EXHIBIT 3.1
 
               AMENDED AND RESTATED CERTIFICATE OF INCORPORATION
 
                                      OF
 
                       AMERICAN ONCOLOGY RESOURCES, INC.
 
     The name of the corporation is "American Oncology Resources, Inc." (the
"Corporation").
 
     The original certificate of incorporation of the Corporation was filed with
the Secretary of State of the State of Delaware on October 30, 1992, under the
name "Ascend Medical Corp.".  Such certificate of incorporation was amended on
each of November 12, 1992, March 10, 1994, May 2, 1995, May 10, 1996 and May 8,
1997.
 
     This Amended and Restated Certificate of Incorporation has been duly
proposed by resolutions adopted and declared advisable by the Board of Directors
of the Corporation, duly adopted by the stockholders of the Corporation and duly
executed and acknowledged by the officers of the Corporation in accordance with
Sections 103, 242 and 245 of the General Corporation Law of the State of
Delaware.
 
     Pursuant to Section 103(d) of the General Corporation Law of the State of
Delaware, the Amended and Restated Certificate of Incorporation shall not be
effective until the Effective Time, as such term is defined in that certain
Agreement and Plan of Merger, dated as of December 11, 1998, by and among the
Corporation, Diagnostic Acquisition, Inc., a Texas corporation, and Physician
Reliance Network, Inc., a Texas corporation, with such Effective Time to not be
later than 12:01 a.m., Central Daylight Time, on the 90th day after the filing
date hereof.
 
     The text of the Certificate of Incorporation of the Corporation, as
amended, is hereby further amended and restated to read in its entirety as
follows:
 
                                   ARTICLE I
 
     The name of the corporation is US Oncology, Inc. (the "Corporation").
 
                                  ARTICLE II
 
     The address of the Corporation's registered office in the State of Delaware
is 1209 Orange Street, Wilmington, New Castle County 19801-1196.  The name of
the Corporation's registered agent at such address is The Corporation Trust
Company.
 
                                  ARTICLE III
 
     The purpose of the Corporation is to engage in any lawful act or activity
for which corporations may be organized under the General Corporation Law of
Delaware.
 
                                  ARTICLE IV
 
     The total number of shares of capital stock which the Corporation shall
have authority to issue is two hundred and one million (252,000,000) shares,
consisting of two million (2,000,000) shares of preferred stock, par value $.01
per share, out of which 500,000 shares have been designated as "Series A
Preferred Stock," and two hundred fifty million (250,000,000) shares of common
stock, par value $.01 per share.
 
     The Board of Directors of the Corporation shall have the power by
resolution to (a) provide for the issuance of shares of preferred stock in
series, (b) determine the number of shares of such stock in any such series, and
(c) fix the designations, preferences, qualifications, limitations, restrictions
and special or relative rights of shares of preferred stock or any series
thereof.
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                                   ARTICLE V
 
     In furtherance and not in limitation of the general powers conferred by the
laws of the State of Delaware, the Board of Directors is expressly authorized to
make, alter or repeal the Bylaws of the Corporation, except as specifically
otherwise provided therein.
 
                                  ARTICLE VI
 
     The number of directors which shall constitute the whole Board of Directors
of the Corporation shall be determined in accordance with the Corporation's
Bylaws.  The directors shall be divided into three classes, designated as Class
I, Class II and Class III.  Each class shall consist, as nearly as possible, of
one-third of the total number of directors constituting the entire board of
directors. The term of the initial Class I directors shall terminate on the date
of the Annual Meeting of Stockholders to be held in 2000; the term of the
initial Class II directors shall terminate on the date of the Annual Meeting of
Stockholders to be held in 2001; and the term of the initial Class III directors
shall terminate on the date of the Annual Meeting of Stockholders to be held in
2002.  At each Annual Meeting of Stockholders following such initial
classification and election, directors elected to succeed those directors whose
terms then expire shall be elected for a term of office to expire at the third
succeeding Annual Meeting of Stockholders after their election.  If the number
of directors is changed, then any increase or decrease in such number shall be
apportioned by the Board of Directors among the classes so as to maintain the
number of directors in each class as nearly as equal as possible.  No reduction
in the authorized number of members of the Board of Directors shall have the
effect of removing any director from office before that director's term of
office expires.   A director may be removed from office at any time but only for
cause and only by the affirmative vote of at least two-thirds of the voting
power of the all outstanding shares of capital stock of the Corporation then
entitled to vote at an election of directors of the Corporation, voting as a
single class.  Except as may otherwise be provided by law, cause for removal
shall exist only if the director whose removal is proposed has been convicted of
a felony by a court of competent jurisdiction and such conviction is no longer
subject to direct appeal or has been adjudged by a court of competent
jurisdiction to be liable for negligence or misconduct in the performance of his
duty to the Corporation in a matter of substantial importance to the
corporation, and such adjudication is no longer subject to direct appeal.
 
