<PAGE>   1
                                                                     EXHIBIT 3.1


                                    RESTATED
                          CERTIFICATE OF INCORPORATION
                                       OF
                               ILEX ONCOLOGY, INC.

         ILEX Oncology, Inc., a corporation organized and existing under the
laws of the State of Delaware, hereby certifies as follows:

         1. The name of the corporation is ILEX Oncology, Inc. and the name
under which the corporation was originally incorporated was Biovensa Inc. The
date of filing of its original Certificate of Incorporation with the Secretary
of State of Delaware is December 14, 1993.

         2. Pursuant to Sections 242 and 245 of the General Corporation Law of
the State of Delaware, this Restated Certificate of Incorporation restates and
integrates and further amends the provisions of the Certificate of Incorporation
of this corporation.

         3. The text of the Restated Certificate of Incorporation as heretofore
amended and supplemented is hereby restated and further amended to read in its
entirety as follows:

         FIRST. The name of the corporation is ILEX Oncology, Inc. (the
"Company").

         SECOND. The address of the registered office of the Company is 1013
Centre Road, in the City of Wilmington, County of New Castle, Delaware. The name
of the Company's registered agent at that office is Corporation Service Company.

         THIRD. The purpose of the Company is to engage in any lawful act or
activity for which corporations may be organized under the General Corporation
Law of Delaware.

         FOURTH. A. AUTHORIZED CAPITAL STOCK. The total number of shares which
the Company shall have the authority to issue shall be 120,000,000 shares, of
which 100,000,000 shares shall be common stock, $.01 par value (the "Common
Stock"), and 20,000,000 shares shall be preferred stock, $.01 par value (the
"Preferred Stock").

         B. COMMON STOCK. The board of directors of the Company (the "Board of
Directors") is hereby authorized to cause shares of Common Stock to be issued
from time to time for such consideration as may be fixed from time to time by
the Board of Directors, or by way of stock split pro rata to the holders of the
Common Stock. The Board of Directors may also determine the proportion of the
proceeds received from the sale of such stock which shall be credited upon the
books of the Company to capital or capital surplus.

         Each share of the Common Stock shall be equal in all respects to every
other share of the Common Stock. Subject to any special voting rights of the
holders of Preferred Stock fixed by or pursuant to the provisions of Paragraph C
of this Article Fourth, the shares of Common Stock shall entitle the holders
thereof to one vote for each share upon all matters upon which stockholders have
the right to vote.



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         No holder of shares of Common Stock shall be entitled as a matter of
right to subscribe for or purchase any part of any new or additional issues of
stock, or securities convertible into stock, of any class whatsoever, whether
now or hereafter authorized, and whether issued for cash, property, services or
otherwise.

         After the requirements with respect to preferential dividends on
Preferred Stock (fixed by or pursuant to the provisions of Paragraph C of this
Article Fourth), if any, shall have been met and after the Company shall have
complied with all the requirements, if any, with respect to the setting aside of
sums as sinking funds or redemption or purchase accounts (fixed by or pursuant
to the provisions of Paragraph C of this Article Fourth) and subject further to
any other conditions which may be fixed by or pursuant to the provisions of
Paragraph C of this Article Fourth, then, but not otherwise, the holders of
Common Stock shall be entitled to receive dividends, if any, as may be declared
from time to time by the Board of Directors, ratably in proportion to the number
of shares of Common Stock held by each such holder.

         After distribution in full of the preferential amount (fixed by or
pursuant to the provisions of Paragraph C of this Article Fourth), if any, to be
distributed to the holders of Preferred Stock in the event of voluntary or
involuntary liquidation, distribution or sale of assets, dissolution or winding
up of the Company, the holders of the Common Stock shall be entitled to receive
all the remaining assets of the Company, tangible and intangible, of whatever
kind available for distribution to stockholders, ratably in proportion to the
number of shares of Common Stock held by each.

         C. PREFERRED STOCK. Shares of Preferred Stock may be divided into and
issued in such series, on such terms and for such consideration as may from time
to time be determined by the Board of Directors of the Company. Each series
shall be so designated as to distinguish the shares thereof from the shares of
all other series and classes. All shares of Preferred Stock shall be identical,
except as to variations between different series in the relative rights and
preferences as permitted or contemplated by the next succeeding sentence.
Authority is hereby vested in the Board of Directors to establish out of shares
of Preferred Stock which are authorized and unissued from time to time one or
more series thereof and to fix and determine the following relative rights and
preferences of shares of each such series:

         (1) the distinctive designation of, and the number of shares which
shall constitute, the series and the "stated value" or "nominal value," if any,
thereof;

