ILLINOIS POWER CO
S-3/A, 1994-09-02
ELECTRIC & OTHER SERVICES COMBINED
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<PAGE>   1
 
   
   AS FILED WITH THE SECURITIES AND EXCHANGE COMMISSION ON SEPTEMBER 2, 1994
    
 
   
                                                   REGISTRATION NOS. 33-55165
    
   
                                                                     33-55165-01
    
- --------------------------------------------------------------------------------
- --------------------------------------------------------------------------------
 
                       SECURITIES AND EXCHANGE COMMISSION
                             WASHINGTON, D.C. 20549
 
                               ------------------
                                    FORM S-3
 
   
                                 PRE-EFFECTIVE
    
   
                                AMENDMENT NO. 1
    
   
                                       TO
    
                             REGISTRATION STATEMENT
                                     UNDER
                           THE SECURITIES ACT OF 1933
 
                               ------------------
 
                             ILLINOIS POWER COMPANY
             (Exact name of registrant as specified in its charter)
                                    ILLINOIS
         (State or other jurisdiction of incorporation or organization)
                                   37-0344645
                      (I.R.S. Employer Identification No.)
                                 LARRY D. HAAB
                CHAIRMAN, PRESIDENT AND CHIEF EXECUTIVE OFFICER
                             ILLINOIS POWER COMPANY
                             500 SOUTH 27TH STREET
                            DECATUR, ILLINOIS 62525
                                 (217) 424-6600
                          ILLINOIS POWER CAPITAL, L.P.
    (Exact name of registrant as specified in Limited Partnership Agreement)
                                    DELAWARE
         (State or other jurisdiction of incorporation or organization)
   
                                   37-1330733
    
                      (I.R.S. Employer Identification No.)
                               C/O LARRY D. HAAB
                CHAIRMAN, PRESIDENT AND CHIEF EXECUTIVE OFFICER
                             ILLINOIS POWER COMPANY
                             500 SOUTH 27TH STREET
                            DECATUR, ILLINOIS 62525
                                 (217) 424-6600
 
  (Address, including zip code, and telephone number, including area code, of
        registrants' principal executive offices and agent for service)
 
                  PLEASE SEND COPIES OF ALL COMMUNICATIONS TO:
 
                             ROBERT J. REGAN, ESQ.
                             SCHIFF HARDIN & WAITE
                                7200 SEARS TOWER
                            CHICAGO, ILLINOIS 60606
                                 (312) 876-1000
                               KEVIN STACEY, ESQ.
                                 REID & PRIEST
                              40 WEST 57TH STREET
                               NEW YORK, NEW YORK
                                 (212) 603-2144
 
                               ------------------
 
    Approximate date of commencement of proposed sale to the public: From time
to time after the effective date of this Registration Statement.
 
                               ------------------
 
    If the only securities being registered on this Form are being offered
pursuant to dividend or interest reinvestment plans, please check the following
box:  / /
 
    IF ANY OF THE SECURITIES BEING REGISTERED ON THIS FORM ARE TO BE OFFERED ON
A DELAYED OR CONTINUOUS BASIS PURSUANT TO RULE 415 UNDER THE SECURITIES ACT OF
1933, OTHER THAN SECURITIES OFFERED ONLY IN CONNECTION WITH DIVIDEND OR INTEREST
REINVESTMENT PLANS, PLEASE CHECK THE FOLLOWING BOX:  /X/
 
   
                               ------------------
    
 
The Registrants hereby amend this Registration Statement on such date or dates
as may be necessary to delay its effective date until the Registrants shall file
a further amendment which specifically states that this Registration Statement
shall thereafter become effective in accordance with Section 8(a) of the
Securities Act of 1933 or until the Registration Statement shall become
effective on such date as the Commission, acting pursuant to said Section 8(a),
may determine.
 
- --------------------------------------------------------------------------------
- --------------------------------------------------------------------------------
<PAGE>   2
 
                                EXPLANATORY NOTE
 
     This Registration Statement contains two forms of Prospectus Supplement to
the Prospectus included herein: the first form is to be used in connection with
an offering by Illinois Power Capital, L.P. of fixed rate Cumulative Monthly
Income Preferred Securities, and the second form is to be used in connection
with an offering by Illinois Power Capital, L.P. of adjustable rate Cumulative
Monthly Income Preferred Securities.
<PAGE>   3
 
     INFORMATION CONTAINED HEREIN IS SUBJECT TO COMPLETION OR AMENDMENT. A
     REGISTRATION STATEMENT RELATING TO THESE SECURITIES HAS BEEN FILED WITH THE
     SECURITIES AND EXCHANGE COMMISSION. THESE SECURITIES MAY NOT BE SOLD NOR
     MAY OFFERS TO BUY BE ACCEPTED PRIOR TO THE TIME THE REGISTRATION STATEMENT
     BECOMES EFFECTIVE. THIS PROSPECTUS SUPPLEMENT SHALL NOT CONSTITUTE AN OFFER
     TO SELL OR THE SOLICITATION OF AN OFFER TO BUY NOR SHALL THERE BE ANY SALE
     OF THESE SECURITIES IN ANY STATE IN WHICH SUCH OFFER, SOLICITATION OR SALE
     WOULD BE UNLAWFUL PRIOR TO REGISTRATION OR QUALIFICATION UNDER THE
     SECURITIES LAWS OF ANY SUCH STATE.
 
   
                 SUBJECT TO COMPLETION, DATED SEPTEMBER 2, 1994
    
   
          PROSPECTUS SUPPLEMENT TO PROSPECTUS DATED SEPTEMBER   , 1994
    
 
                              PREFERRED SECURITIES
                             ILLINOIS POWER CAPITAL
      % CUMULATIVE MONTHLY INCOME PREFERRED SECURITIES ("MIPS"*), SERIES A
              (LIQUIDATION PREFERENCE $25 PER PREFERRED SECURITY)
                GUARANTEED TO THE EXTENT ILLINOIS POWER CAPITAL
                        HAS FUNDS AS SET FORTH HEREIN BY
                             ILLINOIS POWER COMPANY
                         ------------------------------
 
    The     % Cumulative Monthly Income Preferred Securities, Series A (the
"Series A Preferred Securities"), representing the limited partner interests
offered hereby, are being issued by Illinois Power Capital, L.P., a limited
partnership formed under the laws of the State of Delaware ("Illinois Power
Capital"). All of the general partner interests in Illinois Power Capital are
owned by Illinois Power Company, an Illinois corporation (the "Company").
Illinois Power Capital exists for the sole purpose of issuing its partner
interests and using the proceeds thereof to purchase certain debt securities of
the Company. The proceeds of the Series A Preferred Securities will be used by
Illinois Power Capital to purchase the Company's   % Subordinated Deferrable
Interest Debentures, Series A (the "Series A Subordinated Debentures"). The
limited partner interests represented by the Series A Preferred Securities will
have a preference with respect to cash distributions and amounts payable on
liquidation over the general partner interests in Illinois Power Capital.
 
    Holders of the Series A Preferred Securities will be entitled to receive
cumulative preferential cash distributions at an annual rate of     % of the
liquidation preference of $25 per Series A Preferred Security, accruing from the
date of original issuance and payable monthly in arrears on the last day of each
calendar month of each year, commencing         , 1994 ("dividends"). The
payment of dividends and payments on liquidation of Illinois Power Capital or
the redemption of Series A Preferred Securities, to the extent that Illinois
Power Capital has sufficient cash on hand to permit such payments and funds
legally available therefor, are guaranteed by the Company to the extent set
forth herein and in the accompanying Prospectus (the "Guarantee"). See
"Description of the Guarantee" in the accompanying Prospectus. If the Company
fails to make interest payments on the Series A Subordinated Debentures
purchased by Illinois Power Capital with the proceeds of this offering, Illinois
Power Capital will have insufficient funds to pay dividends on the Series A
Preferred Securities. The Guarantee does not provide for payment by the Company
directly of dividends for which Illinois Power Capital does not have sufficient
funds available. In such event, the remedy of a holder of Series A Preferred
Securities is to enforce Illinois Power Capital's rights under the Series A
Subordinated Debentures purchased by Illinois Power Capital from the Company.
 
    The obligations of the Company under the Guarantee are subordinate and
junior in right of payment to all liabilities of the Company, and the Company's
obligations under the Series A Subordinated Debentures are subordinate and
junior in right of payment to all present and future Senior Indebtedness (as
defined in the accompanying Prospectus) of the Company. At June 30, 1994, Senior
Indebtedness of the Company aggregated approximately $2.2 billion.
 
    The Series A Preferred Securities are redeemable at the option of Illinois
Power Capital, in whole or in part, from time to time, on or after         ,
1999, at $25 per Series A Preferred Security plus any accumulated and unpaid
dividends thereon to the date fixed for redemption (the "Redemption Price"), and
will be redeemed at such price from the proceeds of any repayment or redemption
of the Series A Subordinated Debentures. See "Description of Series A Preferred
Securities -- Optional Redemption" and "-- Mandatory Redemption." In addition,
upon the occurrence of certain special events arising from a change in law or a
change in legal interpretation, the Series A Preferred Securities are redeemable
in whole at the Redemption Price at the option of the Company, in its capacity
as the general partner of Illinois Power Capital (the "General Partner"), or the
General Partner may dissolve Illinois Power Capital and cause Series A
Subordinated Debentures to be distributed to the holders of the Series A
Preferred Securities in liquidation of their interests in Illinois Power
Capital. See "Description of Series A Preferred Securities -- Special Event
Redemption or Distribution" and "Description of the Series A Subordinated
Debentures." If the Series A Subordinated Debentures are so distributed, the
Company will use its best efforts to have them listed on the same exchange on
which the Series A Preferred Securities are then listed.
 
    In the event of the dissolution of Illinois Power Capital, the holders of
Series A Preferred Securities will be entitled to a liquidation preference for
each Series A Preferred Security of $25 plus any accumulated and unpaid
dividends thereon to the date of payment, subject to certain limitations,
unless, in connection with such dissolution, Series A Subordinated Debentures
are distributed to the holders of the Series A Preferred Securities. See
"Description of Series A Preferred Securities -- Liquidation Distribution Upon
Dissolution."
 
    SEE "CERTAIN INVESTMENT CONSIDERATIONS" FOR CERTAIN CONSIDERATIONS RELEVANT
TO AN INVESTMENT IN THE SERIES A PREFERRED SECURITIES, INCLUDING THE PERIOD
DURING WHICH AND CIRCUMSTANCES UNDER WHICH PAYMENT OF DIVIDENDS ON THE SERIES A
PREFERRED SECURITIES MAY BE DEFERRED.
 
    Application will be made to list the Series A Preferred Securities on the
New York Stock Exchange.
                         ------------------------------
 
THESE SECURITIES HAVE NOT BEEN APPROVED OR DISAPPROVED BY THE SECURITIES AND
EXCHANGE COMMISSION OR ANY STATE SECURITIES COMMISSION NOR HAS THE SECURITIES
  AND EXCHANGE COMMISSION OR ANY STATE SECURITIES COMMISSION PASSED UPON THE
    ACCURACY OR ADEQUACY OF THIS PROSPECTUS SUPPLEMENT OR THE PROSPECTUS TO
                              WHICH IT RELATES.
          ANY REPRESENTATION TO THE CONTRARY  IS A CRIMINAL OFFENSE.

<TABLE>
<CAPTION>
                                                                    INITIAL PUBLIC    UNDERWRITING     PROCEEDS TO ILLINOIS POWER
                                                                    OFFERING PRICE    COMMISSION(1)          CAPITAL(2)(3)
                                                                    --------------    -------------    --------------------------
<S>                                                                 <C>               <C>              <C>
Per Series A Preferred Security..................................      $                   (2)                  $
Total............................................................      $                   (2)                  $
</TABLE>
 
- ------------------
 
(1) Illinois Power Capital and the Company have agreed to indemnify the several
    Underwriters against certain civil liabilities, including liabilities under
    the Securities Act of 1933, as amended. See "Underwriting."
 
(2) As the proceeds of the sale of the Series A Preferred Securities will be
    loaned to the Company, the Company has agreed in the Underwriting Agreement
    to pay to the Underwriters $    per Series A Preferred Security (or $    in
    the aggregate); provided that such payment will be $
    per Series A Preferred Security sold to certain institutions. Therefore, to
    the extent that Series A Preferred Securities are sold to such institutions,
    the actual amount of Underwriters' compensation will be less than the amount
    specified in the preceding sentence and the Proceeds to Illinois Power
    Capital will be greater than the amount set forth in the table above. See
    "Underwriting."
 
(3) Expenses of the offering which are payable by the Company are estimated to
    be $        .
                         ------------------------------
 
    The Series A Preferred Securities offered hereby are offered severally by
the Underwriters, as specified herein, subject to receipt and acceptance by them
and subject to their right to reject any order in whole or in part. It is
expected that delivery of certificates for the Series A Preferred Securities
will be made only in book-entry form through the facilities of The Depository
Trust Company on or about         , 1994.
- ------------------
 
    * An application has been filed by Goldman, Sachs & Co. with the United
      States Patent and Trademark Office for the registration of the MIPS
      servicemark.
                              GOLDMAN, SACHS & CO.
 
           The date of this Prospectus Supplement is         , 1994.
<PAGE>   4
 
     IN CONNECTION WITH THIS OFFERING, THE UNDERWRITERS MAY OVER-ALLOT OR EFFECT
TRANSACTIONS WHICH STABILIZE OR MAINTAIN THE MARKET PRICE OF THE SECURITIES
OFFERED HEREBY AT LEVELS ABOVE THOSE WHICH MIGHT OTHERWISE PREVAIL IN THE OPEN
MARKET. SUCH TRANSACTIONS MAY BE EFFECTED ON THE NEW YORK STOCK EXCHANGE, IN THE
OVER-THE-COUNTER MARKET OR OTHERWISE. SUCH STABILIZING, IF COMMENCED, MAY BE
DISCONTINUED AT ANY TIME.
 
                                       S-2
<PAGE>   5
 
                       CERTAIN INVESTMENT CONSIDERATIONS
 
     Prospective purchasers of Series A Preferred Securities should carefully
review the information contained elsewhere in this Prospectus Supplement and in
the accompanying Prospectus and should particularly consider the following
matters. Capitalized terms used and not otherwise defined in this Prospectus
Supplement shall have the meanings ascribed thereto in the accompanying
Prospectus.
 
   
     SUBORDINATION OF GUARANTEE AND SERIES A SUBORDINATED DEBENTURES. The
Company's obligations under the Guarantee are subordinate and junior in right of
payment to all other liabilities of the Company. The obligations of the Company
under the Series A Subordinated Debentures are subordinate and junior in right
of payment to all present and future Senior Indebtedness of the Company. At June
30, 1994, Senior Indebtedness of the Company aggregated approximately $2.2
billion. There are no terms in the Series A Preferred Securities, the Series A
Subordinated Debentures or the Guarantee that limit the Company's ability to
incur additional indebtedness, including indebtedness that ranks senior to the
Series A Subordinated Debentures and the Guarantee. See "Description of the
Guarantee -- Status of the Guarantee" and "Description of the Subordinated
Debentures -- Subordination" in the accompanying Prospectus.
    
 
     OPTION TO EXTEND INTEREST PAYMENT PERIOD. The Company has the right under
the Indenture to extend the interest payment period from time to time on the
Series A Subordinated Debentures to a period not exceeding 60 consecutive
months, and, as a consequence, monthly dividends on the Series A Preferred
Securities would be deferred (but would continue to accrue with interest
thereon) by Illinois Power Capital during any such extended interest payment
period. In the event that the Company exercises this right, the Company may not
declare or pay dividends on, or redeem, purchase or acquire, any of its capital
stock until the deferred interest on the Series A Subordinated Debentures is
paid in full. Prior to the termination of any such extension period, the Company
may further extend the interest payment period, provided that such extension
period together with all such previous and further extensions thereof may not
exceed 60 consecutive months. Upon the termination of any extension period and
the payment of all amounts then due, the Company may select a new extension
period, subject to the above requirements. The Company has no current intention
of extending the interest payment period on the Series A Subordinated Debentures
since it desires to continue the declaration and payment of dividends on its
capital stock. See "Description of the Series A Preferred Securities --
Dividends" and "Description of the Series A Subordinated Debentures -- Option to
Extend Interest Payment Period."
 
     Should an extended interest payment period occur, Illinois Power Capital
will continue to accrue income for United States federal income tax purposes
which will be allocated, but not distributed, to holders of record of Series A
Preferred Securities. As a result, such a holder will include such interest in
gross income for United States federal income tax purposes in advance of the
receipt of cash, and will not receive the cash from Illinois Power Capital
related to such income if such a holder disposes of his or her Series A
Preferred Securities prior to the record date for payment of dividends. See
"United States Taxation -- Potential Extension of Interest Payment Period."
 
     SPECIAL EVENT REDEMPTION OR DISTRIBUTION. Upon the occurrence of a Special
Event (as defined herein), the General Partner will elect to either (i) redeem
the Series A Preferred Securities in whole or (ii) dissolve Illinois Power
Capital and cause Series A Subordinated Debentures to be distributed to the
holders of the Series A Preferred Securities in liquidation of their interests
in Illinois Power Capital. The Series A Subordinated Debentures will initially
be issued at face value as a Global Security (as defined herein) and will be
limited in aggregate principal amount to approximately $  million, such amount
being the sum of the aggregate liquidation preference of the Series A Preferred
Securities and the General Partnership Payment (as defined herein). In the case
of a Tax Event (as defined herein), the General Partner may also elect to cause
the Series A Preferred Securities to remain outstanding. See "Description of the
Series A Preferred Securities -- Special Event Redemption or Distribution" and
"Description of the Series A Subordinated Debentures -- General."
 
     Under current United States federal income tax law, the distribution of
Series A Subordinated Debentures in connection with the dissolution of Illinois
Power Capital would not be a taxable event to
 
                                       S-3
<PAGE>   6
holders of the Series A Preferred Securities. Under a change in law, a change in
legal interpretation or the other circumstances giving rise to a Special Event,
however, the dissolution of Illinois Power Capital and the distribution of
Series A Subordinated Debentures in connection with the dissolution of Illinois
Power Capital could be a taxable event to holders of the Series A Preferred
Securities. In the judgment of tax counsel to the Company and Illinois Power
Capital, the series of events which would result in the recognition of taxable
gain by holders of the Series A Preferred Securities, by reason of a dissolution
of Illinois Power Capital in response to a Special Event, is unlikely to occur.
There can be no assurance in this regard, however. See "United States Taxation
- -- Receipt of Series A Subordinated Debentures Upon Dissolution of Illinois
Power Capital."
 
                             ILLINOIS POWER COMPANY
 
     The Company was incorporated under the laws of the State of Illinois on May
25, 1923. Effective May 27, 1994, the Company became a subsidiary of Illinova
Corporation, an exempt holding company under the Public Utility Holding Company
Act of 1935, as amended, pursuant to a merger in which each outstanding share of
the Company's Common Stock was converted into one share of common stock of
Illinova Corporation. The Company is engaged in the generation, transmission,
distribution and sale of electric energy and the distribution and sale of
natural gas in the State of Illinois. Its service area is a widely diversified
industrial and agricultural area comprising approximately 15,000 square miles in
northern, central and southern Illinois. Electric service is provided at retail
to 309 incorporated municipalities, adjacent suburban and rural areas and
numerous unincorporated municipalities having an aggregate population of
approximately 1,283,000. Gas service is provided to 257 incorporated
municipalities, adjacent suburban areas and numerous unincorporated
municipalities having an aggregate population of approximately 935,000. The
larger cities served include Decatur, East St. Louis (gas only), Champaign,
Danville, Belleville, Granite City, Bloomington (electric only), Galesburg,
Urbana and Normal (electric only). The executive offices of the Company are
located at 500 South 27th Street, Decatur, Illinois 62525, and the Company's
telephone number is (217) 424-6600.
 
                             ILLINOIS POWER CAPITAL
 
     Illinois Power Capital is a limited partnership formed under the Delaware
Revised Uniform Limited Partnership Act, as amended (the "Partnership Act").
Illinois Power Capital exists for the sole purpose of issuing its partner
interests, including the Series A Preferred Securities, and using the proceeds
thereof to purchase certain debt securities of the Company, including the Series
A Subordinated Debentures. The Company is the sole general partner (the "General
Partner") of Illinois Power Capital and will manage all of the business and
affairs of Illinois Power Capital. Holders of Series A Preferred Securities will
be limited partners of Illinois Power Capital. The Company, as the General
Partner of Illinois Power Capital, will make capital contributions to Illinois
Power Capital from time to time to the extent required so that the total
contributions made by the General Partner shall at all times be at least equal
to 3% of the total contributions made by all partners. The rights and
obligations of the General Partner and the limited partners of Illinois Power
Capital will be governed by the Partnership Act and by an Amended and Restated
Agreement of Limited Partnership of Illinois Power Capital (the "Partnership
Agreement") substantially in the form filed as an exhibit to the Registration
Statement of which this Prospectus Supplement and the accompanying Prospectus
form a part.
 
                                USE OF PROCEEDS
 
     The proceeds to be received by Illinois Power Capital from the sale of the
Series A Preferred Securities will be used to purchase Series A Subordinated
Debentures of the Company and will be applied by the Company to the payment or
provision for payment at maturity, the purchase or the redemption of outstanding
securities of the Company and for general corporate purposes.
 
                                       S-4
<PAGE>   7
 
                  SUMMARY FINANCIAL INFORMATION OF THE COMPANY
                (THOUSANDS EXCEPT PER SHARE AMOUNTS AND RATIOS)
 
<TABLE>
<CAPTION>
                                                                                               12 MONTHS
                                             YEAR ENDED DECEMBER 31,                             ENDED
                          --------------------------------------------------------------     JUNE 30, 1994
                             1989         1990         1991         1992       1993(A)     (UNAUDITED)(A)(B)
                          ----------   ----------   ----------   ----------   ----------   -----------------
<S>                       <C>          <C>          <C>          <C>          <C>          <C>
INCOME STATEMENT DATA:
  Operating Revenues..... $1,393,778   $1,469,480   $1,474,905   $1,479,449   $1,581,190      $ 1,628,094
  Net Income.............   (288,432)     (78,484)     109,244      122,088      (56,038)         (42,031)
  Preferred Dividend
    Requirements.........     37,365       36,839       30,866       28,854       26,123           24,283
  Net Income Applicable
    to Common Stock......   (325,797)    (115,323)      78,378       93,234      (82,161)         (66,314)
  Earnings Per Share of
    Common Stock.........      (4.34)       (1.53)        1.04         1.23        (1.08)           (0.91)
  Ratio of Earnings to
    Fixed Charges(c).....      (0.52)(d)     0.70(d)      1.85         2.02         0.80(d)          0.93(d)
  Ratio of Earnings to
    Combined Fixed
    Charges and Preferred
    Stock Dividend
    Requirements(c)......      (0.45)(e)     0.60(e)      1.48         1.61         0.70(e)          0.82(e)
</TABLE>
 
<TABLE>
<CAPTION>
                                                                                   AMOUNT     PERCENTAGE
                                                                                 ----------   ----------
<S>                                                                              <C>          <C>
CAPITALIZATION AT JUNE 30, 1994:
  Long-Term Debt...............................................................  $1,868,191       52.2%
  Preferred Stock (not subject to mandatory redemption)........................     303,705        8.5
  Preferred Stock (subject to mandatory redemption)............................      36,000        1.0
  Common Stock Equity..........................................................   1,368,858       38.3
                                                                                 ----------   ----------
      Total Capitalization.....................................................  $3,576,754      100.0%
                                                                                  =========   =========
</TABLE>
 
- ---------------
(a) Subsequent to the Company's merger with Illinova Corporation, net assets of
    Illinova Generating Company (formerly IP Group, Inc.) were transferred in
    the form of a dividend from the Company to Illinova Corporation. The income
    statement data contained herein has been restated to reflect the financial
    results of the Company's current operations.
 
(b) In the opinion of the Company, all adjustments, consisting only of normal
    recurring adjustments, necessary for a fair statement of the results for the
    unaudited twelve-month period ended June 30, 1994, have been made.
 
(c) Earnings used in the calculation of the ratio of earnings to fixed charges
    and the ratio of earnings to combined fixed charges and preferred stock
    dividend requirements include the allowance for funds used during
    construction and the deferred financing costs associated with the Company's
    Clinton Power Station, and are before deduction of income taxes and fixed
    charges. Fixed charges include interest on long-term debt, related
    amortization of debt discount, premium, and expense, other interest and that
    portion of rent expense which is estimated to be representative of the
    interest component. Preferred stock dividend requirements have been
    increased to an amount representing the pre-tax earnings required to cover
    such dividend requirements.
 
(d) The ratios of earnings to fixed charges for the twelve months ended June 30,
    1994 and for the years ended December 31, 1993, 1990 and 1989 of 0.93, 0.80,
    0.70 and (0.52), respectively, indicate that earnings were inadequate to
    cover fixed charges. The dollar amounts of the coverage deficiency for the
    twelve months ended June 30, 1994, and for the years ended 1993, 1990 and
    1989 were approximately $13 million, $37 million, $68 million and $375
    million, respectively. Excluding the loss on disallowed plant costs of $200
    million, net of income taxes, recorded in the
 
                                       S-5
<PAGE>   8
    third quarter of 1993, the ratio of earnings to fixed charges would have
    been 2.42 for the twelve months ended June 30, 1994 and 2.25 for the year
    ended 1993. Excluding the loss on disallowed plant costs of $137 million,
    net of income taxes, recorded in the fourth quarter of 1990, the ratio of
    earnings to fixed charges would have been 1.41 for the year ended 1990.
    Excluding the loss on disallowed plant costs of $346 million, net of income
    taxes, recorded in the first quarter of 1989, the ratio of earnings to fixed
    charges would have been 1.31 for the year ended 1989.
 
(e) The ratios of earnings to combined fixed charges and preferred stock
    dividend requirements for the twelve months ended June 30, 1994 and for the
    years ended December 31, 1993, 1990 and 1989 of 0.82, 0.70, 0.60 and (0.45),
    respectively, indicate that earnings were inadequate to cover combined fixed
    charges and preferred stock dividend requirements. The dollar amounts of the
    coverage deficiency for the twelve months ended June 30, 1994, and for the
    years ended 1993, 1990 and 1989 were approximately $38 million, $63 million,
    $105 million and $412 million, respectively. Excluding the loss on
    disallowed plant costs of $200 million, net of income taxes, recorded in the
    third quarter of 1993, the ratio of earnings to combined fixed charges and
    preferred stock dividend requirements would have been 1.98 for the twelve
    months ended June 30, 1994 and 1.83 for the year ended 1993. Excluding the
    loss on disallowed plant costs of $137 million, net of income taxes,
    recorded in the fourth quarter of 1990, the ratio of earnings to combined
    fixed charges and preferred stock dividend requirements would have been 1.09
    for the year ended 1990. Excluding the loss on disallowed plant costs of
    $346 million, net of income taxes, recorded in the first quarter of 1989,
    the ratio of earnings to combined fixed charges and preferred stock dividend
    requirements would have been 1.06 for the year ended 1989.
 
                                       S-6
<PAGE>   9
 
                DESCRIPTION OF THE SERIES A PREFERRED SECURITIES
 
GENERAL
 
     All of the partnership interests in Illinois Power Capital, other than the
Series A Preferred Securities offered hereby, are owned by the General Partner.
The Partnership Agreement authorizes and creates the Series A Preferred
Securities, which represent limited partner interests in Illinois Power Capital
(the "Preferred Securities"). Preferred Securities may be issued from time to
time in one or more series as described in the accompanying Prospectus. The
limited partner interests represented by the Series A Preferred Securities will
have a preference with respect to dividends and amounts payable on liquidation
over the General Partner's interest in Illinois Power Capital. The Partnership
Agreement does not permit the issuance of any Preferred Securities ranking, as
to participation in profits and dividends and in the assets of Illinois Power
Capital, senior or junior to the Series A Preferred Securities or the incurrence
of any indebtedness by Illinois Power Capital. The summary of certain terms and
provisions of the Series A Preferred Securities set forth below does not purport
to be complete and is subject to, and qualified in its entirety by reference to,
the Partnership Agreement and the Partnership Act.
 
DIVIDENDS
 
     The dividends payable on each Series A Preferred Security will be fixed at
a rate per annum of      % of the liquidation preference of $25 per Preferred
Security. Dividends in arrears for more than one month will bear interest
thereon at the rate per annum of      % thereof. The term "dividends" as used
herein includes any such interest payable unless otherwise stated. The amount of
dividends payable for any period will be computed on the basis of a 360-day year
of twelve 30-day months.
 
     Dividends on the Series A Preferred Securities will be cumulative, will
accrue from the date of initial issuance and will be payable monthly in arrears,
on the last day of each calendar month of each year, commencing        , 1994,
when, as and if available and determined to be so payable by the General
Partner, except as otherwise described below. The Company has the right under
the Indenture to extend the interest payment period from time to time on the
Series A Subordinated Debentures to a period not exceeding 60 consecutive
months, and, as a consequence, monthly dividends on the Series A Preferred
Securities would be deferred (but would continue to accrue with interest) by
Illinois Power Capital during any such extended interest payment period. In the
event that the Company exercises this right, the Company may not declare or pay
dividends on, or redeem, purchase or acquire, any of its capital stock. Prior to
the termination of any such extension period, the Company may further extend the
interest payment period, provided that such extension period together with all
such previous and further extensions thereof may not exceed 60 consecutive
months. Upon the termination of any extension period and the payment of all
amounts then due, the Company may select a new extension period, subject to the
above requirements. See "Description of the Series A Subordinated Debentures --
Interest" and "-- Option to Extend Interest Payment Period."
 
   
     Dividends on the Series A Preferred Securities must be paid on the dates
payable to the extent that Illinois Power Capital has (i) funds legally
available for the payment of such dividends and (ii) cash on hand sufficient to
permit such payments. It is anticipated that Illinois Power Capital's earnings
available for distribution to the holders of the Series A Preferred Securities
will be limited to payments under the Series A Subordinated Debentures in which
Illinois Power Capital will invest the proceeds from the issuance and sale of
the Series A Preferred Securities and the General Partner's capital
contribution. See "Description of the Series A Subordinated Debentures." The
payment of dividends, out of moneys held by Illinois Power Capital, is
guaranteed by the Company as set forth under "Description of the Guarantee" in
the accompanying Prospectus.
    
 
     Dividends on the Series A Preferred Securities will be payable to the
holders thereof as they appear on the books and records of Illinois Power
Capital on the relevant record dates, which, as long as the Series A Preferred
Securities remain in book-entry-only form, will be one Business Day (as defined
below) prior to the relevant payment dates. Subject to any applicable laws and
regulations and the provisions of the Partnership Agreement, each such payment
will be made as described under
 
                                       S-7
<PAGE>   10
 
   
"Book-Entry-Only Issuance -- The Depository Trust Company" below. In the event
the Series A Preferred Securities shall not continue to remain in
book-entry-only form, the General Partner shall have the right to select
relevant record dates which shall be more than one Business Day prior to the
relevant payment dates. In the event that any date on which dividends are
payable on the Series A Preferred Securities is not a Business Day, then payment
of the dividends payable on such date will be made on the next succeeding day
which is a Business Day (and without any interest or other payment in respect of
any such delay) except that, if such Business Day is in the next succeeding
calendar year, such payment shall be made on the immediately preceding Business
Day, in each case with the same force and effect as if made on such date. A
"Business Day" shall mean any day other than a day on which banking institutions
in The City of New York are authorized or required by law to close.
    
 
CERTAIN RESTRICTIONS ON ILLINOIS POWER CAPITAL
 
     If dividends have not been paid in full on the Series A Preferred
Securities, Illinois Power Capital shall not:
 
   
          (i) pay, or set aside for payment, any dividends on any other series
     of Preferred Securities, unless the amount of any dividends paid or set
     aside on any other series of Preferred Securities is paid or set aside on
     such other series of Preferred Securities and the Series A Preferred
     Securities on a pro rata basis on the date such dividends are paid or set
     aside on such other series of Preferred Securities, so that
    
 
             (x) the aggregate amount of dividends paid on the Series A
        Preferred Securities bears to the aggregate amount of dividends paid on
        such other series of Preferred Securities the same ratio as
 
             (y) the aggregate of all accumulated and unpaid dividends in
        respect of the Series A Preferred Securities bears to the aggregate of
        all accumulated and unpaid dividends in respect of such other series of
        Preferred Securities; or
 
          (ii) redeem, purchase or otherwise acquire any other Preferred
     Securities;
 
until, in each case, such time as all accumulated and unpaid dividends on the
Series A Preferred Securities shall have been paid in full for all dividend
periods terminating on or prior to, in the case of clause (i), such payment and,
in the case of clause (ii), the date of such redemption, purchase or
acquisition.
 
     As of the date of this Prospectus Supplement, there are no series of
Preferred Securities outstanding.
 
OPTIONAL REDEMPTION
 
   
     The Series A Preferred Securities are redeemable, at the option of Illinois
Power Capital, in whole or in part, from time to time, on or after             ,
1999, upon not less than 30 nor more than 60 days' notice, at the Redemption
Price; provided, however, that prior to giving any such notice of redemption,
Illinois Power Capital shall have received from the Company a notice of
redemption of Series A Subordinated Debentures in an aggregate principal amount
equal to the aggregate liquidation preference of the Series A Preferred
Securities to be redeemed. In the event that fewer than all the outstanding
Series A Preferred Securities are to be so redeemed, the Series A Preferred
Securities to be redeemed will be selected as described under "Book-Entry-Only
Issuance -- The Depository Trust Company" below. If a partial redemption would
result in the delisting of the Series A Preferred Securities, Illinois Power
Capital may only redeem the Series A Preferred Securities in whole.
    
 
SPECIAL EVENT REDEMPTION OR DISTRIBUTION
 
   
     Subject to the next succeeding sentence, if a Tax Event or an Investment
Company Event (each, as defined below, and, each, a "Special Event") shall occur
and be continuing, the General Partner shall elect to either (i) cause Illinois
Power Capital to redeem the Series A Preferred Securities in whole (and not in
part), upon not less than 30 or more than 60 days' notice at the Redemption
Price within 90 days
    
 
                                       S-8
<PAGE>   11
 
following the occurrence of such Special Event; provided, that, if at the time
there is available to the General Partner the opportunity to eliminate, within
such 90-day period, the Special Event by taking some ministerial action, such as
filing a form or making an election, or pursuing some other similar reasonable
measure, which has no adverse effect on Illinois Power Capital or the General
Partner, the General Partner will pursue such measure in lieu of redemption, or
(ii) dissolve Illinois Power Capital and, after satisfaction of liabilities of
creditors as required by the Partnership Act, cause Series A Subordinated
Debentures to be distributed to the holders of the Series A Preferred Securities
in liquidation of their interests in Illinois Power Capital, within 90 days
following the occurrence of such Special Event. In the case of a Tax Event, the
General Partner may also elect to cause the Series A Preferred Securities to
remain outstanding.
 
   
     In the event of a distribution of Series A Subordinated Debentures as
described in (ii) above, each holder of Series A Preferred Securities would
receive Series A Subordinated Debentures in an aggregate principal amount equal
to the aggregate liquidation preference of $25 per Series A Preferred Security
on the Series A Preferred Securities held by it, with such Series A Subordinated
Debentures bearing interest at a rate per annum equal to the dividend rate per
annum on such Series A Preferred Securities from the last date on which
dividends were paid.
    
 
   
     "Tax Event" means that the General Partner shall have obtained an opinion
of nationally recognized independent tax counsel experienced in such matters to
the effect that, as a result of (a) any amendment to, or change (including any
announced prospective change) in, the laws (or any regulations thereunder) of
the United States or any political subdivision or taxing authority thereof or
therein, (b) any amendment to or change in an interpretation or application of
such laws or regulations by any legislative body, court, governmental agency or
regulatory authority (including the enactment of any legislation and the
publication of any judicial decision or regulatory determination on or after
such date) or (c) any interpretation or pronouncement that provides for a
position with respect to such laws or regulations that differs from the
generally accepted position on        , 1994, which amendment or change is
effective or such interpretation or pronouncement is announced on or after
       , 1994, there is more than an insubstantial risk that (i) Illinois Power
Capital is subject to federal income tax with respect to interest received on
the Series A Subordinated Debentures, (ii) interest payable to Illinois Power
Capital on the Series A Subordinated Debentures will not be deductible for
federal income tax purposes or (iii) Illinois Power Capital is subject to more
than a de minimis amount of other taxes, duties or other governmental charges.
    
 
   
     "Investment Company Event" means the occurrence of a change in law or
regulation or a written change in interpretation or application of law or
regulation by any legislative body, court, governmental agency or regulatory
authority (a "Change in 1940 Act Law") to the effect that Illinois Power Capital
is or will be considered an "investment company" which is required to be
registered under the Investment Company Act of 1940, as amended (the "1940
Act"), which Change in 1940 Act Law becomes effective on or after        , 1994;
provided, that no Investment Company Event shall be deemed to have occurred if
the General Partner obtains a written opinion of nationally recognized
independent counsel experienced in practice under the 1940 Act to the effect
that the General Partner has successfully issued an additional or supplemental
irrevocable and unconditional guarantee (x) of accumulated and unpaid dividends
(whether or not determined to be paid out of moneys legally available therefor)
on the Series A Preferred Securities and (y) of the full amount of the
Liquidation Distribution (as hereinafter defined) on the Series A Preferred
Securities upon a liquidation of Illinois Power Capital (regardless of the
amount of assets of Illinois Power Capital otherwise available for distribution
in such liquidation) to avoid such Change in 1940 Act Law so that in the opinion
of such counsel, notwithstanding such Change in 1940 Act Law, Illinois Power
Capital is not required to be registered as an "investment company" within the
meaning of the 1940 Act.
    
 
     After the date fixed for any distribution of Series A Subordinated
Debentures, upon dissolution of Illinois Power Capital, (i) the Series A
Preferred Securities will no longer be deemed to be outstanding, (ii) The
Depository Trust Company (the "Depository" or "DTC") or its nominee, as the
record holder of the Series A Preferred Securities, will receive a registered
global certificate or certificates representing
 
                                       S-9
<PAGE>   12
 
the Series A Subordinated Debentures to be delivered upon such distribution and
(iii) any certificates representing Series A Preferred Securities not held by
DTC or its nominee will be deemed to represent Series A Subordinated Debentures
having a principal amount equal to the aggregate liquidation preference of such
Series A Preferred Securities until such certificates are presented to the
Company or its agent for transfer or reissuance.
 
MANDATORY REDEMPTION
 
   
     Upon the repayment of the Series A Subordinated Debentures at maturity, or
earlier, the proceeds from such repayment will be applied to redeem the Series A
Preferred Securities, in whole, upon not less than 30 nor more than 60 days'
notice, at the Redemption Price.
    
 
REDEMPTION PROCEDURES
 
   
     Illinois Power Capital may not redeem fewer than all of the outstanding
Series A Preferred Securities unless all accumulated and unpaid dividends have
been paid on all Series A Preferred Securities for all monthly dividend periods
terminating on or prior to the date of redemption.
    
 
     If Illinois Power Capital gives a notice of redemption in respect of Series
A Preferred Securities (which notice will be irrevocable), then, by 12:00 noon,
New York time, on the redemption date, Illinois Power Capital will irrevocably
deposit with DTC funds sufficient to pay the applicable Redemption Price and
will give DTC irrevocable instructions and authority to pay the Redemption Price
to the holders of the Series A Preferred Securities. See "Book-Entry-Only
Issuance -- The Depository Trust Company." If notice of redemption shall have
been given and funds deposited as required, then upon the date of such deposit,
all rights of holders of such Series A Preferred Securities so called for
redemption will cease, except the right of the holders of such Series A
Preferred Securities to receive the Redemption Price, but without interest on
such Redemption Price. In the event that any date fixed for redemption of Series
A Preferred Securities is not a Business Day, then payment of the Redemption
Price payable on such date will be made on the next succeeding day which is a
Business Day (and without any interest or other payment in respect of any such
delay), except that, if such Business Day falls in the next calendar year, such
payment will be made on the immediately preceding Business Day. In the event
that payment of the Redemption Price in respect of Series A Preferred Securities
is improperly withheld or refused and not paid either by Illinois Power Capital
or by the Company pursuant to the Guarantee described under "Description of the
Guarantee" in the accompanying Prospectus, dividends on such Series A Preferred
Securities will continue to accrue at the then applicable rate, from the
original redemption date to the date of payment, in which case the actual
payment date will be considered the date fixed for redemption for purposes of
calculating the Redemption Price.
 
     Subject to the foregoing and applicable law (including, without limitation,
United States federal securities laws), the Company or its subsidiaries may at
any time and from time to time purchase outstanding Series A Preferred
Securities by tender, in the open market or by private agreement.
 
LIQUIDATION DISTRIBUTION UPON DISSOLUTION
 
   
     In the event of any voluntary or involuntary dissolution, winding-up or
termination of Illinois Power Capital, the holders of the Series A Preferred
Securities at the time will be entitled to receive out of the assets of Illinois
Power Capital available for distribution to partners, after satisfaction of
liabilities of creditors as required by the Partnership Act, before any
distribution of assets is made to the General Partner, but together with the
holders of every other series of Preferred Securities outstanding, an amount
equal to, in the case of holders of Series A Preferred Securities, the aggregate
of the liquidation preference of $25 per Series A Preferred Security and all
accumulated and unpaid dividends thereon to the date of payment (the
"Liquidation Distribution"), unless, in connection with such dissolution,
winding-up or termination, Series A Subordinated Debentures in an aggregate
principal amount equal to $25 per Series A Preferred Security have been
distributed on a pro rata basis to the holders of the Series A Preferred
Securities.
    
 
                                      S-10
<PAGE>   13
 
     If, upon any such dissolution, the Liquidation Distribution can be paid
only in part because Illinois Power Capital has insufficient assets available to
pay in full the aggregate Liquidation Distribution and the aggregate maximum
liquidation distributions on any other series of Preferred Securities, then the
amounts payable directly by Illinois Power Capital on the Series A Preferred
Securities and on such other series of Preferred Securities shall be paid on a
pro rata basis, so that
 
          (i) the aggregate amount paid in respect of the Liquidation
     Distribution bears to the aggregate amount paid as liquidation
     distributions on the other series of Preferred Securities the same ratio as
 
          (ii) the aggregate Liquidation Distribution bears to the aggregate
     maximum liquidation distributions on the other series of Preferred
     Securities.
 
     Pursuant to the Partnership Agreement, Illinois Power Capital shall be
dissolved and its affairs shall be wound up: (i) upon the expiration of the term
of Illinois Power Capital on December 31, 2047, (ii) upon the bankruptcy or
withdrawal of the General Partner, (iii) upon the assignment by the General
Partner of its entire interest in Illinois Power Capital when the assignee is
not admitted to Illinois Power Capital as a general partner of Illinois Power
Capital in accordance with the Partnership Agreement, or the filing of a
certificate of dissolution or its equivalent with respect to the General
Partner, or the revocation of the General Partner's charter and the expiration
of 90 days after the date of notice to the General Partner of revocation without
a reinstatement of its charter, or any other event occurs which causes the
General Partner to cease to be a general partner of Illinois Power Capital under
the Partnership Act, unless the business of Illinois Power Capital is continued
in accordance with the Partnership Act, (iv) in accordance with the provisions
of the Series A Preferred Securities, (v) upon the entry of a decree of a
judicial dissolution or (vi) upon the written consent of all partners of
Illinois Power Capital.
 
MERGER, CONSOLIDATION OR AMALGAMATION OF ILLINOIS POWER CAPITAL
 
     Illinois Power Capital may not consolidate, amalgamate, merge with or into,
or be replaced by, or convey, transfer or lease its properties and assets
substantially as an entirety to any corporation or other body, except as
described below. Illinois Power Capital may, without the consent of the holders
of the Series A Preferred Securities, consolidate, amalgamate, merge with or
into, or be replaced by a limited liability company, a limited partnership or a
trust organized as such under the laws of any state of the United States;
provided, that (i) such successor entity either (x) expressly assumes all of the
obligations of Illinois Power Capital under the Series A Preferred Securities or
(y) substitutes for the Series A Preferred Securities other securities having
substantially the same terms as the Series A Preferred Securities (the
"Successor Securities") so long as the Successor Securities rank, with respect
to participation in the profits and dividends or in the assets of the successor
entity, at least as high as the Series A Preferred Securities rank with respect
to participation in the profits and dividends or in the assets of Illinois Power
Capital, (ii) the Company expressly acknowledges such successor entity as the
holder of the Series A Subordinated Debentures, (iii) the Series A Preferred
Securities or any Successor Securities are listed, or any Successor Securities
will be listed upon notification of issuance, on any national securities
exchange or other organization on which the Series A Preferred Securities are
then listed, (iv) such merger, consolidation, amalgamation or replacement does
not cause the Series A Preferred Securities to be downgraded by any "nationally
recognized statistical rating organization," as that term is defined by the
Commission for purposes of Rule 436(g)(2) under the Securities Act, or cause any
Successor Securities to be rated lower than the Series A Preferred Securities
immediately prior to such merger, consolidation, amalgamation or replacement,
(v) such merger, consolidation, amalgamation or replacement does not adversely
affect the powers, preferences and other special rights of the holders of the
Series A Preferred Securities in any material respect, (vi) such successor
entity has a purpose substantially identical to that of Illinois Power Capital
and (vii) prior to such merger, consolidation, amalgamation or replacement, the
Company has received an opinion of nationally recognized independent counsel to
Illinois Power Capital experienced in such matters to the effect that (x) such
successor entity will be treated as a partnership for federal income tax
purposes, (y) following such merger, consolidation, amalgamation or replacement,
the Company and such successor entity will be in compliance with the 1940 Act
without registering thereunder as an investment company and (z) such
 
                                      S-11
<PAGE>   14
 
merger, consolidation, amalgamation or replacement will not adversely affect the
limited liability of the holders of the Series A Preferred Securities.
 
