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                                                                     Exhibit 8.1


                               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
Mortgaged Obligations, issuable in Series (the "Bonds") under the captioned
registration statement, as amended (the "Registration Statement") filed under
the Securities Act of 1933, as amended (the "1933 Act"). The Bonds of each
Series are to be issued pursuant to an indenture (the "Indenture"), as
supplemented by one or more supplemental indentures authorizing such Series
(each a "Series Supplement"). The Indenture will be substantially in the form
filed with the Securities and Exchange Commission (the "Commission") as an
exhibit to the Registration Statement. This opinion is to be filed as an exhibit
to the Registration Statement.

         We have examined originals or copies, certified or otherwise identified
to our satisfaction, of (a) the Issuer's Certificate of Incorporation, (b) the
Issuer's Bylaws, (c) minutes of meetings or unanimous consents in lieu of
meetings of the Issuer's board of directors or shareholders, (d) the Indenture
including the form of Bonds and description of requirements for each Series
Supplement contained therein, (e) the prospectus contained in the Registration
Statement, as filed with the Commission herewith (the "Prospectus"), and (f)
such other documents, records, certificates of 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 and each Series
Supplement will be duly executed and delivered; that the Bonds will be duly
executed and delivered substantially

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Capstead Securities Corporation IV
September 28, 1998
Page 2

in the forms contemplated by the Indenture; and that the Bonds will be sold as
described in the Registration Statement.

         On the basis of the foregoing, we are of the opinion that the
description of federal income tax consequences appearing under the heading
"Certain Federal Income Tax Consequences" in the Prospectus accurately describes
the material federal income tax consequences to holders of Bonds under existing
law and subject to the qualifications and assumptions stated therein.

         The opinions herein are based upon our interpretations of current law,
including court authority and existing Final and Temporary Regulations, which
are subject to change both prospectively and retroactively, and upon the facts
and assumptions discussed herein. This opinion letter is limited to the matters
set forth herein, and no opinions are intended to be implied or may be inferred
beyond those expressly stated herein. Our opinion is rendered as of the date
hereof and we assume no obligation to update or supplement this opinion or any
matter related to this opinion to reflect any change of fact, circumstances, or
law after the date hereof. In addition, our opinion is based on the assumption
that the matter will be properly presented to the applicable court. Furthermore,
our opinion is not binding on the Internal Revenue Service or a court. In
addition, we must note that our opinion represents merely our best legal
judgment on the matters presented and that others may disagree with our
conclusion. There can be no assurance that the Internal Revenue Service will not
take a contrary position or that a court would agree with our opinion if
litigated. In the event any one of the statements, representations or
assumptions we have relied upon to issue this opinion is incorrect, our opinion
might be adversely affected and may not be relied upon.

         We consent to the use and filing of this opinion as Exhibit 8.1 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.