         (2) the rate of dividend applicable to shares of such series, if any;

         (3) the price at and the terms and conditions on which shares of such
series may be redeemed, if any;

         (4) the amount payable upon shares of such series in the event of the
involuntary liquidation of the Company;

         (5) the amount payable upon shares of such series in the event of the
voluntary liquidation of the Company;


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         (6) sinking fund provisions for the redemption or purchase of shares of
such series, if any;

         (7) the terms and conditions on which shares of such series may be
converted, if such shares are issued with the privilege of conversion;

         (8) the voting powers, if any, of the holders of shares of the series
which may, without limiting the generality of the foregoing, include (i) the
right to vote on any or all matters voted upon by the stockholders and (ii) the
right to vote, as a series by itself or together with other series of Preferred
Stock or together with all series of Preferred Stock as a class, upon such
matters, under such circumstances and upon such conditions as the Board of
Directors may fix, including, without limitation, the right, voting as a series
by itself or together with other series of Preferred Stock or together with all
series of Preferred Stock as a class, to elect one or more directors of the
Company in the event there shall have been a failure to pay dividends on any one
or more series of Preferred Stock or under such other circumstances and upon
such conditions as the Board of Directors may determine; and

         (9) any other such rights and preferences as are not inconsistent with
the General Corporation Law of Delaware.

         D. OTHER PROVISIONS.

         (1) The relative powers, preferences, and rights of each series of
Preferred Stock shall be as fixed from time to time by the Board of Directors in
the resolution or resolutions adopted pursuant to the authority granted in
Paragraph C of this Article Fourth, and the consent by class or series vote or
otherwise, of the holders of the Preferred Stock or such of the series of the
Preferred Stock as are from time to time outstanding shall not be required for
the issuance by the Board of Directors of any other series of Preferred Stock
whether the powers, preferences and rights of such other series shall be fixed
by the Board of Directors as senior to, or on a parity with, powers, preferences
and rights of such outstanding series, or any of them, provided, however, that
the Board of Directors may provide in such resolution or resolutions adopted
with respect to any series of Preferred Stock, that the consent of the holders
of a majority (or such greater proportion as shall be therein fixed) of the
outstanding shares of such series voting thereon shall be required for the
issuance of any or all other series of Preferred Stock.

         (2) Subject to the provisions of Section 1 of this Paragraph D, shares
of any series of Preferred Stock may be issued from time to time as the Board of
Directors shall determine and on such terms and for such consideration as shall
be fixed by the Board of Directors.

         (3) Common Stock may be issued from time to time as the Board of
Directors shall determine and on such terms and for such consideration as shall
be fixed by the Board of Directors.

         (4) The Company reserves the right to increase or decrease its
authorized capital stock, or any class or series thereof or to reclassify the
same and to amend, alter, change or repeal any provision contained in this
Restated Certificate of Incorporation or in any amendment thereto, in the manner
now or hereafter prescribed by law, but subject to such conditions and
limitations as are

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hereinbefore prescribed, and all rights conferred upon stockholders in this
Restated Certificate of Incorporation or any amendment thereto, are granted
subject to this reservation.

         (5) No holder of any of the shares or securities convertible into such
shares, or of options, warrants or other rights to purchase or acquire shares of
any class or series of shares, or of other securities of the Company shall have
any preemptive right to purchase, acquire or subscribe for any unissued shares
of any class or series or any additional shares of any class or series to be
issued by reason of any increase in the authorized capital stock of the Company
of any class or series, or bonds, certificate of indebtedness, debenture or
other securities convertible or exchangeable for shares of any class or series,
or carrying any right to purchase or acquire shares of any class or series;
provided that the foregoing shall not prohibit the Company from contracting or
otherwise agreeing to provide for rights of first refusal to holders of its
outstanding securities.

         FIFTH. The business of the Company shall be managed by a Board of
Directors. The number of directors of the Company shall be fixed from time to
time by or pursuant to the By-laws of the Company.

         SIXTH. Election of directors need not be by written ballot.

         SEVENTH. The Company is to have perpetual existence.

         EIGHTH. The Board of Directors is authorized to adopt, amend and repeal
the By-laws of the Company.

         NINTH. Meetings of the stockholders may be held within or without the
State of Delaware, as the By-Laws may provide. The books of the Company may be
kept outside the State of Delaware at such place or places as may be designated
from time to time by the Board of Directors or in the By-Laws of the Company.