VOTING RIGHTS
 
     Except as provided below and under "Description of the Guarantee --
Amendments and Assignment" in the accompanying Prospectus and as otherwise
required by law and the Partnership Agreement, the holders of the Series A
Preferred Securities will have no voting rights.
 
   
     If (i) Illinois Power Capital fails to pay dividends in full on the Series
A Preferred Securities for 18 consecutive monthly dividend periods; (ii) an
Event of Default (as defined in the Indenture) occurs and is continuing on the
Series A Subordinated Debentures; or (iii) the Company is in default on any of
its payment or other obligations under the Guarantee (as described under
"Description of the Guarantee -- Certain Covenants of the Company" in the
accompanying Prospectus), then the holders of the Series A Preferred Securities,
together with the holders of any other series of Preferred Securities having the
right to vote for the appointment of a special representative of Illinois Power
Capital and the limited partners (a "Special Representative") in such event,
acting as a single class, will be entitled by the majority vote of such holders
to appoint and authorize a Special Representative to enforce Illinois Power
Capital's creditor rights under the Series A Subordinated Debentures, to enforce
the rights of the holders of the Series A Preferred Securities under the
Guarantee and to enforce the rights of the holders of the Series A Preferred
Securities to receive dividends on the Series A Preferred Securities. The
Special Representative shall not be admitted as a partner in Illinois Power
Capital or otherwise be deemed to be a partner in Illinois Power Capital and
shall have no liability for the debts, obligations or liabilities of Illinois
Power Capital. For purposes of determining whether Illinois Power Capital has
failed to pay dividends in full for 18 consecutive monthly dividend periods,
dividends shall be deemed to remain in arrears, notwithstanding any payments in
respect thereof, until full cumulative dividends have been or contemporaneously
are paid with respect to all monthly dividend periods terminating on or prior to
the date of payment of such full cumulative dividends. Not later than 30 days
after such right to appoint a Special Representative arises, the General Partner
will convene a meeting for the purpose of appointing a Special Representative.
If the General Partner fails to convene such meeting within such 30-day period,
the holders of 10% in liquidation preference of the outstanding Preferred
Securities will be entitled to convene such meeting. The provisions of the
Partnership Agreement relating to the convening and conduct of the meetings of
the partners will apply with respect to any such meeting. Any Special
Representative so appointed shall cease to be a Special Representative of
Illinois Power Capital and the limited partners if Illinois Power Capital (or
the Company pursuant to the Guarantee) shall have paid in full all accumulated
and unpaid dividends on the Preferred Securities or such default or breach, as
the case may be, shall have been cured, and the General Partner shall continue
the business of Illinois Power Capital without dissolution. Notwithstanding the
appointment of any such Special Representative, the Company shall continue as
General Partner and shall retain all rights under the Indenture, including the
right to extend the interest payment period from time to time to a period not
exceeding 60 consecutive months as provided under "Description of the Series A
Subordinated Debentures -- Option to Extend Interest Payment Period."
    
 
     If any proposed amendment to the Partnership Agreement provides for, or the
General Partner otherwise proposes to effect, (i) any action which would
adversely affect the powers, preferences or special rights of the Series A
Preferred Securities, whether by way of amendment to the Partnership Agreement
or otherwise (including, without limitation, the authorization or issuance of
any limited partner interests in Illinois Power Capital ranking, as to
participation in the profits and dividends or in the assets of Illinois Power
Capital, senior to the Series A Preferred Securities), or (ii) the dissolution,
winding-up or termination of Illinois Power Capital, other than (x) in
connection with the distribution of Series A Subordinated Debentures upon the
occurrence of a Special Event or (y) as described under "Merger, Consolidation
or Amalgamation of Illinois Power Capital" above, then the holders of
outstanding Series A Preferred Securities will be entitled to vote on such
amendment or proposal of the General Partner (but not on any other amendment or
proposal) as a class with all other holders of series of Preferred Securities
similarly affected, and such amendment or proposal shall not be effective except
with the approval of the
 
                                      S-12
<PAGE>   15
holders of 66 2/3% in liquidation preference of such outstanding Preferred
Securities having a right to vote on the matter; provided, however, that no such
approval shall be required if the dissolution, winding-up or termination of
Illinois Power Capital is proposed or initiated upon the initiation of
proceedings, or after proceedings have been initiated, for the dissolution,
winding-up, liquidation or termination of the Company.
 
     The rights attached to the Series A Preferred Securities will be deemed not
to be adversely affected by the creation or issue of, and no vote will be
required for the creation of, any further limited partner interests of Illinois
Power Capital ranking pari passu with the Series A Preferred Securities with
regard to participation in the profits and dividends or in the assets of
Illinois Power Capital. Holders of Series A Preferred Securities have no
preemptive rights.
 
     So long as any Series A Subordinated Debentures are held by Illinois Power
Capital, the General Partner shall not (i) direct the time, method and place of
conducting any proceeding for any remedy available to the Trustee, or executing
any trust or power conferred on the Trustee with respect to such series, (ii)
waive any past default which is waivable under Section 6.06 of the Indenture,
(iii) exercise any right to rescind or annul a declaration that the principal of
all the Series A Subordinated Debentures shall be due and payable or (iv)
consent to any amendment, modification or termination of the Indenture, where
such consent shall be required, without, in each case, obtaining the prior
approval of the holders of at least 66 2/3% in liquidation preference of all
series of Preferred Securities affected thereby, acting as a single class;
provided, however, that where a consent under the Indenture would require the
consent of each holder affected thereby, no such consent shall be given by the
General Partner without the prior consent of each holder of all series of
Preferred Securities affected thereby. The General Partner shall not revoke any
action previously authorized or approved by a vote of any series of Preferred
Securities. The General Partner shall notify all holders of the Series A
Preferred Securities of any notice of default received from the Trustee with
respect to the Series A Subordinated Debentures.
 
     Any required approval of holders of Series A Preferred Securities may be
given at a separate meeting of holders of Preferred Securities convened for such
purpose, at a meeting of all of the partners in Illinois Power Capital or
pursuant to written consent. Illinois Power Capital will cause a notice of any
meeting at which holders of Series A Preferred Securities are entitled to vote,
or of any matter upon which action by written consent of such holders is to be
taken, to be mailed to each holder of record of Series A Preferred Securities.
Each such notice will include a statement setting forth (i) the date of such
meeting or the date by which such action is to be taken, (ii) a description of
any resolution proposed for adoption at such meeting on which such holders are
entitled to vote or of such matter upon which written consent is sought and
(iii) instructions for the delivery of proxies or consents.
 
     No vote or consent of the holders of Series A Preferred Securities will be
required for Illinois Power Capital to redeem and cancel Series A Preferred
Securities in accordance with the Partnership Agreement.
 
     Notwithstanding that holders of Series A Preferred Securities are entitled
to vote or consent under any of the circumstances described above, any of the
Series A Preferred Securities and any other series of Preferred Securities that
are entitled to vote or consent with such Series A Preferred Securities as a
single class at such time that are owned by the Company or any entity owned more
than 50% by the Company, either directly or indirectly, shall not be entitled to
vote or consent and shall, for purposes of such vote or consent, be treated as
if they were not outstanding.
 
     Holders of the Series A Preferred Securities will have no rights to remove
or replace the General Partner.
 
BOOK-ENTRY-ONLY ISSUANCE -- THE DEPOSITORY TRUST COMPANY
 
     DTC will act as securities depository for the Series A Preferred
Securities. The Series A Preferred Securities will be issued only as
fully-registered securities registered in the name of Cede & Co. (DTC's
nominee). One or more fully-registered global Series A Preferred Security
certificates will be issued,
 
                                      S-13
<PAGE>   16
representing in the aggregate the total number of Series A Preferred Securities,
and will be deposited with DTC.
 
     DTC is a limited-purpose trust company organized under the New York Banking
Law, a "banking organization" within the meaning of the New York Banking Law, a
member of the Federal Reserve System, a "clearing corporation" within the
meaning of the New York Uniform Commercial Code, and a "clearing agency"
registered pursuant to the provisions of Section 17A of the Securities Exchange
Act of 1934, as amended (the "Exchange Act"). DTC holds securities that its
participants ("Participants") deposit with DTC. DTC also facilitates the
settlement among Participants of securities transactions, such as transfers and
pledges, in deposited securities through electronic computerized book-entry
changes in Participants' accounts, thereby eliminating the need for physical
movement of securities certificates. Direct Participants include securities
brokers and dealers, banks, trust companies, clearing corporations, and certain
other organizations ("Direct Participants"). DTC is owned by a number of its
Direct Participants and by The New York Stock Exchange, Inc. (the "New York
Stock Exchange"), the American Stock Exchange, Inc., and the National
Association of Securities Dealers, Inc. Access to the DTC system is also
available to others such as securities brokers and dealers, banks and trust
companies that clear through or maintain a custodial relationship with a Direct
Participant, either directly or indirectly ("Indirect Participants"). The rules
applicable to DTC and its Participants are on file with the Commission.
 
     Purchases of Series A Preferred Securities within the DTC system must be
made by or through Direct Participants, which will receive a credit for the
Series A Preferred Securities on DTC's records. The ownership interest of each
actual purchaser of each Series A Preferred Security ("Beneficial Owner") is in
turn to be recorded on the Direct and Indirect Participants' records. Beneficial
Owners will not receive written confirmation from DTC of their purchases, but
Beneficial Owners are expected to receive written confirmations providing
details of the transactions, as well as periodic statements of their holdings,
from the Direct or Indirect Participants through which the Beneficial Owners
purchased Series A Preferred Securities. Transfers of ownership interests in the
Series A Preferred Securities are to be accomplished by entries made on the
books of Participants acting on behalf of Beneficial Owners. Beneficial Owners
will not receive certificates representing their ownership interests in Series A
Preferred Securities, except in the event that use of the book-entry system for
the Series A Preferred Securities is discontinued.
 
     DTC has no knowledge of the actual Beneficial Owners of the Series A
Preferred Securities; DTC's records reflect only the identity of the Direct
Participants to whose accounts such Series A Preferred Securities are credited,
which may or may not be the Beneficial Owners. The Participants will remain
responsible for keeping account of their holdings on behalf of their customers.
 
     Conveyance of notices and other communications by DTC to Direct
Participants, by Direct Participants to Indirect Participants, and by Direct
Participants and Indirect Participants to Beneficial Owners will be governed by
arrangements among them, subject to any statutory or regulatory requirements as
may be in effect from time to time.
 
     Redemption notices shall be sent to Cede & Co. If less than all of the
Series A Preferred Securities are being redeemed, DTC's practice is to determine
by lot the amount of the interest of each Direct Participant in such series to
be redeemed.
 
     Although voting with respect to the Series A Preferred Securities is
limited, in those cases where a vote is required, neither DTC nor Cede & Co.
will itself consent or vote with respect to Series A Preferred Securities. Under
its usual procedures, DTC would mail an Omnibus Proxy to Illinois Power Capital
as soon as possible after the record date. The Omnibus Proxy assigns Cede &
Co.'s consenting or voting rights to those Direct Participants to whose accounts
the Series A Preferred Securities are credited on the record date (identified in
a listing attached to the Omnibus Proxy).
 
     Dividend payments on the Series A Preferred Securities will be made to DTC.
DTC's practice is to credit Direct Participants' accounts on the relevant
payment date in accordance with their respective holdings shown on DTC's records
unless DTC has reason to believe that it will not receive payments on
 
                                      S-14
<PAGE>   17
 
such payment date. Payments by Participants to Beneficial Owners will be
governed by standing instructions and customary practices and will be the
responsibility of such Participant and not of DTC, Illinois Power Capital or the
Company, subject to any statutory or regulatory requirements as may be in effect
from time to time. Payment of dividends to DTC is the responsibility of Illinois
Power Capital, disbursement of such payments to Direct Participants is the
responsibility of DTC, and disbursement of such payments to the Beneficial
Owners is the responsibility of Direct and Indirect Participants.
 
     DTC may discontinue providing its services as securities depository with
respect to the Series A Preferred Securities at any time by giving reasonable
notice to Illinois Power Capital. Under such circumstances, in the event that a
successor securities depository is not obtained, Series A Preferred Security
certificates are required to be printed and delivered. Additionally, Illinois
Power Capital (with the consent of the Company) may decide to discontinue use of
the system of book-entry transfers through DTC (or a successor depository). In
that event, certificates for the Series A Preferred Securities will be printed
and delivered. In each of the above circumstances, the General Partner will
appoint a paying agent with respect to the Series A Preferred Securities.
 
     The information in this section concerning DTC and DTC's book-entry system
has been obtained from sources that Illinois Power Capital believes to be
reliable, but Illinois Power Capital takes no responsibility for the accuracy
thereof.
 
REGISTRAR AND TRANSFER AGENT
 
     The Company will act as registrar and transfer agent for the Series A
Preferred Securities.
 
   
     Registration of transfers of Series A Preferred Securities will be effected
without charge by or on behalf of Illinois Power Capital, but upon payment (with
the giving of such indemnity as Illinois Power Capital or the Company may
require) in respect of any tax or other governmental charges which may be
imposed in relation to it.
    
 
     Illinois Power Capital will not be required to register or cause to be
registered the transfer of Series A Preferred Securities after such Series A
Preferred Securities have been called for redemption.
 
MISCELLANEOUS
 
     Application will be made to list the Series A Preferred Securities on the
New York Stock Exchange.
 
     The General Partner is authorized and directed to conduct its affairs and
to operate Illinois Power Capital in such a way that (i) Illinois Power Capital
will not be deemed to be an "investment company" required to be registered under
the 1940 Act, (ii) Illinois Power Capital will be taxed as a partnership for
federal income tax purposes and (iii) the Series A Subordinated Debentures will
be treated as indebtedness of the Company for federal income tax purposes. In
this connection, the General Partner is authorized to take any action, not
inconsistent with applicable law, the certificate of limited partnership or the
Partnership Agreement, that the General Partner determines in its discretion to
be necessary or desirable for such purposes, as long as such action does not
adversely affect the interests of the holders of the Series A Preferred
Securities.
 
                                      S-15
<PAGE>   18
 
              DESCRIPTION OF THE SERIES A SUBORDINATED DEBENTURES
 
     Set forth below is a description of the specific terms of the Series A
Subordinated Debentures in which Illinois Power Capital will invest with the
proceeds of the issuance and sale of (i) the Series A Preferred Securities and
(ii) the General Partner's capital contribution with respect to the Series A
Preferred Securities (the "General Partnership Payment"). This description
supplements the description of the general terms and provisions of the
Subordinated Debentures set forth in the accompanying Prospectus under the
caption "Description of the Subordinated Debentures." The following description
does not purport to be complete and is qualified in its entirety by reference to
the description in the accompanying Prospectus and the Indenture between the
Company and The First National Bank of Chicago, as Trustee, as supplemented by a
First Supplemental Indenture (the Indenture, as so supplemented, is hereinafter
referred to as the "Indenture").
 
     Under certain circumstances involving the dissolution of Illinois Power
Capital following the occurrence of a Special Event, Series A Subordinated
Debentures may be distributed to the holders of the Series A Preferred
Securities in liquidation of Illinois Power Capital. See "Description of the
Series A Preferred Securities -- Special Event Redemption or Distribution."
 
GENERAL
 
     The Series A Subordinated Debentures will be issued as a series of
Subordinated Debentures under the Indenture. The Series A Subordinated
Debentures will be limited in aggregate principal amount to approximately
$      million, such amount being the sum of the aggregate liquidation
preference of the Series A Preferred Securities and the General Partnership
Payment.
 
     The entire principal amount of the Series A Subordinated Debentures will
become due and payable, together with any accrued and unpaid interest thereon,
including Additional Interest (as hereinafter defined), if any, on       , 2043.
 
     The Series A Subordinated Debentures if distributed to holders of Series A
Preferred Securities upon the dissolution of Illinois Power Capital will
initially be so issued as a Global Security (as defined below). As described
herein, under certain limited circumstances Series A Subordinated Debentures may
be issued in certificated form in exchange for a Global Security. See
"Book-Entry and Settlement" below. In the event that Series A Subordinated
Debentures are issued in certificated form, such Series A Subordinated
Debentures will be in denominations of $25 and integral multiples thereof and
may be transferred or exchanged at the offices described below.
 
     Payments on Series A Subordinated Debentures issued as a Global Security
will be made to DTC, as the depository for the Series A Subordinated Debentures.
In the event Series A Subordinated Debentures are issued in certificated form,
principal and interest will be payable, the transfer of the Series A
Subordinated Debentures will be registrable and the Series A Subordinated
Debentures will be exchangeable for Series A Subordinated Debentures of other
denominations of a like aggregate principal amount at the corporate trust office
of the Trustee in The City of New York; provided, that payment of interest may
be made at the option of the Company by check mailed to the address of the
persons entitled thereto.
 
     If the Series A Subordinated Debentures are distributed to the holders of
Series A Preferred Securities upon the dissolution of Illinois Power Capital,
the Company will use its best efforts to list the Series A Subordinated
Debentures on the New York Stock Exchange or on such other exchange as the
Series A Preferred Securities are then listed and traded on the same part of any
such exchange.
 
MANDATORY PREPAYMENT
 
     If Illinois Power Capital redeems Series A Preferred Securities in
accordance with the terms thereof, the Series A Subordinated Debentures will
become due and payable in a principal amount equal to the aggregate liquidation
preference of the Series A Preferred Securities so redeemed, together with all
accrued and unpaid interest, including Additional Interest, if any. Any payment
pursuant to this provision
 
                                      S-16
<PAGE>   19
 
shall be made prior to 12:00 noon, New York time, on the date of such redemption
or at such other time on such earlier date as the parties thereto shall agree.
 
OPTIONAL REDEMPTION
 
   
     The Company shall have the right to redeem the Series A Subordinated
Debentures, in whole or in part, from time to time, on or after                ,
1999, upon not less than 30 nor more than 60 days' notice, at a redemption price
equal to 100% of the principal amount to be redeemed plus any accrued and unpaid
interest, including Additional Interest, if any, to the redemption date.
    
 
INTEREST
 
     Each Series A Subordinated Debenture will bear interest at the rate of
     % per annum from the original date of issuance until the principal of such
Series A Debenture becomes due and payable, and on any overdue principal and (to
the extent that payment of such interest is enforceable under applicable law) on
any overdue installment of interest at the same rate per annum, payable monthly
in arrears on the last day of each calendar month of each year (each, an
"Interest Payment Date"), commencing                , 1994, to the person in
whose name such Series A Subordinated Debenture is registered, subject to
certain exceptions, at the close of business on the Business Day next preceding
such Interest Payment Date. In the event the Series A Subordinated Debentures
shall not continue to remain in book-entry-only form, the Company shall have the
right to select record dates which shall be more than one Business Day prior to
the Interest Payment Date.
 
     The amount of interest payable for any period will be computed on the basis
of a 360-day year of twelve 30-day months and for any period shorter than a full
month on the basis of actual days elapsed in such period. In the event that any
date on which interest is payable on the Series A Subordinated Debentures is not
a Business Day, then payment of the interest payable on such date will be made
on the next succeeding day which is a Business Day (and without any interest or
other payment in respect of any such delay), except that, if such Business Day
is in the next succeeding calendar year, such payment shall be made on the
immediately preceding Business Day, in each case with the same force and effect
as if made on such date.
 
OPTION TO EXTEND INTEREST PAYMENT PERIOD
 
     So long as the Company is not in default in the payment of interest on any
series of Subordinated Debentures issued under the Indenture, the Company shall
have the right at any time during the term of the Series A Subordinated
Debentures to extend the interest payment period from time to time to a period
not exceeding 60 consecutive months (the "Extension Period"), at the end of
which Extension Period the Company shall pay all interest then accrued and
unpaid (together with interest thereon at the rate specified for the Series A
Subordinated Debentures to the extent permitted by applicable law); provided,
that, during any such Extension Period, the Company shall not declare or pay any
dividend on, or redeem, purchase, acquire or make a liquidation payment with
respect to, any of its capital stock or make any guarantee payments with respect
to the foregoing (other than payments on the Guarantee); and provided further
that any such extended interest payment period may only be selected with respect
to the Series A Subordinated Debentures if an extended interest payment period
of identical length is simultaneously selected for all Subordinated Debentures
then outstanding under the Indenture. Prior to the termination of any such
Extension Period, the Company may further extend the interest payment period,
provided that such Extension Period together with all such previous and further
extensions thereof may not exceed 60 consecutive months. Upon the termination of
any Extension Period and the payment of all amounts then due, the Company may
select a new Extension Period, subject to the above requirements. No interest
shall be due and payable during an Extension Period, except at the end thereof.
 
     If Illinois Power Capital shall be the sole holder of the Series A
Subordinated Debentures, the Company shall give Illinois Power Capital notice of
its selection of such Extension Period one Business Day prior to the earlier of
(i) the next succeeding date on which the dividends on the Series A Preferred
Securities are payable or (ii) the date Illinois Power Capital is required to
give notice to the New York Stock Exchange or other applicable self-regulatory
organization or to holders of the Series A Preferred
 
                                      S-17
<PAGE>   20
 
Securities of the record date or the date such dividend is payable, but in any
event not less than one Business Day prior to such record date. The Company
shall cause Illinois Power Capital to give notice of the Company's selection of
such Extension Period to the holders of the Series A Preferred Securities. If
Illinois Power Capital shall not be the sole holder of the Series A Subordinated
Debentures, the Company shall give the holders of the Series A Subordinated
Debentures notice of its selection of such Extension Period ten Business Days
prior to the earlier of (i) the next succeeding Interest Payment Date or (ii)
the date the Company is required to give notice to the New York Stock Exchange
or other applicable self-regulatory organization, or to holders of the Series A
Subordinated Debentures, of the record or payment date of such related interest
payment, but in any event not less than two Business Days prior to such record
date.
 
ADDITIONAL INTEREST
 
     So long as any Subordinated Debentures remain outstanding, if at any time
Illinois Power Capital shall be required to pay any interest on dividends in
arrears in respect of the Series A Preferred Securities pursuant to the terms
thereof, then the Company will pay as interest to Illinois Power Capital as the
holder of the Series A Subordinated Debentures ("Additional Interest") an amount
equal to such interest on dividends in arrears. In addition, if Illinois Power
Capital would be required to pay any taxes, duties, assessments or governmental
charges of whatever nature (other than withholding taxes) imposed by the United
States, or any other taxing authority, then, in any such case, the Company also
will pay as Additional Interest such amounts as shall be required so that the
net amounts received and retained by Illinois Power Capital after paying any
such taxes, duties, assessments or governmental charges will be not less than
the amounts Illinois Power Capital would have received had no such taxes,
duties, assessments or governmental charges been imposed.
 
SET-OFF
 
     Notwithstanding anything to the contrary in the Indenture, the Company
shall have the right to set-off any payment it is otherwise required to make
thereunder with and to the extent the Company has theretofore made, or is
concurrently on the date of such payment making, a payment under the Guarantee.
 
EVENTS OF DEFAULT
 
   
     In the case any Event of Default (as defined in the Indenture) shall occur
and be continuing, Illinois Power Capital will have the right to declare the
principal of and the interest on the Series A Subordinated Debentures (including
any Additional Interest) and any other amounts payable under the Indenture to be
forthwith due and payable and to enforce its other rights as a creditor with
respect to the Series A Subordinated Debentures. See "Enforcement of Certain
Rights by Special Representative" below for a discussion of certain rights
available to holders of the Series A Preferred Securities upon the occurrence of
an Event of Default.
    
 
ENFORCEMENT OF CERTAIN RIGHTS BY SPECIAL REPRESENTATIVE
 
     If (i) Illinois Power Capital fails to pay dividends in full on the Series
A Preferred Securities for 18 consecutive monthly dividend periods; (ii) an
Event of Default occurs and is continuing on the Series A Subordinated
Debentures; or (iii) the Company is in default on any of its payment or other
obligations under the Guarantee, under the terms of the Series A Preferred
Securities, the holders of outstanding Series A Preferred Securities will have
the rights referred to under "Description of the Series A Preferred Securities
- -- Voting Rights," including the right to appoint a Special Representative,
which Special Representative shall be authorized to exercise Illinois Power
Capital's right to accelerate the principal amount of the Series A Subordinated
Debentures and to enforce Illinois Power Capital's other creditor rights under
the Series A Subordinated Debentures. Notwithstanding the appointment of any
such Special Representative, the Company shall continue as General Partner and
shall retain all rights under
 
                                      S-18
<PAGE>   21
 
the Indenture, including the right to extend the interest payment period from
time to time to a period not exceeding 60 consecutive months.
 
BOOK-ENTRY AND SETTLEMENT
 
     If distributed to holders of Series A Preferred Securities in connection
with the dissolution of Illinois Power Capital as a result of the occurrence of
a Special Event, the Series A Subordinated Debentures will be issued in the form
of one or more global certificates (each, a "Global Security") registered in the
name of a nominee of DTC. Except under the limited circumstances described
below, Series A Subordinated Debentures represented by the Global Security will
not be exchangeable for, and will not otherwise be issuable as, Series A
Subordinated Debentures in definitive form. The Global Securities described
above may not be transferred except by DTC to a nominee of DTC or by a nominee
of DTC to DTC or another nominee of DTC or to a successor depository or its
nominee.
 
     The laws of some jurisdictions require that certain purchasers of
securities take physical delivery of such securities in definitive form. Such
laws may impair the ability to transfer beneficial interests in such a Global
Security.
 
     Except as provided below, owners of beneficial interests in such a Global
Security will not be entitled to receive physical delivery of Series A
Subordinated Debentures in definitive form and will not be considered the
Holders (as defined in the Indenture) thereof for any purpose under the
Indenture, and no Global Security representing Series A Subordinated Debentures
shall be exchangeable, except for another Global Security of like denomination
and tenor to be registered in the name of DTC or its nominee or to a successor
depository or its nominee. Accordingly, each beneficial owner must rely on the
procedures of DTC and, if such person is not a Participant, on the procedures of
the Participant through which such person owns its interest, to exercise any
rights of a Holder under the Indenture.
 
   
     THE DEPOSITORY. DTC will act as security depository for the Series A
Subordinated Debentures. For a description of DTC and the specific terms of the
depository arrangements, see "Description of the Series A Preferred Securities
- -- Book-Entry-Only Issuance -- The Depository Trust Company." As of the date of
this Prospectus Supplement, the description therein of DTC's book-entry system
and DTC's practices as they relate to purchases, transfers, notices and payments
with respect to the Series A Preferred Securities applies in all material
respects to any debt obligations represented by one or more Global Securities
held by DTC.
    
 
     Neither the Company, the Trustee, any paying agent nor any other agent of
the Company or the Trustee will have any responsibility or liability for any
aspect of the records relating to or payments made on account of beneficial
ownership interests in a Global Security for such Series A Subordinated
Debentures or for maintaining, supervising or reviewing any records relating to
such beneficial ownership interests.
 
     DISCONTINUANCE OF THE DEPOSITORY'S SERVICES. A Global Security shall be
exchangeable for Series A Subordinated Debentures registered in the names of
persons other than DTC or its nominee only if (i) DTC notifies the Company that
it is unwilling or unable to continue as a depository for such Global Security
and no successor depository shall have been appointed, or if any time DTC ceases
to be a clearing agency registered under the Exchange Act at a time when DTC is
required to be so registered to act as such depository, (ii) the Company in its
sole discretion determines that such Global Security shall be so exchangeable or
(iii) there shall have occurred an Event of Default with respect to such Series
A Subordinated Debentures. Any Global Security that is exchangeable pursuant to
the preceding sentence shall be exchangeable for Series A Subordinated
Debentures registered in such names as the Depository shall direct. It is
expected that such instructions will be based upon directions received by the
Depository from its Participants with respect to ownership of beneficial
interests in such Global Security.
 
                                      S-19
<PAGE>   22
 
MISCELLANEOUS
 
     For restrictions on certain actions of the General Partner with respect to
Series A Subordinated Debentures held by Illinois Power Capital, see
"Description of the Series A Preferred Securities -- Voting Rights."
 
                        EFFECT OF OBLIGATIONS UNDER THE
               SERIES A SUBORDINATED DEBENTURES AND THE GUARANTEE
 
     As set forth in the Partnership Agreement, the sole purpose of Illinois
Power Capital is to issue partner interests in Illinois Power Capital,
including, without limitation, the Series A Preferred Securities, and to use the
proceeds thereof to purchase the Series A Subordinated Debentures or other
similar debt securities of the Company.
 
     As long as payments of interest and other payments are made when due on the
Series A Subordinated Debentures, such payments will be sufficient to cover
dividends and payments due on the Series A Preferred Securities primarily
because (i) the aggregate principal amount of Series A Subordinated Debentures
will be equal to the sum of the aggregate liquidation preference of the Series A
Preferred Securities and the General Partnership Payment; (ii) the interest rate
and interest and other payment dates on the Series A Subordinated Debentures
will match the dividend rate and dividend and other payment dates for the Series
A Preferred Securities; (iii) the Partnership Agreement provides that the
Company, as General Partner, shall pay for all, and Illinois Power Capital shall
not be obligated to pay, directly or indirectly, for any, costs and expenses of
Illinois Power Capital; and (iv) the Partnership Agreement further provides that
the General Partner shall not cause or permit Illinois Power Capital to, among
other things, engage in any activity that is not consistent with the purposes of
Illinois Power Capital.
 
     If the Company fails to make interest or other payments on the Series A
Subordinated Debentures when due, the Partnership Agreement provides a mechanism
whereby the holders of the Series A Preferred Securities may enforce the rights
of Illinois Power Capital under the Series A Subordinated Debentures through the
appointment of a Special Representative. Payments of dividends and other
payments due on the Series A Preferred Securities out of moneys held by Illinois
Power Capital are guaranteed by the Company to the extent set forth under
"Description of the Guarantee" in the accompanying Prospectus. The Partnership
Agreement also provides, and the Company, under the Guarantee, acknowledges,
that a Special Representative may be appointed to enforce the Guarantee if the
Company is in default on any of its payment obligations under the Guarantee. In
addition, if the General Partner or the Special Representative fails to enforce
the Guarantee, a holder of a Series A Preferred Security may institute a legal
proceeding directly against the Company to enforce its rights under the
Guarantee without first instituting a legal proceeding against Illinois Power
Capital or any other person or entity.
 
     The Company and Illinois Power Capital believe that the above mechanisms
and obligations, taken together, are substantially equivalent to a full and
unconditional guarantee by the Company of payments due on the Series A Preferred
Securities.
 
                             UNITED STATES TAXATION
 
GENERAL
 
     This section is a summary of certain United States federal income tax
considerations that may be relevant to prospective purchasers of Series A
Preferred Securities and represents the opinion of Schiff Hardin & Waite, tax
counsel to the Company and Illinois Power Capital, insofar as it relates to
matters of law and legal conclusions. This section is based upon current
provisions of the Internal Revenue Code of 1986, as amended (the "Code"),
existing and proposed regulations thereunder and current
 
                                      S-20
<PAGE>   23
administrative rulings and court decisions, all of which are subject to change.
Subsequent changes may cause tax consequences to vary substantially from the
consequences described below.
 
     No attempt has been made in the following discussion to comment on all
United States federal income tax matters affecting purchasers of Series A
Preferred Securities. Moreover, the discussion focuses on holders of Series A
Preferred Securities who are individual citizens or residents of the United
States and has only limited application to corporations, estates, trusts or
non-resident aliens. Accordingly, each prospective purchaser of Series A
Preferred Securities should consult, and should depend on, his or her own tax
advisor in analyzing the federal, state, local and foreign tax consequences of
the purchase, ownership or disposition of Series A Preferred Securities.
 
INCOME FROM SERIES A PREFERRED SECURITIES
 
     In the opinion of Schiff Hardin & Waite, Illinois Power Capital will be
treated as a partnership for federal income tax purposes. Accordingly, each
holder of Series A Preferred Securities (a "Preferred Securityholder") will be
required to include in gross income such holder's distributive share of the net
income of Illinois Power Capital. Such income will not exceed dividends received
on such Series A Preferred Securities, except in limited circumstances as
described below under "Potential Extension of Interest Payment Period." No
portion of such income will be eligible for the dividends received deduction.
 
DISPOSITION OF SERIES A PREFERRED SECURITIES
 
     Gain or loss will be recognized on a sale (including a redemption for cash)
of Series A Preferred Securities in an amount equal to the difference between
the amount realized and the Preferred Securityholder's tax basis for the Series
A Preferred Securities sold. Gain or loss recognized by a Preferred
Securityholder on the sale or exchange of a Series A Preferred Security held for
more than one year will generally be taxable as long-term capital gain or loss.
 
RECEIPT OF SERIES A SUBORDINATED DEBENTURES UPON DISSOLUTION OF ILLINOIS POWER
CAPITAL
 
     Under certain circumstances, as described under the caption "Description of
the Series A Preferred Securities -- Special Event Redemption or Distribution,"
Series A Subordinated Debentures may be distributed to the holders of the Series
A Preferred Securities in connection with the dissolution of Illinois Power
Capital. Under current United States federal income tax law, such a distribution
would be treated as a non-taxable exchange to each holder of Series A Preferred
Securities and would result in the holder of Series A Preferred Securities
receiving an aggregate tax basis in the Series A Subordinated Debentures equal
to such holder's aggregate tax basis in its Series A Preferred Securities. A
holder's holding period in the Series A Subordinated Debentures so received in
connection with the dissolution of Illinois Power Capital would include the
period for which the Series A Preferred Securities were held by such holder.
Under a change in law, a change in legal interpretation or the other
circumstances giving rise to a Special Event, however, the dissolution of
Illinois Power Capital and the distribution of Series A Subordinated Debentures
in connection with the dissolution of Illinois Power Capital could be a taxable
event to holders of the Series A Preferred Securities. In the judgment of tax
counsel to the Company and Illinois Power Capital, the series of events which
would result in the recognition of taxable gain by holders of the Series A
Preferred Securities, by reason of a dissolution of Illinois Power Capital in
response to a Special Event, is unlikely to occur. There can be no assurance in
this regard, however.
 
ILLINOIS POWER CAPITAL INFORMATION RETURNS AND AUDIT PROCEDURES
 
     The General Partner will furnish each Series A Preferred Securityholder
with a Schedule K-1 each year setting forth such Preferred Securityholder's
allocable share of income for the prior calendar year. The General Partner is
required to furnish such schedules as soon as practicable following the end of
the year, but in any event prior to March 31.
 
     Any person who holds Series A Preferred Securities as a nominee for another
person is required to furnish to Illinois Power Capital (a) the name, address
and taxpayer identification number of the
 
                                      S-21
<PAGE>   24
 
   
beneficial owner and the nominee; (b) information as to whether the beneficial
owner is (i) a person that is not a United States person, (ii) a foreign
government, an international organization or any wholly-owned agency or
instrumentality of either of the foregoing, or (iii) a tax-exempt entity; (c)
the amount and description of Series A Preferred Securities held, acquired or
transferred for the beneficial owner; and (d) certain information including the
dates of acquisitions and transfers, means of acquisitions and transfers, and
acquisition cost for purchases, as well as the amount of net proceeds from
sales. Brokers and financial institutions are required to furnish additional
information, including whether they are United States persons and certain
information on Series A Preferred Securities they acquire, hold or transfer for
their own accounts. A penalty of $50 per failure (up to a maximum of $100,000
per calendar year) is imposed by the Code for failure to report such information
to Illinois Power Capital. The nominee is required to supply the beneficial
owners of Series A Preferred Securities with the information furnished to
Illinois Power Capital.
    
 
POTENTIAL EXTENSION OF INTEREST PAYMENT PERIOD
 
     Under the terms of the Indenture, the Company has the right to extend from
time to time the interest payment period on the Series A Subordinated Debentures
to a period not exceeding 60 consecutive months. In the event that the Company
exercises this right, the Company may not, among other things, declare or pay
dividends on any of its capital stock. The Company has no current intention of
extending the interest payment period on the Series A Subordinated Debentures
since it desires to continue the declaration and payment of dividends on its
capital stock. In the event that the interest payment period is extended,
Illinois Power Capital will continue to accrue income equal to the amount of the
interest payment due at the end of the Extension Period pursuant to the Code and
Treasury Regulation provisions applicable to original issue discount.
 
     Accrued income will be allocated, but not distributed, to holders of record
on the Business Day preceding the last day of each calendar month. As a result,
holders of record during an Extension Period will include interest in gross
income in advance of the receipt of cash, and any such holders who dispose of
Series A Preferred Securities prior to the record date for the payment of
dividends following such Extension Period will include interest in gross income
but will not receive any cash related thereto from Illinois Power Capital. The
tax basis of a Series A Preferred Security will be increased by the amount of
any interest that is included in income without a receipt of cash, and will be
decreased when and if such cash is subsequently received from Illinois Power
Capital. The subsequent receipt of such cash will not be includible in gross
income.
 
UNITED STATES ALIEN HOLDERS
 
     For purposes of this discussion, a "United States Alien Holder" is any
holder who or which is (i) a nonresident alien individual or (ii) a foreign
corporation, partnership, estate or trust, in either case not subject to United
States federal income tax on a net income basis in respect of a Series A
Preferred Security.
 
     Under current United States federal income tax law, subject to the
discussion below with respect to backup withholding, and assuming satisfaction
by the Company of its withholding tax obligations, if any:
 
          (i) Payments by Illinois Power Capital or any of its paying agents to
     any holder of a Series A Preferred Security who or which is a United States
     Alien Holder will not be subject to United States federal withholding tax
     provided that (a) the beneficial owner of the Series A Preferred Security
     does not actually or constructively own 10% or more of the total combined
     voting power of all classes of capital stock of the Company, (b) the
     beneficial owner of the Series A Preferred Security is not a controlled
     foreign corporation that is related to the Company or Illinois Power
     Capital through stock ownership, and (c) either: (x) the beneficial owner
     of the Series A Preferred Security certifies to Illinois Power Capital or
     its agent, under penalties of perjury, that it is a United States Alien
     Holder and provides its name and address or (y) the holder of the Series A
     Preferred Security is a securities clearing organization, bank or other
     financial institution that holds customers' securities in
 
                                      S-22
<PAGE>   25
 
     the ordinary course of its trade or business (a "financial institution"),
     and such holder certifies to Illinois Power Capital or its agent, under
     penalties of perjury, that such statement has been received from the
     beneficial owner by it or by a financial institution between it and the
     beneficial owner and furnishes Illinois Power Capital or its agent with a
     copy thereof; and
 
          (ii) a United States Alien Holder of a Series A Preferred Security
     will generally not be subject to United States federal withholding tax on
     any gain realized on the sale or exchange of a Series A Preferred Security
     unless such holder is present in the United States for 183 days or more in
     the taxable year of sale and either has a "tax home" in the United States
     or certain other requirements are met.
 
BACKUP WITHHOLDING AND INFORMATION REPORTING
 
     In general, information reporting requirements will apply to payments of
the proceeds of the sale of Series A Preferred Securities within the United
States to noncorporate United States holders, and "backup withholding" at a rate
of 31% will apply to such payments if the United States holder fails to provide
an accurate taxpayer identification number.
 
   
     Payments of the proceeds from the sale by a United States Alien Holder of
Series A Preferred Securities made to or through a foreign office of a broker
will not be subject to information reporting or backup withholding, except that,
if the broker is a United States person, a controlled foreign corporation for
United States tax purposes or a foreign person 50% or more of whose gross income
is effectively connected with a United States trade or business for a specified
three-year period, information reporting may apply to such payments. Payments of
the proceeds from the sale of Series A Preferred Securities to or through the
United States office of a broker are subject to information reporting and backup
withholding unless the holder or beneficial owner certifies as to its non-United
States status or otherwise establishes an exemption from information reporting
and backup withholding.
    
 
                                      S-23
<PAGE>   26
 
                                  UNDERWRITING
 
     Subject to the terms and conditions of the Underwriting Agreement, Illinois
Power Capital has agreed to sell to each of the several Underwriters named
below, and each of the Underwriters, for whom Goldman, Sachs & Co. and
          are acting as Representatives, has severally agreed to purchase from
Illinois Power Capital the respective number of Series A Preferred Securities
set forth opposite its name below:
 
<TABLE>
<CAPTION>
                                                                      NUMBER OF
                                                                      SERIES A
                                                                      PREFERRED
                               UNDERWRITER                           SECURITIES
          -----------------------------------------------------     -------------
          <S>                                                       <C>
          Goldman, Sachs & Co. ................................
                                                                    -------------
                    Total......................................
                                                                    =============
</TABLE>
 
     Under the terms and conditions of the Underwriting Agreement, the
Underwriters are committed to take and pay for all such Series A Preferred
Securities offered hereby, if any are taken.
 
     The Underwriters propose to offer the Series A Preferred Securities in part
directly to the public at the initial public offering price set forth on the
cover page of this Prospectus Supplement, and in part to certain securities
dealers at such price less a concession of $          per Series A Preferred
Security. The Underwriters may allow, and such dealers may reallow, a concession
not in excess of $          per Series A Preferred Security to certain brokers
and dealers. After the Series A Preferred Securities are released for sale to
the public, the offering price and other selling terms may from time to time be
varied by the Representatives.
 
     As the proceeds of the sale of the Series A Preferred Securities will be
loaned to the Company, the Company has agreed in the Underwriting Agreement to
pay to the Underwriters $       per Series A Preferred Security ($       per
Series A Preferred Security sold to certain institutions) for the accounts of
the several Underwriters.
 
     The Company and Illinois Power Capital have agreed, during the period
beginning from the date of the Underwriting Agreement and continuing to and
including the earlier of (i) the date, after the closing date, on which the
distribution of the Series A Preferred Securities ceases, as determined by the
Underwriters, or (ii) 30 days after the closing date, not to offer, sell,
contract to sell, or otherwise dispose of any Series A Preferred Securities, any
limited partner interests of Illinois Power Capital, or any preferred stock or
any other securities of Illinois Power Capital or the Company which are
substantially similar to the Series A Preferred Securities, or any securities
convertible into or exchangeable for Series A Preferred Securities, limited
partner interests, preferred stock or such substantially similar securities of
either Illinois Power Capital or the Company without the prior written consent
of the Underwriters.
 
     Prior to this offering, there has been no public market for the Series A
Preferred Securities. In order to meet one of the requirements for listing the
Series A Preferred Securities on the New York Stock Exchange, the Underwriters
will undertake to sell lots of 100 or more Series A Preferred Securities to a
minimum of 400 beneficial holders.
 
     Illinois Power Capital and the Company have agreed to indemnify the
Underwriters against certain civil liabilities, including liabilities under the
Securities Act.
 
     Certain of the Underwriters engage in transactions with, and from time to
time have performed services for, the Company and its affiliates in the ordinary
course of business.
 
                                      S-24
<PAGE>   27
 
                                 LEGAL OPINIONS
 
     Certain legal matters will be passed upon for the Company and Illinois
Power Capital by Schiff Hardin & Waite, Chicago, Illinois, and for the
Underwriters by Reid & Priest, New York, New York. Certain matters of Delaware
law relating to the validity of the Series A Preferred Securities will be passed
upon by Richards, Layton & Finger, P.A., Wilmington, Delaware, special Delaware
counsel to the Company and Illinois Power Capital. Schiff Hardin & Waite and
Reid & Priest may rely on the opinion of Richards, Layton & Finger, P.A. as to
certain matters of Delaware law, Schiff Hardin & Waite may rely on the opinion
of Reid & Priest as to all matters of New York law, and Reid & Priest may rely
on the opinion of Schiff Hardin & Waite as to all matters of Illinois law.
 
