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                                                                     EXHIBIT 5.1

                                April 15, 2002

US Oncology, Inc.
16825 Northchase Drive, Suite 1300
Houston, Texas  77060

Gentlemen:

     We have acted as special counsel to US Oncology, Inc., a Delaware
corporation (the "Company"), in connection with the preparation and filing of
the Registration Statement on Form S-4 by the Company with the Securities and
Exchange Commission (the "Commission") under the Securities Act of 1933, as
amended (the "Act"), on April 16, 2002 (the "Registration Statement"), with
respect to the issuance by the Company of up to $175,000,000 aggregate principal
amount of its 9 5/8% Senior Subordinated Notes due February 1, 2012 (the "New
Notes") in exchange for up to $175,000,000 aggregate principal amount of its
outstanding 9 5/8% Senior Subordinated Notes due February 1, 2012 (the "Old
Notes"). The New Notes are to be issued in accordance with the provisions of the
Indenture, dated as of February 1, 2002 (the "Indenture"), by and between the
Company and JPMorgan Chase Bank, as Trustee (the "Trustee"). The New Notes are
to be issued pursuant to an exchange offer (the "Exchange Offer") by the Company
to holders of the issued and outstanding Old Notes, as contemplated by the
Registration Rights Agreement, dated as of February 1, 2002 (the "Registration
Rights Agreement"), by and between the Company and UBS Warburg LLC, Deutsche
Bank Alex. Brown Inc. and First Union Securities, Inc.

     This opinion is being furnished in accordance with the requirements of Item
601(b)(5) of Regulation S-K under the Act.

     In connection with this opinion, we have examined originals or copies,
certified or otherwise identified to our satisfaction, of:

     (i)    the Company's Certificate of Incorporation and By-laws, each as
     amended to date;

     (ii)   the Registration Rights Agreement;

     (iii)  the Indenture; and

     (iv)   the form of the New Notes.
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US Oncology, Inc.
April 15, 2002
Page 2


     We have also examined originals or copies, certified, or otherwise
identified to our satisfaction, of such records of the Company and such
agreements, certificates of public officials, certificates of officers or other
representatives of the Company and others, and such other documents,
certificates and records as we have deemed necessary or appropriate as a basis
for the opinions expressed below.

     In our examination, we have assumed, without independent investigation, the
legal capacity of all natural persons, the genuineness of all signatures on all
documents that we have examined, the authenticity of all documents submitted to
us as originals, the conformity to original documents of all documents submitted
to us as certified, conformed or photostatic copies and the authenticity of the
originals of such latter documents.  In conducting our examination of executed
documents or documents to be executed, we have assumed, without independent
investigation, that all parties thereto, other than the Company, had or will
have the power, corporate or other, to enter into and perform all obligations
thereunder and have also assumed, without independent investigation, the due
authorization by all requisite action, corporate or other, and execution and
delivery by such parties of such documents and, except as set forth below with
respect to the Company, the validity and binding effect thereof on such parties.
As to any facts material to the opinion expressed herein which we have not
independently established or verified, we have relied upon oral or written
statements and representations of officers and other representatives of the
Company and others.

     Our opinion set forth herein is limited to the laws of the State of New
York (other than municipal and local ordinances and regulations) that are
normally applicable to transactions of the type contemplated by the Exchange
Offer and to the extent that judicial or regulatory orders or decrees or
consents, approvals, licenses, authorizations, validations, filings, recordings
or registrations with governmental authorities are relevant, to those required
under such laws.  We do not express any opinion with respect to the law of any
jurisdiction other than as set forth above or as to the effect of any such other
law on the opinion stated herein.

     Based upon and subject to the foregoing, and subject to the limitations,
qualifications, exceptions and assumptions set forth herein, we are of the
opinion that when the New Notes have been duly executed by the Company,
authenticated by the Trustee in accordance with the terms of the Indenture, and
delivered upon consummation of the Exchange Offer against receipt of Old Notes
surrendered in exchange therefor in accordance with the terms of the
Registration Rights Agreement and the Indenture, the New Notes will constitute
valid and binding obligations of the Company, enforceable against the Company in
accordance with their terms, except, to the extent that enforcement thereof may
be limited by (i) bankruptcy, insolvency, reorganization, moratorium, fraudulent
conveyance or other similar laws now or hereafter in effect affecting creditors'
rights generally and (ii) general principles of equity (regardless of whether
enforceability is considered in a proceeding at law or in equity), including
reasonableness, good faith, materiality and fair dealing, and the discretion of
the court before which any proceeding therefor may be brought.
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US Oncology, Inc.
April 15, 2002
Page 3


     We hereby consent to the filing of this opinion with the SEC as an exhibit
to the Registration Statement.  We also consent to the reference to our firm
under the caption "Legal matters" in the Registration Statement.  In giving this
consent, we do not thereby admit that we are included in the category of persons
whose consent is required under Section 7 of the Act or the rules and
regulations of the SEC.  This opinion is expressed as of the date hereof, and we
disclaim any undertaking to advise you of any subsequent changes in the facts
stated or assumed herein or of any subsequent changes in applicable law.

                              Very truly yours,

                                   /s/Andrews & Kurth
                              Mayor, Day, Caldwell & Keeton
                                         L.L.P.

JBC/DLC