         TENTH. A director of the Company shall not be personally liable to the
Company or its stockholders for monetary damages for breach of his or her duties
as a director, except for liability (a) for any breach of the director's duty of
loyalty to the Company or its stockholders, (b) for acts or omissions not in
good faith or which involve intentional misconduct or a knowing violation of
law, (c) under Section 174 of the Delaware General Corporation Law; or (d) for
any transaction from which the director derived an improper personal benefit.

         ELEVENTH. A. RIGHT TO INDEMNIFICATION. Each person who was or is a
director of the Company and who was or is made a party or is threatened to be
made a party to or is otherwise involved (including, without limitation, as a
witness) in any action, suit or proceeding, whether civil, criminal,
administrative or investigative (hereinafter a "proceeding"), by reason of the
fact that he or she is or was a director or officer of the Company or is or was
serving at the request of the Company as a director, officer, partner, trustee,
employee or agent of another corporation or of a partnership, joint venture,
trust or other enterprise, including service with respect to an employee benefit
plan (hereinafter an "Indemnified Director"), whether the basis of such
proceeding is alleged action in an official capacity as a director or officer or
in any other capacity while serving as a director


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or officer, shall be indemnified and held harmless by the Company to the fullest
extent permitted by the General Corporation Law of Delaware, as the same exists
or may hereafter be amended (but, in the case of any such amendment, only to the
extent that such amendment permits the Company to provide broader
indemnification rights than such law permitted the Company to provide prior to
such amendment), against all liability, all reasonable expense and all loss
(including, without limitation, judgments, fines, reasonable attorneys' fees,
ERISA excise taxes or penalties and amounts paid in settlement) incurred or
suffered by such Indemnified Director in connection therewith and such
indemnification shall continue as to an Indemnified Director who has ceased to
be a director and shall inure to the benefit of the Indemnified Director's
heirs, executors and administrators. Each person who was or is an officer of the
Company and not a director of the Company and who was or is made a party or is
threatened to be made a party to or is otherwise involved (including, without
limitation, as a witness) in any proceeding, by reason of the fact that he or
she is or was an officer of the Company or is or was serving at the request of
the Company as a director, officer, partner, trustee, employee or agent of
another corporation or of a partnership, joint venture, trust or other
enterprise, including service with respect to an employee benefit plan
(hereinafter an "Indemnified Officer"), whether the basis of such proceeding is
alleged action in an official capacity as an officer or in any other capacity
while serving as an officer, shall be indemnified and held harmless by the
Company against all liability, all reasonable expense and all loss (including,
without limitation, judgments, fines, reasonable attorneys' fees, ERISA excise
taxes or penalties and amounts paid in settlement) incurred or suffered by such
Indemnified Officer to the same extent and under the same conditions that the
Company must indemnify an Indemnified Director pursuant to the immediately
preceding sentence and to such further extent as is not contrary to public
policy and such indemnification shall continue as to an Indemnified Officer who
has ceased to be an officer and shall inure to the benefit of the Indemnified
Officer's heirs, executors and administrators. Notwithstanding the foregoing and
except as provided in Paragraph B of this Article Eleventh with respect to
proceedings to enforce rights to indemnification, the Company shall indemnify
any Indemnified Director or Indemnified Officer in connection with a proceeding
(or part thereof) initiated by such Indemnified Director or Indemnified Officer
only if such proceeding (or part thereof) was authorized by the Board of
Directors of the Company. As hereinafter used in this Article Eleventh, the term
"indemnitee" means any Indemnified Director or Indemnified Officer. Any person
who is or was a director or officer of a subsidiary of the Company shall be
deemed to be serving in such capacity at the request of the Company for purposes
of this Article Eleventh. The right to indemnification conferred in this Article
Eleventh shall include the right to be paid by the Company the expenses incurred
in defending any such proceeding in advance of its final disposition
(hereinafter an "advancement of expenses"); provided, however, that, if the
General Corporation Law of Delaware requires, an advancement of expenses
incurred by an indemnitee who at the time of receiving such advance is a
director of the Company shall be made only upon delivery to the Company of an
undertaking (hereinafter an "undertaking"), by or on behalf of such indemnitee,
to repay all amounts so advanced if it shall ultimately be determined by final
judicial decision from which there is no further right to appeal (hereinafter a
"final adjudication") that such indemnitee is not entitled to be indemnified for
such expenses under this Article Eleventh or otherwise. The right to
indemnification and advancement of expenses conferred in this Paragraph A shall
be a contract right.