                                      S-25
<PAGE>   28
 
- ------------------------------------------------------
- ------------------------------------------------------
 
     NO PERSON HAS BEEN AUTHORIZED TO GIVE ANY INFORMATION OR TO MAKE ANY
REPRESENTATIONS OTHER THAN THOSE CONTAINED IN THIS PROSPECTUS SUPPLEMENT OR THE
PROSPECTUS AND, IF GIVEN OR MADE, SUCH INFORMATION OR REPRESENTATIONS MUST NOT
BE RELIED UPON AS HAVING BEEN AUTHORIZED. THIS PROSPECTUS SUPPLEMENT AND THE
PROSPECTUS DO NOT CONSTITUTE AN OFFER TO SELL OR THE SOLICITATION OF AN OFFER TO
BUY ANY SECURITIES OTHER THAN THE SECURITIES DESCRIBED IN THIS PROSPECTUS
SUPPLEMENT AND THE PROSPECTUS OR AN OFFER TO SELL OR THE SOLICITATION OF AN
OFFER TO BUY SUCH SECURITIES IN ANY CIRCUMSTANCES IN WHICH SUCH OFFER OR
SOLICITATION IS UNLAWFUL. NEITHER THE DELIVERY OF THIS PROSPECTUS SUPPLEMENT AND
THE PROSPECTUS NOR ANY SALE MADE HEREUNDER SHALL, UNDER ANY CIRCUMSTANCES,
CREATE ANY IMPLICATION THAT THE INFORMATION HEREIN OR THEREIN IS CORRECT AS OF
ANY TIME SUBSEQUENT TO THE DATE OF SUCH INFORMATION.
                               ------------------
 
                               TABLE OF CONTENTS
 
                             PROSPECTUS SUPPLEMENT
 
<TABLE>
<CAPTION>
                                        PAGE
                                        ----
<S>                                     <C>
Certain Investment Considerations....    S-3
Illinois Power Company...............    S-4
Illinois Power Capital...............    S-4
Use of Proceeds......................    S-4
Summary Financial Information of
  the Company........................    S-5
Description of the Series A Preferred
  Securities.........................    S-7
Description of the Series A
  Subordinated Debentures............   S-16
Effect of Obligations under the
  Series A Subordinated Debentures
  and the Guarantee..................   S-20
United States Taxation...............   S-20
Underwriting.........................   S-24
Legal Opinions.......................   S-25
             PROSPECTUS
Available Information................      2
Incorporation of Certain Documents by
  Reference..........................      2
Illinois Power Company...............      3
Illinois Power Capital...............      3
Use of Proceeds......................      3
Ratio of Earnings to Combined Fixed
  Charges and Preferred Stock
  Dividend Requirements..............      4
Description of the Preferred
  Securities.........................      5
Description of the Guarantee.........      5
Description of the Subordinated
  Debentures.........................      7
Plan of Distribution.................     12
Legal Opinions.......................     13
Experts..............................     13
</TABLE>
 
- ------------------------------------------------------
- ------------------------------------------------------
 
- ------------------------------------------------------
- ------------------------------------------------------
 
                              PREFERRED SECURITIES
 
                                 ILLINOIS POWER
                                    CAPITAL
 
                            GUARANTEED TO THE EXTENT
                             ILLINOIS POWER CAPITAL
                                HAS FUNDS AS SET
                                FORTH HEREIN BY
 
                                   [IP LOGO]
 
                             ILLINOIS POWER COMPANY
 
                                     % CUMULATIVE
                            MONTHLY INCOME PREFERRED
                              SECURITIES, SERIES A
 
                            ------------------------
                             PROSPECTUS SUPPLEMENT
                            ------------------------
 
                              GOLDMAN, SACHS & CO.
                      REPRESENTATIVES OF THE UNDERWRITERS
 
- ------------------------------------------------------
- ------------------------------------------------------
<PAGE>   29
 
     INFORMATION CONTAINED HEREIN IS SUBJECT TO COMPLETION OR AMENDMENT. A
     REGISTRATION STATEMENT RELATING TO THESE SECURITIES HAS BEEN FILED WITH THE
     SECURITIES AND EXCHANGE COMMISSION. THESE SECURITIES MAY NOT BE SOLD NOR
     MAY OFFERS TO BUY BE ACCEPTED PRIOR TO THE TIME THE REGISTRATION STATEMENT
     BECOMES EFFECTIVE. THIS PROSPECTUS SUPPLEMENT SHALL NOT CONSTITUTE AN OFFER
     TO SELL OR THE SOLICITATION OF AN OFFER TO BUY NOR SHALL THERE BE ANY SALE
     OF THESE SECURITIES IN ANY STATE IN WHICH SUCH OFFER, SOLICITATION OR SALE
     WOULD BE UNLAWFUL PRIOR TO REGISTRATION OR QUALIFICATION UNDER THE
     SECURITIES LAWS OF ANY SUCH STATE.
 
   
                 SUBJECT TO COMPLETION, DATED SEPTEMBER 2, 1994
    
   
          PROSPECTUS SUPPLEMENT TO PROSPECTUS DATED SEPTEMBER   , 1994
    
 
                              PREFERRED SECURITIES
                             ILLINOIS POWER CAPITAL
CUMULATIVE ADJUSTABLE RATE MONTHLY INCOME PREFERRED SECURITIES ("MIPS"*), SERIES
                                       A
              (LIQUIDATION PREFERENCE $25 PER PREFERRED SECURITY)
                GUARANTEED TO THE EXTENT ILLINOIS POWER CAPITAL
                        HAS FUNDS AS SET FORTH HEREIN BY
                             ILLINOIS POWER COMPANY
                         ------------------------------
 
    The Cumulative Adjustable Rate Monthly Income Preferred Securities, Series A
(the "Series A Preferred Securities"), representing the limited partner
interests offered hereby, are being issued by Illinois Power Capital, L.P., a
limited partnership formed under the laws of the State of Delaware ("Illinois
Power Capital"). All of the general partner interests in Illinois Power Capital
are owned by Illinois Power Company, an Illinois corporation (the "Company").
Illinois Power Capital exists for the sole purpose of issuing its partner
interests and using the proceeds thereof to purchase certain debt securities of
the Company. The proceeds of the Series A Preferred Securities will be used by
Illinois Power Capital to purchase the Company's Adjustable Rate Subordinated
Deferrable Interest Debentures, Series A (the "Series A Subordinated
Debentures"). The limited partner interests represented by the Series A
Preferred Securities will have a preference with respect to cash distributions
and amounts payable on liquidation over the general partner interests in
Illinois Power Capital.
 
    Holders of the Series A Preferred Securities will be entitled to receive
cumulative cash distributions accruing from the date of original issuance and
payable monthly in arrears on the last day of each calendar month of each year,
commencing         , 1994 ("dividends"). The dividend rate will be adjusted
quarterly. The rate for the initial period from the date of initial issuance to
        , 1994 will be   % per annum, which is equivalent to $      per Series A
Preferred Security per annum. Thereafter, dividends on the Series A Preferred
Securities will be payable at the "Applicable Rate" from time to time in effect.
The Applicable Rate for any quarter will be equal to   % of the highest of the
"Treasury Bill Rate," the "Ten Year Constant Maturity Rate" and the "Thirty Year
Constant Maturity Rate" determined in advance of such quarter. The Applicable
Rate for any quarter will not be less than   % per annum nor greater than   %
per annum. See "Description of the Series A Preferred Securities -- Dividends."
 
    The payment of dividends and payments on liquidation of Illinois Power
Capital or the redemption of Series A Preferred Securities, to the extent that
Illinois Power Capital has sufficient cash on hand to permit such payments and
funds legally available therefor, are guaranteed by the Company to the extent
set forth herein and in the accompanying Prospectus (the "Guarantee"). See
"Description of the Guarantee" in the accompanying Prospectus. If the Company
fails to make interest payments on the Series A Subordinated Debentures
purchased by Illinois Power Capital with the proceeds of this offering, Illinois
Power Capital will have insufficient funds to pay dividends on the Series A
Preferred Securities. The Guarantee does not provide for payment by the Company
directly of dividends for which Illinois Power Capital does not have sufficient
funds available. In such event, the remedy of a holder of Series A Preferred
Securities is to enforce Illinois Power Capital's rights under the Series A
Subordinated Debentures purchased by Illinois Power Capital from the Company.
 
    The obligations of the Company under the Guarantee are subordinate and
junior in right of payment to all liabilities of the Company, and the Company's
obligations under the Series A Subordinated Debentures are subordinate and
junior in right of payment to all present and future Senior Indebtedness (as
defined in the accompanying Prospectus) of the Company. At June 30, 1994, Senior
Indebtedness of the Company aggregated approximately $2.2 billion.
 
    The Series A Preferred Securities are redeemable at the option of Illinois
Power Capital, in whole or in part, from time to time, on or after         ,
1999, at $25 per Series A Preferred Security plus any accumulated and unpaid
dividends thereon to the date fixed for redemption (the "Redemption Price"), and
will be redeemed at such price from the proceeds of any repayment or redemption
of the Series A Subordinated Debentures. See "Description of Series A Preferred
Securities -- Optional Redemption" and "-- Mandatory Redemption." In addition,
upon the occurrence of certain special events arising from a change in law or a
change in legal interpretation, the Series A Preferred Securities are redeemable
in whole at the Redemption Price at the option of the Company, in its capacity
as the general partner of Illinois Power Capital (the "General Partner"), or the
General Partner may dissolve Illinois Power Capital and cause Series A
Subordinated Debentures to be distributed to the holders of the Series A
Preferred Securities in liquidation of their interests in Illinois Power
Capital. See "Description of Series A Preferred Securities -- Special Event
Redemption or Distribution" and "Description of the Series A Subordinated
Debentures." If the Series A Subordinated Debentures are so distributed, the
Company will use its best efforts to have them listed on the same exchange on
which the Series A Preferred Securities are then listed.
 
    In the event of the dissolution of Illinois Power Capital, the holders of
Series A Preferred Securities will be entitled to a liquidation preference for
each Series A Preferred Security of $25 plus any accumulated and unpaid
dividends thereon to the date of payment, subject to certain limitations,
unless, in connection with such dissolution, Series A Subordinated Debentures
are distributed to the holders of the Series A Preferred Securities. See
"Description of Series A Preferred Securities -- Liquidation Distribution Upon
Dissolution."
 
    SEE "CERTAIN INVESTMENT CONSIDERATIONS" FOR CERTAIN CONSIDERATIONS RELEVANT
TO AN INVESTMENT IN THE SERIES A PREFERRED SECURITIES, INCLUDING THE PERIOD
DURING WHICH AND CIRCUMSTANCES UNDER WHICH PAYMENT OF DIVIDENDS ON THE SERIES A
PREFERRED SECURITIES MAY BE DEFERRED.
 
    Application will be made to list the Series A Preferred Securities on the
New York Stock Exchange.
                         ------------------------------
 
THESE SECURITIES HAVE NOT BEEN APPROVED OR DISAPPROVED BY THE SECURITIES AND
EXCHANGE COMMISSION OR ANY STATE SECURITIES COMMISSION NOR HAS THE SECURITIES
  AND EXCHANGE COMMISSION OR ANY STATE SECURITIES COMMISSION PASSED UPON THE
    ACCURACY OR ADEQUACY OF THIS PROSPECTUS SUPPLEMENT OR THE PROSPECTUS TO
                              WHICH IT RELATES.
          ANY REPRESENTATION TO THE CONTRARY IS A CRIMINAL OFFENSE.
<TABLE>
<CAPTION>
                                                                    INITIAL PUBLIC    UNDERWRITING     PROCEEDS TO ILLINOIS POWER
                                                                    OFFERING PRICE    COMMISSION(1)          CAPITAL(2)(3)
                                                                    --------------    -------------    --------------------------
<S>                                                                 <C>               <C>              <C>
Per Series A Preferred Security..................................      $                   (2)                  $
Total............................................................      $                   (2)                  $
</TABLE>
 
- ------------------
 
(1) Illinois Power Capital and the Company have agreed to indemnify the several
    Underwriters against certain civil liabilities, including liabilities under
    the Securities Act of 1933, as amended. See "Underwriting."
 
(2) As the proceeds of the sale of the Series A Preferred Securities will be
    loaned to the Company, the Company has agreed in the Underwriting Agreement
    to pay to the Underwriters $    per Series A Preferred Security (or $    in
    the aggregate); provided that such payment will be $
    per Series A Preferred Security sold to certain institutions. Therefore, to
    the extent that Series A Preferred Securities are sold to such institutions,
    the actual amount of Underwriters' compensation will be less than the amount
    specified in the preceding sentence and the Proceeds to Illinois Power
    Capital will be greater than the amount set forth in the table above. See
    "Underwriting."
 
(3) Expenses of the offering which are payable by the Company are estimated to
    be $        .
                         ------------------------------
 
    The Series A Preferred Securities offered hereby are offered severally by
the Underwriters, as specified herein, subject to receipt and acceptance by them
and subject to their right to reject any order in whole or in part. It is
expected that delivery of certificates for the Series A Preferred Securities
will be made only in book-entry form through the facilities of The Depository
Trust Company on or about         , 1994.
- ------------------
    * An application has been filed by Goldman, Sachs & Co. with the United
      States Patent and Trademark Office for the registration of the MIPS
      servicemark.
                              GOLDMAN, SACHS & CO.
 
           The date of this Prospectus Supplement is         , 1994.
<PAGE>   30
 
     IN CONNECTION WITH THIS OFFERING, THE UNDERWRITERS MAY OVER-ALLOT OR EFFECT
TRANSACTIONS WHICH STABILIZE OR MAINTAIN THE MARKET PRICE OF THE SECURITIES
OFFERED HEREBY AT LEVELS ABOVE THOSE WHICH MIGHT OTHERWISE PREVAIL IN THE OPEN
MARKET. SUCH TRANSACTIONS MAY BE EFFECTED ON THE NEW YORK STOCK EXCHANGE, IN THE
OVER-THE-COUNTER MARKET OR OTHERWISE. SUCH STABILIZING, IF COMMENCED, MAY BE
DISCONTINUED AT ANY TIME.
 
                                       S-2
<PAGE>   31
 
                       CERTAIN INVESTMENT CONSIDERATIONS
 
     Prospective purchasers of Series A Preferred Securities should carefully
review the information contained elsewhere in this Prospectus Supplement and in
the accompanying Prospectus and should particularly consider the following
matters. Capitalized terms used and not otherwise defined in this Prospectus
Supplement shall have the meanings ascribed thereto in the accompanying
Prospectus.
 
   
     SUBORDINATION OF GUARANTEE AND SERIES A SUBORDINATED DEBENTURES. The
Company's obligations under the Guarantee are subordinate and junior in right of
payment to all other liabilities of the Company. The obligations of the Company
under the Series A Subordinated Debentures are subordinate and junior in right
of payment to all present and future Senior Indebtedness of the Company. At June
30, 1994, Senior Indebtedness of the Company aggregated approximately $2.2
billion. There are no terms in the Series A Preferred Securities, the Series A
Subordinated Debentures or the Guarantee that limit the Company's ability to
incur additional indebtedness, including indebtedness that ranks senior to the
Series A Subordinated Debentures and the Guarantee. See "Description of the
Guarantee -- Status of the Guarantee" and "Description of the Subordinated
Debentures -- Subordination" in the accompanying Prospectus.
    
 
     OPTION TO EXTEND INTEREST PAYMENT PERIOD. The Company has the right under
the Indenture to extend the interest payment period from time to time on the
Series A Subordinated Debentures to a period not exceeding 60 consecutive
months, and, as a consequence, monthly dividends on the Series A Preferred
Securities would be deferred (but would continue to accrue with interest
thereon) by Illinois Power Capital during any such extended interest payment
period. In the event that the Company exercises this right, the Company may not
declare or pay dividends on, or redeem, purchase or acquire, any of its capital
stock until the deferred interest on the Series A Subordinated Debentures is
paid in full. Prior to the termination of any such extension period, the Company
may further extend the interest payment period, provided that such extension
period together with all such previous and further extensions thereof may not
exceed 60 consecutive months. Upon the termination of any extension period and
the payment of all amounts then due, the Company may select a new extension
period, subject to the above requirements. The Company has no current intention
of extending the interest payment period on the Series A Subordinated Debentures
since it desires to continue the declaration and payment of dividends on its
capital stock. See "Description of the Series A Preferred Securities --
Dividends" and "Description of the Series A Subordinated Debentures -- Option to
Extend Interest Payment Period."
 
     Should an extended interest payment period occur, Illinois Power Capital
will continue to accrue income for United States federal income tax purposes
which will be allocated, but not distributed, to holders of record of Series A
Preferred Securities. As a result, such a holder will include such interest in
gross income for United States federal income tax purposes in advance of the
receipt of cash, and will not receive the cash from Illinois Power Capital
related to such income if such a holder disposes of his or her Series A
Preferred Securities prior to the record date for payment of dividends. See
"United States Taxation -- Potential Extension of Interest Payment Period."
 
     SPECIAL EVENT REDEMPTION OR DISTRIBUTION. Upon the occurrence of a Special
Event (as defined herein), the General Partner will elect to either (i) redeem
the Series A Preferred Securities in whole or (ii) dissolve Illinois Power
Capital and cause Series A Subordinated Debentures to be distributed to the
holders of the Series A Preferred Securities in liquidation of their interests
in Illinois Power Capital. The Series A Subordinated Debentures will initially
be issued at face value as a Global Security (as defined herein) and will be
limited in aggregate principal amount to approximately $  million, such amount
being the sum of the aggregate liquidation preference of the Series A Preferred
Securities and the General Partnership Payment (as defined herein). In the case
of a Tax Event (as defined herein), the General Partner may also elect to cause
the Series A Preferred Securities to remain outstanding. See "Description of the
Series A Preferred Securities -- Special Event Redemption or Distribution" and
"Description of the Series A Subordinated Debentures -- General."
 
     Under current United States federal income tax law, the distribution of
Series A Subordinated Debentures in connection with the dissolution of Illinois
Power Capital would not be a taxable event to
 
                                       S-3
<PAGE>   32
holders of the Series A Preferred Securities. Under a change in law, a change in
legal interpretation or the other circumstances giving rise to a Special Event,
however, the dissolution of Illinois Power Capital and the distribution of
Series A Subordinated Debentures in connection with the dissolution of Illinois
Power Capital could be a taxable event to holders of the Series A Preferred
Securities. In the judgment of tax counsel to the Company and Illinois Power
Capital, the series of events which would result in the recognition of taxable
gain by holders of the Series A Preferred Securities, by reason of a dissolution
of Illinois Power Capital in response to a Special Event, is unlikely to occur.
There can be no assurance in this regard, however. See "United States Taxation
- -- Receipt of Series A Subordinated Debentures Upon Dissolution of Illinois
Power Capital."
 
                             ILLINOIS POWER COMPANY
 
     The Company was incorporated under the laws of the State of Illinois on May
25, 1923. Effective May 27, 1994, the Company became a subsidiary of Illinova
Corporation, an exempt holding company under the Public Utility Holding Company
Act of 1935, as amended, pursuant to a merger in which each outstanding share of
the Company's Common Stock was converted into one share of common stock of
Illinova Corporation. The Company is engaged in the generation, transmission,
distribution and sale of electric energy and the distribution and sale of
natural gas in the State of Illinois. Its service area is a widely diversified
industrial and agricultural area comprising approximately 15,000 square miles in
northern, central and southern Illinois. Electric service is provided at retail
to 309 incorporated municipalities, adjacent suburban and rural areas and
numerous unincorporated municipalities having an aggregate population of
approximately 1,283,000. Gas service is provided to 257 incorporated
municipalities, adjacent suburban areas and numerous unincorporated
municipalities having an aggregate population of approximately 935,000. The
larger cities served include Decatur, East St. Louis (gas only), Champaign,
Danville, Belleville, Granite City, Bloomington (electric only), Galesburg,
Urbana and Normal (electric only). The executive offices of the Company are
located at 500 South 27th Street, Decatur, Illinois 62525, and the Company's
telephone number is (217) 424-6600.
 
                             ILLINOIS POWER CAPITAL
 
     Illinois Power Capital is a limited partnership formed under the Delaware
Revised Uniform Limited Partnership Act, as amended (the "Partnership Act").
Illinois Power Capital exists for the sole purpose of issuing its partner
interests, including the Series A Preferred Securities, and using the proceeds
thereof to purchase certain debt securities of the Company, including the Series
A Subordinated Debentures. The Company is the sole general partner (the "General
Partner") of Illinois Power Capital and will manage all of the business and
affairs of Illinois Power Capital. Holders of Series A Preferred Securities will
be limited partners of Illinois Power Capital. The Company, as the General
Partner of Illinois Power Capital, will make capital contributions to Illinois
Power Capital from time to time to the extent required so that the total
contributions made by the General Partner shall at all times be at least equal
to 3% of the total contributions made by all partners. The rights and
obligations of the General Partner and the limited partners of Illinois Power
Capital will be governed by the Partnership Act and by an Amended and Restated
Agreement of Limited Partnership of Illinois Power Capital (the "Partnership
Agreement") substantially in the form filed as an exhibit to the Registration
Statement of which this Prospectus Supplement and the accompanying Prospectus
form a part.
 
                                USE OF PROCEEDS
 
     The proceeds to be received by Illinois Power Capital from the sale of the
Series A Preferred Securities will be used to purchase Series A Subordinated
Debentures of the Company and will be applied by the Company to the payment or
provision for payment at maturity, the purchase or the redemption of outstanding
securities of the Company and for general corporate purposes.
 
                                       S-4
<PAGE>   33
 
                  SUMMARY FINANCIAL INFORMATION OF THE COMPANY
                (THOUSANDS EXCEPT PER SHARE AMOUNTS AND RATIOS)
 
<TABLE>
<CAPTION>
                                                                                               12 MONTHS
                                             YEAR ENDED DECEMBER 31,                             ENDED
                          --------------------------------------------------------------     JUNE 30, 1994
                             1989         1990         1991         1992       1993(A)     (UNAUDITED)(A)(B)
                          ----------   ----------   ----------   ----------   ----------   -----------------
<S>                       <C>          <C>             <C>           <C>          <C>             <C>
INCOME STATEMENT DATA:
  Operating Revenues..... $1,393,778     $1,469,480    $1,474,905    $1,479,449    $1,581,190      $ 1,628,094
  Net Income.............   (288,432)       (78,484)      109,244       122,088       (56,038)         (42,031)
  Preferred Dividend
    Requirements.........     37,365         36,839        30,866        28,854        26,123           24,283
  Net Income Applicable
    to Common Stock......   (325,797)      (115,323)       78,378        93,234       (82,161)         (66,314)
  Earnings Per Share of
    Common Stock.........      (4.34)         (1.53)         1.04          1.23         (1.08)           (0.91)
  Ratio of Earnings to
    Fixed Charges(c).....      (0.52)(d)       0.70(d)       1.85          2.02          0.80(d)          0.91(d)
  Ratio of Earnings to
    Combined Fixed
    Charges and Preferred
    Stock Dividend
    Requirements(c)......      (0.45)(e)       0.60(e)       1.48          1.61          0.70(e)          0.82(e)
</TABLE>
 
<TABLE>
<CAPTION>
                                                                                   AMOUNT     PERCENTAGE
                                                                                 ----------   ----------
<S>                                                                              <C>          <C>
CAPITALIZATION AT JUNE 30, 1994:
  Long-Term Debt...............................................................  $1,868,191       52.2%
  Preferred Stock (not subject to mandatory redemption)........................     303,705        8.5
  Preferred Stock (subject to mandatory redemption)............................      36,000        1.0
  Common Stock Equity..........................................................   1,368,858       38.3
                                                                                 ----------   ----------
      Total Capitalization.....................................................  $3,576,754      100.0%
                                                                                  =========   =========
</TABLE>
 
- ---------------
(a) Subsequent to the Company's merger with Illinova Corporation, net assets of
    Illinova Generating Company (formerly IP Group, Inc.) were transferred in
    the form of a dividend from the Company to Illinova Corporation. The income
    statement data contained herein has been restated to reflect the financial
    results of the Company's current operations.
 
(b) In the opinion of the Company, all adjustments, consisting only of normal
    recurring adjustments, necessary for a fair statement of the results for the
    unaudited twelve-month period ended June 30, 1994, have been made.
 
(c) Earnings used in the calculation of the ratio of earnings to fixed charges
    and the ratio of earnings to combined fixed charges and preferred stock
    dividend requirements include the allowance for funds used during
    construction and the deferred financing costs associated with the Company's
    Clinton Power Station, and are before deduction of income taxes and fixed
    charges. Fixed charges include interest on long-term debt, related
    amortization of debt discount, premium, and expense, other interest and that
    portion of rent expense which is estimated to be representative of the
    interest component. Preferred stock dividend requirements have been
    increased to an amount representing the pre-tax earnings required to cover
    such dividend requirements.
 
(d) The ratios of earnings to fixed charges for the twelve months ended June 30,
    1994 and for the years ended December 31, 1993, 1990 and 1989 of 0.93, 0.80,
    0.70 and (0.52), respectively, indicate that earnings were inadequate to
    cover fixed charges. The dollar amounts of the coverage deficiency for the
    twelve months ended June 30, 1994, and for the years ended 1993, 1990 and
    1989 were approximately $13 million, $37 million, $68 million and $375
    million, respectively. Excluding the loss on disallowed plant costs of $200
    million, net of income taxes, recorded in the
 
                                       S-5
<PAGE>   34
 
    third quarter of 1993, the ratio of earnings to fixed charges would have
    been 2.42 for the twelve months ended June 30, 1994 and 2.25 for the year
    ended 1993. Excluding the loss on disallowed plant costs of $137 million,
    net of income taxes, recorded in the fourth quarter of 1990, the ratio of
    earnings to fixed charges would have been 1.41 for the year ended 1990.
    Excluding the loss on disallowed plant costs of $346 million, net of income
    taxes, recorded in the first quarter of 1989, the ratio of earnings to fixed
    charges would have been 1.31 for the year ended 1989.
 
(e) The ratios of earnings to combined fixed charges and preferred stock
    dividend requirements for the twelve months ended June 30, 1994 and for the
    years ended December 31, 1993, 1990 and 1989 of 0.82, 0.70, 0.60 and (0.45),
    respectively, indicate that earnings were inadequate to cover combined fixed
    charges and preferred stock dividend requirements. The dollar amounts of the
    coverage deficiency for the twelve months ended June 30, 1994, and for the
    years ended 1993, 1990 and 1989 were approximately $38 million, $63 million,
    $105 million and $412 million, respectively. Excluding the loss on
    disallowed plant costs of $200 million, net of income taxes, recorded in the
    third quarter of 1993, the ratio of earnings to combined fixed charges and
    preferred stock dividend requirements would have been 1.98 for the twelve
    months ended June 30, 1994 and 1.83 for the year ended 1993. Excluding the
    loss on disallowed plant costs of $137 million, net of income taxes,
    recorded in the fourth quarter of 1990, the ratio of earnings to combined
    fixed charges and preferred stock dividend requirements would have been 1.09
    for the year ended 1990. Excluding the loss on disallowed plant costs of
    $346 million, net of income taxes, recorded in the first quarter of 1989,
    the ratio of earnings to combined fixed charges and preferred stock dividend
    requirements would have been 1.06 for the year ended 1989.
 
                                       S-6
<PAGE>   35
 
                DESCRIPTION OF THE SERIES A PREFERRED SECURITIES
 
GENERAL
 
     All of the partnership interests in Illinois Power Capital, other than the
Series A Preferred Securities offered hereby, are owned by the General Partner.
The Partnership Agreement authorizes and creates the Series A Preferred
Securities, which represent limited partner interests in Illinois Power Capital
(the "Preferred Securities"). Preferred Securities may be issued from time to
time in one or more series as described in the accompanying Prospectus. The
limited partner interests represented by the Series A Preferred Securities will
have a preference with respect to dividends and amounts payable on liquidation
over the General Partner's interest in Illinois Power Capital. The Partnership
Agreement does not permit the issuance of any Preferred Securities ranking, as
to participation in profits and dividends and in the assets of Illinois Power
Capital, senior or junior to the Series A Preferred Securities or the incurrence
of any indebtedness by Illinois Power Capital. The summary of certain terms and
provisions of the Series A Preferred Securities set forth below does not purport
to be complete and is subject to, and qualified in its entirety by reference to,
the Partnership Agreement and the Partnership Act.
 
DIVIDENDS
 
     Dividends on the Series A Preferred Securities will be cumulative, will
accrue from the date of initial issuance thereof and will be payable monthly in
arrears, on the last day of each calendar month of each year, commencing
           , 1994, when, as and if available and determined to be so payable by
the Company, as the General Partner, except as otherwise described below.
Dividends in arrears for more than one month will bear interest thereon at the
rate per annum equal to the dividend rate during the period of arrearage. The
term "dividends" as used herein includes any such interest payable unless
otherwise stated. The amount of dividends payable for any period will be
computed on the basis of a 360-day year of twelve 30-day months.
 
     The dividend rate will be adjusted quarterly. The rate for the initial
period from the date of initial issuance to            , 1994 will be   % per
annum, which is equivalent to $       per Series A Preferred Security per annum.
Thereafter, dividends on the Series A Preferred Securities will be payable at
the "Applicable Rate" (as defined below) from time to time in effect.
 
     The Company has the right under the Indenture to extend the interest
payment period from time to time on the Series A Subordinated Debentures to a
period not exceeding 60 consecutive months, and, as a consequence, monthly
dividends on the Series A Preferred Securities would be deferred (but would
continue to accrue with interest) by Illinois Power Capital during any such
extended interest payment period. In the event that the Company exercises this
right, the Company may not declare or pay dividends on, or redeem, purchase or
acquire, any of its capital stock. Prior to the termination of any such
extension period, the Company may further extend the interest payment period,
provided that such extension period together with all such previous and further
extensions thereof may not exceed 60 consecutive months. Upon the termination of
any extension period and the payment of all amounts then due, the Company may
select a new extension period, subject to the above requirements. See
"Description of the Series A Subordinated Debentures -- Interest" and "-- Option
to Extend Interest Payment Period."
 
   
     Dividends on the Series A Preferred Securities must be paid on the dates
payable to the extent that Illinois Power Capital has (i) funds legally
available for the payment of such dividends and (ii) cash on hand sufficient to
permit such payments. It is anticipated that Illinois Power Capital's earnings
available for distribution to the holders of the Series A Preferred Securities
will be limited to payments under the Series A Subordinated Debentures in which
Illinois Power Capital will invest the proceeds from the issuance and sale of
the Series A Preferred Securities and the General Partner's capital
contribution. See "Description of the Series A Subordinated Debentures." The
payment of dividends, out of moneys held by Illinois Power Capital, is
guaranteed by the Company as set forth under "Description of the Guarantee" in
the accompanying Prospectus.
    
 
                                       S-7
<PAGE>   36
 
   
     Dividends on the Series A Preferred Securities will be payable to the
holders thereof as they appear on the books and records of Illinois Power
Capital on the relevant record dates, which, as long as the Series A Preferred
Securities remain in book-entry-only form, will be one Business Day (as defined
below) prior to the relevant payment dates. Subject to any applicable laws and
regulations and the provisions of the Partnership Agreement, each such payment
will be made as described under "Book-Entry-Only Issuance -- The Depository
Trust Company" below. In the event the Series A Preferred Securities shall not
continue to remain in book-entry-only form, the General Partner shall have the
right to select relevant record dates which shall be more than one Business Day
prior to the relevant payment dates. In the event that any date on which
dividends are payable on the Series A Preferred Securities is not a Business
Day, then payment of the dividends payable on such date will be made on the next
succeeding day which is a Business Day (and without any interest or other
payment in respect of any such delay) except that, if such Business Day is in
the next succeeding calendar year, such payment shall be made on the immediately
preceding Business Day, in each case with the same force and effect as if made
on such date. A "Business Day" shall mean any day other than a day on which
banking institutions in The City of New York are authorized or required by law
to close.
    
 
     Except as provided below in this paragraph, the "Applicable Rate" for any
quarter (other than the initial period) will be equal to   % of the Effective
Rate (as defined below), but not less than   % per annum nor more than   % per
annum. The "Effective Rate" for any quarter will be equal to the highest of the
Treasury Bill Rate, the Ten Year Constant Maturity Rate and the Thirty Year
Constant Maturity Rate (each as defined below) for such quarter. The Applicable
Rate will be rounded to the nearest five hundredths of a percent. In the event
that Illinois Power Capital determines in good faith that for any reason:
 
          (i) any one of the Treasury Bill Rate, the Ten Year Constant Maturity
     Rate or the Thirty Year Constant Maturity Rate cannot be determined for any
     quarter, then the Effective Rate for such quarter will be equal to the
     higher of whichever two of such rates can be so determined;
 
          (ii) only one of the Treasury Bill Rate, the Ten Year Constant
     Maturity Rate and the Thirty Year Constant Maturity Rate can be determined
     for any quarter, then the Effective Rate for such quarter will be equal to
     whichever such rate can be so determined; or
 
          (iii) none of the Treasury Bill Rate, the Ten Year Constant Maturity
     Rate and the Thirty Year Constant Maturity Rate can be determined for any
     quarter, then the Effective Rate for the preceding quarter will be
     continued for such quarter.
 
     Except as described below in this paragraph, the "Treasury Bill Rate" for
each quarter will be the arithmetic average of the two most recent weekly per
annum secondary market discount rates (or the one weekly per annum secondary
market discount rate, if only one such rate is published during the relevant
Calendar Period (as defined below)) for three-month U.S. Treasury bills, as
published weekly by the Federal Reserve Board (as defined below) during the
Calendar Period immediately preceding the last ten calendar days preceding the
quarter for which the dividend rate on the Series A Preferred Securities is
being determined. In the event that the Federal Reserve Board does not publish
such a weekly per annum secondary market discount rate during any such Calendar
Period, then the Treasury Bill Rate for such quarter will be the arithmetic
average of the two most recent weekly per annum secondary market discount rates
(or the one weekly per annum secondary market discount rate, if only one such
rate is published during the relevant Calendar Period) for three-month U.S.
Treasury bills, as published weekly during such Calendar Period by any Federal
Reserve Bank or by any U.S. Government department or agency selected by Illinois
Power Capital. In the event that a per annum secondary market discount rate for
three-month U.S. Treasury bills is not published by the Federal Reserve Board or
by any Federal Reserve Bank or by any U.S. Government department or agency
during such Calendar Period, then the Treasury Bill Rate for such quarter will
be the arithmetic average of the two most recent weekly per annum secondary
market discount rates (or the one weekly per annum secondary market discount
rate, if only one such rate is published during the relevant Calendar Period)
for all of the U.S. Treasury bills then having remaining maturities of not less
than 80 nor more than 100 days, as published during
 
                                       S-8
<PAGE>   37
such Calendar Period by the Federal Reserve Board, or if the Federal Reserve
Board does not publish such rates, by any Federal Reserve Bank or by any U.S.
Government department or agency selected by Illinois Power Capital. In the event
that Illinois Power Capital determines in good faith that for any reason no such
U.S. Treasury bill rates are published as provided above during such Calendar
Period, then the Treasury Bill Rate for such quarter will be the arithmetic
average of the per annum secondary market discount rates based upon the closing
bids during such Calendar Period for each of the issues of marketable
non-interest-bearing U.S. Treasury securities with a remaining maturity of not
less than 80 nor more than 100 days from the date of each such quotation, as
chosen and quoted daily for each business day in New York City (or less
frequently if daily quotations are not generally available) to Illinois Power
Capital by at least three recognized dealers in U.S. Government securities
selected by Illinois Power Capital. In the event that Illinois Power Capital
determines in good faith that for any reason Illinois Power Capital cannot
determine the Treasury Bill Rate for any quarter as provided above in this
paragraph, the Treasury Bill Rate for such quarter will be the arithmetic
average of the per annum secondary market discount rate based upon the closing
bids during such Calendar Period for each of the issues of marketable
interest-bearing U.S. Treasury securities with a remaining maturity of not less
than 80 nor more than 100 days, as chosen and quoted daily for each business day
in New York City (or less frequently if daily quotations are not generally
available) to Illinois Power Capital by at least three recognized dealers in
U.S. Government securities selected by Illinois Power Capital.
 
     Except as described below in this paragraph, the "Ten Year Constant
Maturity Rate" for each quarter will be the arithmetic average of the two most
recent weekly per annum Ten Year Average Yields (as defined below) (or the one
weekly per annum Ten Year Average Yield, if only one such yield is published
during the relevant Calendar Period), as published weekly by the Federal Reserve
Board during the Calendar Period immediately preceding the last ten calendar
days preceding the quarter for which the dividend rate on the Series A Preferred
Securities is being determined. In the event that the Federal Reserve Board does
not publish such a weekly per annum Ten Year Average Yield during such Calendar
Period, then the Ten Year Constant Maturity Rate for such quarter will be the
arithmetic average of the two most recent weekly per annum Ten Year Average
Yields (or the one weekly per annum Ten Year Average Yield, if only one such
yield is published during the relevant Calendar Period), as published weekly
during such Calendar Period by any Federal Reserve Bank or by any U.S.
Government department or agency selected by Illinois Power Capital. In the event
that a per annum Ten Year Average Yield is not published by the Federal Reserve
Board or by the Federal Reserve Bank or by any U.S. Government department or
agency during such Calendar Period, then the Ten Year Constant Maturity Rate for
such quarter will be the arithmetic average of the two most recent weekly per
annum average yields to maturity (or the one weekly per annum average yield to
maturity, if only one such yield is published during the relevant Calendar
Period) for all of the actively traded marketable U.S. Treasury fixed interest
rate securities (other than Special Securities (as defined below)) then having
remaining maturities of not less than eight nor more than twelve years, as
published during such Calendar Period by the Federal Reserve Board or, if the
Federal Reserve Board does not publish such yields, by any Federal Reserve Bank
or by any U.S. Government department or agency selected by Illinois Power
Capital. In the event that Illinois Power Capital determines in good faith that
for any reason Illinois Power Capital cannot determine the Ten Year Constant
Maturity Rate for any quarter as provided above in this paragraph, then the Ten
Year Constant Maturity Rate for such quarter will be the arithmetic average of
the per annum average yields to maturity based upon the closing bids during such
Calendar Period for each of the issues of actively traded marketable U.S.
Treasury fixed interest rate securities (other than Special Securities) with a
final maturity date not less than eight or more than twelve years from the date
of each such quotation, as chosen and quoted daily for each business day in New
York City (or less frequently if daily quotations are not generally available)
to Illinois Power Capital by at least three recognized dealers in U.S.
Government securities selected by Illinois Power Capital.
 
     Except as described below in this paragraph, the "Thirty Year Constant
Maturity Rate" for each quarter will be the arithmetic average of the two most
recent weekly per annum Thirty Year Average Yields (as defined below) (or the
one weekly per annum Thirty Year Average Yield, if only one such yield is
published during the relevant Calendar Period), as published weekly by the
Federal Reserve Board
 
                                       S-9
<PAGE>   38
 
during the Calendar Period immediately preceding the last ten calendar days
preceding the quarter for which the dividend rate on the Series A Preferred
Securities is being determined. In the event that the Federal Reserve Board does
not publish such a weekly per annum Thirty Year Average Yield during such
Calendar Period, then the Thirty Year Constant Maturity Rate for such quarter
will be the arithmetic average of the two most recent weekly per annum Thirty
Year Average Yields (or the one weekly per annum Thirty Year Average Yield, if
only one such yield is published during the relevant Calendar Period), as
published weekly during such Calendar Period by any Federal Reserve Bank or by
any U.S. Government department or agency selected by Illinois Power Capital. In
the event that a per annum Thirty Year Average Yield is not published by the
Federal Reserve Board or by any Federal Reserve Bank or by any U.S. Government
department or agency during such Calendar Period, then the Thirty Year Constant
Maturity Rate for such quarter will be the arithmetic average of the two most
recent weekly per annum average yields to maturity (or the one weekly per annum
average yield to maturity, if only one such yield is published during the
relevant Calendar Period) for all of the actively traded marketable U.S.
Treasury fixed interest rate securities (other than Special Securities) then
having remaining maturities of not less than twenty-eight nor more than
thirty-two years, as published during such Calendar Period by the Federal
Reserve Board or, if the Federal Reserve Board does not publish such yields, by
any Federal Reserve Bank or by any U.S. Government department or agency selected
by Illinois Power Capital. In the event that Illinois Power Capital determines
in good faith that for any reason Illinois Power Capital cannot determine the
Thirty Year Constant Maturity Rate for any quarter as provided above in this
paragraph, then the Thirty Year Constant Maturity Rate for such quarter will be
the arithmetic average of the per annum average yields to maturity based upon
the closing bids during such Calendar Period for each of the issues of actively
traded marketable U.S. Treasury fixed interest rate securities (other than
Special Securities) with a final maturity date not less than twenty-eight nor
more than thirty-two years from the date of each such quotation, as chosen and
quoted daily for each business day in New York City (or less frequently if daily
quotations are not generally available) to Illinois Power Capital by at least
three recognized dealers in U.S. Government securities selected by Illinois
Power Capital.
 
     The Treasury Bill Rate, the Ten Year Constant Maturity Rate and the Thirty
Year Constant Maturity Rate will each be rounded to the nearest one hundredth of
a percent.
 
     The Applicable Rate with respect to each quarter (other than the initial
period) will be calculated as promptly as practicable by Illinois Power Capital
according to the appropriate method described above. Illinois Power Capital will
cause each Applicable Rate to be published in a newspaper of general circulation
in New York City before the commencement of the quarter to which it applies and
will cause notice of such Applicable Rate to be given to The Depository Trust
Company (the "Depository" or "DTC"), New York, New York, the securities
depository for the Series A Preferred Securities. See "Book-Entry-Only Issuance
- -- The Depository Trust Company" below.
 
     As used above, the term "Calendar Period" means a period of fourteen
calendar days; the term "Federal Reserve Board" means the Board of Governors of
the Federal Reserve System; the term "Special Securities" means securities which
can, at the option of the holder, be surrendered at face value in payment of any
federal estate tax or which provide tax benefits to the holder and are priced to
reflect such tax benefits or which were originally issued at a deep or
substantial discount; the term "Ten Year Average Yield" means the average yield
to maturity for actively traded marketable U.S. Treasury fixed interest rate
securities adjusted to constant maturities of ten years; and the term "Thirty
Year Average Yield" means the average yield to maturity for actively traded
marketable U.S. Treasury fixed interest rate securities adjusted to constant
maturities of thirty years.
 
CERTAIN RESTRICTIONS ON ILLINOIS POWER CAPITAL
 
     If dividends have not been paid in full on the Series A Preferred
Securities, Illinois Power Capital shall not:
 
   
          (i) pay, or set aside for payment, any dividends on any other series
     of Preferred Securities, unless the amount of any dividends paid or set
     aside on any other series of Preferred Securities is
    
 
                                      S-10
<PAGE>   39
 
   
     paid or set aside on such other series of Preferred Securities and the
     Series A Preferred Securities on a pro rata basis on the date such
     dividends are paid or set aside on such other series of Preferred
     Securities, so that
    
 
             (x) the aggregate amount of dividends paid on the Series A
        Preferred Securities bears to the aggregate amount of dividends paid on
        such other series of Preferred Securities the same ratio as
 
             (y) the aggregate of all accumulated and unpaid dividends in
        respect of the Series A Preferred Securities bears to the aggregate of
        all accumulated and unpaid dividends in respect of such other series of
        Preferred Securities; or
 
          (ii) redeem, purchase or otherwise acquire any other Preferred
     Securities;
 
until, in each case, such time as all accumulated and unpaid dividends on the
Series A Preferred Securities shall have been paid in full for all dividend
periods terminating on or prior to, in the case of clause (i), such payment and,
in the case of clause (ii), the date of such redemption, purchase or
acquisition.
 
     As of the date of this Prospectus Supplement, there are no series of
Preferred Securities outstanding.
 
OPTIONAL REDEMPTION
 
   
     The Series A Preferred Securities are redeemable, at the option of Illinois
Power Capital, in whole or in part, from time to time, on or after             ,
1999, upon not less than 30 nor more than 60 days' notice, at the Redemption
Price; provided, however, that prior to giving any such notice of redemption,
Illinois Power Capital shall have received from the Company a notice of
redemption of Series A Subordinated Debentures in an aggregate principal amount
equal to the aggregate liquidation preference of the Series A Preferred
Securities to be redeemed. In the event that fewer than all the outstanding
Series A Preferred Securities are to be so redeemed, the Series A Preferred
Securities to be redeemed will be selected as described under "Book-Entry-Only
Issuance -- The Depository Trust Company" below. If a partial redemption would
result in the delisting of the Series A Preferred Securities, Illinois Power
Capital may only redeem the Series A Preferred Securities in whole.
    
 
SPECIAL EVENT REDEMPTION OR DISTRIBUTION
 
   
     Subject to the next succeeding sentence, if a Tax Event or an Investment
Company Event (each, as defined below, and, each, a "Special Event") shall occur
and be continuing, the General Partner shall elect to either (i) cause Illinois
Power Capital to redeem the Series A Preferred Securities in whole (and not in
part), upon not less than 30 or more than 60 days' notice at the Redemption
Price within 90 days following the occurrence of such Special Event; provided,
that, if at the time there is available to the General Partner the opportunity
to eliminate, within such 90-day period, the Special Event by taking some
ministerial action, such as filing a form or making an election, or pursuing
some other similar reasonable measure, which has no adverse effect on Illinois
Power Capital or the General Partner, the General Partner will pursue such
measure in lieu of redemption, or (ii) dissolve Illinois Power Capital and,
after satisfaction of liabilities of creditors as required by the Partnership
Act, cause Series A Subordinated Debentures to be distributed to the holders of
the Series A Preferred Securities in liquidation of their interests in Illinois
Power Capital, within 90 days following the occurrence of such Special Event. In
the case of a Tax Event, the General Partner may also elect to cause the Series
A Preferred Securities to remain outstanding.
    
 
   
     In the event of a distribution of Series A Subordinated Debentures as
described in (ii) above, each holder of Series A Preferred Securities would
receive Series A Subordinated Debentures in an aggregate principal amount equal
to the aggregate liquidation preference of $25 per Series A Preferred Security
on the Series A Preferred Securities held by it, with such Series A Subordinated
Debentures bearing interest at a rate per annum equal to the dividend rate per
annum on such Series A Preferred Securities from the last date on which
dividends were paid.
    
