Exhibit 5




                          [Letterhead of Arnold & Porter]



                                                 October 14, 1997



Armco Inc.
One Oxford Centre
301 Grant Street
Pittsburgh, Pennsylvania  15219


Ladies and Gentlemen:
     
   We refer to the registration statement under Form S-4, Registration No. 
333-36691 (the "Registration Statement"), filed by Armco Inc., an Ohio 
corporation (the "Company") with the Securities and Exchange of 1933, as 
amended (the "Act"), pursuant to which the Company is registering 
$150,000,000 aggregate principal amount of 9% Senior Notes due 2007 (the 
"Exchange Notes"), under an Indenture dated as of October 1, 1992, between 
the Company and The Fifth Third Bank, as trustee (the "Trustee"), as 
supplemented by Supplemental Indenture No. 1, dated as of October 1, 1992, 
and Supplemental Indenture No. 2, dated as of September 1, 1997, to be issued 
in exchange for $150,000,000 aggregate principal amount of the Company's 9% 
Senior Notes (the "Exchange Offer").  The terms and conditions of the 
Exchange Notes and the Exchange Offer are as set forth in the Registration 
Statement and the prospectus (the "Prospectus") contained therein.

   We have examined originals or copies, certified or otherwise identified to 
our satisfaction, of the Registration Statement, the Indenture, the form of 
Exchange Notes set forth in the Indenture, and such corporate records, 
agreements, documents and other instruments, and such certificates or 
comparable documents of public officials and of officers and representatives 
of the Company, and have made such inquiries of such officers and 
representatives as we have deemed relevant and necessary as a basis for the 
opinions hereinafter set forth.

   Based upon and subject to the foregoing, we are of the opinion that the 
Exchange Notes have been duly authorized by the Company and when the Exchange 
Notes have been duly executed by the Company and authenticated by the Trustee 
in accordance with the terms of the Indenture and issued in 



exchange for the Old Notes in accordance with the terms of the Exchange 
Offer, the Exchange Notes will constitute valid and binding obligations of 
the Company under the laws of the State of New York, subject to bankruptcy, 
insolvency, reorganization, fraudulent conveyance, moratorium, receivership 
and similar laws relating to or affecting creditors' rights generally and to 
equitable principles (regardless of whether enforcement is sought in a 
proceeding in equity or at law).

   The foregoing opinion is limited to the laws of the State of New York and, 
in reliance upon the opinion of Gary R. Hildreth, Vice President, General 
Counsel and Secretary of the Company, an executed copy of which is attached 
hereto (the "Hildreth Opinion"), the laws of the State of Ohio, and we do not 
express any opinion herein concerning the laws of any other jurisdiction.  To 
the extent the foregoing opinion relates to matters governed by the laws of 
the State of Ohio, such opinion is subject to the qualifications and 
limitations expressed in the Hildreth Opinion.

   We hereby consent to the filing of this opinion as an exhibit to the 
Registration Statement and to the reference to this firm under the heading 
"Legal Matters" in the Registration Statement.  In giving the foregoing 
consent, we do not thereby admit that we are in the category of persons whose 
consent is required under Section 7 of the Act or the rules and regulations 
of the Securities and Exchange Commission thereunder. 

   This opinion is solely for your information and is not to be quoted in 
whole or in part, summarized or otherwise referred to without our written 
consent, except as provided in the preceeding paragraph.  This opinion is as 
of the date hereof.  We disclaim any responsibility to update or supplement 
this opinion to reflect any events or state of facts which may hereafter come 
to our attention or any changes in statutes or regulations or any court 
decisions which may hereafter occur.

                                        Very truly yours,

                                        /s/ ARNOLD & PORTER






                                                       Attachment to Exhibit 5

                             [Letterhead of Armco]




                                      October 14, 1997





Arnold & Porter 
399 Park Avenue
New York, New York  10022


Ladies and Gentlemen:

         I refer to the registration statement under Form S-4, Registration 
No. 333-36691 (the "Registration Statement"), filed with the Securities and 
Exchange of 1933, as amended (the "Act"), pursuant to which Armco Inc. (the 
"Company") is registering $150,000,000 aggregate principal amount of 9% 
Senior Notes due 2007 (the "Exchange Notes"), under an Indenture dated as of 
October 1, 1992, between the Company and The Fifth Third Bank, as trustee 
(the "Trustee"), as supplemented by Supplemental Indenture No. 1, dated as of 
October 1, 1992, and Supplemental Indenture No. 2, dated as of September 1, 
1997, to be issued in exchange for $150,000,000 aggregate principal amount of 
the Company's 9% Senior Notes (the "Exchange Offer").  The terms and 
conditions of the Exchange Notes and the Exchange Offer are as set forth in 
the Registration Statement and the prospectus (the "Prospectus") contained 
therein.

         I have examined originals or copies, certified or otherwise 
identified to my satisfaction, of the Registration Statement, the Indenture, 
the form of Exchange Notes set forth in the Indenture, and such corporate 
records, agreements, documents and other instruments, and such certificates 
or comparable documents of public officials and of officers and 
representatives of the Company, and have made such inquiries of such officers 
and representatives as I have deemed relevant and necessary as a basis for 
the opinions hereinafter set forth.

         Based upon and subject to the foregoing, I am of the opinion that 
the Exchange Notes have been duly authorized by the Company and when the 
Exchange Notes have been duly executed by the Company and authenticated by 
the Trustee in accordance with the terms of the Indenture and issued in 
exchange for the Old Notes in accordance with the terms of the 





Exchange Offer, the Exchange  Notes will constitute valid and binding 
obligations of the Company under the laws of the State of Ohio, subject to 
bankruptcy, insolvency, reorganization, fraudulent conveyance, moratorium, 
receivership and similar laws relating to or affecting creditors' rights 
generally and to equitable principles (regardless of whether enforcement is 
sought in a proceeding in equity or at law).

         The foregoing opinion is limited to the laws of the State of Ohio 
and I express no opinion herein concerning the laws of any other jurisdiction.

         I hereby consent to the filing of this opinion as an exhibit to the 
Registration Statement and/or as an attachment to your opinion being filed as 
an exhibit to the Registration Statement (and in this regard I consent to 
your reliance on this opinion) and to be named under the caption "Legal 
Matters" in the Prospectus forming part of the Registration Statement.  In 
giving this consent, I do not thereby admit that I am within the category of 
persons whose consent is required under Section 7 of the Act or the rules and 
regulations of the Securities and Exchange Commission thereunder.

                                 Very truly yours,

                                 /s/ Gary R. Hildreth
                                 Gary R. Hildreth
                                 Vice President, General
                                      Counsel and Secretary