         B. RIGHT OF INDEMNITEE TO BRING SUIT. If a claim under Paragraph A of
this Article Eleventh is not paid in full by the Company within sixty days after
a written claim has been

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received by the Company (except in the case of a claim for an advancement of
expenses, in which case the applicable period shall be twenty days), the
indemnitee may at any time thereafter bring suit against the Company to recover
the unpaid amount of the claim. If successful in whole or in part in any such
suit or in a suit brought by the Company to recover an advancement of expenses
pursuant to the terms of an undertaking, the indemnitee also shall be entitled
to be paid the expense of prosecuting or defending such suit. In (i) any suit
brought by the indemnitee to enforce a right to indemnification hereunder (other
than a suit to enforce a right to an advancement of expenses brought by an
indemnitee who will not be a director of the Company at the time such advance is
made) it shall be a defense that, and (ii) any suit by the Company to recover an
advancement of expenses pursuant to the terms of an undertaking the Company
shall be entitled to recover such expenses upon a final adjudication that, the
indemnitee has not met the standard that makes it permissible hereunder or under
the General Corporation Law of Delaware (the "applicable standard") for the
Company to indemnify the indemnitee for the amount claimed. Neither the failure
of the Company (including its Board of Directors, a committee of the Board of
Directors, independent legal counsel or its stockholders) to have made a
determination prior to the commencement of such suit that indemnification of the
indemnitee is proper in the circumstances because the indemnitee has met the
applicable standard, nor an actual determination by the Company (including its
Board of Directors, a committee of the Board of Directors, independent legal
counsel or its stockholders) that the indemnitee has not met the applicable
standard, shall create a presumption that the indemnitee has not met the
applicable standard or, in the case of such a suit brought by the indemnitee,
shall be a defense to such suit. In any suit brought by the indemnitee to
enforce a right to indemnification or to an advancement of expenses hereunder,
or by the Company to recover an advancement of expenses pursuant to the terms of
an undertaking, the burden of proving that the indemnitee is not entitled to be
indemnified or to such advancement of expenses under this Article Eleventh or
otherwise shall be on the Company.

         C. NON-EXCLUSIVITY OF RIGHTS. The rights to indemnification and to the
advancement of expenses conferred in this Article Eleventh shall not be
exclusive of any other right which any person may have or hereafter acquire
under any statute, this Restated Certificate of Incorporation, any By-Law, any
agreement, any vote of stockholders or disinterested directors or otherwise.

         D. INSURANCE. The Company may maintain insurance, at its expense, to
protect itself and any director, officer, employee or agent of the Company or
another corporation, partnership, joint venture, trust or other enterprise
against any expense, liability or loss, whether or not the Company would have
the power to indemnify such person against such expense, liability or loss under
the General Corporation Law of Delaware.

         E. INDEMNIFICATION OF EMPLOYEES AND AGENTS. The Company may, to the
extent authorized from time to time by the Board of Directors, grant rights to
indemnification and to the advancement of expenses to any employee or agent of
the Company and to any person serving at the request of the Company as an agent
or employee of another corporation or of a joint venture, trust or other
enterprise to the fullest extent of the provisions of this Article Eleventh with
respect to the indemnification and advancement of expenses of either directors
or officers of the Company.


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<PAGE>   7




         F. REPEAL OR MODIFICATION. Any repeal or modification of any provision
of this Article Eleventh shall not adversely affect any rights to
indemnification and to advancement of expenses that any person may have at the
time of such repeal or modification with respect to any acts or omissions
occurring prior to such repeal or modification.

         G. SEVERABILITY. In case any one or more of the provisions of this
Article Eleventh, or any application thereof, shall be invalid, illegal or
unenforceable in any respect, the validity, legality and enforceability of the
remaining provisions in this Article Eleventh, and any other application
thereof, shall not in any way be affected or impaired thereby.

         TWELFTH. The Company reserves the right to amend, alter, change, or
repeal any provision contained in this Restated Certificate of Incorporation, in
the manner now or hereafter prescribed by law, and all rights conferred upon the
stockholders herein are granted subject to this reservation.

         IN WITNESS WHEREOF, this Restated Certificate of Incorporation has been
executed this 31st day of May 2000.



                                By: /s/ RONALD G. TEFTELLER
                                   ----------------------------------------
                                        Ronald G. Tefteller, Vice President

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                       CERTIFICATE OF DESIGNATION, POWERS,
                             PREFERENCES AND RIGHTS

                                       of

                            SERIES I PREFERRED STOCK

                                       of

                               ILEX ONCOLOGY, INC.