 
                                      S-11
<PAGE>   40
 
     "Tax Event" means that the General Partner shall have obtained an opinion
of nationally recognized independent tax counsel experienced in such matters to
the effect that, as a result of (a) any amendment to, or change (including any
announced prospective change) in, the laws (or any regulations thereunder) of
the United States or any political subdivision or taxing authority thereof or
therein, (b) any amendment to or change in an interpretation or application of
such laws or regulations by any legislative body, court, governmental agency or
regulatory authority (including the enactment of any legislation and the
publication of any judicial decision or regulatory determination on or after
such date) or (c) any interpretation or pronouncement that provides for a
position with respect to such laws or regulations that differs from the
generally accepted position on        , 1994, which amendment or change is
effective or such interpretation or pronouncement is announced on or after
       , 1994, there is more than an insubstantial risk that (i) Illinois Power
Capital is subject to federal income tax with respect to interest received on
the Series A Subordinated Debentures, (ii) interest payable to Illinois Power
Capital on the Series A Subordinated Debentures will not be deductible for
federal income tax purposes or (iii) Illinois Power Capital is subject to more
than a de minimis amount of other taxes, duties or other governmental charges.
 
   
     "Investment Company Event" means the occurrence of a change in law or
regulation or a written change in interpretation or application of law or
regulation by any legislative body, court, governmental agency or regulatory
authority (a "Change in 1940 Act Law") to the effect that Illinois Power Capital
is or will be considered an "investment company" which is required to be
registered under the Investment Company Act of 1940, as amended (the "1940
Act"), which Change in 1940 Act Law becomes effective on or after        , 1994;
provided, that no Investment Company Event shall be deemed to have occurred if
the General Partner obtains a written opinion of nationally recognized
independent counsel experienced in practice under the 1940 Act to the effect
that the General Partner has successfully issued an additional or supplemental
irrevocable and unconditional guarantee (x) of accumulated and unpaid dividends
(whether or not determined to be paid out of moneys legally available therefor)
on the Series A Preferred Securities and (y) of the full amount of the
Liquidation Distribution (as hereinafter defined) on the Series A Preferred
Securities upon a liquidation of Illinois Power Capital (regardless of the
amount of assets of Illinois Power Capital otherwise available for distribution
in such liquidation) to avoid such Change in 1940 Act Law so that in the opinion
of such counsel, notwithstanding such Change in 1940 Act Law, Illinois Power
Capital is not required to be registered as an "investment company" within the
meaning of the 1940 Act.
    
 
     After the date fixed for any distribution of Series A Subordinated
Debentures, upon dissolution of Illinois Power Capital, (i) the Series A
Preferred Securities will no longer be deemed to be outstanding, (ii) The
Depository Trust Company (the "Depository" or "DTC") or its nominee, as the
record holder of the Series A Preferred Securities, will receive a registered
global certificate or certificates representing the Series A Subordinated
Debentures to be delivered upon such distribution and (iii) any certificates
representing Series A Preferred Securities not held by DTC or its nominee will
be deemed to represent Series A Subordinated Debentures having a principal
amount equal to the aggregate liquidation preference of such Series A Preferred
Securities until such certificates are presented to the Company or its agent for
transfer or reissuance.
 
MANDATORY REDEMPTION
 
   
     Upon the repayment of the Series A Subordinated Debentures at or earlier,
the proceeds from such repayment will be applied to redeem the Series A
Preferred Securities, in whole, upon not less than 30 nor more than 60 days'
notice, at the Redemption Price.
    
 
REDEMPTION PROCEDURES
 
   
     Illinois Power Capital may not redeem fewer than all of the outstanding
Series A Preferred Securities unless all accumulated and unpaid dividends have
been paid on all Series A Preferred Securities for all monthly dividend periods
terminating on or prior to the date of redemption.
    
 
                                      S-12
<PAGE>   41
 
     If Illinois Power Capital gives a notice of redemption in respect of Series
A Preferred Securities (which notice will be irrevocable), then, by 12:00 noon,
New York time, on the redemption date, Illinois Power Capital will irrevocably
deposit with DTC funds sufficient to pay the applicable Redemption Price and
will give DTC irrevocable instructions and authority to pay the Redemption Price
to the holders of the Series A Preferred Securities. See "Book-Entry-Only
Issuance -- The Depository Trust Company." If notice of redemption shall have
been given and funds deposited as required, then upon the date of such deposit,
all rights of holders of such Series A Preferred Securities so called for
redemption will cease, except the right of the holders of such Series A
Preferred Securities to receive the Redemption Price, but without interest on
such Redemption Price. In the event that any date fixed for redemption of Series
A Preferred Securities is not a Business Day, then payment of the Redemption
Price payable on such date will be made on the next succeeding day which is a
Business Day (and without any interest or other payment in respect of any such
delay), except that, if such Business Day falls in the next calendar year, such
payment will be made on the immediately preceding Business Day. In the event
that payment of the Redemption Price in respect of Series A Preferred Securities
is improperly withheld or refused and not paid either by Illinois Power Capital
or by the Company pursuant to the Guarantee described under "Description of the
Guarantee" in the accompanying Prospectus, dividends on such Series A Preferred
Securities will continue to accrue at the then applicable rate, from the
original redemption date to the date of payment, in which case the actual
payment date will be considered the date fixed for redemption for purposes of
calculating the Redemption Price.
 
     Subject to the foregoing and applicable law (including, without limitation,
United States federal securities laws), the Company or its subsidiaries may at
any time and from time to time purchase outstanding Series A Preferred
Securities by tender, in the open market or by private agreement.
 
LIQUIDATION DISTRIBUTION UPON DISSOLUTION
 
   
     In the event of any voluntary or involuntary dissolution, winding-up or
termination of Illinois Power Capital, the holders of the Series A Preferred
Securities at the time will be entitled to receive out of the assets of Illinois
Power Capital available for distribution to partners, after satisfaction of
liabilities of creditors as required by the Partnership Act, before any
distribution of assets is made to the General Partner, but together with the
holders of every other series of Preferred Securities outstanding, an amount
equal to, in the case of holders of Series A Preferred Securities, the aggregate
of the liquidation preference of $25 per Series A Preferred Security and all
accumulated and unpaid dividends thereon to the date of payment (the
"Liquidation Distribution"), unless, in connection with such dissolution,
winding-up or termination, Series A Subordinated Debentures in an aggregate
principal amount equal to $25 per Series A Preferred Security have been
distributed on a pro rata basis to the holders of the Series A Preferred
Securities.
    
 
     If, upon any such dissolution, the Liquidation Distribution can be paid
only in part because Illinois Power Capital has insufficient assets available to
pay in full the aggregate Liquidation Distribution and the aggregate maximum
liquidation distributions on any other series of Preferred Securities, then the
amounts payable directly by Illinois Power Capital on the Series A Preferred
Securities and on such other series of Preferred Securities shall be paid on a
pro rata basis, so that
 
          (i) the aggregate amount paid in respect of the Liquidation
     Distribution bears to the aggregate amount paid as liquidation
     distributions on the other series of Preferred Securities the same ratio as
 
          (ii) the aggregate Liquidation Distribution bears to the aggregate
     maximum liquidation distributions on the other series of Preferred
     Securities.
 
     Pursuant to the Partnership Agreement, Illinois Power Capital shall be
dissolved and its affairs shall be wound up: (i) upon the expiration of the term
of Illinois Power Capital on December 31, 2047, (ii) upon the bankruptcy or
withdrawal of the General Partner, (iii) upon the assignment by the General
Partner of its entire interest in Illinois Power Capital when the assignee is
not admitted to Illinois Power Capital as a general partner of Illinois Power
Capital in accordance with the Partnership Agreement, or the filing of a
certificate of dissolution or its equivalent with respect to the General
Partner, or the revocation
 
                                      S-13
<PAGE>   42
of the General Partner's charter and the expiration of 90 days after the date of
notice to the General Partner of revocation without a reinstatement of its
charter, or any other event occurs which causes the General Partner to cease to
be a general partner of Illinois Power Capital under the Partnership Act, unless
the business of Illinois Power Capital is continued in accordance with the
Partnership Act, (iv) in accordance with the provisions of the Series A
Preferred Securities, (v) upon the entry of a decree of a judicial dissolution
or (vi) upon the written consent of all partners of Illinois Power Capital.
 
MERGER, CONSOLIDATION OR AMALGAMATION OF ILLINOIS POWER CAPITAL
 
     Illinois Power Capital may not consolidate, amalgamate, merge with or into,
or be replaced by, or convey, transfer or lease its properties and assets
substantially as an entirety to any corporation or other body, except as
described below. Illinois Power Capital may, without the consent of the holders
of the Series A Preferred Securities, consolidate, amalgamate, merge with or
into, or be replaced by a limited partnership or a trust organized as such under
the laws of any state of the United States; provided, that (i) such successor
entity either (x) expressly assumes all of the obligations of Illinois Power
Capital under the Series A Preferred Securities or (y) substitutes for the
Series A Preferred Securities other securities having substantially the same
terms as the Series A Preferred Securities (the "Successor Securities") so long
as the Successor Securities rank, with respect to participation in the profits
and dividends or in the assets of the successor entity, at least as high as the
Series A Preferred Securities rank with respect to participation in the profits
and dividends or in the assets of Illinois Power Capital, (ii) the Company
expressly acknowledges such successor entity as the holder of the Series A
Subordinated Debentures, (iii) the Series A Preferred Securities or any
Successor Securities are listed, or any Successor Securities will be listed upon
notification of issuance, on any national securities exchange or other
organization on which the Series A Preferred Securities are then listed, (iv)
such merger, consolidation, amalgamation or replacement does not cause the
Series A Preferred Securities to be downgraded by any "nationally recognized
statistical rating organization," as that term is defined by the Commission for
purposes of Rule 436(g)(2) under the Securities Act, or cause any Successor
Securities to be rated lower than the Series A Preferred Securities immediately
prior to such merger, consolidation, amalgamation or replacement, (v) such
merger, consolidation, amalgamation or replacement does not adversely affect the
powers, preferences and other special rights of the holders of the Series A
Preferred Securities in any material respect, (vi) such successor entity has a
purpose substantially identical to that of Illinois Power Capital and (vii)
prior to such merger, consolidation, amalgamation or replacement, the Company
has received an opinion of nationally recognized independent counsel to Illinois
Power Capital experienced in such matters to the effect that (x) such successor
entity will be treated as a partnership for federal income tax purposes, (y)
following such merger, consolidation, amalgamation or replacement, the Company
and such successor entity will be in compliance with the 1940 Act without
registering thereunder as an investment company and (z) such merger,
consolidation, amalgamation or replacement will not adversely affect the limited
liability of the holders of the Series A Preferred Securities.
 
VOTING RIGHTS
 
     Except as provided below and under "Description of the Guarantee --
Amendments and Assignment" in the accompanying Prospectus and as otherwise
required by law and the Partnership Agreement, the holders of the Series A
Preferred Securities will have no voting rights.
 
     If (i) Illinois Power Capital fails to pay dividends in full on the Series
A Preferred Securities for 18 consecutive monthly dividend periods; (ii) an
Event of Default (as defined in the Indenture) occurs and is continuing on the
Series A Subordinated Debentures; or (iii) the Company is in default on any of
its payment or other obligations under the Guarantee (as described under
"Description of the Guarantee -- Certain Covenants of the Company" in the
accompanying Prospectus), then the holders of the Series A Preferred Securities,
together with the holders of any other series of Preferred Securities having the
right to vote for the appointment of a special representative of Illinois Power
Capital and the limited partners (a "Special Representative") in such event,
acting as a single class, will be entitled by the majority vote of
 
                                      S-14
<PAGE>   43
 
   
such holders to appoint and authorize a Special Representative to enforce
Illinois Power Capital's creditor rights under the Series A Subordinated
Debentures, to enforce the rights of the holders of the Series A Preferred
Securities under the Guarantee and to enforce the rights of the holders of the
Series A Preferred Securities to receive dividends on the Series A Preferred
Securities. The Special Representative shall not be admitted as a partner in
Illinois Power Capital or otherwise be deemed to be a partner in Illinois Power
Capital and shall have no liability for the debts, obligations or liabilities of
Illinois Power Capital. For purposes of determining whether Illinois Power
Capital has failed to pay dividends in full for 18 consecutive monthly dividend
periods, dividends shall be deemed to remain in arrears, notwithstanding any
payments in respect thereof, until full cumulative dividends have been or
contemporaneously are paid with respect to all monthly dividend periods
terminating on or prior to the date of payment of such full cumulative
dividends. Not later than 30 days after such right to appoint a Special
Representative arises, the General Partner will convene a meeting for the
purpose of appointing a Special Representative. If the General Partner fails to
convene such meeting within such 30-day period, the holders of 10% in
liquidation preference of the outstanding Preferred Securities will be entitled
to convene such meeting. The provisions of the Partnership Agreement relating to
the convening and conduct of the meetings of the partners will apply with
respect to any such meeting. Any Special Representative so appointed shall cease
to be a Special Representative of Illinois Power Capital and the limited
partners if Illinois Power Capital (or the Company pursuant to the Guarantee)
shall have paid in full all accumulated and unpaid dividends on the Preferred
Securities or such default or breach, as the case may be, shall have been cured,
and the General Partner shall continue the business of Illinois Power Capital
without dissolution. Notwithstanding the appointment of any such Special
Representative, the Company shall continue as General Partner and shall retain
all rights under the Indenture, including the right to extend the interest
payment period from time to time to a period not exceeding 60 consecutive months
as provided under "Description of the Series A Subordinated Debentures -- Option
to Extend Interest Payment Period."
    
 
     If any proposed amendment to the Partnership Agreement provides for, or the
General Partner otherwise proposes to effect, (i) any action which would
adversely affect the powers, preferences or special rights of the Series A
Preferred Securities, whether by way of amendment to the Partnership Agreement
or otherwise (including, without limitation, the authorization or issuance of
any limited partner interests in Illinois Power Capital ranking, as to
participation in the profits and dividends or in the assets of Illinois Power
Capital, senior to the Series A Preferred Securities), or (ii) the dissolution,
winding-up or termination of Illinois Power Capital, other than (x) in
connection with the distribution of Series A Subordinated Debentures upon the
occurrence of a Special Event or (y) as described under "Merger, Consolidation
or Amalgamation of Illinois Power Capital" above, then the holders of
outstanding Series A Preferred Securities will be entitled to vote on such
amendment or proposal of the General Partner (but not on any other amendment or
proposal) as a class with all other holders of series of Preferred Securities
similarly affected, and such amendment or proposal shall not be effective except
with the approval of the holders of 66 2/3% in liquidation preference of such
outstanding Preferred Securities having a right to vote on the matter; provided,
however, that no such approval shall be required if the dissolution, winding-up
or termination of Illinois Power Capital is proposed or initiated upon the
initiation of proceedings, or after proceedings have been initiated, for the
dissolution, winding-up, liquidation or termination of the Company.
 
     The rights attached to the Series A Preferred Securities will be deemed not
to be adversely affected by the creation or issue of, and no vote will be
required for the creation of, any further limited partner interests of Illinois
Power Capital ranking pari passu with the Series A Preferred Securities with
regard to participation in the profits and dividends or in the assets of
Illinois Power Capital. Holders of Series A Preferred Securities have no
preemptive rights.
 
     So long as any Series A Subordinated Debentures are held by Illinois Power
Capital, the General Partner shall not (i) direct the time, method and place of
conducting any proceeding for any remedy available to the Trustee, or executing
any trust or power conferred on the Trustee with respect to such series, (ii)
waive any past default which is waivable under Section 6.06 of the Indenture,
(iii) exercise any right to rescind or annul a declaration that the principal of
all the Series A Subordinated Debentures
 
                                      S-15
<PAGE>   44
shall be due and payable or (iv) consent to any amendment, modification or
termination of the Indenture, where such consent shall be required, without, in
each case, obtaining the prior approval of the holders of at least 66 2/3% in
liquidation preference of all series of Preferred Securities affected thereby,
acting as a single class; provided, however, that where a consent under the
Indenture would require the consent of each holder affected thereby, no such
consent shall be given by the General Partner without the prior consent of each
holder of all series of Preferred Securities affected thereby. The General
Partner shall not revoke any action previously authorized or approved by a vote
of any series of Preferred Securities. The General Partner shall notify all
holders of the Series A Preferred Securities of any notice of default received
from the Trustee with respect to the Series A Subordinated Debentures.
 
     Any required approval of holders of Series A Preferred Securities may be
given at a separate meeting of holders of Preferred Securities convened for such
purpose, at a meeting of all of the partners in Illinois Power Capital or
pursuant to written consent. Illinois Power Capital will cause a notice of any
meeting at which holders of Series A Preferred Securities are entitled to vote,
or of any matter upon which action by written consent of such holders is to be
taken, to be mailed to each holder of record of Series A Preferred Securities.
Each such notice will include a statement setting forth (i) the date of such
meeting or the date by which such action is to be taken, (ii) a description of
any resolution proposed for adoption at such meeting on which such holders are
entitled to vote or of such matter upon which written consent is sought and
(iii) instructions for the delivery of proxies or consents.
 
     No vote or consent of the holders of Series A Preferred Securities will be
required for Illinois Power Capital to redeem and cancel Series A Preferred
Securities in accordance with the Partnership Agreement.
 
     Notwithstanding that holders of Series A Preferred Securities are entitled
to vote or consent under any of the circumstances described above, any of the
Series A Preferred Securities and any other series of Preferred Securities that
are entitled to vote or consent with such Series A Preferred Securities as a
single class at such time that are owned by the Company or any entity owned more
than 50% by the Company, either directly or indirectly, shall not be entitled to
vote or consent and shall, for purposes of such vote or consent, be treated as
if they were not outstanding.
 
     Holders of the Series A Preferred Securities will have no rights to remove
or replace the General Partner.
 
BOOK-ENTRY-ONLY ISSUANCE -- THE DEPOSITORY TRUST COMPANY
 
     DTC will act as securities depository for the Series A Preferred
Securities. The Series A Preferred Securities will be issued only as
fully-registered securities registered in the name of Cede & Co. (DTC's
nominee). One or more fully-registered global Series A Preferred Security
certificates will be issued, representing in the aggregate the total number of
Series A Preferred Securities, and will be deposited with DTC.
 
     DTC is a limited-purpose trust company organized under the New York Banking
Law, a "banking organization" within the meaning of the New York Banking Law, a
member of the Federal Reserve System, a "clearing corporation" within the
meaning of the New York Uniform Commercial Code, and a "clearing agency"
registered pursuant to the provisions of Section 17A of the Securities Exchange
Act of 1934, as amended (the "Exchange Act"). DTC holds securities that its
participants ("Participants") deposit with DTC. DTC also facilitates the
settlement among Participants of securities transactions, such as transfers and
pledges, in deposited securities through electronic computerized book-entry
changes in Participants' accounts, thereby eliminating the need for physical
movement of securities certificates. Direct Participants include securities
brokers and dealers, banks, trust companies, clearing corporations, and certain
other organizations ("Direct Participants"). DTC is owned by a number of its
Direct Participants and by The New York Stock Exchange, Inc. (the "New York
Stock Exchange"), the American Stock Exchange, Inc., and the National
Association of Securities Dealers, Inc. Access to the DTC system is also
available to others such as securities brokers and dealers, banks and trust
companies that clear through or maintain a custodial relationship with a Direct
Participant, either directly or indirectly
 
                                      S-16
<PAGE>   45
("Indirect Participants"). The rules applicable to DTC and its Participants are
on file with the Commission.
 
     Purchases of Series A Preferred Securities within the DTC system must be
made by or through Direct Participants, which will receive a credit for the
Series A Preferred Securities on DTC's records. The ownership interest of each
actual purchaser of each Series A Preferred Security ("Beneficial Owner") is in
turn to be recorded on the Direct and Indirect Participants' records. Beneficial
Owners will not receive written confirmation from DTC of their purchases, but
Beneficial Owners are expected to receive written confirmations providing
details of the transactions, as well as periodic statements of their holdings,
from the Direct or Indirect Participants through which the Beneficial Owners
purchased Series A Preferred Securities. Transfers of ownership interests in the
Series A Preferred Securities are to be accomplished by entries made on the
books of Participants acting on behalf of Beneficial Owners. Beneficial Owners
will not receive certificates representing their ownership interests in Series A
Preferred Securities, except in the event that use of the book-entry system for
the Series A Preferred Securities is discontinued.
 
     DTC has no knowledge of the actual Beneficial Owners of the Series A
Preferred Securities; DTC's records reflect only the identity of the Direct
Participants to whose accounts such Series A Preferred Securities are credited,
which may or may not be the Beneficial Owners. The Participants will remain
responsible for keeping account of their holdings on behalf of their customers.
 
     Conveyance of notices and other communications by DTC to Direct
Participants, by Direct Participants to Indirect Participants, and by Direct
Participants and Indirect Participants to Beneficial Owners will be governed by
arrangements among them, subject to any statutory or regulatory requirements as
may be in effect from time to time.
 
     Redemption notices shall be sent to Cede & Co. If less than all of the
Series A Preferred Securities are being redeemed, DTC's practice is to determine
by lot the amount of the interest of each Direct Participant in such series to
be redeemed.
 
     Although voting with respect to the Series A Preferred Securities is
limited, in those cases where a vote is required, neither DTC nor Cede & Co.
will itself consent or vote with respect to Series A Preferred Securities. Under
its usual procedures, DTC would mail an Omnibus Proxy to Illinois Power Capital
as soon as possible after the record date. The Omnibus Proxy assigns Cede &
Co.'s consenting or voting rights to those Direct Participants to whose accounts
the Series A Preferred Securities are credited on the record date (identified in
a listing attached to the Omnibus Proxy).
 
     Dividend payments on the Series A Preferred Securities will be made to DTC.
DTC's practice is to credit Direct Participants' accounts on the relevant
payment date in accordance with their respective holdings shown on DTC's records
unless DTC has reason to believe that it will not receive payments on such
payment date. Payments by Participants to Beneficial Owners will be governed by
standing instructions and customary practices and will be the responsibility of
such Participant and not of DTC, Illinois Power Capital or the Company, subject
to any statutory or regulatory requirements as may be in effect from time to
time. Payment of dividends to DTC is the responsibility of Illinois Power
Capital, disbursement of such payments to Direct Participants is the
responsibility of DTC, and disbursement of such payments to the Beneficial
Owners is the responsibility of Direct and Indirect Participants.
 
     DTC may discontinue providing its services as securities depository with
respect to the Series A Preferred Securities at any time by giving reasonable
notice to Illinois Power Capital. Under such circumstances, in the event that a
successor securities depository is not obtained, Series A Preferred Security
certificates are required to be printed and delivered. Additionally, Illinois
Power Capital (with the consent of the Company) may decide to discontinue use of
the system of book-entry transfers through DTC (or a successor depository). In
that event, certificates for the Series A Preferred Securities will be printed
and delivered. In each of the above circumstances, the General Partner will
appoint a paying agent with respect to the Series A Preferred Securities.
 
                                      S-17
<PAGE>   46
 
     The information in this section concerning DTC and DTC's book-entry system
has been obtained from sources that Illinois Power Capital believes to be
reliable, but Illinois Power Capital takes no responsibility for the accuracy
thereof.
 
REGISTRAR AND TRANSFER AGENT
 
     The Company will act as registrar and transfer agent for the Series A
Preferred Securities.
 
   
     Registration of transfers of Series A Preferred Securities will be effected
without charge by or on behalf of Illinois Power Capital, but upon payment (with
the giving of such indemnity as Illinois Power Capital or the Company may
require) in respect of any tax or other governmental charges which may be
imposed in relation to it.
    
 
     Illinois Power Capital will not be required to register or cause to be
registered the transfer of Series A Preferred Securities after such Series A
Preferred Securities have been called for redemption.
 
MISCELLANEOUS
 
     Application will be made to list the Series A Preferred Securities on the
New York Stock Exchange.
 
   
     The General Partner is authorized and directed to conduct its affairs and
to operate Illinois Power Capital in such a way that (i) Illinois Power Capital
will not be deemed to be an "investment company" required to be registered under
the 1940 Act, (ii) Illinois Power Capital will be taxed as a partnership for
federal income tax purposes and (iii) the Series A Subordinated Debentures will
be treated as indebtedness of the Company for federal income tax purposes. In
this connection, the General Partner is authorized to take any action, not
inconsistent with applicable law, the certificate of limited partnership or the
Partnership Agreement, that the General Partner determines in its discretion to
be necessary or desirable for such purposes, as long as such action does not
adversely affect the interests of the holders of the Series A Preferred
Securities.
    
 
                                      S-18
<PAGE>   47
 
              DESCRIPTION OF THE SERIES A SUBORDINATED DEBENTURES
 
     Set forth below is a description of the specific terms of the Series A
Subordinated Debentures in which Illinois Power Capital will invest with the
proceeds of the issuance and sale of (i) the Series A Preferred Securities and
(ii) the General Partner's capital contribution with respect to the Series A
Preferred Securities (the "General Partnership Payment"). This description
supplements the description of the general terms and provisions of the
Subordinated Debentures set forth in the accompanying Prospectus under the
caption "Description of the Subordinated Debentures." The following description
does not purport to be complete and is qualified in its entirety by reference to
the description in the accompanying Prospectus and the Indenture between the
Company and The First National Bank of Chicago, as Trustee, as supplemented by a
First Supplemental Indenture (the Indenture, as so supplemented, is hereinafter
referred to as the "Indenture").
 
     Under certain circumstances involving the dissolution of Illinois Power
Capital following the occurrence of a Special Event, Series A Subordinated
Debentures may be distributed to the holders of the Series A Preferred
Securities in liquidation of Illinois Power Capital. See "Description of the
Series A Preferred Securities -- Special Event Redemption or Distribution."
 
GENERAL
 
     The Series A Subordinated Debentures will be issued as a series of
Subordinated Debentures under the Indenture. The Series A Subordinated
Debentures will be limited in aggregate principal amount to approximately
$      million, such amount being the sum of the aggregate liquidation
preference of the Series A Preferred Securities and the General Partnership
Payment.
 
     The entire principal amount of the Series A Subordinated Debentures will
become due and payable, together with any accrued and unpaid interest thereon,
including Additional Interest (as hereinafter defined), if any, on
               , 2043.
 
     The Series A Subordinated Debentures if distributed to holders of Series A
Preferred Securities upon the dissolution of Illinois Power Capital will
initially be so issued as a Global Security (as defined below). As described
herein, under certain limited circumstances Series A Subordinated Debentures may
be issued in certificated form in exchange for a Global Security. See
"Book-Entry and Settlement" below. In the event that Series A Subordinated
Debentures are issued in certificated form, such Series A Subordinated
Debentures will be in denominations of $25 and integral multiples thereof and
may be transferred or exchanged at the offices described below.
 
     Payments on Series A Subordinated Debentures issued as a Global Security
will be made to DTC, as the depository for the Series A Subordinated Debentures.
In the event Series A Subordinated Debentures are issued in certificated form,
principal and interest will be payable, the transfer of the Series A
Subordinated Debentures will be registrable and the Series A Subordinated
Debentures will be exchangeable for Series A Subordinated Debentures of other
denominations of a like aggregate principal amount at the corporate trust office
of the Trustee in The City of New York; provided, that payment of interest may
be made at the option of the Company by check mailed to the address of the
persons entitled thereto.
 
     If the Series A Subordinated Debentures are distributed to the holders of
Series A Preferred Securities upon the dissolution of Illinois Power Capital,
the Company will use its best efforts to list the Series A Subordinated
Debentures on the New York Stock Exchange or on such other exchange as the
Series A Preferred Securities are then listed and traded on the same part of any
such exchange.
 
MANDATORY PREPAYMENT
 
     If Illinois Power Capital redeems Series A Preferred Securities in
accordance with the terms thereof, the Series A Subordinated Debentures will
become due and payable in a principal amount equal to the aggregate liquidation
preference of the Series A Preferred Securities so redeemed, together with all
accrued and unpaid interest, including Additional Interest, if any. Any payment
pursuant to this provision
 
                                      S-19
<PAGE>   48
 
shall be made prior to 12:00 noon, New York time, on the date of such redemption
or at such other time on such earlier date as the parties thereto shall agree.
 
OPTIONAL REDEMPTION
 
   
     The Company shall have the right to redeem the Series A Subordinated
Debentures, in whole or in part, from time to time, on or after                ,
1999, upon not less than 30 nor more than 60 days' notice, at a redemption price
equal to 100% of the principal amount to be redeemed plus any accrued and unpaid
interest, including Additional Interest, if any, to the redemption date.
    
 
INTEREST
 
     Each Series A Subordinated Debenture shall bear interest at an interest
rate which will be adjusted quarterly. The rate for the initial period from the
date of initial issuance to            , 1994 will be   % per annum. Thereafter,
interest on the Series A Subordinated Debentures will be payable at the
"Applicable Rate" in effect from time to time. The Applicable Rate for any
quarter will be equal to   % of the highest of the "Treasury Bill Rate," the
"Ten Year Constant Maturity Rate" and the "Thirty Year Constant Maturity Rate"
determined in advance of such quarter. The Applicable Rate for any quarter will
not be less   % per annum nor greater than   % per annum. The "Treasury Bill
Rate," the "Ten Year Constant Maturity Rate" and the "Thirty Year Constant
Maturity Rate" with respect to any quarter shall be determined by Illinois Power
Capital in the same manner as, and consistent with its determinations with
respect to, quarters for the purposes of dividends payable on the Series A
Preferred Securities. See "Description of the Series A Preferred Securities --
Dividends."
 
     Such interest is payable monthly in arrears on the last day of each
calendar month of each year (each, an "Interest Payment Date"), commencing
           , 1994, to the person in whose name such Series A Subordinated
Debenture is registered, subject to certain exceptions, at the close of business
on the Business Day next preceding such Interest Payment Date. In the event the
Series A Subordinated Debentures shall not continue to remain in book-entry-only
form, the Company shall have the right to select record dates which shall be
more than one Business Day prior to the Interest Payment Date.
 
     The amount of interest payable for any period will be computed on the basis
of a 360-day year of twelve 30-day months and for any period shorter than a full
month, on the basis of actual days elapsed in such period. In the event that any
date on which interest is payable on the Series A Subordinated Debentures is not
a Business Day, then payment of the interest payable on such date will be made
on the next succeeding day which is a Business Day (and without any interest or
other payment in respect of any such delay), except that, if such Business Day
is in the next succeeding calendar year, such payment shall be made on the
immediately preceding Business Day, in each case with the same force and effect
as if made on such date.
 
OPTION TO EXTEND INTEREST PAYMENT PERIOD
 
     So long as the Company is not in default in the payment of interest on any
series of Subordinated Debentures issued under the Indenture, the Company shall
have the right at any time during the term of the Series A Subordinated
Debentures to extend the interest payment period from time to time to a period
not exceeding 60 consecutive months (the "Extension Period"), at the end of
which Extension Period the Company shall pay all interest then accrued and
unpaid (together with interest thereon at the rate specified for the Series A
Subordinated Debentures to the extent permitted by applicable law); provided,
that, during any such Extension Period, the Company shall not declare or pay any
dividend on, or redeem, purchase, acquire or make a liquidation payment with
respect to, any of its capital stock or make any guarantee payments with respect
to the foregoing (other than payments on the Guarantee); and provided further
that any such extended interest payment period may only be selected with respect
to the Series A Subordinated Debentures if an extended interest payment period
of identical length is simultaneously selected for all Subordinated Debentures
then outstanding under the Indenture. Prior to the termination of any such
 
                                      S-20
<PAGE>   49
 
Extension Period, the Company may further extend the interest payment period,
provided that such Extension Period together with all such previous and further
extensions thereof may not exceed 60 consecutive months. Upon the termination of
any Extension Period and the payment of all amounts then due, the Company may
select a new Extension Period, subject to the above requirements. No interest
shall be due and payable during an Extension Period, except at the end thereof.
 
     If Illinois Power Capital shall be the sole holder of the Series A
Subordinated Debentures, the Company shall give Illinois Power Capital notice of
its selection of such Extension Period one Business Day prior to the earlier of
(i) the next succeeding date on which the dividends on the Series A Preferred
Securities are payable or (ii) the date Illinois Power Capital is required to
give notice to the New York Stock Exchange or other applicable self-regulatory
organization or to holders of the Series A Preferred Securities of the record
date or the date such dividend is payable, but in any event not less than one
Business Day prior to such record date. The Company shall cause Illinois Power
Capital to give notice of the Company's selection of such Extension Period to
the holders of the Series A Preferred Securities. If Illinois Power Capital
shall not be the sole holder of the Series A Subordinated Debentures, the
Company shall give the holders of the Series A Subordinated Debentures notice of
its selection of such Extension Period ten Business Days prior to the earlier of
(i) the next succeeding Interest Payment Date or (ii) the date the Company is
required to give notice to the New York Stock Exchange or other applicable self-
regulatory organization, or to holders of the Series A Subordinated Debentures,
of the record or payment date of such related interest payment, but in any event
not less than two Business Days prior to such record date.
 
ADDITIONAL INTEREST
 
     So long as any Subordinated Debentures remain outstanding, if at any time
Illinois Power Capital shall be required to pay any interest on dividends in
arrears in respect of the Series A Preferred Securities pursuant to the terms
thereof, then the Company will pay as interest to Illinois Power Capital as the
holder of the Series A Subordinated Debentures ("Additional Interest") an amount
equal to such interest on dividends in arrears. In addition, if Illinois Power
Capital would be required to pay any taxes, duties, assessments or governmental
charges of whatever nature (other than withholding taxes) imposed by the United
States, or any other taxing authority, then, in any such case, the Company also
will pay as Additional Interest such amounts as shall be required so that the
net amounts received and retained by Illinois Power Capital after paying any
such taxes, duties, assessments or governmental charges will be not less than
the amounts Illinois Power Capital would have received had no such taxes,
duties, assessments or governmental charges been imposed.
 
SET-OFF
 
     Notwithstanding anything to the contrary in the Indenture, the Company
shall have the right to set-off any payment it is otherwise required to make
thereunder with and to the extent the Company has theretofore made, or is
concurrently on the date of such payment making, a payment under the Guarantee.
 
EVENTS OF DEFAULT
 
   
     In the case any Event of Default (as defined in the Indenture) shall occur
and be continuing, Illinois Power Capital will have the right to declare the
principal of and the interest on the Series A Subordinated Debentures (including
any Additional Interest) and any other amounts payable under the Indenture to be
forthwith due and payable and to enforce its other rights as a creditor with
respect to the Series A Subordinated Debentures. See "Enforcement of Certain
Rights by Special Representative" below for a discussion of certain rights
available to holders of the Series A Preferred Securities upon the occurrence of
an Event of Default.
    
 
                                      S-21
<PAGE>   50
 
ENFORCEMENT OF CERTAIN RIGHTS BY SPECIAL REPRESENTATIVE
 
     If (i) Illinois Power Capital fails to pay dividends in full on the Series
A Preferred Securities for 18 consecutive monthly dividend periods; (ii) an
Event of Default occurs and is continuing on the Series A Subordinated
Debentures; or (iii) the Company is in default on any of its payment or other
obligations under the Guarantee, under the terms of the Series A Preferred
Securities, the holders of outstanding Series A Preferred Securities will have
the rights referred to under "Description of the Series A Preferred Securities
- -- Voting Rights," including the right to appoint a Special Representative,
which Special Representative shall be authorized to exercise Illinois Power
Capital's right to accelerate the principal amount of the Series A Subordinated
Debentures and to enforce Illinois Power Capital's other creditor rights under
the Series A Subordinated Debentures. Notwithstanding the appointment of any
such Special Representative, the Company shall continue as General Partner and
shall retain all rights under the Indenture, including the right to extend the
interest payment period from time to time to a period not exceeding 60
consecutive months.
 
BOOK-ENTRY AND SETTLEMENT
 
     If distributed to holders of Series A Preferred Securities in connection
with the dissolution of Illinois Power Capital as a result of the occurrence of
a Special Event, the Series A Subordinated Debentures will be issued in the form
of one or more global certificates (each, a "Global Security") registered in the
name of a nominee of DTC. Except under the limited circumstances described
below, Series A Subordinated Debentures represented by the Global Security will
not be exchangeable for, and will not otherwise be issuable as, Series A
Subordinated Debentures in definitive form. The Global Securities described
above may not be transferred except by DTC to a nominee of DTC or by a nominee
of DTC to DTC or another nominee of DTC or to a successor depository or its
nominee.
 
     The laws of some jurisdictions require that certain purchasers of
securities take physical delivery of such securities in definitive form. Such
laws may impair the ability to transfer beneficial interests in such a Global
Security.
 
     Except as provided below, owners of beneficial interests in such a Global
Security will not be entitled to receive physical delivery of Series A
Subordinated Debentures in definitive form and will not be considered the
Holders (as defined in the Indenture) thereof for any purpose under the
Indenture, and no Global Security representing Series A Subordinated Debentures
shall be exchangeable, except for another Global Security of like denomination
and tenor to be registered in the name of DTC or its nominee or to a successor
depository or its nominee. Accordingly, each beneficial owner must rely on the
procedures of DTC and, if such person is not a Participant, on the procedures of
the Participant through which such person owns its interest, to exercise any
rights of a Holder under the Indenture.
 
   
     THE DEPOSITORY. DTC will act as security depository for the Series A
Subordinated Debentures. For a description of DTC and the specific terms of the
depository arrangements, see "Description of the Series A Preferred Securities
- -- Book-Entry-Only Issuance -- The Depository Trust Company." As of the date of
this Prospectus Supplement, the description therein of DTC's book-entry system
and DTC's practices as they relate to purchases, transfers, notices and payments
with respect to the Series A Preferred Securities applies in all material
respects to any debt obligations represented by one or more Global Securities
held by DTC.
    
 
     Neither the Company, the Trustee, any paying agent nor any other agent of
the Company or the Trustee will have any responsibility or liability for any
aspect of the records relating to or payments made on account of beneficial
ownership interests in a Global Security for such Series A Subordinated
Debentures or for maintaining, supervising or reviewing any records relating to
such beneficial ownership interests.
 
     DISCONTINUANCE OF THE DEPOSITORY'S SERVICES. A Global Security shall be
exchangeable for Series A Subordinated Debentures registered in the names of
persons other than DTC or its nominee only if (i) DTC notifies the Company that
it is unwilling or unable to continue as a depository for such Global
 
                                      S-22
<PAGE>   51
Security and no successor depository shall have been appointed, or if any time
DTC ceases to be a clearing agency registered under the Exchange Act at a time
when DTC is required to be so registered to act as such depository, (ii) the
Company in its sole discretion determines that such Global Security shall be so
exchangeable or (iii) there shall have occurred an Event of Default with respect
to such Series A Subordinated Debentures. Any Global Security that is
exchangeable pursuant to the preceding sentence shall be exchangeable for Series
A Subordinated Debentures registered in such names as the Depository shall
direct. It is expected that such instructions will be based upon directions
received by the Depository from its Participants with respect to ownership of
beneficial interests in such Global Security.
 
MISCELLANEOUS
 
     For restrictions on certain actions of the General Partner with respect to
Series A Subordinated Debentures held by Illinois Power Capital, see
"Description of the Series A Preferred Securities -- Voting Rights."
 
                        EFFECT OF OBLIGATIONS UNDER THE
               SERIES A SUBORDINATED DEBENTURES AND THE GUARANTEE
 
     As set forth in the Partnership Agreement, the sole purpose of Illinois
Power Capital is to issue partner interests in Illinois Power Capital,
including, without limitation, the Series A Preferred Securities, and to use the
proceeds thereof to purchase the Series A Subordinated Debentures or other
similar debt securities of the Company.
 
     As long as payments of interest and other payments are made when due on the
Series A Subordinated Debentures, such payments will be sufficient to cover
dividends and payments due on the Series A Preferred Securities primarily
because (i) the aggregate principal amount of Series A Subordinated Debentures
will be equal to the sum of the aggregate liquidation preference of the Series A
Preferred Securities and the General Partnership Payment; (ii) the interest rate
and interest and other payment dates on the Series A Subordinated Debentures
will match the dividend rate and dividend and other payment dates for the Series
A Preferred Securities; (iii) the Partnership Agreement provides that the
Company, as General Partner, shall pay for all, and Illinois Power Capital shall
not be obligated to pay, directly or indirectly, for any, costs and expenses of
Illinois Power Capital; and (iv) the Partnership Agreement further provides that
the General Partner shall not cause or permit Illinois Power Capital to, among
other things, engage in any activity that is not consistent with the purposes of
Illinois Power Capital.
 
     If the Company fails to make interest or other payments on the Series A
Subordinated Debentures when due, the Partnership Agreement provides a mechanism
whereby the holders of the Series A Preferred Securities may enforce the rights
of Illinois Power Capital under the Series A Subordinated Debentures through the
appointment of a Special Representative. Payments of dividends and other
payments due on the Series A Preferred Securities out of moneys held by Illinois
Power Capital are guaranteed by the Company to the extent set forth under
"Description of the Guarantee" in the accompanying Prospectus. The Partnership
Agreement also provides, and the Company, under the Guarantee, acknowledges,
that a Special Representative may be appointed to enforce the Guarantee if the
Company is in default on any of its payment obligations under the Guarantee. In
addition, if the General Partner or the Special Representative fails to enforce
the Guarantee, a holder of a Series A Preferred Security may institute a legal
proceeding directly against the Company to enforce its rights under the
Guarantee without first instituting a legal proceeding against Illinois Power
Capital or any other person or entity.
 
     The Company and Illinois Power Capital believe that the above mechanisms
and obligations, taken together, are substantially equivalent to a full and
unconditional guarantee by the Company of payments due on the Series A Preferred
Securities.
 
                                      S-23
<PAGE>   52
 
                             UNITED STATES TAXATION
 
GENERAL
 
     This section is a summary of certain United States federal income tax
considerations that may be relevant to prospective purchasers of Series A
Preferred Securities and represents the opinion of Schiff Hardin & Waite, tax
counsel to the Company and Illinois Power Capital, insofar as it relates to
matters of law and legal conclusions. This section is based upon current
provisions of the Internal Revenue Code of 1986, as amended (the "Code"),
existing and proposed regulations thereunder and current administrative rulings
and court decisions, all of which are subject to change. Subsequent changes may
cause tax consequences to vary substantially from the consequences described
below.
 
     No attempt has been made in the following discussion to comment on all
United States federal income tax matters affecting purchasers of Series A
Preferred Securities. Moreover, the discussion focuses on holders of Series A
Preferred Securities who are individual citizens or residents of the United
States and has only limited application to corporations, estates, trusts or
non-resident aliens. Accordingly, each prospective purchaser of Series A
Preferred Securities should consult, and should depend on, his or her own tax
advisor in analyzing the federal, state, local and foreign tax consequences of
the purchase, ownership or disposition of Series A Preferred Securities.
 
INCOME FROM SERIES A PREFERRED SECURITIES
 
     In the opinion of Schiff Hardin & Waite, Illinois Power Capital will be
treated as a partnership for federal income tax purposes. Accordingly, each
holder of Series A Preferred Securities (a "Preferred Securityholder") will be
required to include in gross income such holder's distributive share of the net
income of Illinois Power Capital. Such income will not exceed dividends received
on such Series A Preferred Securities, except in limited circumstances as
described below under "Potential Extension of Interest Payment Period." No
portion of such income will be eligible for the dividends received deduction.
 
DISPOSITION OF SERIES A PREFERRED SECURITIES
 
     Gain or loss will be recognized on a sale (including a redemption for cash)
of Series A Preferred Securities in an amount equal to the difference between
the amount realized and the Preferred Securityholder's tax basis for the Series
A Preferred Securities sold. Gain or loss recognized by a Preferred
Securityholder on the sale or exchange of a Series A Preferred Security held for
more than one year will generally be taxable as long-term capital gain or loss.
 
RECEIPT OF SERIES A SUBORDINATED DEBENTURES UPON DISSOLUTION OF ILLINOIS POWER
CAPITAL
 
     Under certain circumstances, as described under the caption "Description of
the Series A Preferred Securities -- Special Event Redemption or Distribution,"
Series A Subordinated Debentures may be distributed to the holders of the Series
A Preferred Securities in connection with the dissolution of Illinois Power
Capital. Under current United States federal income tax law, such a distribution
would be treated as a non-taxable exchange to each holder of Series A Preferred
Securities and would result in the holder of Series A Preferred Securities
receiving an aggregate tax basis in the Series A Subordinated Debentures equal
to such holder's aggregate tax basis in its Series A Preferred Securities. A
holder's holding period in the Series A Subordinated Debentures so received in
connection with the dissolution of Illinois Power Capital would include the
period for which the Series A Preferred Securities were held by such holder.
Under a change in law, a change in legal interpretation or the other
circumstances giving rise to a Special Event, however, the dissolution of
Illinois Power Capital and the distribution of Series A Subordinated Debentures
in connection with the dissolution of Illinois Power Capital could be a taxable
event to holders of the Series A Preferred Securities. In the judgment of tax
counsel to the Company and Illinois Power Capital, the series of events which
would result in the recognition of taxable gain by holders of the Series A
Preferred Securities, by reason of a dissolution of Illinois Power Capital in
response to a Special Event, is unlikely to occur. There can be no assurance in
this regard, however.
 
                                      S-24
<PAGE>   53
 
ILLINOIS POWER CAPITAL INFORMATION RETURNS AND AUDIT PROCEDURES
 
     The General Partner will furnish each Series A Preferred Securityholder
with a Schedule K-1 each year setting forth such Preferred Securityholder's
allocable share of income for the prior calendar year. The General Partner is
required to furnish such schedules as soon as practicable following the end of
the year, but in any event prior to March 31.
 
