Indiana Michigan Power Company, an
Indiana  corporation  (the  "Company"),  in  connection  with  the  Registration
Statement on Form S-3 (the  "Registration  Statement") filed by the Company with
the Securities and Exchange  Commission (the "Commission")  under the Securities
Act of 1933, as amended (the "Act"), relating to Unsecured Notes (the "Unsecured
Notes")  to be  issued  under an  Indenture,  dated as of  October  1, 1998 (the
"Indenture"),  between  the Company  and The Bank of New York,  as Trustee  (the
"Trustee"). The Unsecured Notes may be issued and sold or delivered from time to
time as set forth in the  Registration  Statement,  any amendment  thereto,  the
prospectus   contained  therein  (the   "Prospectus")  and  supplements  to  the
Prospectus  and  pursuant  to Rule 415  under the Act for an  aggregate  initial
offering price not to exceed $300,000,000.

                  We have examined the Registration Statement and the Indenture,
which has been filed  with the  Commission  as an  exhibit  to the  Registration
Statement.  We also have examined the  originals,  or duplicates or certified or
conformed copies, of such records,  agreements,  instruments and other documents
and have made such other and further  investigations  as we have deemed relevant
and necessary in connection with the opinions  expressed herein. As to questions
of fact material to this  opinion,  we have relied upon  certificates  of public
officials and of officers and representatives of the Company.

                  In rendering the opinions set forth below, we have assumed the
genuineness  of all  signatures,  the legal  capacity  of natural  persons,  the
authenticity  of all documents  submitted to us as originals,  the conformity to
original  documents of all documents  submitted to us as duplicates or certified
or  conformed  copies,  and the  authenticity  of the  originals  of such latter
documents. We also have assumed that: (1) the Indenture is the valid and legally
binding obligation of the Trustee; and (2) the Company is validly existing under
the laws of Indiana.

                  We  have  assumed  further  that  (1)  the  Company  has  duly
authorized, executed and delivered the Indenture and (2) execution, delivery and
performance by the Company of Indenture and the Unsecured  Notes do not and will
not violate the laws of Indiana or any other applicable laws (excepting the laws
of the State of New York and the Federal laws of the United States).



Indiana Michigan Power Company            2                 October 6, 1999

                  Based upon the  foregoing,  and subject to the  qualifications
and  limitations  stated  herein,  we are of the opinion that:  assuming (a) the
taking of all  necessary  corporate  action to approve the issuance and terms of
the Unsecured  Notes,  the terms of the offering  thereof and related matters by
the Board of Directors of the Company,  a duly  constituted and acting committee
of such  Board  or duly  authorized  officers  of the  Company  (such  Board  of
Directors,  committee or  authorized  officers  being  referred to herein as the
"Board")  and (b) the due  execution,  authentication,  issuance and delivery of
such Unsecured Notes, upon payment of the consideration therefor provided for in
the applicable  definitive purchase,  underwriting or similar agreement approved
by the Board and  otherwise in accordance  with the  provisions of the Indenture
and such  agreement,  such  Unsecured  Notes will  constitute  valid and legally
binding obligations of the Company enforceable against the Company in accordance
with  their  terms,  subject  to  the  effects  of (i)  bankruptcy,  insolvency,
fraudulent  conveyance,  reorganization,   moratorium  and  other  similar  laws
relating to or affecting  creditors'  rights  generally,  (ii) general equitable
principles (whether considered in a proceeding in equity or at law) and (iii) an
implied covenant of good faith and fair dealing.

                  We are members of the Bar of the State of New York,  and we do
not  express  any opinion  herein  concerning  any law other than the law of the
State of New York and the Federal law of the United States.

                  We hereby  consent  to the  filing of this  opinion  letter as
Exhibit 5 to the  Registration  Statement  and to the use of our name  under the
caption  "Legal  Opinions"  in  the  Prospectus  included  in  the  Registration
Statement.

                                Very truly yours,

                         /s/ Simpson Thacher & Bartlett

                           SIMPSON THACHER & BARTLETT