             Pursuant to Section 151 of the General Corporation Law
                            of the State of Delaware


                  The undersigned, Ronald G. Tefteller, the Vice President,
General Counsel and Corporate Secretary of ILEX Oncology, Inc., a Delaware
corporation (the "Company"), hereby certifies that pursuant to authority granted
to and vested in the Board of Directors of the Company by the provisions of the
Restated Certificate of Incorporation of the Company, the Board of Directors of
the Company has duly adopted the following resolutions creating a series of
Preferred Stock designated as the Series I Preferred Stock:

                  "RESOLVED, that pursuant to Article Fourth of the Restated
Certificate of Incorporation of ILEX Oncology, Inc., a Delaware corporation (the
"Corporation"), which (a) authorizes the Corporation to issue 20,000,000 shares
of Preferred Stock, par value $.01 per share ("Preferred Stock"), none of which
are issued and outstanding at the date hereof, and (b) expressly vests in the
Board of Directors of the Corporation (the "Board"), subject to the limitations
prescribed by law and the provisions of said Article Fourth, the authority to
provide by resolution or resolutions for the issuance of shares of Preferred
Stock in series and, by filing a certificate pursuant to the General Corporation
Law of the State of Delaware, to establish from time to time the number of
shares to be included in each of such series and to fix the designation, powers,
preferences and rights of the shares of each of such series, or of particular
holders thereof, the Board hereby fixes the powers, preferences and rights of
the shares of a series of Preferred Stock and the qualifications, limitations
and restrictions thereof, as follows:

                  Section 1. Designation and Amount. The shares of such series
shall be designated "Series I Preferred Stock", and the number of shares
constituting the Series I Preferred Stock shall initially be 50,000. The number
of shares of Series I Preferred Stock may be increased or decreased from time to
time by resolution of the Board, provided that no such decrease shall reduce the
number of shares of Series I Preferred Stock to less than the sum of (a) the
number of shares of Series I Preferred Stock then outstanding, (b) the number of
shares of Series I Preferred Stock that the


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<PAGE>   9

Corporation is obligated to issue upon the exercise of then outstanding rights,
options or warrants and (c) the number of shares of Series I Preferred Stock
that the Corporation is obligated to issue upon the conversion of then
outstanding convertible securities.

                  Section 2. Dividends and Distributions.

                  (a) Subject to the rights of holders of shares of any series
of Preferred Stock that ranks prior to the Series I Preferred Stock with respect
to dividends, the holders of shares of Series I Preferred Stock, in preference
to the rights of holders of shares of Common Stock, par value $.01 per share
("Common Stock"), of the Corporation with respect to dividends, and in
preference to the rights of holders of shares of any series of Preferred Stock
that ranks junior to the Series I Preferred Stock with respect to dividends,
shall be entitled to receive, when, as and if declared by the Board out of funds
legally available for that purpose, quarterly dividends, which shall be payable
in cash except as hereinafter provided, on the first day of January, April, July
and October in each year during which a share or fraction of a share of Series I
Preferred Stock is outstanding (each such date being referred to herein as a
"Quarterly Dividend Payment Date"), commencing on the first Quarterly Dividend
Payment Date after the first issuance of a share or fraction of a share of
Series I Preferred Stock, each such dividend to be in an amount per share
(rounded to the nearest cent) equal to:

                  (i) subject to the provision for adjustment set forth in the
         next succeeding sentence,

                           (A) 1,000 times the aggregate per share amount of all
                  cash dividends declared on the Common Stock after the
                  immediately preceding Quarterly Dividend Payment Date or, with
                  respect to the first Quarterly Dividend Payment Date, after
                  the first issuance of any share or fraction of a share of
                  Series I Preferred Stock, plus

                           (B) 1,000 times the aggregate per share amount, which
                  shall be payable in kind, of all non-cash dividends or other
                  distributions (other than (x) a dividend on the Common Stock
                  that is payable in shares of Common Stock or (y) a
                  distribution solely on account of a reclassification of, or
                  other split-up, division or combination of shares of, Common
                  Stock) declared on the Common Stock after the immediately
                  preceding Quarterly Dividend Payment Date or, with respect to
                  the first Quarterly Dividend Payment Date, after the first
                  issuance of any share or fraction of a share of Series I
                  Preferred Stock; or

                  (ii) if no dividend or other distribution (other than (x) a
         dividend on the Common Stock that is payable in shares of Common Stock
         or (y) a distribution solely on account of a reclassification of, or
         other split-up, division or combination of shares of, Common Stock)
         shall have been declared on the Common Stock after the immediately
         preceding Quarterly Dividend Payment Date or, with respect to the first
         Quarterly Dividend Payment Date, after the first issuance of any share
         or fraction of a share of Series I Preferred Stock, $.01.