   
     Any person who holds Series A Preferred Securities as a nominee for another
person is required to furnish to Illinois Power Capital (a) the name, address
and taxpayer identification number of the beneficial owner and the nominee; (b)
information as to whether the beneficial owner is (i) a person that is not a
United States person, (ii) a foreign government, an international organization
or any wholly-owned agency or instrumentality of either of the foregoing, or
(iii) a tax-exempt entity; (c) the amount and description of Series A Preferred
Securities held, acquired or transferred for the beneficial owner; and (d)
certain information including the dates of acquisitions and transfers, means of
acquisitions and transfers, and acquisition cost for purchases, as well as the
amount of net proceeds from sales. Brokers and financial institutions are
required to furnish additional information, including whether they are United
States persons and certain information on Series A Preferred Securities they
acquire, hold or transfer for their own accounts. A penalty of $50 per failure
(up to a maximum of $100,000 per calendar year) is imposed by the Code for
failure to report such information to Illinois Power Capital. The nominee is
required to supply the beneficial owners of Series A Preferred Securities with
the information furnished to Illinois Power Capital.
    
 
POTENTIAL EXTENSION OF INTEREST PAYMENT PERIOD
 
     Under the terms of the Indenture, the Company has the right to extend from
time to time the interest payment period on the Series A Subordinated Debentures
to a period not exceeding 60 consecutive months. In the event that the Company
exercises this right, the Company may not, among other things, declare dividends
on any of its capital stock. The Company has no current intention of extending
the interest payment period on the Series A Subordinated Debentures since it
desires to continue the declaration and payment of dividends on its capital
stock. In the event that the interest payment period is extended, Illinois Power
Capital will continue to accrue income equal to the amount of the interest
payment due at the end of the Extension Period pursuant to the Code and Treasury
Regulation provisions applicable to original issue discount.
 
     Accrued income will be allocated, but not distributed, to holders of record
on the Business Day preceding the last day of each calendar month. As a result,
holders of record during an Extension Period will include interest in gross
income in advance of the receipt of cash, and any such holders who dispose of
Series A Preferred Securities prior to the record date for the payment of
dividends following such Extension Period will include interest in gross income
but will not receive any cash related thereto from Illinois Power Capital. The
tax basis of a Series A Preferred Security will be increased by the amount of
any interest that is included in income without a receipt of cash, and will be
decreased when and if such cash is subsequently received from Illinois Power
Capital. The subsequent receipt of such cash will not be includible in gross
income.
 
UNITED STATES ALIEN HOLDERS
 
     For purposes of this discussion, a "United States Alien Holder" is any
holder who or which is (i) a nonresident alien individual or (ii) a foreign
corporation, partnership, estate or trust, in either case not subject to United
States federal income tax on a net income basis in respect of a Series A
Preferred Security.
 
     Under current United States federal income tax law, subject to the
discussion below with respect to backup withholding, and assuming satisfaction
by the Company of its withholding tax obligations, if any:
 
          (i) Payments by Illinois Power Capital or any of its paying agents to
     any holder of a Series A Preferred Security who or which is a United States
     Alien Holder will not be subject to United States
 
                                      S-25
<PAGE>   54
 
     federal withholding tax provided that (a) the beneficial owner of the
     Series A Preferred Security does not actually or constructively own 10% or
     more of the total combined voting power of all classes of capital stock of
     the Company,(b) the beneficial owner of the Series A Preferred Security is
     not a controlled foreign corporation that is related to the Company or
     Illinois Power Capital through stock ownership, and (c) either: (x) the
     beneficial owner of the Series A Preferred Security certifies to Illinois
     Power Capital or its agent, under penalties of perjury, that it is a United
     States Alien Holder and provides its name and address or (y) the holder of
     the Series A Preferred Security is a securities clearing organization, bank
     or other financial institution that holds customers' securities in the
     ordinary course of its trade or business (a "financial institution"), and
     such holder certifies to Illinois Power Capital or its agent, under
     penalties of perjury, that such statement has been received from the
     beneficial owner by it or by a financial institution between it and the
     beneficial owner and furnishes Illinois Power Capital or its agent with a
     copy thereof; and
 
          (ii) a United States Alien Holder of a Series A Preferred Security
     will generally not be subject to United States federal withholding tax on
     any gain realized on the sale or exchange of a Series A Preferred Security
     unless such holder is present in the United States for 183 days or more in
     the taxable year of sale and either has a "tax home" in the United States
     or certain other requirements are met.
 
BACKUP WITHHOLDING AND INFORMATION REPORTING
 
     In general, information reporting requirements will apply to payments of
the proceeds of the sale of Series A Preferred Securities within the United
States to noncorporate United States holders, and "backup withholding" at a rate
of 31% will apply to such payments if the United States holder fails to provide
an accurate taxpayer identification number.
 
   
     Payments of the proceeds from the sale by a United States Alien Holder of
Series A Preferred Securities made to or through a foreign office of a broker
will not be subject to information reporting or backup withholding, except that,
if the broker is a United States person, a controlled foreign corporation for
United States tax purposes or a foreign person 50% or more of whose gross income
is effectively connected with a United States trade or business for a specified
three-year period, information reporting may apply to such payments. Payments of
the proceeds from the sale of Series A Preferred Securities to or through the
United States office of a broker are subject to information reporting and backup
withholding unless the holder or beneficial owner certifies as to its non-United
States status or otherwise establishes an exemption from information reporting
and backup withholding.
    
 
                                      S-26
<PAGE>   55
 
                                  UNDERWRITING
 
     Subject to the terms and conditions of the Underwriting Agreement, Illinois
Power Capital has agreed to sell to each of the several Underwriters named
below, and each of the Underwriters, for whom Goldman, Sachs & Co. and
          are acting as Representatives, has severally agreed to purchase from
Illinois Power Capital the respective number of Series A Preferred Securities
set forth opposite its name below:
 
<TABLE>
<CAPTION>
                                                                      NUMBER OF
                                                                      SERIES A
                                                                      PREFERRED
                               UNDERWRITER                           SECURITIES
          -----------------------------------------------------     -------------
          <S>                                                       <C>
          Goldman, Sachs & Co. ................................
                                                                    -------------
                    Total......................................
                                                                    =============
</TABLE>
 
     Under the terms and conditions of the Underwriting Agreement, the
Underwriters are committed to take and pay for all such Series A Preferred
Securities offered hereby, if any are taken.
 
     The Underwriters propose to offer the Series A Preferred Securities in part
directly to the public at the initial public offering price set forth on the
cover page of this Prospectus Supplement, and in part to certain securities
dealers at such price less a concession of $          per Series A Preferred
Security. The Underwriters may allow, and such dealers may reallow, a concession
not in excess of $          per Series A Preferred Security to certain brokers
and dealers. After the Series A Preferred Securities are released for sale to
the public, the offering price and other selling terms may from time to time be
varied by the Representatives.
 
     As the proceeds of the sale of the Series A Preferred Securities will be
loaned to the Company, the Company has agreed in the Underwriting Agreement to
pay to the Underwriters $     per Series A Preferred Security ($     per Series
A Preferred Security sold to certain institutions) for the accounts of the
several Underwriters.
 
     The Company and Illinois Power Capital have agreed, during the period
beginning from the date of the Underwriting Agreement and continuing to and
including the earlier of (i) the date, after the closing date, on which the
distribution of the Series A Preferred Securities ceases, as determined by the
Underwriters, or (ii) 30 days after the closing date, not to offer, sell,
contract to sell, or otherwise dispose of any Series A Preferred Securities, any
limited partner interests of Illinois Power Capital, or any preferred stock or
any other securities of Illinois Power Capital or the Company which are
substantially similar to the Series A Preferred Securities, or any securities
convertible into or exchangeable for Series A Preferred Securities, limited
partner interests, preferred stock or such substantially similar securities of
either Illinois Power Capital or the Company without the prior written consent
of the Underwriters.
 
     Prior to this offering, there has been no public market for the Series A
Preferred Securities. In order to meet one of the requirements for listing the
Series A Preferred Securities on the New York Stock Exchange, the Underwriters
will undertake to sell lots of 100 or more Series A Preferred Securities to a
minimum of 400 beneficial holders.
 
     Illinois Power Capital and the Company have agreed to indemnify the
Underwriters against certain civil liabilities, including liabilities under the
Securities Act.
 
     Certain of the Underwriters engage in transactions with, and from time to
time have performed services for, the Company and its affiliates in the ordinary
course of business.
 
                                      S-27
<PAGE>   56
 
                                 LEGAL OPINIONS
 
     Certain legal matters will be passed upon for the Company and Illinois
Power Capital by Schiff Hardin & Waite, Chicago, Illinois, and for the
Underwriters by Reid & Priest, New York, New York. Certain matters of Delaware
law relating to the validity of the Series A Preferred Securities will be passed
upon by Richards, Layton & Finger, P.A., Wilmington, Delaware, special Delaware
counsel to the Company and Illinois Power Capital. Schiff Hardin & Waite and
Reid & Priest may rely on the opinion of Richards, Layton & Finger, P.A. as to
certain matters of Delaware law. Schiff Hardin & Waite may rely on the opinion
of Reid & Priest as to all matters of New York law, and Reid & Priest may rely
on the opinion of Schiff Hardin & Waite as to all matters of Illinois law.
 
                                      S-28
<PAGE>   57
 
- ------------------------------------------------------
- ------------------------------------------------------
 
     NO PERSON HAS BEEN AUTHORIZED TO GIVE ANY INFORMATION OR TO MAKE ANY
REPRESENTATIONS OTHER THAN THOSE CONTAINED IN THIS PROSPECTUS SUPPLEMENT OR THE
PROSPECTUS AND, IF GIVEN OR MADE, SUCH INFORMATION OR REPRESENTATIONS MUST NOT
BE RELIED UPON AS HAVING BEEN AUTHORIZED. THIS PROSPECTUS SUPPLEMENT AND THE
PROSPECTUS DO NOT CONSTITUTE AN OFFER TO SELL OR THE SOLICITATION OF AN OFFER TO
BUY ANY SECURITIES OTHER THAN THE SECURITIES DESCRIBED IN THIS PROSPECTUS
SUPPLEMENT AND THE PROSPECTUS OR AN OFFER TO SELL OR THE SOLICITATION OF AN
OFFER TO BUY SUCH SECURITIES IN ANY CIRCUMSTANCES IN WHICH SUCH OFFER OR
SOLICITATION IS UNLAWFUL. NEITHER THE DELIVERY OF THIS PROSPECTUS SUPPLEMENT AND
THE PROSPECTUS NOR ANY SALE MADE HEREUNDER SHALL, UNDER ANY CIRCUMSTANCES,
CREATE ANY IMPLICATION THAT THE INFORMATION HEREIN OR THEREIN IS CORRECT AS OF
ANY TIME SUBSEQUENT TO THE DATE OF SUCH INFORMATION.
                               ------------------
 
                               TABLE OF CONTENTS
 
                             PROSPECTUS SUPPLEMENT
 
<TABLE>
<CAPTION>
                                        PAGE
                                        ----
<S>                                     <C>
Certain Investment Considerations....    S-3
Illinois Power Company...............    S-4
Illinois Power Capital...............    S-4
Use of Proceeds......................    S-4
Summary Financial Information of
  the Company........................    S-5
Description of the Series A Preferred
  Securities.........................    S-7
Description of the Series A
  Subordinated Debentures............   S-19
Effect of Obligations under the
  Series A Subordinated Debentures
  and the Guarantee..................   S-23
United States Taxation...............   S-24
Underwriting.........................   S-27
Legal Opinions.......................   S-28
             PROSPECTUS
Available Information................      2
Incorporation of Certain Documents by
  Reference..........................      2
Illinois Power Company...............      3
Illinois Power Capital...............      3
Use of Proceeds......................      3
Ratio of Earnings to Combined Fixed
  Charges and Preferred Stock
  Dividend Requirements..............      4
Description of the Preferred
  Securities.........................      5
Description of the Guarantee.........      5
Description of the Subordinated
  Debentures.........................      7
Plan of Distribution.................     12
Legal Opinions.......................     13
Experts..............................     13
</TABLE>
 
- ------------------------------------------------------
- ------------------------------------------------------
 
- ------------------------------------------------------
- ------------------------------------------------------
 
                              PREFERRED SECURITIES
 
                                 ILLINOIS POWER
                                    CAPITAL
 
                            GUARANTEED TO THE EXTENT
                             ILLINOIS POWER CAPITAL
                                HAS FUNDS AS SET
                                FORTH HEREIN BY
 
                                   [IP LOGO]
 
                             ILLINOIS POWER COMPANY
 
                           CUMULATIVE ADJUSTABLE RATE
                                 MONTHLY INCOME
                             PREFERRED SECURITIES,
                                    SERIES A
 
                            ------------------------
                             PROSPECTUS SUPPLEMENT
                            ------------------------
 
                              GOLDMAN, SACHS & CO.
                      REPRESENTATIVES OF THE UNDERWRITERS
 
- ------------------------------------------------------
- ------------------------------------------------------
<PAGE>   58
 
     Information contained herein is subject to completion or amendment. A
     registration statement relating to these securities has been filed with the
     Securities and Exchange Commission. These securities may not be sold nor
     may offers to buy be accepted prior to the time the registration statement
     becomes effective. This prospectus shall not constitute an offer to sell or
     the solicitation of an offer to buy nor shall there by any sale of these
     securities in any State in which such offer, solicitation or sale would be
     unlawful prior to registration or qualification under the securities laws
     of any such State.
 
   
PROSPECTUS       SUBJECT TO COMPLETION, DATED SEPTEMBER 2, 1994
    
                                  $100,000,000
 
                             ILLINOIS POWER CAPITAL
 
                              PREFERRED SECURITIES
           GUARANTEED TO THE EXTENT ILLINOIS POWER CAPITAL HAS FUNDS
                             AS SET FORTH HEREIN BY
 
                             ILLINOIS POWER COMPANY
                               ------------------
 
     Illinois Power Capital, L.P. ("Illinois Power Capital"), a Delaware limited
partnership, all of the general partner interests in which are owned by Illinois
Power Company (the "Company"), may offer, from time to time, its preferred
securities, representing limited partner interests ("Preferred Securities"), in
one or more series. The payment of periodic cash distributions ("dividends")
with respect to Preferred Securities of any series, out of funds held by
Illinois Power Capital and legally available therefor, and payments on
liquidation or redemption with respect to the Preferred Securities are
guaranteed by the Company to the extent described herein (the "Guarantee"). The
Company's obligations under the Guarantee are subordinate and junior in right of
payment to all other liabilities of the Company. Subordinated Deferrable
Interest Debentures of the Company ("Subordinated Debentures") will also be
issued and sold from time to time in one or more series by the Company to
Illinois Power Capital in connection with the investment of the proceeds from
the offering of Preferred Securities. Subordinated Debentures subsequently may
be distributed to holders of Preferred Securities in connection with a
dissolution of Illinois Power Capital upon the occurrence of certain events as
may be described in an accompanying Prospectus Supplement (a "Prospectus
Supplement"). The Subordinated Debentures will be unsecured and subordinate and
junior in right of payment to all present and future Senior Indebtedness of the
Company.
 
     The specific designation, number of Preferred Securities, dividend rate (or
method of determination thereof), and any other rights, preferences, privileges,
limitations and restrictions relating to the Preferred Securities of the
particular series in respect of which this Prospectus is being delivered will be
set forth in a Prospectus Supplement pertaining to such series.
 
     The Preferred Securities may be offered in amounts, at prices and on terms
to be determined at the time of offering; provided, however, that the aggregate
initial public offering price of all Preferred Securities offered hereby shall
not exceed $100,000,000.
                               ------------------
 
THESE SECURITIES HAVE NOT BEEN APPROVED OR DISAPPROVED BY THE SECURITIES AND
  EXCHANGE COMMISSION OR ANY STATE SECURITIES COMMISSION NOR HAS THE
     SECURITIES AND EXCHANGE COMMISSION OR ANY STATE SECURITIES COMMISSION
      PASSED UPON THE ACCURACY OR ADEQUACY OF THIS PROSPECTUS. ANY
        REPRESENTATION TO THE CONTRARY IS A CRIMINAL OFFENSE.
                               ------------------
 
     The Preferred Securities may be sold to or through underwriters or dealers
as designated from time to time. See "Plan of Distribution." The names of any
such underwriters or dealers involved in the sale of the Preferred Securities of
the particular series in respect of which this Prospectus is being delivered,
the number of Preferred Securities to be purchased by any such underwriters or
dealers and any applicable commissions or discounts will be set forth in the
Prospectus Supplement. The net proceeds to the Company will also be set forth in
the Prospectus Supplement.
                               ------------------
 
   
               The date of this Prospectus is September   , 1994.
    
<PAGE>   59
 
                             AVAILABLE INFORMATION
 
         The Company is subject to the informational requirements of the
Securities Exchange Act of 1934, as amended (the "Exchange Act"), and in
accordance therewith files reports, proxy statements and other information with
the Securities and Exchange Commission (the "Commission"). Reports, proxy
statements and other information filed by the Company with the Commission may be
inspected and copied at the public reference facilities maintained by the
Commission at Room 1024, 450 Fifth Street, N.W., Washington, D.C. 20549, and at
the Commission's Regional Offices located at Suite 1400, Northwestern Atrium
Center, 500 West Madison Street, Chicago, Illinois 60661 and at 13th Floor,
Seven World Trade Center, New York, New York 10048. Copies of such material may
be obtained from the public reference section of the Commission, 450 Fifth
Street, N.W., Washington, D.C. 20549, at prescribed rates. Such reports, proxy
statements and other information concerning the Company may also be inspected at
the offices of the New York Stock Exchange, 20 Broad Street, New York, New York
10005 and the Chicago Stock Exchange, 440 South LaSalle Street, Chicago,
Illinois 60605, on which exchanges certain of the Company's securities are
listed. In addition, such reports, proxy statements and other information
concerning the Company can be inspected at the principal office of the Company,
500 South 27th Street, Decatur, Illinois 62525.
 
     This Prospectus does not contain all the information set forth in the
Registration Statement on Form S-3 (together with all amendments and exhibits
thereto, the "Registration Statement"), which the Company and Illinois Power
Capital have filed with the Commission under the Securities Act of 1933, as
amended (the "Securities Act"). Statements contained or incorporated by
reference herein concerning the provisions of documents are necessarily
summaries of such documents, and each statement is qualified in its entirety by
reference to the Registration Statement.
 
     No separate financial statements of Illinois Power Capital have been
included herein. The Company and Illinois Power Capital do not consider that
such financial statements would be material to holders of Preferred Securities
because Illinois Power Capital is a newly formed special purpose entity, has no
operating history and no independent operations and is not engaged in, and does
not propose to engage in, any activity other than as set forth below. See
"Illinois Power Capital."
 
                INCORPORATION OF CERTAIN DOCUMENTS BY REFERENCE
 
     The following documents heretofore filed by the Company with the Commission
pursuant to the Exchange Act are incorporated herein by reference:
 
          1. The Company's Annual Report on Form 10-K for the year ended
     December 31, 1993;
 
          2. The Company's Current Reports on Form 8-K dated February 9, 1994
     and May 27, 1994; and
 
          3. The Company's Quarterly Reports on Form 10-Q for the quarters ended
     March 31, 1994 and June 30, 1994.
 
     All documents subsequently filed by the Company pursuant to Sections 13(a),
13(c), 14 or 15(d) of the Exchange Act after the date of this Prospectus and
prior to the termination of the offering of the Preferred Securities offered
hereby, shall be deemed to be incorporated by reference in this Prospectus and
to be a part hereof from the date of filing of such documents. Any statement
contained in a document incorporated or deemed to be incorporated by reference
herein shall be deemed to be modified or superseded for purposes of this
Prospectus to the extent that a statement contained herein or in any other
subsequently filed document which also is or is deemed to be incorporated by
reference herein or in the Prospectus Supplement modifies or supersedes such
statement. Any such statement so modified or superseded shall not be deemed,
except as so modified or superseded, to constitute a part of this Prospectus.
 
         THE COMPANY WILL PROVIDE WITHOUT CHARGE TO EACH PERSON TO WHOM A COPY
OF THIS PROSPECTUS HAS BEEN DELIVERED, ON THE WRITTEN OR ORAL REQUEST OF SUCH
PERSON, A COPY OF ANY OR ALL OF THE DOCUMENTS REFERRED TO ABOVE WHICH HAVE BEEN
OR MAY BE INCORPORATED IN THIS PROSPECTUS BY REFERENCE, OTHER THAN EXHIBITS TO
SUCH DOCUMENTS WHICH ARE NOT SPECIFICALLY INCORPORATED BY REFERENCE INTO THE
INFORMATION THAT THE PROSPECTUS INCORPORATES. REQUESTS FOR SUCH COPIES SHOULD BE
DIRECTED TO MR. ALEC G. DREYER, CONTROLLER, ILLINOIS POWER COMPANY, 500 SOUTH
27TH STREET, DECATUR, ILLINOIS 62525, TELEPHONE NUMBER: (217) 424-6600.
 
                                        2
<PAGE>   60
 
                             ILLINOIS POWER COMPANY
 
   
     The Company was incorporated under the laws of the State of Illinois on May
25, 1923. Effective May 27, 1994, the Company became a subsidiary of Illinova
Corporation, an exempt holding company under the Public Utility Holding Company
Act of 1935, as amended, pursuant to a merger in which each outstanding share of
the Company's Common Stock was converted into one share of common stock of
Illinova Corporation. The Company is engaged in the generation, transmission,
distribution and sale of electric energy and the distribution and sale of
natural gas in the State of Illinois. Its service area is a widely diversified
industrial and agricultural area comprising approximately 15,000 square miles in
northern, central and southern Illinois. Electric service is provided at retail
to 309 incorporated municipalities, adjacent suburban and rural areas and
numerous unincorporated municipalities having an aggregate population of
approximately 1,283,000. Gas service is provided to 257 incorporated
municipalities, adjacent suburban areas and numerous unincorporated
municipalities having an aggregate population of approximately 935,000. The
larger cities served include Decatur, East St. Louis (gas only), Champaign,
Danville, Belleville, Granite City, Bloomington (electric only), Galesburg,
Urbana and Normal (electric only). The executive offices of the Company are
located at 500 South 27th Street, Decatur, Illinois 62525, and the Company's
telephone number is (217) 424-6600.
    
 
                             ILLINOIS POWER CAPITAL
 
     Illinois Power Capital is a limited partnership formed under the Delaware
Revised Uniform Limited Partnership Act, as amended (the "Partnership Act").
Illinois Power Capital exists for the sole purpose of issuing its partner
interests and using the proceeds thereof to purchase certain debt securities of
the Company. The Company is the sole general partner (the "General Partner") of
Illinois Power Capital and will manage all of the business and affairs of
Illinois Power Capital. Holders of Preferred Securities will be limited partners
of Illinois Power Capital. The Company, as the General Partner of Illinois Power
Capital, will make capital contributions to Illinois Power Capital from time to
time to the extent required so that the total contributions made by the General
Partner shall at all times be at least equal to 3% of the total contributions
made by all partners. The rights and obligations of the General Partner and the
limited partners of Illinois Power Capital will be governed by the Partnership
Act and by an Amended and Restated Agreement of Limited Partnership of Illinois
Power Capital (the "Partnership Agreement") substantially in the form filed as
an exhibit to the Registration Statement of which this Prospectus and the
accompanying Prospectus Supplement form a part.
 
     Illinois Power Capital's principal place of business and registered office
in the State of Delaware is c/o The Corporation Trust Company, Corporation Trust
Center, 1209 Orange Street, Wilmington, New Castle County, Delaware 19801,
telephone: (302) 658-7581.
 
                                USE OF PROCEEDS
 
     The proceeds to be received by Illinois Power Capital from the sale of the
Preferred Securities will be used to purchase Subordinated Debentures of the
Company and, unless otherwise specified in any Prospectus Supplement, will be
applied by the Company to the payment or provision for payment at maturity, the
purchase or the redemption of outstanding securities of the Company and for
general corporate purposes.
 
                                        3
<PAGE>   61
 
          RATIO OF EARNINGS TO FIXED CHARGES AND RATIO OF EARNINGS TO
        COMBINED FIXED CHARGES AND PREFERRED STOCK DIVIDEND REQUIREMENTS
 
<TABLE>
<CAPTION>
                                            YEAR ENDED DECEMBER 31,                      12 MONTHS
                                ------------------------------------------------           ENDED
                                1989        1990       1991     1992     1993(A)      JUNE 30, 1994(A)
                                -----       ----       ----     ----     -------      ----------------
<S>                             <C>         <C>        <C>      <C>      <C>          <C>
Ratio of Earnings to Fixed
  Charges(b)..................  (0.52)(c)   0.70(c)    1.85     2.02       0.80(c)          0.93(c)
Ratio of Earnings to Combined
  Fixed Charges and Preferred
  Stock Dividend
  Requirements(b).............  (0.45)(d)   0.60(d)    1.48     1.61       0.70(d)          0.82(d)
</TABLE>
 
- ---------------
 
(a) Subsequent to the Company's merger with Illinova Corporation, net assets of
     Illinova Generating Company (formerly IP Group, Inc.) were transferred in
     the form of a dividend from the Company to Illinova Corporation. The
     information contained herein has been restated to reflect the financial
     results of the Company's current operations.
 
(b) Earnings used in the calculation of the ratio of earnings to fixed charges
     and the ratio of earnings to combined fixed charges and preferred stock
     dividend requirements include the allowance for funds used during
     construction and the deferred financing costs associated with the Company's
     Clinton Power Station, and are before deduction of income taxes and fixed
     charges. Fixed charges include interest on long-term debt, related
     amortization of debt discount, premium, and expense, other interest and
     that portion of rent expense which is estimated to be representative of the
     interest component. Preferred stock dividend requirements have been
     increased to an amount representing the pre-tax earnings required to cover
     such dividend requirements.
 
(c) The ratios of earnings to fixed charges for the twelve months ended June 30,
     1994 and for the years ended December 31, 1993, 1990 and 1989 of 0.93,
     0.80, 0.70 and (0.52), respectively, indicate that earnings were inadequate
     to cover fixed charges. The dollar amounts of the coverage deficiency for
     the twelve months ended June 30, 1994, and for the years ended 1993, 1990
     and 1989 were approximately $13 million, $37 million, $68 million and $375
     million, respectively. Excluding the loss on disallowed plant costs of $200
     million, net of income taxes, recorded in the third quarter of 1993, the
     ratio of earnings to fixed charges would have been 2.42 for the twelve
     months ended June 30, 1994 and 2.25 for the year ended 1993. Excluding the
     loss on disallowed plant costs of $137 million, net of income taxes,
     recorded in the fourth quarter of 1990, the ratio of earnings to fixed
     charges would have been 1.41 for the year ended 1990. Excluding the loss on
     disallowed plant costs of $346 million, net of income taxes, recorded in
     the first quarter of 1989, the ratio of earnings to fixed charges would
     have been 1.31 for the year ended 1989.
 
(d) The ratios of earnings to combined fixed charges and preferred stock
     dividend requirements for the twelve months ended June 30, 1994 and for the
     years ended December 31, 1993, 1990 and 1989 of 0.82, 0.70, 0.60 and
     (0.45), respectively, indicate that earnings were inadequate to cover
     combined fixed charges and preferred stock dividend requirements. The
     dollar amounts of the coverage deficiency for the twelve months ended June
     30, 1994, and for the years ended 1993, 1990 and 1989 were approximately
     $38 million, $63 million, $105 million and $412 million, respectively.
     Excluding the loss on disallowed plant costs of $200 million, net of income
     taxes, recorded in the third quarter of 1993, the ratio of earnings to
     combined fixed charges and preferred stock dividend requirements would have
     been 1.98 for the twelve months ended June 30, 1994 and 1.83 for the year
     ended 1993. Excluding the loss on disallowed plant costs of $137 million,
     net of income taxes, recorded in the fourth quarter of 1990, the ratio of
     earnings to combined fixed charges and preferred stock dividend
     requirements would have been 1.09 for the year ended 1990. Excluding the
     loss on disallowed plant costs of $346 million, net of income taxes,
     recorded in the first quarter of 1989, the ratio of earnings to combined
     fixed charges and preferred stock dividend requirements would have been
     1.06 for the year ended 1989.
 
                                        4
<PAGE>   62
 
                    DESCRIPTION OF THE PREFERRED SECURITIES
 
     Illinois Power Capital may issue, from time to time, Preferred Securities,
in one or more series, having terms described in the Prospectus Supplement
relating thereto. The limited partnership agreement of Illinois Power Capital
will be amended and restated (as so amended and restated, the "Partnership
Agreement") to authorize the establishment of one or more series of Preferred
Securities, having such terms, including dividends, redemption, voting,
liquidation rights and such other preferred, deferred or other special rights or
such restrictions as shall be set forth therein or otherwise established by the
General Partner pursuant thereto. Reference is made to the Prospectus Supplement
relating to the Preferred Securities of a particular series for specific terms,
including (i) the distinctive designation of such series which shall distinguish
it from other series; (ii) the number of Preferred Securities included in such
series, which number may be increased or decreased from time to time unless
otherwise provided by the General Partner in creating the series; (iii) the
annual dividend rate (or method of determining such rate) for Preferred
Securities of such series and the date or dates upon which such dividends shall
be payable; provided, however, dividends on any series of Preferred Securities
shall be payable on a monthly basis to holders of such series of Preferred
Securities as of a record date in each month during which such series of
Preferred Securities are outstanding; (iv) whether dividends on Preferred
Securities of such series shall be cumulative, and, in the case of Preferred
Securities of any series having cumulative dividend rights, the date or dates or
method of determining the date or dates from which dividends on Preferred
Securities of such series shall be cumulative; (v) the amount or amounts which
shall be paid out of the assets of Illinois Power Capital to the holders of
Preferred Securities of such series upon voluntary or involuntary dissolution,
winding-up or termination of Illinois Power Capital; (vi) the price or prices at
which, the period or periods within which and the terms and conditions upon
which Preferred Securities of such series may be redeemed or purchased, in whole
or in part, at the option of Illinois Power Capital or the General Partner;
(vii) the obligation, if any, of Illinois Power Capital to purchase or redeem
Preferred Securities of such series and the price or prices at which, the period
or periods within which and the terms and conditions upon which Preferred
Securities of such series shall be purchased or redeemed, in whole or in part,
pursuant to such obligation; (viii) the voting rights, if any, of Preferred
Securities of such series in addition to those required by law, including the
number of votes per Preferred Security and any requirement for the approval by
the holders of Preferred Securities, or of Preferred Securities of one or more
series, or of both, as a condition to specified action or amendments to the
Partnership Agreement; and (ix) any other relative rights, preferences,
privileges, limitations or restrictions of Preferred Securities of the series
not inconsistent with the Partnership Agreement or with applicable law. All
Preferred Securities offered hereby will be guaranteed by the Company to the
extent set forth below under "Description of the Guarantee." Any applicable
federal income tax considerations applicable to any offering of Preferred
Securities will be described in the Prospectus Supplement relating thereto.
 
                          DESCRIPTION OF THE GUARANTEE
 
     Set forth below is a summary of information concerning the Guarantee which
will be executed and delivered by the Company for the benefit of the holders
from time to time of Preferred Securities. The summary does not purport to be
complete and is subject in all respects to the provisions of, and is qualified
in its entirety by reference to, the Guarantee, which is filed as an exhibit to
the Registration Statement of which this Prospectus forms a part.
 
GENERAL
 
     The Company will irrevocably and unconditionally agree, to the extent set
forth herein, to pay in full, to the holders of the Preferred Securities of each
series, the Guarantee Payments (as defined below) (except to the extent paid by
Illinois Power Capital), as and when due, regardless of any defense, right of
set-off or counterclaim which Illinois Power Capital may have or assert. The
following payments with respect to any series of Preferred Securities to the
extent not paid by Illinois Power Capital (the "Guarantee Payments") will be
subject to the Guarantee (without duplication): (i) any accumulated and unpaid
dividends which are required to be paid on the Preferred Securities of such
series, to the
 
                                        5
<PAGE>   63
 
extent Illinois Power Capital shall have sufficient cash on hand to permit such
payment and funds legally available therefor, (ii) the redemption price,
including all accumulated and unpaid dividends (the "Redemption Price"), payable
with respect to any Preferred Securities called for redemption by Illinois Power
Capital to the extent Illinois Power Capital shall have sufficient cash on hand
to permit such payment and funds legally available therefor, and (iii) upon a
liquidation of Illinois Power Capital, the lesser of (a) the aggregate of the
liquidation preference and all accumulated and unpaid dividends on the Preferred
Securities of such series to the date of payment and (b) the amount of assets of
Illinois Power Capital remaining available for distribution to holders of
Preferred Securities of such series in liquidation of Illinois Power Capital.
The Company's obligation to make a Guarantee Payment may be satisfied by direct
payment of the required amounts by the Company to the holders of Preferred
Securities or by causing Illinois Power Capital to pay such amounts to such
holders.
 
CERTAIN COVENANTS OF THE COMPANY
 
     In the Guarantee, the Company will covenant that, so long as any Preferred
Securities remain outstanding, the Company will not declare or pay any dividend
on, or redeem, purchase, acquire or make a liquidation payment with respect to,
any of its capital stock or make any guarantee payment with respect to the
foregoing if at such time the Company shall be in default with respect to its
payment or other obligations under the Guarantee or there shall have occurred
and is continuing any event that would constitute an Event of Default under the
Indenture.
 
AMENDMENTS AND ASSIGNMENT
 
     Except with respect to any changes which do not adversely affect the rights
of holders of Preferred Securities (in which case no vote will be required), the
Guarantee may be changed only with the prior approval of the holders of not less
than 66 2/3% in liquidation preference of the outstanding Preferred Securities
of each affected series (voting together as one class). The manner of obtaining
any such approval of holders of the Preferred Securities of each series will be
as set forth in an accompanying Prospectus Supplement. All guarantees and
agreements contained in the Guarantee shall bind the successors, assigns,
receivers, trustees and representatives of the Company and shall inure to the
benefit of the holders of the Preferred Securities then outstanding.
 
TERMINATION OF THE GUARANTEE
 
     The Guarantee will terminate and be of no further force and effect as to
the Preferred Securities of any series upon full payment of the Redemption Price
of all Preferred Securities of such series, and will terminate completely upon
full payment of the amounts payable upon liquidation of Illinois Power Capital.
The Guarantee will continue to be effective or will be reinstated, as the case
may be, if at any time any holder of Preferred Securities of any series must
restore payment of any sums paid under such series of Preferred Securities or
the Guarantee.
 
STATUS OF THE GUARANTEE
 
   
     The Guarantee will constitute an unsecured obligation of the Company and
will rank (i) subordinate and junior in right of payment to all liabilities of
the Company, (ii) pari passu with the most senior preferred or preference stock
now or hereafter issued by the Company and with any guarantee now or hereafter
entered into by the Company in respect of any preferred or preference stock of
any affiliate of the Company and (iii) senior to the Company's Common Stock. The
Partnership Agreement provides that each holder of Preferred Securities by
acceptance thereof agrees to the subordination provisions and other terms of the
Guarantee.
    
 
     The Guarantee will constitute a guarantee of payment and not of collection.
The Guarantee will be deposited with the General Partner to be held for the
benefit of the holders of each series of the Preferred Securities. In the event
of the appointment of a Special Representative to, among other things, enforce
the Guarantee, the Special Representative may take possession of the Guarantee
for such purpose. If no
 
                                        6
<PAGE>   64
Special Representative has been appointed to enforce the Guarantee, the General
Partner has the right to enforce the Guarantee on behalf of the holders of each
series of the Preferred Securities. The holders of not less than 10% in
aggregate liquidation preference of the Preferred Securities have the right to
direct the time, method and place of conducting any proceeding for any remedy
available in respect of the Guarantee, including the giving of directions to the
General Partner or the Special Representative, as the case may be. If the
General Partner or the Special Representative fails to enforce the Guarantee as
above provided, any holder of Preferred Securities may institute a legal
proceeding directly against the Company to enforce its rights under the
Guarantee, without first instituting a legal proceeding against Illinois Power
Capital or any other person or entity. The Guarantee will not be discharged
except by payment of the Guarantee Payments in full to the extent not paid by
Illinois Power Capital and by complete performance of all obligations under the
Guarantee.
 
GOVERNING LAW
 
     The Guarantee will be governed by and construed in accordance with the laws
of the State of Illinois.
 
                   DESCRIPTION OF THE SUBORDINATED DEBENTURES
 
     Subordinated Debentures may be issued from time to time in one or more
series under an Indenture, (the "Indenture"), between the Company and The First
National Bank of Chicago, as Trustee (the "Trustee"). The following summary does
not purport to be complete and is subject in all respects to the provisions of,
and is qualified in its entirety by reference to, the Indenture, which is filed
as an exhibit to the Registration Statement of which this Prospectus forms a
part. Whenever particular provisions or defined terms in the Indenture are
referred to herein, such provisions or defined terms are incorporated by
reference herein. Section and Article references used herein are references to
provisions of the Indenture unless otherwise noted.
 
GENERAL
 
     The Subordinated Debentures will be unsecured, subordinated obligations of
the Company. The Indenture does not limit the aggregate principal amount of
Subordinated Debentures which may be issued thereunder and provides that the
Subordinated Debentures may be issued thereunder from time to time in one or
more series.
 
     The Subordinated Debentures are issuable in one or more series pursuant to
an indenture supplemental to the Indenture or a resolution of the Company's
Board of Directors or an authorized committee thereof (each, a "Supplemental
Indenture"). The aggregate principal amount of Subordinated Debentures relating
to Preferred Securities of any series will be set forth in the Prospectus
Supplement for such series and will be equal to the sum of the aggregate
liquidation preference of the Preferred Securities for such series and the
General Partner's capital contribution with respect to the Preferred Securities
for such series. Subordinated Debentures relating to Preferred Securities of any
series subsequently may be distributed pro rata to holders of Preferred
Securities of such series in connection with the dissolution of Illinois Power
Capital upon the occurrence of certain events described in the Prospectus
Supplement relating to the Preferred Securities of such series.
 
     The Restated Articles of Incorporation, as amended, of the Company limit
the amount of unsecured indebtedness that the Company may issue or assume,
without the consent of the holders of a majority of the total number of shares
of preferred stock then outstanding, to 20% of the aggregate of the total
principal amount of all outstanding bonds or other securities representing
secured indebtedness of the Company and the capital and surplus of the Company
as then stated on the Company's books. At July 31, 1994, the Company could have
issued approximately $210 million of unsecured indebtedness (such as the
Subordinated Debentures) without violating this provision.
 
     Reference is made to the Prospectus Supplement which will accompany this
Prospectus for the following terms of the series of Subordinated Debentures
being offered thereby: (i) the specific title of
 
                                        7
<PAGE>   65
 
such Subordinated Debentures; (ii) any limit on the aggregate principal amount
of such Subordinated Debentures; (iii) the date or dates on which the principal
of such Subordinated Debentures is payable or the method of determination of
such date or dates; (iv) the rate or rates at which such Subordinated Debentures
will bear interest or the method of determination of such rate or rates
(including the rates at which overdue principal shall bear interest, if
different, and, if applicable, the rate or rates at which overdue premiums or
interest shall bear interest, if any); (v) the date or dates from which such
interest shall accrue, the interest payment dates on which such interest will be
payable or the manner of determination of such interest payment dates and the
record dates for the determination of holders to whom interest is payable on any
such interest payment dates; (vi) the right, if any, to extend the interest
payment periods and the maximum duration of any such extension; (vii) the period
or periods within which, the price or prices at which and the terms and
conditions upon which such Subordinated Debentures may be redeemed, in whole or
in part, at the option of the Company; (viii) the obligation, if any, of the
Company to redeem or purchase such Subordinated Debentures pursuant to any
sinking fund or analogous provisions or at the option of the holder thereof and
the period or periods, the price or prices at which, and the terms and
conditions upon which, such Subordinated Debentures shall be redeemed or
purchased, in whole or part, pursuant to such obligation; (ix) the form of such
Subordinated Debentures; (x) if other than denominations of $25 or any integral
multiple thereof, the denominations in which such Subordinated Debentures shall
be issuable; (xi) any and all other terms with respect to such series; and (xii)
whether such Subordinated Debentures are issuable as a global security, and in
such case, the identity of the depository.
 
     The Indenture does not contain any provisions that afford holders of
Subordinated Debentures protection in the event of a highly leveraged
transaction involving the Company.
 
SUBORDINATION
 
     The Indenture provides that the Subordinated Debentures are subordinate and
junior in right of payment to all Senior Indebtedness (as defined below) of the
Company as provided in the Indenture. No payment of principal of (including
redemption and sinking fund payments), premium, if any, or interest on, the
Subordinated Debentures may be made if any Senior Indebtedness is not paid when
due, any applicable grace period with respect to such default has ended and such
default has not been cured or waived or has ceased to exist, or if the maturity
of any Senior Indebtedness has been accelerated because of a default. Upon any
distribution of assets of the Company to creditors upon any dissolution,
winding-up, liquidation or reorganization, whether voluntary or involuntary or
in bankruptcy, insolvency, receivership or other proceedings, all principal of,
and premium, if any, and interest due or to become due on, all Senior
Indebtedness must be paid in full before the holders of the Subordinated
Debentures are entitled to receive or retain any payment. The rights of the
holders of the Subordinated Debentures will be subrogated to the rights of the
holders of Senior Indebtedness to receive payments or distributions applicable
to Senior Indebtedness until all amounts owing on the Subordinated Debentures
are paid in full.
 
     The term "Senior Indebtedness" shall mean the principal of, premium, if
any, interest on and any other payment due pursuant to any of the following,
whether outstanding at the date of execution of the Indenture or thereafter
incurred, created or assumed:
 
          (a) all indebtedness of the Company (other than non-recourse
     indebtedness and indebtedness issued under the Indenture) evidenced by
     notes, debentures, bonds or other securities sold by the Company for money;
 
          (b) all indebtedness of others of the kinds described in the preceding
     clause (a) assumed by or guaranteed in any manner by the Company (other
     than the Guarantee) or in effect guaranteed by the Company by an agreement
     to purchase, contingent or otherwise; and
 
   
          (c) all renewals, extensions or refundings of indebtedness of the
     kinds described in either of the preceding clauses (a) and (b) unless, in
     the case of any particular indebtedness, renewal, extension or refunding,
     the instrument creating or evidencing the same or the assumption or
    
 
                                        8
<PAGE>   66
 
     guarantee of the same expressly provides that such indebtedness, renewal,
     extension or refunding is not superior in right of payment to or is pari
     passu with the Subordinated Debentures.
 
Such Senior Indebtedness shall continue to be Senior Indebtedness and to be
entitled to the benefits of the subordination provisions irrespective of any
amendment, modification or waiver of any term of such Senior Indebtedness.
 
     The Indenture does not limit the aggregate amount of Senior Indebtedness
which may be issued. As of June 30, 1994, Senior Indebtedness of the Company
aggregated approximately $2.2 billion.
 
CERTAIN COVENANTS OF THE COMPANY
 
   
     The Company will covenant that it will not declare or pay any dividend on,
or redeem, purchase, acquire or make a distribution or liquidation payment with
respect to, any of its capital stock, if at such time (i) there shall have
occurred and be continuing any event that would constitute an Event of Default
under any Indenture, (ii) the Company shall be in default with respect to its
payment or any obligations under the Guarantee or (iii) the Company shall have
given notice of its selection of an extended interest payment period as provided
in the Indenture and such period, or any extension thereof, shall be continuing.
The Company will also covenant (i) to remain the sole general partner of
Illinois Power Capital and maintain 100% ownership of the general partner
interests thereof; provided, that any permitted successor of the Company under
the Indenture may succeed to the Company's duties as General Partner, (ii) to
contribute capital to the extent required to maintain its capital at an amount
equal to at least 3% of the total capital contributions to Illinois Power
Capital, (iii) not to voluntarily dissolve, wind-up or terminate Illinois Power
Capital, except in connection with the distribution of Subordinated Debentures
to the holders of Preferred Securities in liquidation of Illinois Power Capital
and in connection with certain mergers, consolidations or amalgamations
permitted by the Partnership Agreement, (iv) to timely perform all of its duties
as the general partner in Illinois Power Capital (including the duty to pay
dividends on the Preferred Securities) and (v) to use its reasonable efforts to
cause Illinois Power Capital to remain a limited partnership and otherwise
continue to be treated as a partnership for United States federal income tax
purposes.
    
 
FORM, EXCHANGE, REGISTRATION AND TRANSFER
 
   
     Subordinated Debentures of each series will be issued in registered form
and either will be in certificated form or will be represented by one or more
global securities. If not represented by one or more global securities,
Subordinated Debentures may be presented for registration of transfer (with the
form of transfer endorsed thereon duly executed) or exchange, at the office of
the Debenture Registrar, without service charge and upon payment of any taxes
and other governmental charges. Such transfer or exchange will be effected upon
the Company or the Debenture Registrar being satisfied with the documents of
title and identity of the person making the request. The Company has appointed
the Trustee as Debenture Registrar with respect to the Subordinated Debentures.
    
 
     The Company shall not be required to (i) issue, register the transfer of or
exchange any Subordinated Debenture during a period beginning at the opening of
business 15 days before any mailing of Notice of Redemption of less than all the
outstanding Subordinated Debentures of the series of which such Subordinated
Debenture is a part, and ending at the close of business on the day of such
mailing or (ii) register the transfer of or exchange any Subordinated Debentures
called for redemption.
 