     Nominations of persons for election to the Board of Directors of the
Corporation may be made at a meeting of stockholders of the Corporation either
by or at the direction of the Nominating Committee of the Board of Directors or
by any stockholder of record entitled to vote in the election of directors at
such meeting who has complied with the notice procedures set forth in this
paragraph of this Article VI.  A stockholder who desires to nominate a person
for election to the Board of Directors at a meeting of stockholders of the
Corporation and who is eligible to make such nomination must give timely written
notice of the proposed nomination to the Secretary of the Corporation.  To be
timely, a stockholder's notice given pursuant to this paragraph must be received
at the principal executive office of the Corporation not less than one hundred
twenty (120) calendar days in advance of the date which is one year later than
the date of the proxy statement of the Corporation released to stockholders of
the Corporation in connection with the previous year's annual meeting of
stockholders of the Corporation; provided, however, that if no annual meeting of
stockholders of the Corporation was held the previous year or if the date of the
forthcoming annual meeting of stockholders has been changed by more than thirty
(30) calendar days from the date contemplated at the time of the previous year's
proxy statement or if the forthcoming meeting is not an annual meeting of
stockholders of the Corporation, then to be timely such stockholder's notice
must be so received not later than the close of business on the tenth day
following the earlier of (a) the day on which notice of the date of the
forthcoming meeting was mailed or given to stockholders by or on behalf of the
corporation or (b) the day on which public disclosure of the date of the
forthcoming meeting was made by or on behalf of the Corporation.  Such
stockholder's notice to the Secretary of the Corporation shall set forth (a) as
to each person whom the stockholder proposes to nominate for election or re-
election as a director (i) the name, age, business address and residence address
of such person, (ii) the principal occupation or employment of such person;
(iii) the class and number of shares of capital stock of the Corporation which
are then beneficially owned by such person, (iv) any other information relating
to such person that is required by law or regulation to be disclosed in
solicitations of proxies for the election of
 
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directors of the Corporation and (v) such person's written consent to being
named as a nominee for election as a director and to serve as a director if
elected and (b) as to the stockholder giving the notice, (i) the name and
address, as they appear in the stock records of the Corporation, of such
stockholder, (ii) the class and number of shares of capital stock of the
Corporation which are then beneficially owned by such stockholder, (iii) a
description of all arrangements or understandings between such stockholder and
each nominee for election as a director and any other person or persons (naming
such person or persons) relating to the nomination proposed to be made by such
stockholder, and (iv) any other information required by law or regulation to be
provided by a stockholder intending to nominate a person for election as a
director of the Corporation. At the request of the Board of Directors, any
person nominated by or at the direction of the Board of Directors for election
as a director of the Corporation shall furnish to the Secretary of the
Corporation the information concerning such nominee which is required to be set
forth in a stockholder's notice of a proposed nomination. No person shall be
eligible for election as a director of the Corporation unless nominated in
compliance with the procedures set forth in this paragraph. The chairman of a
meeting of stockholders of the corporation shall refuse to accept the nomination
of any person not made in compliance with the procedures set forth in this
paragraph, and such defective nomination shall be disregarded.
 
                                  ARTICLE VII
 
     A director of the Corporation shall have no personal liability to the
Corporation or its stockholders for monetary damages for breach of fiduciary
duty as a director except to the extent that Section 102(b)(7) (or any successor
provision) of the General Corporation Law of Delaware, as amended from time to
time, expressly provides that the liability of a director may not be eliminated
or limited.
 
                                 ARTICLE VIII
 
     Whenever a compromise or arrangement is proposed between this Corporation
and its creditors or any class of them and/or between this Corporation and its
stockholders or any class of them, any court of equitable jurisdiction within
the State of Delaware may, on the application in a summary way of this
Corporation or of any creditor or stockholder thereof or on the application of
any receiver or receivers appointed for this Corporation under the provisions of
Section 291 of Title 8 of the Delaware Code or on the application of trustees in
dissolution or of any receiver or receivers appointed for this Corporation under
the provisions of Section 279 of Title 8 of the Delaware Code, order a meeting
of the creditors or class of creditors, and/or of the stockholders or class of
stockholders of this Corporation, as the case may be, to be summoned in such
manner as the said court directs.  If a majority in number representing three-
fourths in value of the creditors or class of creditors, and/or of the
stockholders or class of stockholders of this Corporation, as the case may be,
agree to any compromise or arrangement and to any reorganization of this
Corporation as consequence of such compromise or arrangement, the said
compromise or arrangement and the said reorganization shall, if sanctioned by
the court to which the said application has been made, be binding on all the
creditors or class of creditors, and/or on all the stockholders or class of
stockholders of this Corporation, as the case may be, and also on this
Corporation.
 
                                  ARTICLE IX
 
     The term of existence of the Corporation shall be perpetual.
 
                                   ARTICLE X
 
     No action shall be taken by stockholders of the Corporation except at an
annual meeting or special meeting of the stockholders of the Corporation.
 
     Special meetings of the stockholders, for any purpose or purposes, may be
called by  the Chairman of the Board or the President of the Corporation and
shall be called by the President or Secretary of the Corporation at the request
of a majority of the Board of Directors of the Corporation.  No stockholders,
individually or collectively shall have the power to call a special meeting.
Business transacted at any special meeting shall be limited to the purposes
stated in the notice.
 
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                                  ARTICLE XI
 
     Notwithstanding any provision of this Certificate of Incorporation or the
Bylaws of the Corporation to the contrary, the affirmative vote of the holders
of at least two-thirds of the voting power of all outstanding shares of the
capital stock of the Corporation then entitled to vote in an election of
directors, voting as a single class, shall be required to alter, amend or repeal
Article VI, Article X or this Article XI of this Certificate of Incorporation,
or any provision thereof, or to adopt any provision of this Certificate of
Incorporation or the Bylaws of the Corporation that is inconsistent with any of
the provisions of Article VI, of Article X or of this Article XI of this
Certificate of Incorporation.
 
     IN WITNESS WHEREOF, the Corporation has caused this Amended and Restated
Certificate of Incorporation to be signed by its Chairman of the Board and Chief
Executive Officer and attested by its Secretary this 15th  day of June, 1999.
 
 
                              AMERICAN ONCOLOGY RESOURCES, INC.
 
 
 
                              By: /s/ R. Dale Ross
                                 ---------------------------------------
                                 R. Dale Ross, Chairman of the Board
                                 and Chief Executive Officer
 
 
Attest:
 
 
/s/ L. Fred Pounds
-----------------------------------
L. Fred Pounds, Assistant Secretary