In the event that the Corporation shall at any time after April 10, 2001, (1)
declare a dividend on the Common Stock that is payable in shares of Common
Stock, (2) reclassify the Common Stock or (3)


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<PAGE>   10


otherwise effect a split-up, division or combination of shares of Common Stock,
then in each such case the amount per share to which holders of shares of Series
I Preferred Stock were entitled immediately prior to such event under Section
2(a)(i) shall be adjusted by multiplying such amount by a fraction, the
numerator of which shall be the number of shares of Common Stock that are
outstanding immediately after such event and the denominator of which shall be
the number of shares of Common Stock that were outstanding immediately prior to
such event.

         (b) Immediately after the Board declares a dividend or other
distribution on the Common Stock (other than (x) a dividend on the Common Stock
that is payable in shares of Common Stock or (y) a distribution solely on
account of a reclassification of, or other split-up, division or combination of
shares of, Common Stock), if any share or fraction of a share of Series I
Preferred Stock is then outstanding, the Board shall declare a dividend on the
Series I Preferred Stock, which shall be payable at the time and in the amount
provided in Section 2(a). If (i) any share or fraction of a share of Series I
Preferred stock is then outstanding, (ii) no dividend or other distribution
(other than (x) a dividend on the Common Stock that is payable in shares of
Common Stock or (y) a distribution solely on account of a reclassification of,
or other split-up, division or combination of shares of, Common Stock) shall
have been declared on the Common Stock during the period between the immediately
preceding Quarterly Dividend Payment Date and the next succeeding Quarterly
Dividend Payment Date or, with respect to the first Quarterly Dividend Payment
Date, between the date of the first issuance of any share or fraction of a share
of Series I Preferred Stock and such first Quarterly Dividend Payment Date, and
(iii) there are funds legally available for the payment of a dividend on the
Series I Preferred Stock, the Board shall, at any time prior to such next
succeeding Quarterly Dividend Payment Date or such first Quarterly Dividend
Payment Date, as the case may be, declare a dividend of $1.00 per share on the
Series I Preferred Stock, which shall be payable on such next succeeding
Quarterly Dividend Payment Date or such first Quarterly Dividend Payment Date,
as the case may be.

         (c) Dividends on shares of Series I Preferred Stock shall begin to
accrue and be cumulative from the Quarterly Dividend Payment Date that
immediately precedes the date of issuance of such shares unless (i) the date of
issuance of such shares is prior to the record date for the determination of
holders of shares of Series I Preferred Stock entitled to receive a dividend on
the first Quarterly Dividend Payment Date, in which event dividends on such
shares shall begin to accrue and be cumulative from the date of issuance of such
shares, (ii) the date of issuance of such shares is a Quarterly Dividend Payment
Date, in which event dividends on such shares shall begin to accrue and be
cumulative from such Quarterly Dividend Payment Date, or (iii) the date of
issuance of such shares is a date after the record date for the determination of
holders of shares of Series I Preferred Stock entitled to receive a dividend on
the Quarterly Dividend Payment Date that next succeeds the date of issuance of
such shares, in which event dividends on such shares shall begin to accrue and
be cumulative from such next succeeding Quarterly Dividend Payment Date. Accrued
but unpaid dividends on shares of Series I Preferred Stock shall not bear
interest. If a dividend is declared on the Series I Preferred Stock and the
total amount of that dividend is less than the total amount of all dividends
accrued and payable on all shares of Series I Preferred Stock at the time of
payment of that dividend, then the portion of the total amount of that dividend
to be allocated to each of such shares shall be determined by multiplying the
total amount of that dividend by a fraction, the numerator of which shall be the
total amount of all dividends accrued and payable on that share at that time and


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<PAGE>   11




the denominator of which shall be the total amount of all dividends accrued and
payable on all such shares at that time. The Board may fix a record date for the
determination of holders of shares of Series I Preferred Stock entitled to
receive a dividend or other distribution on the Series I Preferred Stock, which
record date shall be no more than 30 days prior to the date fixed for the
payment of that dividend or other distribution.

         (d) If at any time (i) any holder of shares of Series I Preferred Stock
would have been entitled under the foregoing provisions of this Section 2 to
have received by that time a dividend on such shares, assuming that such
dividend had been declared, out of funds legally available for that purpose, at
the time and in the amount provided in the foregoing provisions of this Section
2, and (ii) such dividend or any part thereof has not been paid to such holder,
then such dividend or part thereof shall be considered accrued and payable at
that time.

         Section 3. Voting.