PAYMENT AND PAYING AGENTS
 
     Payment of principal of and premium, if any, on any Subordinated Debenture
will be made only against surrender to the Paying Agent of such Subordinated
Debenture. Principal of and any premium and interest, if any, on Subordinated
Debentures will be payable, subject to any applicable laws and regulations, at
the office of such Paying Agent or Paying Agents as the Company may designate
from time to time, except that at the option of the Company payment of any
interest may be made by check mailed to the address of the person entitled
thereto as such address shall appear in the Debenture
 
                                        9
<PAGE>   67
Register with respect to such Subordinated Debentures. Payment of interest on a
Subordinated Debenture on any Interest Payment Date will be made to the person
in whose name such Subordinated Debenture (or Predecessor Security) is
registered at the close of business on the Regular Record Date for such interest
payment.
 
     The Company will act as Paying Agent with respect to the Subordinated
Debentures. The Company may at any time designate additional Paying Agents or
rescind the designation of any Paying Agents or approve a change in the office
through which any Paying Agent acts, except that the Company will be required to
maintain a Paying Agent in each Place of Payment for each series of the
respective Subordinated Debentures.
 
     All moneys paid by the Company to a Paying Agent for the payment of the
principal of or premium or interest, if any, on any Subordinated Debenture of
any series which remain unclaimed at the end of two years after such principal,
premium, if any, or interest shall have become due and payable will be repaid to
the Company and the holder of such Subordinated Debenture will thereafter look
only to the Company for payment thereof.
 
GLOBAL DEBENTURES
 
     If any Subordinated Debentures of a series are represented by one or more
global securities, the applicable Prospectus Supplement will describe the
circumstances, if any, under which beneficial owners of interests in any such
Global Debenture may exchange such interests for Subordinated Debentures of such
series and of like tenor and principal amount in any authorized form and
denomination. Principal of and any premium and interest on a Global Debenture
will be payable in the manner described in the applicable Prospectus Supplement.
 
     The specific terms of the depository arrangement with respect to any
portion of a series of Subordinated Debentures to be represented by a Global
Debenture will be described in the applicable Prospectus Supplement.
 
MODIFICATION OF THE INDENTURE
 
     The Indenture contains provisions permitting the Company and the Trustee,
with consent of the holders of not less than a majority in principal amount of
the Subordinated Debentures of each series which are affected by the
modification, to modify the Indenture or any Supplemental Indenture affecting
that series or the rights of the holders of that series of Subordinated
Debentures; provided, that no such modification may, without the consent of the
holder of each outstanding Subordinated Debenture affected thereby, (i) extend
the fixed maturity of any Subordinated Debentures of any series, or reduce the
principal amount thereof, or reduce the rate or extend the time of payment of
interest thereon, or reduce any premium payable upon the redemption thereof,
without the consent of the holder of each Subordinated Debenture so affected or
(ii) reduce the percentage of Subordinated Debentures, the holders of which are
required to consent to any such supplemental indenture, without the consent of
the holders of each Subordinated Debenture then outstanding and affected
thereby.
 
     In addition, the Company and the Trustee may execute, without the consent
of any holder of Subordinated Debentures, any Supplemental Indenture for certain
other usual purposes including the creation of any new series of Subordinated
Debentures.
 
                                       10
<PAGE>   68
 
EVENTS OF DEFAULT
 
     The Indenture provides that any one or more of the following described
events, which has occurred and is continuing, constitutes an "Event of Default"
with respect to each series of Subordinated Debentures:
 
          (a) failure for 10 days to pay interest on the Subordinated Debentures
     of that series, including any Additional Interest in respect thereof, when
     due, provided that a valid extension of an interest payment period by the
     Company in accordance with a Supplemental Indenture shall not constitute a
     failure to pay interest for this purpose; or
 
          (b) failure to pay principal or premium, if any, on the Subordinated
     Debentures of that series when due, whether at maturity, upon redemption by
     declaration or otherwise, or to make any sinking fund payment with respect
     to that series; or
 
          (c) failure to observe or perform any other covenant (other than those
     specifically relating to another series) contained in the Indenture for 90
     days after notice; or
 
          (d) the dissolution, winding-up or termination of Illinois Power
     Capital, except in connection with the distribution of Subordinated
     Debentures to the holders of Preferred Securities in liquidation of
     Illinois Power Capital and in connection with certain mergers,
     consolidations or amalgamations permitted by the Partnership Agreement; or
 
          (e) certain events in bankruptcy, insolvency or reorganization of the
     Company or Illinois Power Capital.
 
   
     The holders of a majority in aggregate outstanding principal amount of any
series of the Subordinated Debentures have the right to direct the time, method
and place of conducting any proceeding for any remedy available to the Trustee
for that series. The Trustee or the holders of not less than 25% in aggregate
outstanding principal amount of any particular series of the Subordinated
Debentures (unless the principal of all of the Subordinated Debentures of that
series has been declared due and payable) may declare the principal due and
payable immediately on default with respect to such series, but the holders of a
majority in aggregate outstanding principal amount of such series may annul such
declaration and waive the default if the default has been cured and a sum
sufficient to pay all matured installments of interest and principal and any
premium has been deposited with the Trustee.
    
 
   
     The holders of a majority in aggregate outstanding principal amount of all
series of the Subordinated Debentures affected thereby may, on behalf of the
holders of all of the Subordinated Debentures of such series, waive any past
default, except a default in the payment of principal, premium, if any, or
interest. The Company is required to file annually with the Trustee a
certificate as to whether or not the Company is in compliance with all the
conditions and covenants under the Indenture.
    
 
CONSOLIDATION, MERGER AND SALE
 
     The Indenture does not contain any covenant which restricts the Company's
ability to merge or consolidate with or into any other corporation, sell or
convey all or substantially all of its assets to any person, firm or corporation
or otherwise engage in restructuring transactions.
 
DEFEASANCE AND DISCHARGE
 
     Under the terms of the Indenture, the Company will be discharged from any
and all obligations in respect of the Subordinated Debentures of any series
(except in each case for certain obligations to register the transfer or
exchange of Subordinated Debentures, replace stolen, lost or mutilated
Subordinated Debentures, maintain paying agencies and hold moneys for payment in
trust) if the Company deposits with the Trustee, in trust, moneys or Government
Obligations, in an amount sufficient to pay all the principal of, and interest
on, the Subordinated Debentures of such series on the dates such payments are
due in accordance with the terms of such Subordinated Debentures.
 
                                       11
<PAGE>   69
 
GOVERNING LAW
 
     The Indenture and the Subordinated Debentures will be governed by, and
construed in accordance with, the laws of the State of New York.
 
INFORMATION CONCERNING THE TRUSTEE
 
     The Trustee shall have and be subject to all the duties and
responsibilities specified with respect to an indenture trustee under the Trust
Indenture Act. Subject to such provision, the Trustee is under no obligation to
exercise any of the powers vested in it by the Indenture at the request of any
holder of Subordinated Debentures, unless offered reasonable indemnity by such
holder against the costs, expenses and liabilities which might be incurred
thereby. The Trustee is not required to expand or risk its own funds or
otherwise incur personal financial liability in the performance of its duties if
the Trustee reasonably believes that repayment or adequate indemnity is not
reasonably assured to it.
 
     The Company maintains a deposit account and banking relationship with the
Trustee.
 
MISCELLANEOUS
 
     The Company will have the right at all times to assign any of its rights or
obligations under the Indenture to a direct or indirect wholly-owned subsidiary
of the Company; provided, that, in the event of any such assignment, the Company
will remain liable for all such obligations. Subject to the foregoing, the
Indenture will be binding upon and inure to the benefit of the parties thereto
and their respective successors and assigns. The Indenture provides that it may
not otherwise be assigned by the parties thereto.
 
                              PLAN OF DISTRIBUTION
 
     Illinois Power Capital may offer or sell Preferred Securities to one or
more underwriters for public offering and sale by them. Illinois Power Capital
may sell Preferred Securities as soon as practicable after effectiveness of the
Registration Statement, provided that favorable market conditions exist. Any
such underwriter involved in the offer and sale of the Preferred Securities will
be named in an applicable Prospectus Supplement.
 
     Underwriters may offer and sell the Preferred Securities at a fixed price
or prices, which may be changed, or from time to time at market prices
prevailing at the time of sale, at prices related to such prevailing market
prices or at negotiated prices. In connection with the sale of Preferred
Securities, underwriters may be deemed to have received compensation from the
Company and/or Illinois Power Capital in the form of underwriting discounts or
commissions. Underwriters may sell Preferred Securities to or through dealers,
and such dealers may receive compensation in the form of discounts, concessions
or commissions from the underwriters.
 
     Any underwriting compensation paid by the Company and/or Illinois Power
Capital to underwriters in connection with the offering of Preferred Securities,
and any discounts, concessions or commissions allowed by underwriters to
participating dealers, will be set forth in an applicable Prospectus Supplement.
Underwriters and dealers participating in the distribution of the Preferred
Securities may be deemed to be underwriters, and any discounts and commissions
received by them and any profit realized by them on resale of the Preferred
Securities may be deemed to be underwriting discounts and commissions, under the
Securities Act. Underwriters and dealers may be entitled, under agreement with
the Company or Illinois Power Capital, to indemnification against and
contribution toward certain civil liabilities, including liabilities under the
Securities Act, and to reimbursement by the Company and/or Illinois Power
Capital for certain expenses.
 
     Underwriters and dealers may engage in transactions with, or perform
services for, the Company and/or Illinois Power Capital and/or any of their
affiliates in the ordinary course of business.
 
                                       12
<PAGE>   70
 
     Each series of Preferred Securities will be a new issue of securities and
will have no established trading market. Any underwriters to whom Preferred
Securities are sold by Illinois Power Capital for public offering and sale may
make a market in such Preferred Securities, but such underwriters will not be
obligated to do so and may discontinue any market making at any time without
notice. The Preferred Securities may or may not be listed on a national
securities exchange. No assurance can be given as to the liquidity of or the
trading markets for any Preferred Securities.
 
                                 LEGAL OPINIONS
 
     Certain legal matters will be passed upon for the Company and Illinois
Power Capital by Schiff Hardin & Waite, Chicago, Illinois, and for any
underwriters by Reid & Priest, New York, New York. Certain matters of Delaware
law relating to the validity of the Preferred Securities will be passed upon by
Richards, Layton & Finger, P.A., Wilmington, Delaware, special Delaware counsel
to the Company and Illinois Power Capital. Schiff Hardin & Waite and Reid &
Priest may rely on the opinion of Richards, Layton & Finger, P.A. as to certain
matters of Delaware law. Schiff Hardin & Waite may rely on the opinion of Reid &
Priest as to all matters of New York law, and Reid & Priest may rely on the
opinion of Schiff Hardin & Waite as to all matters of Illinois law.
 
                                    EXPERTS
 
     The financial statements incorporated in this Prospectus by reference to
the Company's Annual Report on Form 10-K for the year ended December 31, 1993
have been so incorporated in reliance on the report (which contains an
explanatory paragraph relating to the Company's change in its method of
accounting for income taxes, as discussed in Note 1 to the financial statements)
of Price Waterhouse LLP, independent accountants, given on the authority of said
firm as experts in auditing and accounting.
 
                                       13
<PAGE>   71
 
                                    PART II
 
                     INFORMATION NOT REQUIRED IN PROSPECTUS
 
ITEM 14.  OTHER EXPENSES OF ISSUANCE AND DISTRIBUTION.
 
<TABLE>
<CAPTION>
    <S>                                                                             <C>
    Securities and Exchange Commission registration fee........................     $ 34,483*
    New York Stock Exchange listing fees.......................................       45,000
    Printing expenses..........................................................       50,000
    Legal fees and expenses....................................................      125,000
    Independent accountant's fees and expenses.................................       15,000
    Blue Sky and legal investment fees and expenses............................       15,000
    Rating agencies fees and expenses..........................................       50,000
    Indenture Trustee fees and expenses........................................        5,000
    Miscellaneous..............................................................       10,517
                                                                                    --------
      Total....................................................................     $350,000
                                                                                    ========
</TABLE>
 
- ---------------
 
* Actual. All other expenses are estimated.
 
ITEM 15.  INDEMNIFICATION OF DIRECTORS AND OFFICERS.
 
     Under Section 8.75 of the Illinois Business Corporation Act of 1983, the
Company is empowered, subject to the procedures and limitations stated therein,
to indemnify any person against expenses (including attorneys' fees), judgments,
fines and amounts paid in settlement actually and reasonably incurred by such
person in connection with any threatened, pending or completed action, suit or
proceeding to which such person is made a party or threatened to be made a party
by reason of such person being or having been a director, officer, employee or
agent of the Company, or serving or having served at the request of the Company
as a director, officer, employee or agent of another corporation, partnership,
joint venture, trust or other enterprise. Section 8.75 further provides that
indemnification pursuant to its provisions is not exclusive of other rights of
indemnification to which a person may be entitled under any by-law, agreement,
vote of stockholders or disinterested directors, or otherwise, and that such
indemnification shall continue as to a director, officer, employee or agent of
the Company who has ceased to serve in such capacity, and shall inure to the
benefit of the heirs, executors and administrators of such a person.
 
     The Company's By-Laws provide, in substance, that the Company shall
indemnify any person against expenses (including attorneys' fees), judgments,
fines and amounts paid in settlement actually and reasonably incurred by such
person in connection with any threatened, pending or completed action, suit or
proceeding, whether civil, criminal, administrative or investigative, to which
such person is made a party or threatened to be made a party by reason of such
person being or having been a director, officer, employee or agent of the
Company, or serving or having served at the request of the Company in one or
more of the foregoing capacities with another corporation, partnership, joint
venture, trust or other enterprise. The indemnification is not exclusive of
other rights and shall continue as to a person who has ceased to be a director,
officer, employer or agent and shall inure to the benefit of his heirs,
executors and administrators.
 
     The Company presently has an insurance policy which, among other things,
includes liability insurance coverage for officers and directors under which
officers and directors are covered against any "loss" arising from any claim or
claims made against them by reason of any "wrongful act" in their respective
capacities of directors or officers. "Loss" is specifically defined to exclude
fines and penalties, as well as matters deemed uninsurable under the law
pursuant to which the insurance policy shall be construed. The policy also
contains other specific exclusions, including illegally obtained personal profit
or advantages, and dishonesty. The policy also provides for reimbursement to the
Company for loss
<PAGE>   72
incurred by having indemnified officers or directors as authorized by state
statute, the Company's By-Laws or any other agreement.
 
The Partnership Agreement provides, in part, as follows:
 
     "Section 9.6 Indemnification.  To the fullest extent permitted by
applicable law, the Partnership shall indemnify and hold harmless each
Indemnified Person from and against any loss, damage or claim incurred by such
Indemnified Person by reason of any act or omission performed or omitted by such
Indemnified Person in good faith on behalf of the Partnership and in a manner
reasonably believed to be within the scope of authority conferred on such
Indemnified Person by this Agreement, except that no Indemnified Person shall be
entitled to be indemnified in respect of any loss, damage or claim incurred by
such Indemnified Person by reason of gross negligence or willful misconduct,
with respect to such acts or omissions; provided, however, that any indemnity
under this Section 9.6 shall be provided out of and to the extent of Partnership
assets only, and no Covered Person shall have any personal liability on account
thereof. To the fullest extent permitted by applicable law, expenses (including
legal fees) incurred by an Indemnified Person in defending any claim, demand,
action, suit or proceeding shall, from time to time, be advanced by the
Partnership prior to the final disposition of such claim, demand, action, suit
or proceeding upon receipt by the Partnership of an undertaking by or on behalf
of the Indemnified Person to repay such amount if it shall be determined that
the Indemnified Person is not entitled to be indemnified as authorized in
Section 9.6."
 
     Applicable Delaware partnership law provides authority for limited
partnerships to indemnify under certain circumstances any partner or other
person from and against any and all claims and demands.
 
     The foregoing rights of indemnification shall apply to any liability of any
director or officer, partner or other person (or his legal representatives)
arising under any of the provisions of the Securities Act of 1933, as amended,
only to the extent that such rights of indemnification may be determined to be
valid by a court of competent jurisdiction.
 
ITEM 16.  LIST OF EXHIBITS.
 
     The exhibits to this Registration Statement are listed in the Exhibit Index
elsewhere herein.
 
ITEM 17.  UNDERTAKINGS.
 
     The undersigned registrants hereby undertake:
 
     (1) To file, during any period in which offers or sales are being made, a
post-effective amendment to this Registration Statement:
 
          (a) To include any prospectus required by Section 10(a)(3) of the
     Securities Act of 1933, as amended (the "Securities Act");
 
          (b) To reflect in the prospectus any facts or events arising after the
     effective date of the Registration Statement (or the most recent
     post-effective amendment thereof) which, individually or in the aggregate,
     represent a fundamental change in the information set forth in the
     Registration Statement; and
 
          (c) To include any material information with respect to the plan of
     distribution not previously disclosed in the Registration Statement or any
     material change to such information in the Registration Statement;
 
provided, however, that paragraphs 1(a) and 1(b) do not apply if the information
required to be included in a post-effective amendment by those paragraphs is
contained in periodic reports filed by the registrants pursuant to Section 13 or
Section 15(d) of the Securities Exchange Act of 1934, as amended (the "Exchange
Act") that are incorporated by reference in this Registration Statement;
 
                                      II-2
<PAGE>   73
 
     (2) That, for the purpose of determining any liability under the Securities
Act, each such post-effective amendment shall be deemed to be a new registration
statement relating to the securities offered therein, and the offering of such
securities at that time shall be deemed to be the initial bona fide offering
thereof;
 
     (3) To remove from registration by means of a post-effective amendment any
of the securities being registered which remain unsold at the termination of the
offering; and
 
     (4) That for purposes of determining any liability under the Securities
Act, each filing of the Company's annual report pursuant to Section 13(a) or
Section 15(d) of the Exchange Act that is incorporated by reference in this
Registration Statement shall be deemed to be a new registration statement
relating to the securities offered therein, and the offering of such securities
at that time shall be deemed to be the initial bona fide offering thereof.
 
     Insofar as indemnification for liabilities arising under the Securities Act
may be permitted to directors, officers and controlling persons of the
registrants pursuant to the provisions referred to in Item 15 above, or
otherwise, the registrants have been advised that in the opinion of the
Commission such indemnification is against public policy as expressed in the
Securities Act and is therefore, unenforceable. In the event that a claim for
indemnification against such liabilities (other than the payment by the
registrants of expenses incurred or paid by a director, officer or controlling
person of the registrants in the successful defense of any action, suit or
proceeding) is asserted by such director, officer or controlling person in
connection with the securities being registered, the registrants will, unless in
the opinion of their counsel the matter has been settled by controlling
precedent, submit to a court of appropriate jurisdiction the question whether
such indemnification is against public policy as expressed in the Securities Act
and will be governed by the final adjudication of such issue.
 
     The undersigned registrants hereby further undertake that:
 
     (1) for purposes of determining any liability under the Securities Act, the
information omitted from the form of prospectus filed as part of this
Registration Statement in reliance upon Rule 430A and contained in a form of
prospectus filed by the registrants pursuant to Rule 424(b)(1) or (4) or 497(h)
under the Securities Act shall be deemed to be part of this Registration
Statement as of the time it was declared effective; and (2) for the purpose of
determining any liability under the Securities Act, each post-effective
amendment that contains a form of prospectus shall be deemed to be a new
registration statement relating to the securities offered therein, and the
offering of such securities at that time shall be deemed to be the initial bona
fide offering thereof.
 
                                      II-3
<PAGE>   74
 
                                   SIGNATURES
 
   
     Pursuant to the requirements of the Securities Act of 1933, Illinois Power
Company has duly caused this amendment to its registration statement to be
signed on its behalf by the undersigned, thereunto duly authorized, in the City
of Decatur, and State of Illinois on the 2nd of September, 1994.
    
 
                                         ILLINOIS POWER COMPANY
                                           (Registrant)
 
   
                                          By:    /s/ LARRY F. ALTENBAUMER
    
 
                                            ------------------------------------
   
                                                    Larry F. Altenbaumer
    
   
                                                 Senior Vice President and
    
   
                                                  Chief Financial Officer
    
<PAGE>   75
 
   
     Pursuant to the requirements of the Securities Act of 1933, Illinois Power
Capital, L.P. has duly caused this amendment to its registration statement to be
signed on its behalf by the undersigned, thereunto duly authorized in the City
of Decatur, and State of Illinois on the 2nd day of September, 1994.
    
 
                                          ILLINOIS POWER CAPITAL, L.P.
                                           (Registrant)
                                           By: Illinois Power Company, its
                                         general partner
 
   
                                          By:    /s/ LARRY F. ALTENBAUMER
    
 
                                            ------------------------------------
   
                                                    Larry F. Altenbaumer
    
   
                                                 Senior Vice President and
    
                                                  Chief Financial Officer
<PAGE>   76
 
   
     Pursuant to the requirements of the Securities Act of 1933, this amendment
to registration statement has been signed below on behalf of each of Illinois
Power Company and Illinois Power Capital, L.P. by the following persons in their
capacities as officers or directors, as indicated below, of Illinois Power
Company and on the dates indicated.
    
 
   
<TABLE>
<CAPTION>
              SIGNATURE                               TITLE                        DATE
- -------------------------------------  -----------------------------------  ------------------
<S>                                    <C>                                  <C>
             LARRY D. HAAB*            Chairman, President, Chief
- -------------------------------------  Executive
            Larry D. Haab              Officer and Director
    (Principal Executive Officer)

      /s/ LARRY F. ALTENBAUMER         Senior Vice President and Chief
- -------------------------------------  Financial Officer
        Larry F. Altenbaumer
    (Principal Financial Officer)

                                                                            September 2, 1994
         /s/ ALEC G. DREYER            Controller
- -------------------------------------
           Alec G. Dreyer
            (Controller)

            RICHARD R. BERRY*          Director
- -------------------------------------
          Richard R. Berry

           DONALD E. LASATER*          Director
- -------------------------------------
          Donald E. Lasater

           DONALD S. PERKINS*          Director
- -------------------------------------
          Donald S. Perkins
</TABLE>
    
<PAGE>   77
 
   
<TABLE>
<CAPTION>
              SIGNATURE                               TITLE                        DATE
- -------------------------------------  -----------------------------------  ------------------
<S>                                    <C>                                  <C>
            ROBERT M. POWERS*          Director
- -------------------------------------
          Robert M. Powers

            WALTER D. SCOTT*           Director
- -------------------------------------
           Walter D. Scott

           RONALD L. THOMPSON*         Director
- -------------------------------------
         Ronald L. Thompson

            WALTER M. VANNOY*          Director
- -------------------------------------
          Walter M. Vannoy

                                                                            September 2, 1994
          MARILOU VON FERSTEL*         Director
- -------------------------------------
         Marilou von Ferstel

            CHARLES W. WELLS*          Director
- -------------------------------------
          Charles W. Wells

             JOHN D. ZEGLIS*           Director
- -------------------------------------
           John D. Zeglis
                                       Director
- -------------------------------------
         Vernon K. Zimmerman

   *By:   /s/ LARRY F. ALTENBAUMER
- -------------------------------------
        Larry F. Altenbaumer
         as Attorney-in-Fact
</TABLE>
    
<PAGE>   78
 
                                 EXHIBIT INDEX
 
   
<TABLE>
<CAPTION>
     EXHIBITS                                  DESCRIPTION                                 PAGE
     ---------     -------------------------------------------------------------------     ----
     <S>           <C>                                                                     <C>
      1            Form of Underwriting Agreement.

      3(a)         Restated Articles of Incorporation of the Company, as amended
                   through April 19, 1984. Filed as Exhibit 19 to the Company's
                   Quarterly Report on Form 10-Q for the Quarter Ended June 30, 1984.
                   File No. 1-3004.*

      3(b)         Amendment to the Restated Articles of Incorporation of the Company
                   dated April 19, 1989. Filed as Exhibit 19 to the Company's
                   Quarterly Report on Form 10-Q for the Quarter Ended March 31, 1989.
                   File No. 1-3004.*

      3(c)         Statement of Resolution Establishing the Series of Serial Preferred
                   Stock, without par value, designated as Cumulative Preferred Stock,
                   Adjustable Rate Series B. Filed as Exhibit 4(b) to the Company's
                   Quarterly Report on Form 10-Q for the Quarter Ended March 31, 1985.
                   File No. 1-3004.*

      3(d)         Statement of Resolution Establishing the Series of Serial Preferred
                   Stock, $50 par value, designated as 8.00% Cumulative Preferred
                   Stock. Filed as Exhibit 3(f) to the Company's Annual Report on Form
                   10-K for the Year Ended December 31, 1986. File No. 1-3004.*

      3(e)         Statement of Resolution Establishing the Series of Serial Preferred
                   Stock, $50 par value, designated as 7.75% Cumulative Preferred
                   Stock. Filed as Exhibit 3(g) to the Company's Annual Report on Form
                   10-K for the Year Ended December 31, 1986. File No. 1-3004.*

      3(f)         By-Laws of the Company, as amended. Filed as Exhibit 3(f) to the
                   Company's Quarterly Report on Form 10-Q for the Quarter Ended March
                   31, 1993. File No. 1-3004.*

      4(a)         Certificate of Limited Partnership of Illinois Power Capital,
                   L.P.**

      4(b)         Agreement of Limited Partnership of Illinois Power Capital, L.P.**

      4(c)         Revised Form of Amended and Restated Agreement of Limited
                   Partnership of Illinois Power Capital, L.P.

      4(d)         Revised Form of Action of the Company, as the General Partner of
                   Illinois Power Capital, L.P., Creating Series A Preferred
                   Securities.

      4(e)         Form of Indenture between the Company and The First National Bank
                   of Chicago.**

      4(e)(1)      Cross-reference sheet showing the location in the Indenture of the
                   provisions of Sections 310 through 318(a) of the Trust Indenture
                   Act of 1939, as amended.**

      4(f)         Form of Supplemental Indenture to Indenture to be used in
                   connection with the issuance of Subordinated Debentures and fixed
                   rate Preferred Securities.**

      4(g)         Form of Supplemental Indenture to Indenture to be used in
                   connection with the issuance of Subordinated Debentures and
                   adjustable rate Preferred Securities.**

      4(h)         Form of Preferred Security Certificate (contained in the Form of
                   Amended and Restated Agreement of Limited Partnership of Illinois
                   Power Capital filed as Exhibit 4(c) to this Registration
                   Statement).**
</TABLE>
    
 
- ---------------
 
   
 * Incorporated herein by reference.
    
 
   
** Previously filed.
    
<PAGE>   79
 
   
<TABLE>
     <S>           <C>                                                                     
      4(i)         Form of Subordinated Debenture (contained in the Form of Indenture
                   filed as Exhibit 4(e) to this Registration Statement).**

      4(j)         Form of Guarantee Agreement with respect to the Preferred
                   Securities.**

      5(a)         Opinion of Schiff Hardin & Waite.**

      5(b)         Opinion of Richards, Layton & Finger, P.A.**

      8            Tax opinion of Schiff Hardin & Waite (contained in its opinion
                   filed as Exhibit 5(a) to this Registration Statement).**

     12            Statement of Computations of Ratio of Earnings to Fixed Charges and
                   Ratio of Earnings to Combined Fixed Charges and Preferred Stock
                   Dividend Requirements.**

     23(a)         Consent of Schiff Hardin & Waite (contained in its opinion filed as
                   Exhibit 5(a) to this Registration Statement).**

     23(b)         Consent of Richards, Layton & Finger, P.A. (contained in its
                   opinion filed as Exhibit 5(b) to this Registration Statement).**

     23(c)         Consent of Price Waterhouse, LLP.**

     24            Powers of Attorney (set forth on the signature page of this
                   Registration Statement).**

     25            Statement of Eligibility of Trustee under the Trust Indenture Act
                   of 1939, as amended.**
</TABLE>
    
 
- ---------------
   
** Previously filed.
    

<PAGE>   1
                                                                       EXHIBIT 1

                          ILLINOIS POWER CAPITAL, L.P.
            CUMULATIVE MONTHLY INCOME PREFERRED SECURITIES, SERIES A
              (LIQUIDATION PREFERENCE $25 PER PREFERRED SECURITY)
                                 GUARANTEED BY
                             ILLINOIS POWER COMPANY


                             Underwriting Agreement


                                                            ______________, 1994


Goldman, Sachs & Co.
[INSERT NAMES OF CO-MANAGERS]
  [As Representatives of the Several Underwriters]
    c/o Goldman, Sachs & Co.
        85 Broad Street
        New York, New York 10004

Ladies and Gentlemen:

        Illinois Power Capital, L.P., a limited partnership formed under the
laws of the State of Delaware (the "Partnership"), and Illinois Power Company,
an Illinois corporation, as guarantor (the "Guarantor") and provider of certain
Guarantor Securities (as defined below), propose, subject to the terms and
conditions stated herein, that the Partnership issue and sell to the
Underwriters named in Schedule I hereto (the "Underwriters") an aggregate of
__________ limited partner interests of the Partnership of a series designated
the Cumulative Monthly Income Preferred Securities, Series A (liquidation
preference $25 per Preferred Security) (the "Preferred Securities"), guaranteed
pursuant to the Guarantee Agreement of the Guarantor (the "Guarantee"), as to
the payment of dividends, as, if, and when declared and as to payments on
liquidation or redemption and entitled to the benefits of the Guarantor
Securities (as defined below) described in the Final Supplemented Prospectus
(as defined in Section 1(a) hereof) provided by the Guarantor.  The proceeds
from the sale of the Preferred Securities will be used by the Partnership to
purchase subordinated debentures (the "Debentures") issued by the Guarantor
pursuant to the Subordinated Indenture (the "Indenture"), dated as of
__________, 1994, between the Guarantor and The First National Bank of Chicago,
as trustee (the "Trustee").  The Debentures and the Guarantee are hereinafter
referred to collectively as the "Guarantor Securities," and the Preferred
Securities and the Guarantor Securities are hereinafter referred to
collectively as the "Securities."





<PAGE>   2
         1.      Each of the Partnership and the Guarantor jointly and
severally represents and warrants to, and agrees with, each of the Underwriters
that:

         (a)     The Guarantor meets the requirement for use of Form S-3 under
the Securities Act of 1933, as amended (the "Act"), and a registration
statement on Form S-3 (File No. 33-__________) in respect of the Securities has
been filed with the Securities and Exchange Commission (the "Commission") under
the Act; such registration statement and any post-effective amendment thereto,
each in the form heretofore delivered or to be delivered to the Underwriters,
and to you for each of the other Underwriters (except that copies of the
registration statement and any post-effective amendment delivered to you for
each of the other Underwriters need not include exhibits but shall include all
documents incorporated by reference therein), have been declared effective by
the Commission in such form; no other document included or incorporated by
reference in the registration statement has heretofore been filed, or
transmitted for filing, with the Commission; and no stop order suspending the
effectiveness of such registration statement has been issued and no proceeding
for that purpose has been initiated or threatened by the Commission (any
preliminary prospectus, as supplemented by a preliminary prospectus supplement,
included in such registration statement or filed with the Commission pursuant
to Rule 424(a) of the rules and regulations of the Commission under the Act,
being hereinafter called a "Preliminary Prospectus"; the various parts of such
registration statement, including all exhibits thereto and the documents then
incorporated by reference therein, each as amended at the time such part of the
registration statement became effective, being hereinafter called the
"Registration Statement"; the prospectus relating to the Securities, in the
form in which it was included in the Registration Statement at the time it
became effective, being hereinafter called the "Prospectus"; any reference
herein to any Preliminary Prospectus or the Prospectus shall be deemed to refer
to and include the documents incorporated by reference therein pursuant to Item
12 of Form S-3 under the Act, as of the date of such Preliminary Prospectus or
Prospectus, as the case may be; any reference to any amendment or supplement to
any Preliminary Prospectus or the Prospectus shall be deemed to refer to and
include any documents filed after the date of such Preliminary Prospectus or
Prospectus, as the case may be, under the Securities Exchange Act of 1934, as
amended (the "Exchange Act"), and incorporated by reference in such Preliminary
Prospectus or Prospectus, as the case may be; and any reference to any
amendment to the Registration Statement shall be deemed to refer to and include
any annual report of the Guarantor filed pursuant to Section 13(a) or 15(d) of
the Exchange Act after the effective date of the Registration Statement that is
incorporated by reference in the Registration Statement; and the Prospectus as
supplemented on __________, 1994, in the form in which it was filed with the
Commission pursuant to Rule 424(b) under the Act, including any



                                     -2-
<PAGE>   3
documents incorporated by reference therein as of the date of such filing,
being hereinafter called the "Preliminary Supplemented Prospectus;" and the
Prospectus as amended or supplemented in final form in the form in which it is
filed with the Commission pursuant to Rule 424(b) under the Act in accordance
with Section 5(a) hereof, including any documents incorporated by reference
therein as of the date of such filing, being hereinafter called the "Final
Supplemented Prospectus");

         (b)     The documents incorporated by reference in the Registration
Statement or Prospectus, when they became effective or were filed with the
Commission, as the case may be, conformed in all material respects to the
requirements of the Act or the Exchange Act, as applicable, and the rules and
regulations of the Commission thereunder, and as of such time none of such
documents contained an untrue statement of a material fact or omitted to state
a material fact required to be stated therein or necessary to make the
statements therein, in the light of the circumstances under which they were
made, not misleading; and any further documents so filed and incorporated by
reference in the Prospectus or any further amendment or supplement thereto,
when such documents become effective or are filed with the Commission, as the
case may be, will conform in all material respects to the requirements of the
Act or the Exchange Act, as applicable, and the rules and regulations of the
Commission thereunder and will not contain an untrue statement of a material
fact or omit to state a material fact required to be stated therein or
necessary to make the statements therein, in the light of the circumstances
under which they were made, not misleading; provided, however, that this
representation and warranty shall not apply to any statements or omissions made
in reliance upon and in conformity with information furnished in writing to the
Partnership or the Guarantor by an Underwriter through you expressly for use in
the Preliminary Supplemented Prospectus or the Final Supplemented Prospectus;

         (c)     Each Preliminary Prospectus, at the time of filing thereof,
conformed in all material respects to the requirements of the Act and the rules
and regulations of the Commission thereunder and did not contain an untrue
statement of a material fact or omit to state a material fact required to be
stated therein or necessary to make the statements therein, in the light of the
circumstances under which they were made, not misleading; provided, however,
that this representation and warranty shall not apply to any statements or
omissions made in reliance upon and in conformity with information furnished in
writing to the Partnership or the Guarantor by an Underwriter through you
expressly for use therein;

         (d)     The Registration Statement, the Prospectus and, to the extent
not used to confirm sales of the Securities, the Preliminary Supplemented
Prospectus, conform, and the Final Supplemented Prospectus and any further
amendments or supplements to the Registration Statement or the Prospectus, when
any such


                                     -3-
<PAGE>   4
post-effective amendments are declared effective or supplements are filed with
the Commission, as the case may be, will conform, in all material respects to
the requirements of the Act, the Trust Indenture Act of 1939, as amended (the
"Trust Indenture Act") and the rules and regulations of the Commission
thereunder and do not and will not, (i) as of the applicable effective date as
to the Registration Statement and any amendment thereto, (ii) as of the filing
date of the Preliminary Supplemented Prospectus, and (iii) as of the applicable
filing date as to the Final Supplemented Prospectus and any Prospectus as
further amended or supplemented, contain an untrue statement of a material fact
or omit to state a material fact necessary in order to make the statements
therein, in the light of the circumstances under which they were made, not
misleading; provided, however, that neither the Guarantor nor the Partnership
makes any representations and warranties as to (A) that part of the
Registration Statement which shall constitute the Statement of Eligibility
(Form T-1) under the Trust Indenture Act (the "Form T-1"), or (B) the
information contained in or omitted from the Registration Statement or the
Final Supplemented Prospectus in reliance upon and in conformity with
information furnished in writing to the Partnership or the Guarantor by an
Underwriter through you expressly for use therein;

         (e)     The Partnership has no subsidiaries.  Neither the Partnership,
the Guarantor nor any of the Guarantor's other subsidiaries has sustained,
since the date of the latest audited financial statements included or
incorporated by reference in the Final Supplemented Prospectus, any material
loss or interference with its business from fire, explosion, flood or other
calamity, whether or not covered by insurance, or from any labor dispute or
court or governmental action, order or decree, otherwise than as set forth or
contemplated in the Final Supplemented Prospectus, and, since the respective
dates as of which information is given in the Registration Statement and the
Final Supplemented Prospectus there has not been any material change in the
capital stock or long-term debt of the Guarantor or any of its subsidiaries
(determined on a consolidated basis) or any material adverse change, or any
development involving a prospective material adverse change, in or affecting
the general affairs, management, financial position, stockholders' equity or
results of operations of the Guarantor and its subsidiaries (taken as a whole),
otherwise than as set forth or contemplated in the Final Supplemented
Prospectus;

         (f)     The Order of the Illinois Commerce Commission (the "ICC")
approving the purchase by the Guarantor of a general partner interest in the
Partnership in connection with the issue and sale of the Preferred Securities,
the issuance of the Debentures and the execution of the Guarantee (the "Order")
has been duly issued and remains in full force and effect without amendment or
modification, and is not the subject of any appeal or other proceeding;



                                     -4-
<PAGE>   5
         (g)     The Partnership has been duly formed and is validly existing
in good standing as a limited partnership under the laws of the State of
Delaware, with power and authority to own its properties and conduct its
business as described in the Preliminary Supplemented Prospectus and the Final
Supplemented Prospectus, and has been duly qualified as a foreign limited
partnership for the transaction of business and is in good standing under the
laws of each jurisdiction in which it owns or leases properties, or conducts
any business, so as to require such qualification, or is subject to no material
liability or disability by reason of the failure to be so qualified in any such
jurisdiction;

         (h)     The Guarantor has been duly incorporated and is validly
existing as a corporation in good standing under the laws of the State of
Illinois, with power and authority (corporate and other) to own its properties
and conduct its business as described in the Preliminary Supplemented
Prospectus and Final Supplemented Prospectus and has been duly qualified as a
foreign corporation for the transaction of business and is in good standing
under the laws of each other jurisdiction in which it owns or leases properties
or conducts any business, so as to require such qualification, or is subject to
no material liability or disability by reason of the failure to be so qualified
in any such jurisdiction; and each subsidiary of the Guarantor (other than the
Partnership) has been duly incorporated and is validly existing as a
corporation in good standing under the laws of its jurisdiction of
incorporation;

         (i)     The Guarantor has no significant subsidiaries within the
meaning of Regulation S-X; all of the outstanding shares of common stock of the
Guarantor are owned by Illinova Corporation, an Illinois corporation (the
"Parent");

         (j)     The Preferred Securities have been duly and validly authorized
and, when issued and delivered against payment therefor as provided herein and
in the Partnership Agreement (as defined below), will be duly and validly
issued and fully paid and nonassessable limited partner interests in the
Partnership and will conform as to legal matters to the description thereof
contained in the Final Supplemented Prospectus;

         (k)     The issuance and delivery of the Debentures have been duly
authorized and, when issued and delivered and when the Debentures have been
duly executed, authenticated, issued and delivered in accordance with this
Agreement, the Indenture and the Debentures will constitute valid and legally
binding obligations of the Guarantor entitled to the benefits provided by the
Indenture; subject, as to enforcement, to bankruptcy, insolvency,
reorganization and other laws of general applicability relating to or affecting
creditors' rights and to general equity principles; the Indenture will have
been duly authorized, executed and delivered and, at the Time of Delivery (as
defined below), the Indenture will be duly qualified under the Trust Indenture
Act and



                                     -5-
<PAGE>   6
will constitute a valid and legally binding obligation of the Guarantor,
enforceable in accordance with its terms, subject, as to enforcement, to
bankruptcy, insolvency, reorganization and other laws of general applicability
relating to or affecting creditors' rights and to general equity principles;
the Debentures and the Indenture conform as to legal matters to the
descriptions thereof in the Final Supplemented Prospectus; and the Indenture
will be substantially in the form filed as an exhibit to the Registration
Statement;

         (l)     The Amended and Restated Agreement of Limited Partnership of
the Partnership dated the date hereof (the "Partnership Agreement") has been
duly authorized by the Guarantor and constitutes a legal, valid and binding
agreement of the Guarantor and is enforceable against the Guarantor in
accordance with its terms, subject, as to enforcement, to the effect upon the
Partnership Agreement of (1) bankruptcy, insolvency, moratorium, receivership,
reorganization, liquidation, fraudulent conveyance and other similar laws
relating to or affecting the rights and remedies of creditors generally, and
(2) principles of equity (regardless of whether considered and applied in a
proceeding in equity or at law);

         (m)     The issuance of the Guarantee has been duly authorized by the
Guarantor and, when executed and delivered by the Guarantor, will constitute a
valid and legally binding obligation of the Guarantor, enforceable in
accordance with its terms, subject, as to enforcement, to bankruptcy,
insolvency, reorganization and other laws of general applicability relating to
or affecting creditors' rights and to general equity principles; the Guarantee
will conform as to legal matters to the description thereof in the Final
Supplemented Prospectus;

         (n)     All of the issued general partner interests of the Partnership
are owned by the Guarantor and have been duly and validly authorized and
validly issued, and the interest of the Guarantor is free and clear of all
liens, encumbrances, equities or claims; and the Partnership is not a party to
or otherwise bound by any agreement other than this Agreement, the Partnership
Agreement and the agreements contemplated by the Final Supplemented Prospectus;

         (o)     The Partnership is not in violation of its Certificate of
Limited Partnership or the Partnership Agreement, or in default in the
performance or observance of any material obligation, agreement, covenant or
condition contained in any contract, agreement or other instrument to which it
is a party or by which it may be bound, the effect of which is material to the
Partnership, and neither the execution or delivery of this Agreement, the
consummation of the transactions herein contemplated, the fulfillment of the
terms hereof, nor compliance with the terms and provisions hereof will conflict
with, or result




                                     -6-
<PAGE>   7
in a breach or violation of, or constitute a default under (i) its Certificate
of Limited Partnership or the Partnership Agreement, or any contract, agreement
or other instrument to which the Partnership is a party or by which it may be
bound or (ii) any statute, order, rule or regulation applicable to the
Partnership of any court or any federal or state governmental agency or body
having jurisdiction over the Partnership or over any of its properties; and no
consent, approval, authorization, order, registration or qualification of or
with any such court or governmental agency or body is required solely as a
result of the issuance and sale or delivery by the Partnership of the
Securities pursuant to this Agreement, the execution, delivery and performance
by the Partnership of this Agreement, or the consummation of the transactions
contemplated in this Agreement, except as set forth in Section 1(f) above and
except for the registration under the Act of the Securities, the qualification
of the Indenture under the Trust Indenture Act and such consents, approvals,
authorizations, registrations or qualifications as may be required under state
securities or Blue Sky laws in connection with the purchase of the Preferred
Securities and the distribution of the Securities by the Underwriters;

         (p)     The Guarantor is not in violation of its Restated Articles of
Incorporation, as amended (the "Restated Articles"), or its By-Laws, as amended
(the "By-Laws"), or in default in the performance or observance of any material
obligation, agreement, covenant or condition contained in any contract,
agreement or other instrument to which it is a party or by which it may be
bound, the effect of which is material to the Guarantor, and neither the
execution or delivery of this Agreement, the consummation of the transactions
herein contemplated, the fulfillment of the terms hereof, nor compliance with
the terms and provisions hereof will conflict with, or result in a breach or
violation of, or constitute a default under (i) the Restated Articles, the
By-Laws, or any contract, agreement or other instrument to which the Guarantor
is a party or by which it may be bound or (ii) any statute, order, rule or
regulation applicable to the Guarantor of any court or any federal or state
governmental agency or body having jurisdiction over the Guarantor or over its
properties; and no consent, approval, authorization, order, registration or
qualification of or with any such court or governmental agency or body is
required for the issuance and sale or delivery of the Securities or the
consummation by the Guarantor of the transactions contemplated by this
Agreement, except as set forth in Section 1(f) above and except for the
registration under the Act of the Securities, the qualification of the
Indenture under the Trust Indenture Act and such consents, approvals,
authorizations, registrations or qualifications as may be required under state
securities or Blue Sky laws in connection with the purchase of the Preferred
Securities and the distribution of the Securities by the Underwriters;




                                     -7-
<PAGE>   8
         (q)     Other than as set forth in the Final Supplemented Prospectus,
there are no legal or governmental proceedings pending to which the Guarantor
or any of its subsidiaries is a party or of which any property of the Guarantor
or any of its subsidiaries is the subject which, if determined adversely to the
Guarantor or any of its subsidiaries, would individually or in the aggregate
have a material adverse effect on the consolidated position, stockholders'
equity or results of operations of the Guarantor and its subsidiaries taken as
a whole; and, to the best of the Guarantor's knowledge, no such proceedings are
threatened or contemplated by governmental authorities or threatened by others;

         (r)     Price Waterhouse LLP, who have audited certain financial
statements of the Guarantor and its other subsidiaries, are independent
certified public accountants with respect to the Guarantor as required by the
Act and the rules and regulations of the Commission thereunder;

         (s)     There are no contracts or documents of the Partnership or the
Guarantor or any of the Guarantor's subsidiaries that are required to be filed
as exhibits to the Registration Statement or to any of the documents
incorporated by reference therein by the Act, the Trust Indenture Act or the
Exchange Act or by the rules and regulations of the Commission thereunder that
have not been so filed;

         (t)     There are no contracts, agreements or understandings between
the Partnership or the Guarantor and any person granting such person the right
to require the Partnership or the Guarantor to file a registration statement
under the Act with respect to any partnership interest of the Partnership or
any preferred stock of the Guarantor owned or to be owned by such person or to
require the Partnership or the Guarantor to include such securities in the
securities registered pursuant to the Registration Statement or in any
securities being registered pursuant to any other registration statement filed
by the Partnership or the Guarantor under the Act;

         (u)     Neither the Partnership nor the Guarantor nor any of the
Guarantor's other subsidiaries is and, after giving effect to the offering and
sale of the Preferred Securities, will be an "investment company" or an entity
"controlled" by an "investment company," as such terms are defined in the
Investment Company Act of 1940, as amended (the "Investment Company Act"); and

         (v)     The Partnership is not a "holding company" within the meaning
of the Public Utility Holding Company Act of 1935, as amended ("PUHCA"); the
Parent is a "holding company" as defined in PUHCA by reason of its ownership of
all the outstanding shares of common stock of the Guarantor, and the Guarantor
is a "holding company," but the Guarantor and Parent are each exempt from
PUHCA, except for the provisions of Section 9(a)(2) thereof, by virtue of




                                     -8-
<PAGE>   9
Section 3(a)(2) thereof and Section 3(a)(1) thereof and Rule 2 thereunder,
respectively.

