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                                                                     Exhibit 5.1


                               September 28, 1998



Capstead Securities Corporation IV
2711 N. Haskell, Suite 1000
Dallas, Texas 75204


         Re:      Capstead Securities Corporation IV
                  Registration Statement on Form S-3
                  Registration No. 33-42337

Ladies and Gentlemen:

         We have acted as counsel for Capstead Securities Corporation IV, a
corporation organized under the laws of the State of Delaware (the "Issuer"), in
connection with the proposed issuance by the Issuer of its collateralized
mortgage obligations (the "Bonds"). The Bonds of each series are to be issued
pursuant to an indenture as supplemented by one or more supplemental indentures
between the Issuer and the trustee (the "Trustee") authorizing each such series
(each a "Series Supplement"). (The indenture, in the form filed as an exhibit to
the Issuer's Registration Statement referred to below, and each Series
Supplement are herein referred to collectively as the "Indenture"). This opinion
is to be filed as an exhibit to the captioned registration statement relating to
the Bonds on Form S-3 (the "Registration Statement") filed with the Securities
and Exchange Commission under the Securities Act of 1933, as amended (the "1933
Act").

         We have examined originals or copies, certified or otherwise identified
to our satisfaction, of the Issuer's organizational documents, the Indenture and
the form of Bonds included therein and such other documents, records,
certificates of the Issuer and public officials and other instruments as we have
deemed necessary for the purposes of rendering this opinion. In addition, we
have assumed that the Indenture will be duly executed and delivered; that the
Bonds will be duly executed and delivered substantially in the forms
contemplated by the Indenture; and that the Bonds will be sold as described in
the Registration Statement.

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Capstead Securities Corporation IV
September 28, 1998
Page 2




         Based upon the foregoing, we are of the opinion that the Bonds are in
due and proper form, and assuming the due authorization, execution and delivery
of the Indenture by the Issuer and the Trustee and the due authorization of the
Bonds by all necessary action on the part of the Issuer, when validly executed,
authenticated and issued in accordance with the Indenture and delivered against
payment therefor, the Bonds will constitute valid and binding obligations of the
Issuer, enforceable against the Issuer in accordance with their terms, except
that the enforceability thereof may be subject to (a) bankruptcy, insolvency,
reorganization, arrangement, moratorium, fraudulent, or preferential conveyance
or other similar laws now or hereinafter in effect relating to creditors' rights
generally, and (b) general principles of equity (regardless of whether such
enforceability is considered in a proceeding in equity or at law).

         The opinion expressed above is subject to the qualification that we do
not purport to be experts as to the laws of any jurisdiction other than the
United States, the States of Texas and New York and the General Corporation Law
of the State of Delaware, and we express no opinion herein as to the effect that
the laws and decisions of courts of any such other jurisdiction may have upon
such opinions.

         We consent to the use and filing of this opinion as Exhibit 5.1 to the
Registration Statement and to the reference to our firm under the caption "Legal
Matters" in the Prospectus Supplement and Prospectus contained therein. In
giving such consent we do not imply or admit that we are within the category of
persons whose consent is required under Section 7 of the 1933 Act or the rules
and regulations of the Securities and Exchange Commission thereunder.

                                        Very truly yours,


                                        /s/ Andrews & Kurth L.L.P.