         (a) Subject to the provision for adjustment set forth in the next
succeeding sentence, each share of Series I Preferred Stock shall, except as
otherwise provided by law, entitle the holder thereof to 1,000 votes on each
matter that is submitted to a vote of stockholders of the Corporation. In the
event that the Corporation shall at any time after April 10, 2001, (i) declare a
dividend on the Common Stock that is payable in shares of Common Stock, (ii)
reclassify the Common Stock or (iii) otherwise effect a split-up, division or
combination of shares of Common Stock, then in each such case the number of
votes per share to which holders of shares of Series I Preferred Stock were
entitled immediately prior to such event shall be adjusted by multiplying such
number by a fraction, the numerator of which shall be the number of shares of
Common Stock that are outstanding immediately after such event and the
denominator of which shall be the number of shares of Common Stock that were
outstanding immediately prior to such event.

         (b) Except as otherwise provided by law or in the Restated Certificate
of Incorporation of the Corporation or the resolution or resolutions of the
Board providing for the issuance of shares of Preferred Stock (including but not
limited to these resolutions):

                  (i) the holders of shares of Series I Preferred Stock, the
         holders of shares of Common Stock and the holders of shares of any
         other class or series of capital stock of the Corporation having
         general voting rights shall vote together as a single class on each
         matter that is submitted to a vote of stockholders of the Corporation,
         and

                  (ii) the holders of shares of Series I Preferred Stock shall
         not have any special voting rights.

         Section 4. Certain Restrictions. Unless and until all dividends at the
time accrued and payable on all shares of Series I Preferred Stock have been
paid in full, the Corporation shall not:

                  (a) declare or pay any dividend, or make any other
         distribution, on any class or series of capital stock of the
         Corporation that ranks junior, either with respect to dividends


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<PAGE>   12


         or upon liquidation, dissolution or winding up, to the Series I
         Preferred Stock (any such class or series being referred to herein as
         "Junior Stock");

                  (b) declare or pay any dividend, or make any other
         distribution, on any class or series of capital stock of the
         Corporation that ranks in parity, either with respect to dividends or
         upon liquidation, dissolution or winding up, with the Series I
         Preferred Stock (any such class or series being referred to herein as
         "Parity Stock"), except dividends that are paid ratably on all shares
         of Series I Preferred Stock on which dividends are at the time accrued
         and payable and all shares of Parity Stock on which dividends are at
         the time accrued and payable in proportion to the total amounts of
         dividends at the time accrued and payable on all such shares;

                  (c) redeem, purchase or otherwise acquire for consideration
         any shares of Junior Stock, provided that the Corporation may at any
         time redeem, purchase or otherwise acquire shares of Junior Stock in
         exchange for shares of other Junior Stock; or

                  (d) redeem, purchase or otherwise acquire for consideration
         any shares of Series I Preferred Stock or any shares of Parity Stock,
         except in accordance with an offer to purchase made in writing to all
         holders of such shares upon terms that the Board, after considering the
         relative rights and preferences of the respective series and classes of
         such shares, considers in good faith will result in fair and equitable
         treatment among the holders of such shares.

                  Section 5. Reacquired Shares. Any shares of Series I Preferred
Stock that are purchased or otherwise acquired by the Corporation in any manner
whatsoever shall be retired and canceled promptly after the acquisition thereof.
Upon their cancellation, all of such shares shall become authorized but unissued
shares of Preferred Stock and thereafter may be issued as part of another series
of Preferred Stock, subject to the rights of holders (if any) of shares of
Series I Preferred Stock set forth in these resolutions.

                  Section 6. Liquidation, Dissolution or Winding Up. Upon any
liquidation, dissolution or winding up of the Corporation:

                  (a) no distribution shall be made to the holders of shares of
         Junior Stock unless, prior to such distribution, the Corporation shall
         have paid to each holder of shares of Series I Preferred Stock the sum
         of (i) $100 per share of Series I Preferred Stock held by such holder
         (such amount per share being referred to herein as the "Preference
         Amount") plus (ii) the total amount of all dividends at the time
         accrued and payable on all shares of Series I Preferred Stock held by
         such holder;

                  (b) no distribution shall be made to the holders of shares of
         Parity Stock, except distributions that are made ratably on both all
         shares of Series I Preferred Stock and all shares of Parity Stock in
         proportion to the total amounts to which the holders of all such shares
         are entitled upon such liquidation, dissolution or winding up; and



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<PAGE>   13


                  (c) each holder of shares of Series I Preferred Stock shall be
         entitled to receive the sum of (i) the total amount of all dividends at
         the time accrued and payable on all shares of Series I Preferred Stock
         held by such holder plus (ii) an aggregate amount per share (such
         amount per share being referred to herein as the "Distributable
         Amount"), inclusive of the Preference Amount but subject to the
         provision for adjustment set forth in the next succeeding sentence, of
         Series I Preferred Stock held by such holder that is equal to 1,000
         times the aggregate per share amount to be distributed to holders of
         shares of Common Stock upon such liquidation, dissolution or winding
         up.