         2.      Subject to the terms and conditions herein set forth, the
Partnership agrees to issue and sell to each of the Underwriters, and each of
the Underwriters agrees, severally and not jointly, to purchase from the
Partnership, at a purchase price per Preferred Security of $__________, the
number of Preferred Securities set forth opposite the name of such Underwriter
in Schedule I hereto.  The Guarantor agrees to issue the Guarantor Securities
concurrently with the issuance and sale of the Preferred Securities as
contemplated herein.

         The Guarantor hereby guarantees the timely performance by the
Partnership of its obligations under this Section 2, Section 6 and Section 11.
As the proceeds of the sale of the Preferred Securities will be loaned to the
Guarantor, the Guarantor hereby agrees to pay at the Time of Delivery (as
defined in Section 4 hereof) to Goldman, Sachs & Co. for the accounts of the
several Underwriters, an amount equal to $__________ per Preferred Security for
the Preferred Securities to be delivered by the Partnership hereunder at the
Time of Delivery; provided, however, that such compensation will be an amount
equal to $__________ per Preferred Security for Preferred Securities sold to
certain institutions and to be delivered by the Partnership hereunder at the
Time of Delivery.  The Underwriters shall inform the Guarantor in writing, not
later than the business day prior to the Time of Delivery, of the number of
Preferred Securities sold to such institutions.

         3.      Upon the authorization by you of the release of the Preferred
Securities, the several Underwriters propose to offer the Preferred Securities
for sale upon the terms and conditions set forth in the Final Supplemented
Prospectus.

         4.      A certificate or certificates in definitive form for the
Preferred Securities to be purchased by each Underwriter hereunder, and in such
denominations and registered in such names as Goldman, Sachs & Co. may request
upon at least forty-eight hours prior notice to the Partnership, shall be
delivered by or on behalf of the Partnership to the Depository (as defined
below) for the account of each such Underwriter, against payment by such
Underwriter or on its behalf of the purchase price therefor by certified or
official bank check or checks or wire transfer in New York Clearing House (next
day) funds.  The time, date and location of such delivery and payment shall be
9:30 a.m. New York time, on _________, 1994, or at such other time and date as
you and the Partnership or the Guarantor may agree upon in writing at the
offices of Reid & Priest, 40 West 57th Street, New York, New York 10019.  Such
time and date for delivery of the Preferred Securities is herein called the
"Time of Delivery."  Such certificates will be made available for checking and
packaging at least twenty-four hours prior to the Time of Delivery at the
office of The Depository




                                     -9-
<PAGE>   10
Trust Company (the "Depository"), 55 Water Street, New York, New York 10004.

         At the Time of Delivery, the Guarantor will pay, or cause to be paid,
the compensation payable to the Underwriters under Section 2 hereof by
certified or official bank check or checks or wire transfer in New York
Clearing House (next day) funds.

         5.      Each of the Partnership and the Guarantor jointly agrees with
each of the Underwriters:

         (a)     To prepare the Final Supplemented Prospectus in a form
approved by you and to file such Final Supplemented Prospectus pursuant to Rule
424(b) under the Act not later than the Commission's close of business on the
second business day following the execution and delivery of this Agreement, or,
if applicable, such earlier time as may be required by Rule 424(b) under the
Act; (ii) to make no further amendment or any supplement to the Registration
Statement or Final Supplemented Prospectus prior to the Time of Delivery which
shall be disapproved by you promptly after reasonable notice thereof; (iii) to
advise you promptly of any such amendment or supplement after the Time of
Delivery and furnish you with copies thereof; (iv) in the case of the
Guarantor, to file promptly all reports and any definitive proxy or information
statements required to be filed by the Guarantor with the Commission pursuant
to Section 13(a), 13(c), 14 or 15(d) of the Exchange Act for so long as the
delivery of a prospectus is required in connection with the offering or sale of
the Securities and during such same period to advise you, promptly after it
receives notice thereof, of the time when any amendment to the Registration
Statement has been filed or becomes effective or any supplement to the
Prospectus or any amended Prospectus has been filed with the Commission, of the
issuance by the Commission of any stop order or of any order preventing or
suspending the use of any prospectus relating to the Securities, of the
suspension of the qualification of such Securities for offering or sale in any
jurisdiction, of the initiation or threatening of any proceeding for any such
purpose, or of any request by the Commission for the amending or supplementing
of the Registration Statement or Prospectus or for additional information; and
(v) in the event of the issuance of any stop order or of any such order
preventing or suspending the use of any prospectus or suspending any such
qualification, promptly to use its best efforts to obtain the withdrawal of
such order;

         (b)     Promptly, from time to time, to take such action as you may
reasonably request to qualify the Securities for offering and sale under the
securities laws of such jurisdictions as you may request and to comply with
such laws so as to permit the continuance of sales and dealings therein in such
jurisdictions for as long as may be necessary to complete the distribution of
the Securities, provided that in connection therewith neither the



                                     -10-

<PAGE>   11
Partnership nor the Guarantor shall be required to qualify as a foreign
partnership or corporation or to file a general consent to service of process
in any jurisdiction or to comply with any other requirement of such laws
reasonably deemed by the Guarantor to be unduly burdensome;

         (c)     To furnish the Underwriters with copies of the Final
Supplemented Prospectus in such quantities as you may from time to time
reasonably request, and, if the delivery of a prospectus is required at any
time in connection with the offering or sale of the Securities and if at such
time any event shall have occurred as a result of which the Final Supplemented
Prospectus as then amended or supplemented would include an untrue statement of
a material fact or omit to state any material fact necessary in order to make
the statements therein, in light of the circumstances under which they were
made when such Final Supplemented Prospectus is delivered, not misleading, or,
if for any other reason it shall be necessary during such same period to amend
or supplement the Final Supplemented Prospectus or to file under the Exchange
Act any document incorporated by reference in the Final Supplemented Prospectus
in order to comply with the Act or the Exchange Act or the Trust Indenture Act
and the rules and regulations of the Commission thereunder, to notify you and
to file such document and to prepare and furnish without charge to each
Underwriter and any dealer in securities as many copies as you may from time to
time reasonably request of an amended Final Supplemented Prospectus or a
supplement to the Final Supplemented Prospectus which will correct such
statement or omission or effect such compliance;

         (d)     In the case of the Guarantor, to make generally available to
its securityholders as soon as practicable, but in any event not later than
eighteen months after the effective date of the Registration Statement (as
defined in Rule 158(c) under the Act), an earnings statement of the Guarantor
and its subsidiaries (which need not be audited) complying with Section 11(a)
of the Act and the rules and regulations of the Commission thereunder
(including, at the option of the Guarantor, Rule 158);

         (e)     During the period beginning from the date hereof and
continuing to and including the earlier of (i) the termination of trading
restrictions for the Securities, as notified to the Partnership and the
Guarantor by you, and (ii) the date which is 30 days after Time of Delivery,
each of the Partnership and the Guarantor agrees not to offer, sell, contract
to sell or otherwise dispose of any Preferred Securities, any limited
partnership interests of the Partnership, or any preferred stock of the
Guarantor or any other securities of the Partnership or the Guarantor which are
substantially similar to the Preferred Securities, or any securities
convertible into or exchangeable for, or that represent the right to receive
Preferred Securities, limited partnership interests, preferred stock or any
such substantially similar securities (other than pursuant to employee



                                     -11-

<PAGE>   12
stock option plans existing on, or upon the conversion of convertible or
exchangeable securities outstanding as of the date hereof) of either the
Partnership or the Guarantor, without your prior written consent; and

         (f)     To use its best efforts to list, subject to notice of
issuance, the Preferred Securities on the New York Stock Exchange.

         6.      The Partnership and the Guarantor jointly and severally
covenant and agree with the several Underwriters that the Partnership and the
Guarantor will pay or cause to be paid the following:  (i) the fees,
disbursements and expenses of the Partnership's and the Guarantor's counsel and
accountants in connection with the registration of the Securities under the Act
and all other expenses in connection with the preparation, printing and filing
of the Registration Statement, any Preliminary Prospectus, the Prospectus, the
Preliminary Supplemented Prospectus, the Final Supplemented Prospectus and
amendments and supplements thereto and the mailing and delivering of copies
thereof to the Underwriters and dealers; (ii) the cost of printing or producing
any Agreement Among Underwriters, this Agreement, the Indenture, any Blue Sky
Memorandum, closing documents (including any compilations thereof) and any
other documents in connection with the offering, purchase, sale and delivery of
the Securities; (iii) all expenses in connection with the qualification of the
Securities for offering and sale under state securities laws as provided in
Section 5(b) hereof, including the fees and disbursements of counsel for the
Underwriters in connection with such qualification and in connection with the
Blue Sky Memorandum; (iv) any fees charged by securities rating services for
rating the Securities; (v) any fees and expenses in connection with the listing
the Securities on the New York Stock Exchange; (vi) the cost of preparing
certificates for the Securities; (vii) the fees and expenses of the Trustee and
any agent of the Trustee and the fees and disbursements of counsel for the
Trustee in connection with the Indenture and the Debentures; (viii) the cost
and charges of any transfer agent or registrar; (ix) the cost of qualifying the
Securities with the Depository; and (x) all other costs and expenses incident
to the performance of its obligations hereunder which are not otherwise
specifically provided for in this Section.  It is understood, however, that,
except as provided in this Section, Sections 8 and 11 hereof, the Underwriters
will pay all of their own costs and expenses, including the fees of their
counsel, transfer taxes on resale of any of the Securities by them, and any
advertising expenses connected with any offers they may make.

         7.      The obligations of the Underwriters hereunder shall be
subject, in their discretion, to the condition that all representations and
warranties and other statements of each of the Partnership and the Guarantor
herein are, at and as of the Time of Delivery, true and correct, the condition
that each of the



                                     -12-

<PAGE>   13
Partnership and the Guarantor shall have performed all of their obligations
hereunder theretofore to be performed, and the following additional conditions:

         (a)     The Final Supplemented Prospectus shall have been filed with
the Commission pursuant to Rule 424(b) within the applicable time period
prescribed for such filing by the rules and regulations under the Act and in
accordance with Section 5(a) hereof; no stop order suspending the effectiveness
of the Registration Statement or any part thereof shall have been issued and no
proceeding for that purpose shall have been initiated or contemplated or
threatened by the Commission; and all requests for additional information on
the part of the Commission shall have been complied with to your reasonable
satisfaction;

         (b)     Reid & Priest, counsel for the Underwriters, shall have
furnished to you such opinion or opinions, dated the Time of Delivery, with
respect to:  the incorporation of the Guarantor and the formation of the
Partnership; insofar as the federal laws of the United States and the laws of
the States of New York, Delaware and Illinois are concerned, the validity of
the Guarantor Securities; this Agreement; the Preferred Securities; the
Indenture; the Registration Statement; the Final Supplemented Prospectus; and
other related matters as you may reasonably request, and such counsel shall
have received such papers and information as they may reasonably request to
enable them to pass upon such matters; provided, that in rendering such
opinion, Reid & Priest may rely upon the opinion of Schiff Hardin & Waite
delivered pursuant to subsection (c) hereof as to all matters of Illinois law
and upon the opinion of Richards, Layton & Finger, P.A. delivered pursuant to
subsection (e) hereof as to matters of Delaware law relating to the
Partnership, the Preferred Securities and the Partnership Agreement;

         (c)     Schiff Hardin & Waite, counsel to the Guarantor, shall have
furnished to you its written opinion, dated the Time of Delivery, in form and
substance satisfactory to you, to the effect that:

                            (i)   The Partnership has been duly qualified as a
         foreign limited partnership for the transaction of business and is in
         good standing under the laws of each jurisdiction in which it owns or
         leases properties, or conducts any business, so as to require such
         qualification, or is subject to no material liability or disability by
         reason of the failure to be so qualified in any such jurisdiction;

                           (ii)   The Guarantor has been duly incorporated and
         is validly existing as a corporation in good standing under the laws
         of the State of Illinois, with power and authority (corporate and
         other) to own its properties and conduct its business as described in
         the Preliminary Supplemented


                                     -13-


<PAGE>   14
         Prospectus and Final Supplemented Prospectus and has been duly
         qualified as a foreign corporation for the transaction of business and
         is in good standing under the laws of each other jurisdiction in which
         it owns or leases properties or conducts any business, so as to
         require such qualification, or is subject to no material liability or
         disability by reason of the failure to be so qualified in any such
         jurisdiction (such counsel being entitled to rely in respect of the
         opinion in the foregoing clause upon opinions of local counsel and in
         respect of matters of fact upon certificates of officers of the
         Guarantor, provided that such counsel shall state that he believes
         that both you and he are justified in relying upon such opinions and
         certificates);

                          (iii)   All of the issued general partner interests
         in the Partnership have been duly and validly authorized and validly
         issued, are fully paid and nonassessable and are owned by the
         Guarantor, free and clear of all liens, encumbrances, equities or
         claims; and the Partnership is not a party to or otherwise bound by
         any agreement other than this Agreement, the Partnership Agreement and
         the agreements contemplated by the Final Supplemented Prospectus; and
         the Preferred Securities conform as to legal matters to the
         description thereof contained in the Final Supplemented Prospectus;

                           (iv)   To the best knowledge of such counsel there
         is no pending or threatened action, suit or proceeding before any
         court or governmental agency, authority or body or any arbitrator
         involving the Partnership, the Guarantor or any of the Guarantor's
         subsidiaries or any property of the Guarantor or any of its
         subsidiaries, of a character required to be disclosed in the
         Registration Statement which is not adequately disclosed in the Final
         Supplemented Prospectus, and there is no contract or other document of
         a character required to be described in the Registration Statement or
         Final Supplemented Prospectus, or to be filed as an exhibit, which is
         not described in the Final Supplemented Prospectus or filed as
         required; and the statements included or incorporated in the Final
         Supplemented Prospectus describing any legal proceedings or material
         contracts or agreements relating to the Partnership or the Guarantor
         fairly summarize such matters;

                            (v)   The Preferred Securities have been validly
         issued and, subject to the qualifications set forth herein, are fully
         paid and nonassessable limited partner interests in the Partnership,
         as to which, assuming that the limited partners of the Partnership who
         have purchased Preferred Securities (the "Preferred Security
         Holders"), as limited partners of the Partnership, do not participate
         in the control of the business of the Partnership, the Preferred
         Security Holders, as limited partners of the Partnership, will have no



                                     -14-

<PAGE>   15
         liability in excess of their obligations to make payments provided for
         in the Partnership Agreement and their share of the Partnership's
         assets and undistributed profits (subject to the obligation of a
         Preferred Security Holder to repay any funds wrongfully distributed to
         it); and the Preferred Securities conform as to legal matters to the
         descriptions thereof in the Final Supplemented Prospectus;

                           (vi)   The issuance and delivery of the Debentures
         have been duly authorized, and the Debentures have been duly executed,
         authenticated, issued and delivered in accordance with the Indenture,
         and the Debentures constitute valid and legally binding obligations of
         the Guarantor entitled to the benefits provided by the Indenture;
         subject, as to enforcement, to bankruptcy, insolvency, reorganization
         and other laws of general applicability relating to or affecting
         creditors' rights and to general equity principles; the Indenture has
         been duly authorized, executed and delivered and has been duly
         qualified under the Trust Indenture Act and constitutes a valid and
         legally binding obligation of the Guarantor, enforceable in accordance
         with its terms, subject, as to enforcement, to bankruptcy, insolvency,
         reorganization and other laws of general applicability relating to or
         affecting creditors' rights and to general equity principles; and the
         Debentures and the Indenture conform as to legal matters to the
         descriptions thereof in the Final Supplemented Prospectus;

                          (vii)   The issuance of the Guarantee has been duly
         authorized and the Guarantee has been duly executed and delivered by
         the Guarantor and constitutes a valid and legally binding obligation
         of the Guarantor, enforceable in accordance with its terms, subject,
         as to enforcement, to bankruptcy, insolvency, reorganization and other
         laws of general applicability relating to or affecting creditors'
         rights and to general equity principles; and the Guarantee conforms as
         to legal matters to the description thereof in the Final Supplemented
         Prospectus;

                         (viii)   The Partnership Agreement has been duly
         authorized and constitutes a legal, valid and binding agreement of the
         Guarantor and is enforceable against the Guarantor in accordance with
         its terms, subject, as to enforcement, (A) to the effect upon the
         Partnership Agreement of (1) bankruptcy, insolvency, moratorium,
         receivership, reorganization, liquidation, fraudulent conveyance and
         other similar laws relating to or affecting the rights and remedies of
         creditors generally, and (2) principles of equity (regardless of
         whether considered and applied in a proceeding in equity or at law),
         and (B) to the fact that no opinion is expressed on the effect upon
         the Partnership Agreement of applicable law relating to fiduciary
         duties;



                                     -15-

<PAGE>   16
                           (ix)   This Agreement has been duly authorized,
         executed and delivered by each of the Partnership and the Guarantor;

                            (x)   The Order has been duly issued and remains in
         full force and effect without amendment or modification, and is not
         the subject of any appeal or other proceeding;

                           (xi)   The issuance and sale by the Partnership of
         the Preferred Securities, the issuance and sale of the Debentures by
         the Guarantor, the compliance by the Partnership and the Guarantor
         with all of the provisions of this Agreement, the execution, delivery
         and performance by the Guarantor of the Guarantee and the consummation
         of the transactions herein and therein contemplated will not conflict
         with or result in a breach or violation of any of the terms or
         provisions of, or constitute a default under, any agreement or
         instrument known to such counsel to which the Partnership or the
         Guarantor is a party or by which the Partnership or the Guarantor is
         bound or to which any of the property of the Partnership or the
         Guarantor is subject, the Certificate of Limited Partnership and the
         Partnership Agreement, the Restated Articles or By-laws of the
         Guarantor, or any statute, order, rule or regulation known to such
         counsel of any court or any federal or state governmental body having
         jurisdiction over the Partnership, the Guarantor or any of their
         properties; and no consent, approval, authorization, order,
         registration or qualification of or with any court or governmental
         agency or body is required solely as a result of the issuance, sale or
         delivery of the Securities or the consummation of the transactions
         contemplated by this Agreement, except for (i) the Order, (ii) the
         registration under the Act of the Securities, (iii) the qualification
         of the Indenture under the Trust Indenture Act and (iv) such consents,
         approvals, authorizations, registrations or qualifications as may be
         required under state securities or Blue Sky laws in connection with
         the purchase of the Preferred Securities and the distribution of the
         Securities by the Underwriters;

                          (xii)   The Partnership is not a "holding company"
         within the meaning of PUHCA; the Parent is a "holding company" as
         defined in PUHCA by reason of its ownership of all the outstanding
         shares of common stock of the Guarantor, and the Guarantor is a
         "holding company," but the Guarantor and the Parent are each exempt
         from PUHCA, except for the provisions of Section 9(a)(2) thereof, by
         virtue of Section 3(a)(2) thereof and Section 3(a)(1) thereof and Rule
         2 thereunder, respectively;

                         (xiii)   Neither the Partnership nor the Guarantor is
         and, after giving effect to the offering and sale of the Preferred
         Securities, will be an "investment company" or an



                                     -16-

<PAGE>   17
         entity "controlled" by an "investment company," as such terms are
         defined in the Investment Company Act;

                          (xiv)   Each part of the Registration Statement when
         such part became effective and the Final Supplemented Prospectus as of
         its date and any amendments or supplements thereto made by the
         Guarantor and the Partnership prior to the Time of Delivery as of the
         date of such amendment or supplement complied as to form in all
         material respects with the requirements of the Act and the Trust
         Indenture Act and the rules and regulations thereunder; such counsel
         has no reason to believe that, as of its effective date, the
         Registration Statement or any further amendment thereto made by the
         Guarantor and the Partnership prior to the Time of Delivery contained
         an untrue statement of a material fact or omitted to state a material
         fact required to be stated therein or necessary to make the statements
         therein not misleading or that, as of its date, the Final Supplemented
         Prospectus and any further amendment or supplement thereto made by the
         Guarantor and the Partnership prior to the Time of Delivery, contained
         an untrue statement of a material fact or omitted to state a material
         fact necessary to make the statements therein, in the light of the
         circumstances under which they were made, not misleading, or that, as
         of the Time of Delivery, either the Registration Statement or the
         Final Supplemented Prospectus as amended or supplemented or any
         further amendment or supplement thereto made by the Guarantor and the
         Partnership prior to the Time of Delivery contains an untrue statement
         of a material fact or omits to state a material fact necessary to make
         the statements therein, in the light of the circumstances under which
         they were made, not misleading; provided, that such counsel need not
         express any belief (A) as to the financial statements and related
         schedules in or incorporated by reference in the Registration
         Statement and the Final Supplemented Prospectus, (B) as to any
         information contained therein that was furnished to the Partnership or
         the Guarantor in writing by any Underwriter through you expressly for
         use therein or (C) as to any statements contained in the Form T-1
         filed as an exhibit to the Registration Statement; and such counsel
         does not know of any amendment to the Registration Statement required
         to be filed or of any contracts or other documents of a character
         required to be filed as an exhibit to the Registration Statement or
         required to be incorporated by reference into the Final Supplemented
         Prospectus as amended or supplemented or required to be described in
         the Registration Statement or the Final Supplemented Prospectus as
         amended or supplemented which are not filed or incorporated by
         reference or described as required; and

                           (xv)   The documents incorporated by reference in
         the Final Supplemented Prospectus or any amendment or supplement



                                     -17-

<PAGE>   18
         thereto (other than the financial statements and related schedules
         therein, as to which such counsel need express no opinion), when they
         became effective under the Act or were filed with the Commission under
         the Exchange Act, as the case may be, complied as to form in all
         material respects with the requirements of the Act or the Exchange
         Act, as applicable, and the rules and regulations of the Commission
         thereunder; and such counsel has no reason to believe that any of such
         documents, when such documents became effective or were so filed, as
         the case may be, contained, in the case of a registration statement
         which became effective under the Act, an untrue statement of a
         material fact or omitted to state a material fact required to be
         stated therein or necessary to make the statements therein, in the
         light of the circumstances under which they were made, not misleading,
         or, in the case of other documents which were filed under the Act or
         the Exchange Act with the Commission, an untrue statement of a
         material fact or omitted to state a material fact necessary in order
         to make the statements therein, in light of the circumstances under
         which they were made when such documents were so filed, not
         misleading.

         In addition, Schiff Hardin & Waite shall include advice that it
confirms its opinion as set forth under "United States Taxation" in the Final
Supplemented Prospectus.

         The foregoing opinions may be limited to the laws of New York,
Delaware and the State of Illinois and federal securities laws.  In rendering
its opinion, such counsel may rely, as to matters of Delaware law relating to
the Partnership, the Preferred Securities and the Partnership Agreement, upon
the opinion of Richards, Layton & Finger, P.A., delivered pursuant to
subsection (d) hereof, and as to matters of New York law relating to the
Debentures and the Indenture, upon the opinion of Reid & Priest, delivered
pursuant to subsection (b) hereof;

         (d)     Richards, Layton & Finger, P.A., special Delaware counsel to
the Partnership and the Guarantor, shall have furnished to you their opinion,
dated the Time of Delivery, in form and substance satisfactory to you, to the
effect that:

                            (i)   The Partnership has been duly formed and is
         validly existing in good standing as a limited partnership under the
         laws of the State of Delaware;

                           (ii)   Under the Partnership Agreement and the
         Delaware Revised Uniform Limited Partnership Act, 6 Del. Code Section
         17-101, et seq. (the "Delaware Act"), the Partnership has all
         necessary partnership power and authority to own its properties and
         conduct its business, all as described in the Final Supplemented
         Prospectus;


                                     -18-


<PAGE>   19
                          (iii)   The general partner interests in the
         Partnership issued to the Guarantor have been duly and validly
         authorized and are validly issued;

                           (iv)   The Preferred Securities have been duly and
         validly authorized and are validly issued and, subject to the
         qualifications set forth herein, are fully paid and nonassessable
         limited partner interests in the Partnership, as to which, assuming
         that the limited partners of the Partnership who have purchased
         Preferred Securities (the "Preferred Security Holders"), as limited
         partners of the Partnership, do not participate in the control of the
         business of the Partnership, the Preferred Security Holders, as
         limited partners of the Partnership, will have no liability in excess
         of their obligations to make payments provided for in the Partnership
         Agreement and their share of the Partnership's assets and
         undistributed profits (subject to the obligation of a Preferred
         Security Holder to repay any funds wrongfully distributed to it);

                            (v)   There are no provisions in the Partnership
         Agreement the inclusion of which, subject to the terms and conditions
         therein, or, assuming that the Preferred Security Holders, as limited
         partners of the Partnership, take no action other than actions
         permitted by the Partnership Agreement, the exercise of which, in
         accordance with the terms and conditions therein, would cause the
         Preferred Security Holders, as limited partners of the Partnership, to
         be deemed to be participating in the control of the business of the
         Partnership;

                           (vi)   The Partnership Agreement constitutes a
         legal, valid and binding agreement of the Guarantor, and is
         enforceable against the Guarantor, in accordance with its terms,
         subject, as to enforcement, (A) to the effect upon the Partnership
         Agreement of (1) bankruptcy, insolvency, moratorium, receivership,
         reorganization, liquidation, fraudulent conveyance and other similar
         laws relating to or affecting the rights and remedies of creditors
         generally, and (2) principles of equity (regardless of whether
         considered and applied in a proceeding in equity or at law), and (B)
         to the fact that no opinion is expressed on the effect upon the
         Partnership Agreement of applicable law relating to fiduciary duties;

                          (vii)   Under the Partnership Agreement and the
         Delaware Act, the Partnership has all necessary partnership power and
         authority to execute and deliver, and to perform its obligations
         under, this Agreement;

                         (viii)   Under the Partnership Agreement and the
         Delaware Act, the execution and delivery by the Partnership of



                                     -19-

<PAGE>   20
         this Agreement, and the performance by the Partnership of its
         obligations hereunder, have been duly authorized by all necessary
         partnership action on the part of the Partnership;

                           (ix)   The issuance and sale by the Partnership of
         the Preferred Securities pursuant to this Agreement and the execution,
         delivery and performance by the Partnership of this Agreement will not
         violate (a) any Delaware statute, rule or regulation, (b) the
         Certificate of Limited Partnership of the Partnership or the
         Partnership Agreement;

                            (x)   No consent, approval, authorization, order,
         registration or qualification of or with any Delaware court or
         Delaware governmental agency or body is required solely as a result of
         the issuance, sale or delivery by the Partnership of the Preferred
         Securities pursuant to this Agreement, the execution, delivery and
         performance by the Partnership of this Agreement or the consummation
         of the transaction contemplated in this Agreement;

                           (xi)   Such counsel has reviewed the statements in
         the Final Supplemented Prospectus under the caption "Illinois Power
         Capital" and, insofar as it contains statements of Delaware law, such
         statements are fairly presented; and

                          (xii)   Assuming that the Partnership is treated as a
         partnership for federal income tax purposes, and assuming that the
         Partnership derives no income from or connected with sources within
         the State of Delaware and has no assets, activities (other than the
         maintenance of a registered office and registered agent in the State
         of Delaware and the filing of documents with the Delaware Secretary of
         State) or employees in the State of Delaware, the Preferred Security
         Holders (other than those Preferred Security Holders who reside or are
         domiciled in the State of Delaware), will have no liability for income
         taxes imposed by the State of Delaware solely as a result of their
         participation in the Partnership, and the Partnership will not be
         liable for any income tax imposed by the State of Delaware.

         (e)     On the date of this Agreement and at the Time of Delivery,
Price Waterhouse LLP shall have furnished to you a letter, dated the date of
delivery thereof, to the effect set forth in Annex I hereto, and with respect
to such letter dated the Time of Delivery, as to such other matters as you may
reasonably request and in form and substance satisfactory to you;

         (f)     (i)      Neither the Partnership, the Guarantor nor any of the
Guarantor's other subsidiaries shall have sustained, since the date of the
latest audited financial statements included or incorporated by reference in
the Final Supplemented Prospectus, any loss or interference with its business
from fire, explosion, flood



                                     -20-

<PAGE>   21
or other calamity, whether or not covered by insurance, or from any labor
dispute or court or governmental action, order or decree, otherwise than as set
forth or contemplated in the Final Supplemented Prospectus, and, (ii) since the
respective dates as of which information is given in the Final Supplemented
Prospectus there shall not have been any change in the capital stock or
long-term debt of the Guarantor or any of its subsidiaries (determined on a
consolidated basis) or any change, or any development involving a prospective
change, in or affecting the general affairs, management, financial position,
stockholders' equity or results of operations of the Guarantor and its
subsidiaries, otherwise than as set forth or contemplated in the Final
Supplemented Prospectus, the effect of which, in any such case described in
clause (i) or (ii), is in your judgment so material and adverse as to make it
impracticable or inadvisable to proceed with the public offering or delivery of
the Securities on the terms and in the manner contemplated in the Final
Supplemented Prospectus;

         (g)     On or after the date hereof (i) no downgrading shall have
occurred in the rating accorded the Preferred Securities or any of the
Guarantor's debt securities or preferred stock (including the Guarantee) by any
"nationally recognized statistical rating organization," as that term is
defined by the Commission for purposes of Rule 436(g)(2) under the Act, and
(ii) no such organization shall have publicly announced that it has under
surveillance or review, with possible negative implications, its rating of any
of the Partnership's or the Guarantor's debt securities or preferred stock.

         (h)     On or after the date hereof there shall not have occurred any
of the following:  (i) a suspension or material limitation in trading in
securities generally on the New York Stock Exchange; (ii) a suspension or
material limitation in trading in the Guarantor's securities on the New York
Stock Exchange; (iii) a general moratorium on commercial banking activities
declared by either federal or New York State authorities; or (iv) the outbreak
or escalation of hostilities involving the United States or the declaration by
the United States of a national emergency or war, if the effect of any such
event specified in this clause (iv) in your judgment makes it impracticable or
inadvisable to proceed with the public offering or the delivery of the
Preferred Securities on the terms and in the manner contemplated in the Final
Supplemented Prospectus;

         (i)     The Preferred Securities shall have been duly listed, subject
to notice of issuance, on the New York Stock Exchange;

         (j)     The Guarantor shall have furnished or caused to be furnished
to you at the Time of Delivery, a certificate or certificates of the general
partner of the Partnership and a



                                     -21-

<PAGE>   22
certificate or certificates of officers of the Guarantor, respectively,
satisfactory to you as to (i) the accuracy of the representations and
warranties of the Partnership and the Guarantor herein at and as of the Time of
Delivery, (ii) the performance by each of the Partnership and the Guarantor of
all of their obligations hereunder to be performed at or prior to the Time of
Delivery, (iii) the matters set forth in subsections (a) and (g) of this
Section and (iv) such other matters as you may reasonably request; and

         (k)     A Special Event (as defined in the Final Supplemented
Prospectus) shall not have occurred and be continuing.

         8.      (a)      The Partnership and the Guarantor will jointly and
severally indemnify and hold harmless each Underwriter against any losses,
claims, damages or liabilities, joint or several, to which such Underwriter may
become subject, under the Act or otherwise, insofar as such losses, claims,
damages or liabilities (or actions in respect thereof) arise out of or are
based upon an untrue statement or alleged untrue statement of a material fact
contained in any Preliminary Prospectus, the Registration Statement, the
Prospectus, the Preliminary Supplemented Prospectus, the Final Supplemented
Prospectus or any other prospectus relating to the Securities, or any amendment
or supplement thereto, or arise out of or are based upon the omission or
alleged omission to state therein a material fact required to be stated therein
or necessary to make the statements therein, in the light of the circumstances
under which they were made, not misleading, and will reimburse each Underwriter
for any legal or other expenses reasonably incurred by such Underwriter in
connection with investigating or defending any such action or claim as such
expenses are incurred; provided, however, that neither the Partnership nor the
Guarantor shall be liable in any such case to the extent that any such loss,
claim, damage or liability arises out of or is based upon an untrue statement
or alleged untrue statement or omission or alleged omission made in any
Preliminary Prospectus, the Registration Statement, the Prospectus, the
Preliminary Supplemented Prospectus, the Final Supplemented Prospectus or any
other prospectus relating to the Securities or any such amendment or supplement
in reliance upon and in conformity with written information furnished to the
Partnership or the Guarantor through you expressly for use therein;

         (b)     Each Underwriter will indemnify and hold harmless the
Partnership and the Guarantor against any losses, claims, damages or
liabilities to which the Partnership or the Guarantor may become subject, under
the Act or otherwise, insofar as such losses, claims, damages or liabilities
(or actions in respect thereof) arise out of or are based upon an untrue
statement or alleged untrue statement of a material fact contained in any
Preliminary Prospectus, the Registration Statement, the Prospectus, the
Preliminary Supplemented Prospectus, the Final Supplemented Prospectus and any
other prospectus relating to the Securities, or



                                     -22-

<PAGE>   23
any amendment or supplement thereto, or arise out of or are based upon the
omission or alleged omission to state therein a material fact required to be
stated therein or necessary to make the statements therein not misleading, in
each case to the extent, but only to the extent, that such untrue statement or
alleged untrue statement or omission or alleged omission was made in any
Preliminary Prospectus, the Registration Statement, the Prospectus, the
Preliminary Supplemented Prospectus, the Final Supplemented Prospectus and any
other prospectus relating to the Securities, or any such amendment or
supplement in reliance upon and in conformity with written information
furnished to the Partnership or the Guarantor by such Underwriter through you
expressly for use therein; and will reimburse the Partnership and the Guarantor
for any legal or other expenses reasonably incurred by the Partnership or the
Guarantor in connection with investigating or defending any such action or
claim as such expenses are incurred.

         (c)     Promptly after receipt by an indemnified party under
subsection (a) or (b) above of notice of the commencement of any action, such
indemnified party shall, if a claim in respect thereof is to be made against
the indemnifying party under such subsection, notify the indemnifying party in
writing of the commencement thereof; but that the omission so to notify the
indemnifying party shall not relieve it from any liability which it may have to
any indemnifying party otherwise than under such subsection.  In case any such
action shall be brought against any indemnified party and it shall notify the
indemnifying party of the commencement thereof, the indemnifying party shall be
entitled to participate therein and, to the extent that it shall wish, jointly
with any other indemnifying party similarly notified, to assume the defense
thereof, with counsel satisfactory to such indemnified party (who shall not,
except with the consent of the indemnified party, be counsel to the
indemnifying party), and, after notice from the indemnifying party to such
indemnified party of its election so to assume the defense thereof, the
indemnifying party shall not be liable to such indemnified party under such
subsection for any legal expenses of other counsel or any other expenses, in
each case subsequently incurred by such indemnified party, in connection with
the defense thereof other than reasonable costs of investigation.  No
indemnifying party shall, without the written consent of the indemnified party,
effect the settlement or compromise of, or consent to the entry of any judgment
with respect to, any pending or threatened action or claim in respect of which
indemnification or contribution may be sought hereunder (whether or not the
indemnified party is an actual or potential party to such action or claim)
unless such settlement, compromise or judgment (i) includes an unconditional
release of the indemnified party from all liability arising out of such action
or claim and (ii) does not include any statement as to, or an admission of,
fault, culpability or a failure to act, by or on behalf of any indemnified
party.



                                     -23-

<PAGE>   24
         (d)     If the indemnification provided for in this Section 8 is
unavailable to or insufficient to hold harmless an indemnified party under
subsection (a) or (b) above in respect of any losses, claims, damages or
liabilities (or actions in respect thereof) referred to therein, then each
indemnifying party shall contribute to the amount paid or payable by such
indemnified party as a result of such losses, claims, damages or liabilities
(or actions in respect thereof) in such proportion as is appropriate to reflect
the relative benefits received by the Partnership and the Guarantor on the one
hand and the Underwriters on the other from the offering of the Securities.
If, however, the allocation provided by the immediately preceding sentence is
not permitted by applicable law or if the indemnified party failed to give
notice required under subsection (c) above, then each indemnifying party shall
contribute to such amount paid or payable by such indemnified party in such
proportion as is appropriate to reflect not only such relative benefits but
also the relative fault of the Partnership and the Guarantor on the one hand
and the Underwriters on the other in connection with the statements or
omissions which resulted in such losses, claims, damages or liabilities (or
actions in respect thereof), as well as any other relevant equitable
considerations.  The relative benefits received by the Partnership and the
Guarantor on the one hand and such Underwriters on the other shall be deemed to
be in the same proportions as the total net proceeds from the offering (before
deducting expenses) received by the Partnership and the Guarantor bear to the
total underwriting discounts and commissions received by such Underwriters.
The relative fault shall be determined by reference to, among other things,
whether the untrue or alleged untrue statement of a material fact or the
omission or alleged omission to state a material fact relates to information
supplied by the Partnership and the Guarantor on the one hand or such
Underwriters on the other and the parties' relative intent, knowledge, access
to information and opportunity to correct or prevent such statement or
omission.  The Partnership, the Guarantor and the Underwriters agree that it
would not be just and equitable if contribution pursuant to this subsection (d)
were determined by pro rata allocation (even if the Underwriters were treated
as one entity for such purpose) or by any other method of allocation which does
not take account of the equitable considerations referred to above in this
subsection (d).  The amount paid or payable by an indemnified party as a result
of the losses, claims, damages or liabilities (or actions in respect thereof)
referred to above in this subsection (d) shall be deemed to include any legal
or other expenses reasonably incurred by such indemnified party in connection
with investigating or defending any such action or claim.  Notwithstanding the
provisions of this subsection (d), no Underwriter shall be required to
contribute any amount in excess of the amount by which the total price at which
the Securities underwritten by it and distributed to the public were offered to
the public exceeds the amount of any damages which such Underwriter has
otherwise been required to pay by reason of such untrue or alleged untrue
statement or omission or alleged



                                     -24-

<PAGE>   25
omission.  No person guilty of fraudulent misrepresentation (within the meaning
of Section 11(f) of the Act) shall be entitled to contribution from any person
who was not guilty of such fraudulent misrepresentation.  The obligations of
the Underwriters in this subsection (d) to contribute are several in proportion
to their respective underwriting obligations with respect to the Securities and
not joint.

         (e)     The obligations of the Partnership and the Guarantor under
this Section 8 shall be in addition to any liability which the Partnership and
the Guarantor may otherwise have and shall extend, upon the same terms and
conditions, to each person, if any, who controls any Underwriter within the
meaning of the Act; and the obligations of the Underwriters under this Section
8 shall be in addition to any liability which the respective Underwriters may
otherwise have and shall extend, upon the same terms and conditions, to each
officer and director of the Partnership and the Guarantor and to each person,
if any, who controls the Partnership or the Guarantor within the meaning of the
Act.

         9.      (a)      If any Underwriter shall default in its obligation to
purchase the Preferred Securities which it has agreed to purchase hereunder,
you may, in your discretion, arrange for you or another party or other parties
to purchase such Preferred Securities on the terms contained herein.  If within
thirty-six hours after such default by any Underwriter you do not arrange for
the purchase of such Preferred Securities, then the Partnership and the
Guarantor shall be entitled to a further period of thirty-six hours within
which to procure another party or other parties satisfactory to you to purchase
such Preferred Securities on such terms.  In the event that, within the
respective prescribed periods, you notify the Partnership and the Guarantor
that you have so arranged for the purchase of such Preferred Securities, or the
Partnership or the Guarantor notifies you that it has so arranged for the
purchase of the Preferred Securities, you or the Partnership and the Guarantor
shall have the right to postpone the Time of Delivery for a period of not more
than seven days, in order to effect whatever changes may thereby be made
necessary in the Registration Statement or the Final Supplemented Prospectus,
or in any other documents or arrangements, and the Partnership and the
Guarantor agree to file promptly any amendments or supplements to the
Registration Statement or the Prospectus which in your opinion may thereby be
made necessary.  The term "Underwriter" as used in this Agreement shall include
any person substituted under this Section with like effect as if such person
had originally been a party to this Agreement with respect to such Preferred
Securities.

         (b)     If, after giving effect to any arrangements for the purchase
of the Preferred Securities of a defaulting Underwriter or Underwriters by you
and the Partnership and the Guarantor as provided in subsection (a) above, the
aggregate number of such Preferred Securities which remains unpurchased does
not exceed one-



                                     -25-

<PAGE>   26
eleventh of the aggregate number of all the Preferred Securities, then the
Partnership and the Guarantor shall have the right to require each
non-defaulting Underwriter to purchase the number of Preferred Securities which
such Underwriter agreed to purchase hereunder and, in addition, to require each
non-defaulting Underwriter to purchase its pro rata share (based on the number
of Preferred Securities which such Underwriter agreed to purchase hereunder) of
the Preferred Securities of such defaulting Underwriter or Underwriters for
which such arrangements have not been made; but nothing herein shall relieve a
defaulting Underwriter from liability for its default.

         (c)     If, after giving effect to any arrangements for the purchase
of the Preferred Securities of a defaulting Underwriter or Underwriters by you,
the Partnership and the Guarantor as provided in subsection (a) above, the
aggregate principal amount of the Preferred Securities which remains
unpurchased exceeds one-eleventh of the aggregate number of the Preferred
Securities, or if the Partnership and the Guarantor shall not exercise the
right described in subsection (b) above to require non-defaulting Underwriters
to purchase Preferred Securities of a defaulting Underwriter or Underwriters,
then this Agreement shall thereupon terminate, without liability on the part of
any non-defaulting Underwriter, the Partnership or the Guarantor, except for
the expenses to be borne by the Partnership, the Guarantor and the Underwriters
as provided in Section 6 hereof and the indemnity and contribution agreements
in Section 8 hereof; but nothing herein shall relieve a defaulting Underwriter
from liability for its default.

         10.     The respective indemnities, agreements, representations,
warranties and other statements of the Partnership, the Guarantor, and of the
several Underwriters, as set forth in this Agreement or made by or on behalf of
them, respectively, pursuant to this Agreement, shall remain in full force and
effect, regardless of any investigation (or any statement as to the results
thereof) made by or on behalf of any Underwriter or any controlling person of
any Underwriter, or the Partnership, the Guarantor or any officer or director
or controlling person of the Partnership or the Guarantor, and shall survive
delivery of and payment for the Preferred Securities.

         11.     If this Agreement shall be terminated pursuant to Section 9
hereof, neither the Partnership nor the Guarantor shall then be under any
liability to any Underwriter except as provided in Section 6 and Section 8
hereof; but, if for any other reason, the Preferred Securities are not
delivered by or on behalf of the Partnership or the related Guarantor
Securities issuable by the Guarantor are not concurrently issued by the
Guarantor as provided herein, the Partnership and the Guarantor will reimburse
the Underwriters through you for all out-of-pocket expenses approved in writing
by you, including fees and disbursements of counsel,



                                     -26-

<PAGE>   27
reasonably incurred by the Underwriters in making preparations for the
purchase, sale and delivery of the Preferred Securities (or Guarantor
Securities not so issued), but the Partnership and the Guarantor shall then be
under no further liability to any Underwriter except as provided in Sections 6
and 8 hereof.

         12.     In all dealings hereunder, you shall act on behalf of the
Underwriters, and the parties hereto shall be entitled to act and rely upon any
statement, request, notice or agreement on behalf of any Underwriter made or
given by you jointly or by Goldman, Sachs & Co. on behalf of you as the
representatives.

         All statements, requests, notices, and agreements hereunder shall be
in writing, and if to the Underwriters shall be delivered or sent by mail,
telex or facsimile transmission to you in care of Goldman, Sachs & Co.; and if
to the Partnership or the Guarantor shall be delivered or sent by mail, telex
or facsimile transmission to the address of the Guarantor set forth in the
Registration Statement, Attention: Controller; provided, however, that any
notice to any Underwriter pursuant to Section 8(c) hereof shall be delivered or
sent by mail, telex or facsimile transmission to such Underwriter at its
address set forth in its Underwriters' Questionnaire, or telex constituting
such Questionnaire, which address will be supplied to the Partnership or the
Guarantor upon your request.  Any such statements, requests, notices or
agreements shall take effect upon receipt thereof.