In the event that the Corporation shall at any time after April 10, 2001, (1)
declare a dividend on the Common Stock that is payable in shares of Common
Stock, (2) reclassify the Common Stock or (3) otherwise effect a split-up,
division or combination of shares of Common Stock, then in each such case the
Distributable Amount to which a holder of shares of Series I Preferred Stock was
entitled immediately prior to such event shall be adjusted by multiplying such
Distributable Amount by a fraction, the numerator of which shall be the number
of shares of Common Stock that are outstanding immediately after such event and
the denominator of which shall be the number of shares of Common Stock that were
outstanding immediately prior to such event.

         Section 7. Consolidation, Merger, etc. If the Corporation shall enter
into any consolidation, merger, share exchange or other transaction in which all
outstanding shares of Common Stock are exchanged for or changed into other
securities, cash, other property or any combination thereof, then each
outstanding share of Series I Preferred Stock shall at the same time be
similarly exchanged for or changed into an amount per share, subject to the
provision for adjustment set forth in the next succeeding sentence, equal to
1,000 times the aggregate amount of securities, cash and other property for
which each outstanding share of Common Stock is exchanged or into which each
outstanding share of Common Stock is changed. In the event that the Corporation
shall at any time after April 10, 2001, (1) declare a dividend on the Common
Stock that is payable in shares of Common Stock, (2) reclassify the Common Stock
or (3) otherwise effect a split-up, division or combination of shares of Common
Stock, then in each such case the amount per share for which Series I Preferred
Stock would be exchanged, or into the amount which Series I Preferred Stock
would be changed, immediately prior to such event under the immediately
preceding sentence of this Section 7, shall be adjusted by multiplying such
amount by a fraction, the numerator of which shall be the number of shares of
Common Stock that are outstanding immediately after such event and the
denominator of which shall be the number of shares of Common Stock that were
outstanding immediately prior to such event.

         Section 8. Redemption. The shares of Series I Preferred Stock shall not
be redeemable.

         Section 9. Ranking. The Series I Preferred Stock shall rank junior to
each other series of Preferred Stock, both with respect to dividends and upon
liquidation, dissolution or winding up, unless the certificate of designation,
powers, preferences and rights of such other series of Preferred Stock shall
provide otherwise.

         Section 10. Amendment. If any share or fraction of a share of Series I
Preferred Stock is outstanding, neither the Restated Certificate of
Incorporation of the Corporation nor the resolution


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<PAGE>   14


or resolutions of the Board providing for the issuance of shares of Preferred
Stock (including but not limited to these resolutions) shall be amended in any
manner that would materially alter or change the powers, preferences or rights
of holders of shares of Series I Preferred Stock so as to affect such holders
adversely unless that amendment shall have received the affirmative vote of the
holders of a majority of the outstanding shares of Series I Preferred Stock
voting separately as a class. Notwithstanding the foregoing provisions of this
Section 10, whether or not a share or a fraction of a share of Series I
Preferred Stock is outstanding, (a) the Board may from time to time provide by
resolution or resolutions for the issuance of shares of Preferred Stock of one
or more series that rank prior to the Series I Preferred Stock, either with
respect to dividends or upon liquidation, dissolution or winding up, or both
with respect to dividends and upon liquidation, dissolution or winding up, and
(b) no vote or consent of any holder of shares of Series I Preferred Stock shall
be required either as a condition to the adoption of such resolution or
resolutions or as a condition to the issuance of such shares of Preferred Stock.

         Section 11. Fractional Shares. Series I Preferred Stock may be issued
in fractions of a share. Each holder of a fraction of a share of Series I
Preferred Stock shall be entitled to exercise voting rights, to receive
dividends and other distributions, and to have all other rights of the holders
of whole shares of Series I Preferred Stock in proportion to the fraction of a
share of Series I Preferred Stock held by that holder.

         RESOLVED FURTHER, that the proper officers of the Corporation be, and
each of them hereby is, authorized to execute a Certificate of Designation,
Powers, Preferences and Rights of Series I Preferred Stock of the Corporation
pursuant to Section 151 of the General Corporation Law of the State of Delaware
and to take all appropriate action to cause that Certificate to be filed,
recorded and become effective in accordance with Section 103 of the General
Corporation Law of the State of Delaware."

         IN WITNESS WHEREOF, this Certificate has been executed effective the
10th day of April, 2001.


                                           /s/ RONALD G. TEFTELLER
                                   -------------------------------------------
                                               Ronald G. Tefteller
                                   Vice President, General Counsel and Corporate
                                   Secretary



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