         13.     This Agreement shall be binding upon, and inure solely to the
benefit of, the parties hereto and, to the extent provided in Sections 8 and 10
hereof, the officers and directors of the Partnership and the Guarantor and
each person who controls the Partnership and the Guarantor or any Underwriter,
and their respective heirs, executors, administrators, successors and assigns,
and no other person shall acquire or have any right under or by virtue of this
Agreement.  No purchaser of any of the Preferred Securities from any
Underwriter shall be deemed a successor or assign by reason merely of such
purchase.

         14.     Time shall be of the essence of this Agreement.  As used
herein, the term "business day" shall mean any day when the Commission's office
in Washington, D.C. is open for business.

         15.     THIS AGREEMENT SHALL BE GOVERNED BY AND CONSTRUED IN
ACCORDANCE WITH THE LAWS OF THE STATE OF NEW YORK.

         16.     This Agreement may be executed by any one or more of the
parties hereto in any number of counterparts, each of which shall be deemed to
be an original, but all such respective counterparts shall together constitute
one and the same instrument.

         If the foregoing is in accordance with your understanding, please sign
and return to us __ counterparts hereof,



                                     -27-

<PAGE>   28
and upon the acceptance hereof by you, on behalf of each of the Underwriters,
this letter and such acceptance hereof shall constitute a binding agreement
among each of the Underwriters, on the one hand, and the Partnership and the
Guarantor, on the other hand.  It is understood that your acceptance of this
letter on behalf of each of the Underwriters is pursuant to the authority set
forth in a form of Agreement Among Underwriters, the form of which shall be
submitted to the Partnership and the Guarantor for examination, upon request,
but without warranty on your part as to the authority of the signers thereof.

                                         Very truly yours,


                                         ILLINOIS POWER CAPITAL, L.P.


                                         By:_________________________________  
                                            ILLINOIS POWER COMPANY,
                                              as General Partner



                                         ILLINOIS POWER COMPANY


                                         By:_________________________________  
                                            Name:
                                            Title:

Accepted as of the date hereof:


[                             ]


By:____________________________                                                
         Goldman, Sachs & Co.


On behalf of each of the several Underwriters









                                     -28-
<PAGE>   29
                                                                      SCHEDULE I

                                                         Total Number of
                                                      Preferred Securities
                Underwriter                              to be Purchased   
                Goldman, Sachs & Co.                  $



                                                       ---------------
Total . . . . . . . . . . . . . . . . . . . .         $
                                                       ===============





<PAGE>   30
                                                                         ANNEX I


        Pursuant to Section 7(e) of the Underwriting Agreement, Price 
Waterhouse LLP shall furnish letters to the Underwriters to the effect that:

        (i)   They are independent certified public accountants with respect to 
the Guarantor and its subsidiaries within the meaning of the Act and the 
published rules and regulations of the Commission thereunder;

        (ii)   In their opinion, the financial statements and any supplementary 
financial information and schedules examined by them and included or 
incorporated by reference in the Registration Statement or the Prospectus 
comply as to form in all material respects with the applicable accounting 
requirements of the Act or the Exchange Act, as applicable, and the related 
published rules and regulations thereunder;

        (iii)   They have made a review in accordance with standards
established by the American Institute of Certified Public Accountants of the
unaudited condensed consolidated statements of income, consolidated balance
sheets and consolidated statements of cash flows included in the Guarantor's
quarterly reports on Form 10-Q incorporated by reference into the Prospectus;
and on the basis of specified procedures including inquiries of officials of
the Guarantor who have responsibility for financial and accounting matters
regarding whether the unaudited condensed consolidated financial statements
referred to in paragraph (vi)(A)(i) below comply as to form in all material
respects with the applicable accounting requirements of the Act and the
Exchange Act and the related published rules and regulations thereunder,
nothing came to their attention that caused them to believe that the unaudited
condensed consolidated financial statements do not comply as to form in all
material respects with the applicable accounting requirements of the Act and
the Exchange Act and the related published rules and regulations thereunder;

        (iv)   The unaudited selected financial information with respect to the
consolidated results of operations and financial position of the Guarantor for
the five most recent fiscal years included in the Prospectus and included or
incorporated by reference in Item 6 of the Guarantor's Annual Report on Form
10-K for the most recent fiscal year agrees with the corresponding amounts
(after restatement where applicable) in the audited consolidated financial
statements for such five fiscal years which were included or incorporated by
reference in the Guarantor's Annual Reports on Form 10-K for such fiscal years;

        (v)   They have compared the information in the Prospectus under the
caption "Ratio of Earnings to Fixed Charges





<PAGE>   31
                                                                         ANNEX I
                                                                          Page 2


and Ratio of Earnings to Combined Fixed Charges and Preferred Stock Dividend
Requirements" with the disclosure requirements of item 503(d) of Regulation S-K
and on the basis of limited procedures specified in such letter nothing came to
their attention as a result of the foregoing procedures that caused them to
believe that such information does not conform in all material respects with
the disclosure requirements of item 503(d) of Regulation S-K;

        (vi)   On the basis of limited procedures, not constituting an
examination in accordance with generally accepted auditing standards,
consisting of a reading of the unaudited financial statements and other
information referred to below, a reading of the latest available interim
financial statements of the Guarantor and its subsidiaries, inspection of the
minute books of the Guarantor and its subsidiaries since the date of the latest
audited financial statements included or incorporated by reference in the
Prospectus, inquiries of officials of the Guarantor and its subsidiaries
responsible for financial and accounting matters and such other inquiries and
procedures as may be specified in such letter, nothing came to their attention
that caused them to believe that:

                (A)  (i)  the unaudited condensed consolidated statements of
         income, consolidated balance sheets and consolidated statements of
         cash flows included in the Guarantor's Quarterly Reports on Form 10-Q
         incorporated by reference in the Prospectus do not comply as to form
         in all material respects with the applicable accounting requirements
         of the Exchange Act and the related published rules and regulations
         thereunder, or (ii) any material modifications should be made to the
         unaudited condensed consolidated statements of income, consolidated
         balance sheets and consolidated statements of cash flows included in
         the Guarantor's Quarterly Reports on Form 10-Q incorporated by
         reference in the Prospectus, for them to be in conformity with
         generally accepted accounting principles;

                (B)      the unaudited income statement data and balance sheet
         items included in the Prospectus under the caption "Summary Financial
         Information of the Company" do not agree with the corresponding items
         in the unaudited consolidated financial statements from which such
         data and items were derived, and any such unaudited data and items
         were not determined on a basis substantially consistent with the basis
         for the corresponding amounts in the audited consolidated financial
         statements included or incorporated by reference in the Guarantor's
         Annual Report on Form 10-K for the most recent fiscal year;





<PAGE>   32
                                                                         ANNEX I
                                                                          Page 3



                (C)      the unaudited financial statements which were not
         included in the Prospectus but from which were derived (i) the
         unaudited condensed financial statements referred to in clause (A) and
         (ii) the unaudited income statement data and balance sheet items
         included in the Prospectus under the caption "Summary Financial
         Information of the Company" and referred to in Clause (B) were not
         determined on a basis substantially consistent with the basis for the
         audited financial statements included or incorporated by reference in
         the Guarantor's Annual Report on Form 10-K for the most recent fiscal
         year;

                (D)      as of a specified date not more than five days prior
         to the date of such letter, there have been any changes in the
         consolidated capital stock or any increase in the consolidated
         long-term debt of the Guarantor and its subsidiaries, or any decreases
         in consolidated current assets or stockholders' equity, in each case
         as compared with amounts shown in the latest balance sheet included or
         incorporated by reference in the Prospectus, except in each case for
         changes, increases or decreases which the Prospectus discloses have
         occurred or may occur or which are described in such letter; and

                (E)      for the period from the date of the latest income
         statement included or incorporated by reference in the Prospectus to
         the specified date referred to in Clause (D) there were any decreases
         in consolidated revenues or operating income or the total or per share
         amounts of consolidated net income of the Guarantor and its
         subsidiaries, in each case as compared with the comparable period of
         the preceding year, except in each case for increases or decreases
         which the Prospectus discloses have occurred or may occur or which are
         described in such letter; and

        (vii)   In addition to the examination referred to in their report
included or incorporated by reference in the Prospectus and the limited
procedures, inspection of minute books, inquiries and other procedures referred
to in paragraphs (iii) and (vi) above, they have carried out certain specified
procedures, not constituting an examination in accordance with generally
accepted auditing standards, with respect to certain amounts, percentages and
financial information specified by the representatives of the Underwriters (the
"Representatives") which are derived from the general accounting records of the
Guarantor and its subsidiaries, which appear in the Prospectus (excluding
documents incorporated by reference), or in Part II of, or in exhibits and
schedules to, the Registration Statement specified by the Representatives or in





<PAGE>   33
                                                                         ANNEX I
                                                                          Page 4


documents incorporated by reference in the Prospectus specified by the
Representatives, and have compared certain of such amounts, percentages and
financial information with the accounting records of the Guarantor and its
subsidiaries and have found them to be in agreement.

        For purposes of this letter, all references in this Annex I to the
Prospectus shall be deemed to the Final Supplemented Prospectus in the form in
which it is proposed to be filed but otherwise as defined in the Underwriting
Agreement (including all documents incorporated by reference therein) as of the
date of the letter delivered on the date of the Underwriting Agreement and to
the Final Supplemented Prospectus as defined in the Underwriting Agreement
(including all documents incorporated by reference therein), or, if the
Prospectus has at such time been further amended or supplemented, to the
Prospectus as so further amended or supplemented, as of the date of the letter
delivered at the Time of Delivery.






<PAGE>   1
                                                                    EXHIBIT 4(C)



                         AMENDED AND RESTATED AGREEMENT

                                       OF

                              LIMITED PARTNERSHIP

                                       OF

                          ILLINOIS POWER CAPITAL, L.P.
<PAGE>   2
                               TABLE OF CONTENTS


                                   ARTICLE I

                 FORMATION AND CONTINUATION OF THE PARTNERSHIP;
                    ADMISSION OF PREFERRED SECURITY HOLDERS;
            RETURN OF INITIAL LIMITED PARTNER'S CAPITAL CONTRIBUTION

<TABLE>
 <S>            <C>                                                                                    <C>
 Section 1.1.   Formation and Continuation of the Partnership  . . . . . . . . . . . . . . . . . . .    1
 Section 1.2.   Name   . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .    2
 Section 1.3.   Business of the Partnership  . . . . . . . . . . . . . . . . . . . . . . . . . . . .    2
 Section 1.4.   Term   . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .    2
 Section 1.5.   Registered Agent and Office  . . . . . . . . . . . . . . . . . . . . . . . . . . . .    2
 Section 1.6.   Principal Place of Business  . . . . . . . . . . . . . . . . . . . . . . . . . . . .    2
 Section 1.7.   Name and Business Address of General Partner   . . . . . . . . . . . . . . . . . . .    2
 Section 1.8.   Admission of Holders of Preferred Securities   . . . . . . . . . . . . . . . . . . .    2
                                                                                                   
                                                                                                   
                                  ARTICLE II                                                       
                                                                                                   
                                 DEFINED TERMS                                                     
                                                                                                   
 Section 2.1.   Definitions  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .    3
 Section 2.2.   Headings   . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .    8
                                                                                                   
                                                                                                   
                                  ARTICLE III                                                      
                                                                                                   
                   CAPITAL CONTRIBUTIONS, REPRESENTATION OF                                        
            PREFERRED SECURITY HOLDER'S INTEREST; CAPITAL ACCOUNTS                                 
                                                                                                   
 Section 3.1.   Capital Contributions  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .    8
 Section 3.2.   Preferred Security Holder's Interest Represented by Preferred Securities   . . . . .    8
 Section 3.3.   Capital Accounts   . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .    9
 Section 3.4.   Interest on Capital Contributions  . . . . . . . . . . . . . . . . . . . . . . . . .    9
 Section 3.5.   Withdrawal and Return of Capital Contributions   . . . . . . . . . . . . . . . . . .    9
                                                                                                   
                                                                                                   
                                  ARTICLE IV                                                       
                                                                                                   
                                  ALLOCATIONS                                                      
                                                                                                   
 Section 4.1.   Profits and Losses   . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .    9
 Section 4.2.   Other Allocation Provisions  . . . . . . . . . . . . . . . . . . . . . . . . . . . .   10
 Section 4.3.   Allocations for Income Tax Purposes  . . . . . . . . . . . . . . . . . . . . . . . .   11
 Section 4.4.   Withholding  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .   11
</TABLE>       





                                      -i-
<PAGE>   3
<TABLE>
                                                             ARTICLE V

                                                             DIVIDENDS

  <S>            <C>                                                                                   <C>
  Section 5.1.   Dividends  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .   12
  Section 5.2.   Limitations on Distributions   . . . . . . . . . . . . . . . . . . . . . . . . . . .   12
                                                                                             
                                                                                             
                                                            ARTICLE VI
                                                                 
                                                 ISSUANCE OF PREFERRED SECURITIES
                                                                                             
  Section 6.1.   General Provisions Regarding Preferred Securities  . . . . . . . . . . . . . . . . .   12
  Section 6.2.   Voting Rights  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .   15
  Section 6.3.   Mergers  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .   17
                                                                                             
                                                                                             
                                                            ARTICLE VII
                                                                 
                                               BOOKS OF ACCOUNT, RECORDS AND REPORTS
                                                                                             
  Section 7.1.   Books and Records  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .   17
  Section 7.2.   Accounting Method  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .   18
                                                                                             
                                                                                             
                                                           ARTICLE VIII
                                                                 
                                                     POWERS, RIGHTS AND DUTIES
                                                      OF THE LIMITED PARTNERS
  Section 8.1.   Limitations  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .   18
  Section 8.2.   Liability  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .   18
  Section 8.3.   Priority   . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .   18
                                                                                             
                                                                 
                                                            ARTICLE IX
                                                                 
                                                     POWERS, RIGHTS AND DUTIES
                                                      OF THE GENERAL PARTNER
                                                                 
  Section 9.1.   Authority  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .   19
  Section 9.2.   Powers and Duties of General Partner   . . . . . . . . . . . . . . . . . . . . . . .   19
  Section 9.3.   Liability  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .   20
  Section 9.4.   Exculpation  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .   20
  Section 9.5.   Fiduciary Duty   . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .   20
  Section 9.6.   Indemnification  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .   21
  Section 9.7.   Outside Businesses   . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .   21
  Section 9.8.   Limits on General Partner's Powers   . . . . . . . . . . . . . . . . . . . . . . . .   22
  Section 9.9.   Tax Matters Partner  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .   22
  Section 9.10.  Expenses   . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .   22
</TABLE>   





                                      -ii-
<PAGE>   4
<TABLE>

                                                             ARTICLE X
                                                                 
                                                TRANSFERS OF INTERESTS BY PARTNERS

 <S>            <C>                                                                                          <C>
 Section 10.1.  Transfer of Interests  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .   23
 Section 10.2.  Transfer of LP Certificates  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .   23
 Section 10.3.  Persons Deemed Preferred Security Holders  . . . . . . . . . . . . . . . . . . . . . . . .   23
 Section 10.4.  Book Entry Interests   . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .   24
 Section 10.5.  Notices to Clearing Agency   . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .   24
 Section 10.6.  Appointment of Successor Clearing Agency   . . . . . . . . . . . . . . . . . . . . . . . .   24
 Section 10.7.  Definitive LP Certificates; Appointment of Paying Agent(s)   . . . . . . . . . . . . . . .   24
                                                                                                   
                                                                 
                                                            ARTICLE XI
                                                                 
                                                     WITHDRAWAL; DISSOLUTION;
                                              LIQUIDATION AND DISTRIBUTION OF ASSETS
                                                                                                   
 Section 11.1.  Withdrawal of Partners   . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .   25
 Section 11.2.  Dissolution of the Partnership   . . . . . . . . . . . . . . . . . . . . . . . . . . . . .   25
 Section 11.3.  Liquidation  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .   26
 Section 11.4.  Distribution in Liquidation  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .   27
 Section 11.5.  Rights of Limited Partners   . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .   27
 Section 11.6.  Termination  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .   27
                                                                                                   
                                                                                                   
                                                            ARTICLE XII
                                                                 
                                                      AMENDMENTS AND MEETINGS
                                                                                                   
 Section 12.1.  Amendments   . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .   27
 Section 12.2.  Amendment of Certificate   . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .   27
 Section 12.3.  Meetings of the Partners   . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .   27
                                                                                                   
                                                                                                   
                                                           ARTICLE XIII
                                                                 
                                                           MISCELLANEOUS
                                                                                                   
 Section 13.1.  Notices  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .   29
 Section 13.2.  Entire Agreement   . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .   29
 Section 13.3.  Governing Law  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .   29
 Section 13.4.  Effect   . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .   29
 Section 13.5.  Pronouns and Number  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .   29
 Section 13.6.  Captions   . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .   29
 Section 13.7.  Partial Enforceability   . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .   29
 Section 13.8.  Counterparts   . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .   30
 Section 13.9.  Waiver of Partition  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .   30
 Section 13.10. Remedies   . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .   30
</TABLE>         





                                     -iii-
<PAGE>   5
                         AMENDED AND RESTATED AGREEMENT
                             OF LIMITED PARTNERSHIP

                                       OF

                          ILLINOIS POWER CAPITAL, L.P.

                This AMENDED AND RESTATED AGREEMENT OF LIMITED PARTNERSHIP of
Illinois Power Capital, L.P. (the "Partnership"), dated as of _____________,
1994, among Illinois Power Company, an Illinois corporation ("Illinois Power"),
as the general partner, Illinova Corporation, an Illinois corporation, as the
initial limited partner (the "Initial Limited Partner") and such other Persons
(as defined herein) who become Limited Partners (as defined herein) as provided
herein;

                                  WITNESSETH:

                WHEREAS, Illinois Power and the Initial Limited Partner entered
into an Agreement of Limited Partnership, dated as of August 17, 1994, (the
"Original Limited Partnership Agreement");

                WHEREAS, the Certificate of Limited Partnership of the
Partnership was filed with the Office of the Secretary of State of the State of
Delaware on August 17, 1994; and

                WHEREAS, the Partners (as defined herein) desire to continue
the Partnership as a limited partnership under the Act (as defined herein) and
to amend and restate the Original Limited Partnership Agreement in its
entirety;

                NOW, THEREFORE, in consideration of the agreements and
obligations set forth herein and for other good and valuable consideration,
receipt and sufficiency of which are hereby acknowledged, the parties hereto
agree to amend and restate the Original Limited Partnership Agreement in its
entirety and hereby agree as follows:


                                   ARTICLE I

                 FORMATION AND CONTINUATION OF THE PARTNERSHIP;
                    ADMISSION OF PREFERRED SECURITY HOLDERS;
            RETURN OF INITIAL LIMITED PARTNER'S CAPITAL CONTRIBUTION

                Section 1.1.   Formation and Continuation of the Partnership.
The Partnership was formed as a limited partnership under the Act by the filing
by the General Partner (as defined herein) of the Certificate (as defined
herein) with the Office of the Secretary of State of the State of Delaware on
August 17, 1994 and the entering into by the General Partner and the Initial
Limited Partner of the Original Limited Partnership Agreement.  The parties
hereto agree to continue the Partnership as a limited partnership under the
Act.  The General Partner, for itself and as agent for the Limited Partners,
shall make every reasonable effort to assure that all certificates and
documents are properly executed and shall accomplish all filing, recording,
publishing and other acts necessary or appropriate for compliance with all the
requirements for the continuation of the Partnership as a limited partnership
under the Act and under all other laws of





                                      -1-
<PAGE>   6
the State of Delaware or such other jurisdictions in which the General Partner
determines that the Partnership may conduct business.  The rights, liabilities
and duties of the Partners shall be as provided in the Act except as modified
by this Agreement.  Where not otherwise specified in this Agreement, the Act
governs the rights and obligations of the parties to this Agreement.

                Section 1.2.   Name.  The name of the Partnership is "Illinois
Power Capital, L.P.", as such name may be modified from time to time by the
General Partner following written notice to the Limited Partners.  The
Partnership business may be conducted under the name of the Partnership or any
other name deemed advisable by the General Partner.

                Section 1.3.   Business of the Partnership.  The sole purpose
of the Partnership is (a) to issue partnership interests in the Partnership,
including, without limitation, Preferred Securities (as defined herein), and to
use the proceeds thereof to purchase Subordinated Debentures (as defined
herein) or other similar debt securities of Illinois Power and (b) except as
otherwise limited herein, to enter into, make and perform all contracts and
other undertakings, and engage in all activities and transactions as the
General Partner may reasonably deem necessary or advisable to the carrying out
of the foregoing purpose of the Partnership.

                Section 1.4.   Term.  The term of the Partnership commenced on
the date the Certificate was filed with the Secretary of State of the State of
Delaware and shall continue until December 31, 2047, unless the Partnership is
dissolved before such date in accordance with the provisions of this Agreement.

                Section 1.5.   Registered Agent and Office.  The Partnership's
registered agent and office in the State of Delaware shall be The Corporation
Trust Company, Corporation Trust Center, 1209 Orange Street, Wilmington, New
Castle County, Delaware 19801.  At any time, and from time to time, the General
Partner may designate another registered agent and/or registered office.

                Section 1.6.   Principal Place of Business.  The principal
place of business of the Partnership shall be at c/o The Corporation Trust
Company, Corporation Trust Center, 1209 Orange Street, Wilmington, New Castle
County, Delaware 19801.  Upon 10 days written notice to the Limited Partners,
the General Partner may change the location of the Partnership's principal
place of business.

                Section 1.7.   Name and Business Address of General Partner.
The name and business address of the General Partner are as follows:

                Illinois Power Company
                500 South 27th Street
                Decatur, Illinois  62525
                Attention:  President

The General Partner may change its name or business address from time to time,
in which event the General Partner shall promptly notify the Limited Partners
of any such change.

                Section 1.8.   Admission of Holders of Preferred Securities.

                (a)    Without the necessity of executing this Agreement, upon
receipt by a Person of an LP Certificate (as defined herein) and payment of the
Purchase Price (as defined herein) for the Preferred Securities represented by
such LP Certificate in connection with the initial issuance by the





                                      -2-
<PAGE>   7
Partnership of such Preferred Securities, which shall be deemed to constitute a
request by such Person that the books and records of the Partnership reflect
such Person's admission as a Limited Partner, such Person shall be admitted to
the Partnership as a Limited Partner and shall become bound by this Agreement.

                (b)    Following the first admission of a Preferred Security
Holder (as defined herein) to the Partnership as a Limited Partner pursuant to
paragraph (a) above, the Initial Limited Partner shall receive the return of
his capital contribution without interest or deduction, but will continue to be
a limited partner of the Partnership.  While the Initial Limited Partner shall
continue to be a limited partner of the Partnership, the Initial Limited
Partner shall only have such rights, if any, as are expressly provided to the
Initial Limited Partner pursuant to this Agreement.

                (c)    The name and mailing address of each Partner and the
amount contributed by such Partner to the capital of the Partnership shall be
listed on the books and records of the Partnership.  The General Partner shall
be required to update the books and records from time to time as necessary to
accurately reflect the information therein.


                                   ARTICLE II

                                 DEFINED TERMS

                Section 2.1.   Definitions.  Unless the context otherwise
requires, the terms defined in this Article II shall, for the purposes of this
Agreement, have the meanings herein specified.

                "Act" means the Delaware Revised Uniform Limited Partnership
Act, 6 Del.C. Section 17-101, et seq., as amended from time to time.

                "Action" has the meaning set forth in Section 6.1(b).

                "Adjusted Capital Account" has the meaning set forth in Section
4.2(d)(i).

                "Affiliate" means, with respect to a specified Person, (a) any
Person directly or indirectly owning, controlling or holding with power to vote
10% or more of the outstanding voting securities or other ownership interests
of the specified Person, (b) any Person 10% or more of whose outstanding voting
securities or other ownership interests are directly or indirectly owned,
controlled or held with power to vote by the specified Person, (c) any Person
directly or indirectly controlling, controlled by, or under common control with
the specified Person, (d) a partnership in which the specified Person is a
general partner, (e) any officer or director of the specified Person, and (f)
if the specified Person is an officer, director, general partner or employee,
any other entity for which the specified Person acts in any such capacity.

                "Agreement" means this Amended and Restated Agreement of
Limited Partnership of the Partnership, as amended, modified, supplemented or
restated from time to time.

                "Book Entry Interests" means a beneficial interest in the LP
Certificates, ownership and transfers of which shall be made through book
entries by a Clearing Agency as described in Section 10.4.





                                      -3-
<PAGE>   8
                "Business Day" means any day other than a day on which banking
institutions in The City of New York are authorized or required by law to
close.

                "Capital Account" has the meaning set forth in Section 3.3.

                "Certificate" means the Certificate of Limited Partnership of
the Partnership filed with the Secretary of State of the State of Delaware on
August 17, 1994, and any and all amendments thereto and restatements thereof.

                "Clearing Agency" means an organization registered as a
"Clearing Agency" pursuant to Section 17A of the Exchange Act that is acting as
depository for the Preferred Securities and in whose name shall be registered a
global LP Certificate and which shall undertake to effect book entry transfers
and pledges of the Preferred Securities.

                "Clearing Agency Participant" means a broker, dealer, bank,
other financial institution or other Person for whom from time to time the
Clearing Agency effects book entry transfers and pledges of securities
deposited with the Clearing Agency.

                "Code" means the Internal Revenue Code of 1986, as amended from
time to time, or any corresponding federal tax statute enacted after the date
of this Agreement.  A reference to a specific section (Section ) of the Code
refers not only to such specific section but also to any corresponding
provision of any federal tax statute enacted after the date of this Agreement,
as such specific section or corresponding provision is in effect on the date of
application of the provisions of this Agreement containing such reference.

                "Covered Person" means any Partner, any Affiliate of a Partner
or any officers, directors, shareholders, partners, members, employees,
representatives or agents of a Partner or its respective Affiliates, or any
employee or agent of the Partnership or its Affiliates or any Special
Representative.

                "Definitive LP Certificates" has the meaning set forth in
Section 10.4.

                "Dividends" means the distributions of income paid or payable
to any Limited Partner who is a Preferred Security Holder pursuant to the terms
of the Preferred Securities held by such Limited Partner, including any
interest payable in respect of arrears.

                "DTC" means The Depository Trust Company, the initial Clearing
Agency.

                "Exchange Act" means the Securities Exchange Act of 1934, as
amended.

                "Fiscal Year" means (i) the period commencing upon the
formation of the Partnership and ending on December 31, 1994, and (ii) any
subsequent twelve (12) month period commencing on January 1 and ending on
December 31.

                "General Partner" means Illinois Power, in its capacity as
general partner of the Partnership, and any additional or successor general
partner in the Partnership admitted as a general partner of the Partnership
pursuant to this Agreement.

                "Guarantee" means the Guarantee Agreement dated as of
________________, 1994 of Illinois Power in respect of the Preferred
Securities.





                                      -4-
<PAGE>   9
                "Holders" means, with respect to a series of Preferred
Securities, Preferred Security Holders in whose name an LP Certificate
representing Preferred Securities of such series is registered.

                "Illinois Power" has the meaning set forth in the forepart of
this Agreement.

                "Indemnified Person" means the General Partner, any Special
Representative, any Affiliate of the General Partner or any Special
Representative, or any officers, directors, shareholders, partners, members,
employees, representatives or agents of the General Partner or any Special
Representative, or any employee or agent of the Partnership or its Affiliates.

                "Indenture" means the Indenture dated as of _____________, 1994
between Illinois Power and The First National Bank of Chicago, as trustee (the
"Trustee"), pursuant to which the Subordinated Debentures are issued in one or
more series.

                "Initial Limited Partner" means Illinova Corporation.

                "Initial Preferred Limited Partners" means the Persons admitted
as Limited Partners pursuant to Section 1.8(a) in connection with the initial
issuance by the Partnership of Preferred Securities.

                "Interest" means the entire ownership interest of a Partner in
the Partnership at any particular time, including, without limitation, its
interest in the capital, profits, losses and distributions of the Partnership.

                "Investment Company Event" means the occurrence of a change in
law or regulation or a written change in interpretation or application of law
or regulation by any legislative body, court, governmental agency or regulatory
authority (a "Change in 40 Act Law") to the effect that the Partnership is or
will be considered an "investment company" which is required to be registered
under the Investment Company Act of 1940, as amended (the "1940 Act"), which
Change in 40 Act Law becomes effective on or after __________________, 1994;
provided, however, that no Investment Company Event shall be deemed to have
occurred if the General Partner obtains a written opinion of nationally
recognized independent counsel to the Partnership experienced in practice under
the 1940 Act to the effect that the General Partner has successfully issued an
additional or supplemental irrevocable and unconditional guarantee (i) of
accrued and unpaid dividends (whether or not determined to be paid out of
monies legally available therefor) on the Preferred Securities and (ii) of the
full amount of the Liquidation Distribution on the Preferred Securities upon a
liquidation of the Partnership (regardless of the amount of assets of the
Partnership otherwise available for distribution in such liquidation) to avoid
such Change in 40 Act Law so that in the opinion of such counsel,
notwithstanding such Change in 40 Act Law, the Partnership is not required to
be registered as an "investment company" within the meaning of the 1940 Act.

                "Limited Partner" means any Person who is admitted to the
Partnership as a limited partner of the Partnership pursuant to the terms of
this Agreement, including the Preferred Security Holders, in each such Person's
capacity as a limited partner of the Partnership.

                "Liquidation Distribution" has the meaning set forth in the
applicable Action relating to a series of Preferred Securities.





                                      -5-
<PAGE>   10
                "Loss Carried Forward Amount" means as of the first day of any
month for any series, an amount equal to the excess of (x) all Net Loss
allocated to the Holders of such series of Preferred Securities from the date
of issuance of such series of Preferred Securities through and including the
day prior to the first day of such month pursuant to Section 4.1(b)(ii) over
(y) the amount of Net Income allocated to the Holders of such series of
Preferred Securities pursuant to Section 4.1(a)(ii) in all prior calendar
months.

                "LP Certificate" means a certificate of partnership interest
substantially in the form attached hereto as Annex A, evidencing the Preferred
Securities held by a Limited Partner, with such modifications to such form as
may be necessary to reflect the specific terms and provisions of a particular
series of Preferred Securities.

                "Majority in liquidation preference of the Preferred
Securities" means Holder(s) of a series of Preferred Securities or, as the
context may require, Holder(s) of more than one series of Preferred Securities
voting as a class, who are the record owners of Preferred Securities whose
liquidation preference (including the preference amount that would be paid on
redemption or maturity, plus accumulated and unpaid dividends, whether or not
declared, to the date upon which the voting percentages are determined)
represents more than 50% of the above liquidation preference of all Preferred
Securities of such series or, as applicable, multiple series.

                "Net Income" and "Net Loss", respectively, for any period means
the income and loss, respectively, of the Partnership for such period as
determined in accordance with the method of accounting followed by the
Partnership for federal income tax purposes, including, for all purposes, any
income exempt from tax and any expenditures of the Partnership which are
described in Code Section 705(a)(2)(B); provided, however, that any item
allocated under Section 4.2 shall be excluded from the computation of Net
Income and Net Loss.

                "Partners" means the General Partner and the Limited Partners,
collectively, where no distinction is required by the context in which the term
is used.

                "Partnership" means the limited partnership heretofore formed
and continued under this Agreement under the name "Illinois Power Capital,
L.P."

                "Paying Agent" has the meaning set forth in Section 10.7.

                "Person" means any individual, corporation, limited liability
company, association, partnership, trust or other entity.

                "Preferred Securities" means the limited partner interests in
the Partnership described in Article VI.

                "Preferred Security Holder" has the meaning set forth in
Section 10.3.

                "Preferred Security Owner" means, with respect to a Book Entry
Interest, a Person who is the beneficial owner of such Book Entry Interest, as
reflected on the books of the Clearing Agency, or on the books of a Person
maintaining an account with such Clearing Agency (directly as a Clearing Agency
Participant or as an indirect participant, in each case in accordance with the
rules of such Clearing Agency).





                                      -6-
<PAGE>   11
                "Purchase Price" for any Preferred Security means the amount
paid for such Preferred Security in the initial sale by the Partnership of such
Preferred Security.

                "Regulations" means the income tax regulations, including
temporary regulations, promulgated under the Code, as such regulations may be
amended from time to time.

                "Securities Act" means the Securities Act of 1933, as amended.

                "66-2/3% in liquidation preference of the Preferred Securities"
means Holder(s) of a series of Preferred Securities or, as the context may
require, Holder(s) of more than one series of Preferred Securities voting as a
class, who are the record owners of Preferred Securities whose liquidation
preference (including the preference amount that would be paid on redemption or
maturity, plus accumulated and unpaid dividends, whether or not declared, to
the date upon which the voting percentages are determined) represents more than
66-2/3% of the above liquidation preference of all Preferred Securities of such
series or, as applicable, multiple series.

                "Special Event" means a Tax Event or an Investment Company Act
Event.

                "Special Representative" has the meaning specified in Section
6.2.

                "Subordinated Debentures" means any series of subordinated
debentures issued by Illinois Power under the Indenture.

                "Successor Securities" has the meaning specified in Section 6.3.

                "Tax Event" means that the General Partner shall have obtained
an opinion of nationally recognized independent tax counsel experienced in such
matters to the effect that, as a result of (a) any amendment to, or change
(including any announced prospective change) in, the laws (or any regulations
thereunder) of the United States or any political subdivision or taxing
authority thereof or therein, (b) any amendment to or change in an
interpretation or application of such laws or regulations by any legislative
body, court, governmental agency or regulatory authority (including the
enactment of any legislation and the publication of any judicial decision or
regulatory determination on or after such date), or (c) any interpretation or
pronouncement that provides for a position with respect to such laws or
regulations that differs from the generally accepted position on _____________
_______, 1994, which amendment or change is effective or such interpretation or
pronouncement is announced on or after _______________, 1994, there is more than
an insubstantial risk that (i) the Partnership is subject to federal income tax
with respect to interest received on the Subordinated Debentures, (ii) interest
payable to the Partnership on the Subordinated Debentures will not be
deductible by the payor for federal income tax purposes or (iii) the
Partnership is subject to more than a de minimus amount of other taxes, duties
or other governmental charges.

                "Tax Matters Partner" means the General Partner designated as
such in Section 9.9.

                "10% in liquidation preference of the Preferred Securities"
means Holders(s) of a series of Preferred Securities or, as the context may
require, Holder(s) of more than one series of Preferred Securities voting as a
class, who are the record owners of Preferred Securities whose liquidation
preference (including the preference amount that would be paid on redemption or
maturity, plus accumulated and unpaid dividends, whether or not declared, to
the date upon which the voting percentages are determined) represents more than
10% of the above liquidation preference of all Preferred Securities of such
series or, as applicable, multiple series.





                                      -7-
<PAGE>   12
                "Underwriting Agreement" means an Underwriting Agreement among
the Partnership and the underwriters named therein relating to the issuance and
sale of the Preferred Securities.

                Section 2.2.   Headings. The headings and subheadings in this
Agreement are included for convenience and identification only and are in no
way intended to describe, interpret, define or limit the scope, extent or
intent of this Agreement or any provision hereof.


                                  ARTICLE III

                    CAPITAL CONTRIBUTIONS, REPRESENTATION OF
             PREFERRED SECURITY HOLDER'S INTEREST; CAPITAL ACCOUNTS

                Section 3.1.   Capital Contributions.

                (a)    The General Partner has, on or prior to the date hereof,
contributed an aggregate of $_______________ to the capital of the Partnership,
which amount is equal to at least 3% of the total capital contributions to the
Partnership on the date hereof, after taking into account the contribution of
the Initial Preferred Limited Partners referred to in paragraph (c) of this
Section 3.1.  Subject to Section 4.1(c), the General Partner shall from time to
time make such additional capital contributions as are necessary to maintain
its Capital Account balance at least equal to 3% of the aggregate positive
Capital Account balances of all Partners.

                (b)    The Initial Limited Partner has, prior to the date
hereof, contributed the amount of $1 to the capital of the Partnership which
amount is being returned to the Initial Limited Partner.

                (c)    With respect to each of the Initial Preferred Limited
Partners, there has been, on the date hereof, contributed to the capital of the
Partnership an amount equal to the Purchase Price for the Preferred Securities
acquired by it (such amount being such Person's capital contribution to the
Partnership).

                (d)    After the date hereof with respect to each Person who 
is issued a Preferred Security by the Partnership in connection with the initial
issuance by the Partnership of such Preferred Security, there shall be 
contributed to the capital of the Partnership an amount equal to the Purchase 
Price for such Preferred Security (such amount being such Person's capital 
contribution to the Partnership).

                (e)    No Limited Partner shall at any time be required to make
any additional capital contributions to the Partnership.

                Section 3.2.   Preferred Security Holder's Interest Represented
by Preferred Securities.  A Preferred Security Holder's interest in the
Partnership shall be represented by the Preferred Securities held by such
Preferred Security Holder.  Each Preferred Security Holder's respective
Preferred Securities shall be set forth on the books and records of the
Partnership.  Each Limited Partner, including a Preferred Security Holder,
hereby agrees that its interest in the Partnership and in its Preferred
Securities shall for all purposes be personal property.  No Limited Partner,
including a Preferred Security Holder, shall have an interest in specific
Partnership property.





                                      -8-
<PAGE>   13
                Section 3.3.   Capital Accounts.  An individual capital account
(a "Capital Account") shall be established and maintained on the books of the
Partnership for each Partner in compliance with Section Section
1.704-1(b)(2)(iv) and 1.704-2 of the Regulations.  Subject to the preceding
sentence, each Capital Account will be credited with the capital contributions
made and the profits allocated to such Partner (or predecessor in interest) and
debited by the distributions made and losses allocated to the Partner (or
predecessor thereof).

                Section 3.4.   Interest on Capital Contributions.  No Partner
shall be entitled to interest on or with respect to any capital contribution to
the Partnership.

                Section 3.5.   Withdrawal and Return of Capital Contributions.
No Partner shall be entitled to withdraw any part of such Partner's capital
contribution to the Partnership or to receive any distributions from the
Partnership, except as provided in this Agreement.


                                  ARTICLE IV

                                  ALLOCATIONS

                Section 4.1.   Profits and Losses.  Except as provided in
Section 4.2,

                (a)    the Partnership's Net Income for each calendar month
shall be allocated as follows:

                    (i)        First, to the Holders of each series of
        Preferred Securities as of the record date in such calendar month for
        the payment of Dividends on such series of Preferred Securities in an
        amount equal to the excess of (x) all Dividends accumulated on such
        series of Preferred Securities (in accordance with the Action creating
        such series) from their date of issuance through and including the
        close of such calendar month over (y) the amount of Net Income
        allocated to the Holders of such series of Preferred Securities
        pursuant to this Section 4.1(a)(i) in all prior calendar months;
        provided, however, that (A) as to any series of Preferred Securities as
        to which Dividends are not cumulative, no Dividend shall be deemed to
        accumulate until the Partnership has actually paid (or set aside money
        to pay) such Dividend and (B) Dividends as to Preferred Securities that
        are cumulative and are not payable at the end of each calendar month
        shall be deemed to accumulate in a manner consistent with the Action
        creating such Preferred Securities.  Amounts allocated to all Holders
        of any series of Preferred Securities shall be allocated among such
        Holders in proportion to the number of Preferred Securities of such
        series held by such Holders.

                   (ii)        Second, 100% to the Holders of any series of
        Preferred Securities up to an amount equal to the Loss Carried Forward
        Amount for such series as of the first day of such month.  Amounts
        allocated to all Holders of any series of Preferred Securities shall be
        allocated among such Holders in proportion to the number of Preferred
        Securities of such series held by such Holders.

                   (iii)       Any remaining Net Income shall be allocated to 
        the General Partner.

                (b)    The Partnership's Net Loss for any Fiscal Year shall be
        allocated as follows:





                                      -9-
<PAGE>   14
                    (i)        First, to the General Partner until the General
        Partner's Capital Account is reduced to zero; provided, however, that
        the aggregate amount of Net Losses allocated to the General Partner
        pursuant to this Section 4.1(b)(i) shall not exceed the sum of 3% of
        the total capital contributions of all Partners plus the aggregate Net
        Income allocated to the General Partner pursuant to Section 4.1.

                   (ii)        Second, to the Holders of each series of
        Preferred Securities in proportion to the aggregate Capital Account
        balances of the Holders of such series of Preferred Securities
        (calculated taking into account only contributions, distributions and
        allocations related to such series), until the Capital Account balances
        of such Holders are reduced to zero; provided, however, that the
        General Partner shall make appropriate adjustments in these
        allocations, in accordance with Section 4.1(c) with respect to any
        Preferred Securities as to which Net Income has been allocated with
        respect to Dividends that accrued but were not paid.  Amounts allocated
        to the Holders of any series of Preferred Securities shall be allocated
        among such Holders in proportion to the number of Preferred Securities
        of such series held by such Holders.

                  (iii)        Any remaining Net Loss shall be allocated to the
        General Partner.

                (c)    The General Partner shall make such changes to the
allocations in Sections 4.1(a) and 4.1(b) in the year of the Partnership's
liquidation as it deems reasonably necessary so that amounts distributed to the
Preferred Security Holders in such year in accordance with Section 11.4(a)(ii)
shall equal their Liquidation Distributions; provided, however, that no
allocation pursuant to this Section 4.1(c) may result in the General Partner
being required to make any Capital Contributions pursuant to Section 3.1.

                Section 4.2.   Other Allocation Provisions.

                (a)    For purposes of determining the profits, losses or any
other items allocable to any period, profits, losses and any such other items
shall be determined on a daily, monthly or other basis, as determined by the
General Partner using any method that is permissible under Section 706 of the
Code and the Regulations.

                (b)    The Partners are aware of the income tax consequences of
the allocations made by this Article IV and hereby agree to be bound by the
provisions of this Article IV in reporting their shares of Partnership income
and loss for income tax purposes.

                (c)    Notwithstanding anything to the contrary that may be
expressed or implied in this Article IV, the interest of the General Partner in
each item of income, gain, loss, deduction and credit will be equal to at least
(i) at any time that aggregate capital contributions to the Partnership are
equal to or less than $50,000,000, 1% of each such item and (ii) at any time
that aggregate capital contributions to the Partnership are greater than
$50,000,000, at least 1%, multiplied by a fraction (not exceeding one and not
less than 0.2), the numerator of which is $50,000,000 and the denominator of
which is the lesser of the aggregate Capital Account balances of the Capital
Accounts of all Partners at such time and the aggregate capital contributions
to the Partnership of all Partners at such time, of such item.

                (d)    (i)     If during any taxable year, a Partner
unexpectedly receives an adjustment, allocation or distribution described in
Section 1.704-1(b)(2)(ii)(d)(4), (5) or (6) of the Regulations, which causes or
increases a deficit balance in the Partner's Adjusted Capital Account





                                      -10-
<PAGE>   15
(as defined below), there shall be allocated to the Partner items of
Partnership income and gain (consisting of a pro rata portion of each item of
Partnership income, including gross income and gain for such year) in an amount
and manner sufficient to eliminate such deficit.  The foregoing is intended to
be a "qualified income offset" provision as described in Section
1.704-1(b)(2)(ii)(d) of the Regulations and shall be interpreted and applied in
all respects in accordance with that Regulation.

                A Partner's "Adjusted Capital Account" at any time shall equal
the Partner's Capital Account at such time (x) increased by the sum of (A) the
amount of the Partner's share of Partnership minimum gain (as defined in
Section Section 1.704-2(g)(1) and (3) of the Regulations) and (B) the amount of
the Partner's share of the minimum gain attributable to a "partner non-recourse
debt" (as defined in Regulations Section 1.704-2(i)(5)) and (y) decreased by
reasonably excepted adjustments, allocations and distributions described in
Section Section 1.704-1(b)(2)(ii)(d)(4), (5) and (6) of the Regulations.

                   (ii)        While this Agreement does not contain certain
provisions required by Section Section 1.704-1(b) and 1.704-2 of the
Regulations because those provisions apply to transactions that are not
expected to occur, the Partners intend that the allocations under Section 4.1
conform to Section Section 1.704-1(b) and 1.704-2 of the Regulations
(including, without limitation, the minimum gain chargeback, chargeback of
partner nonrecourse debt minimum gain and partner nonrecourse debt provisions
of such Regulation), and the General Partner shall make such changes in the
allocations under Section 4.1 as it believes are reasonably necessary to meet
the requirements of such Regulations.

                (e)    Solely for the purpose of adjusting the Capital Accounts
of the Partners, and not for tax purposes, if any property is distributed in
kind to any Partner, the difference between its fair market value and its book
value at the time of distribution shall be treated as gain or loss recognized
by the Partnership and allocated pursuant to the provisions of Section 4.1;
provided, however, that Net Income and Net Loss allocated as a result of the
distribution of any series of Subordinated Debentures to the Holders of any
series of Preferred Securities or to the General Partner (or both) shall be
allocated to the Partner receiving the Subordinated Debentures in proportion to
the amount of Subordinated Debentures distributed to them. For this purpose,
the fair market value of any property shall be determined by the General
Partner in its sole discretion, provided, however, that the value of any
Subordinated Debenture shall at all times be treated as equal to the value of
any Preferred Security if the interest rate on and principal amount of the
Subordinated Debenture is the same as the Dividend payable on and the
liquidation preference with respect to the Preferred Security.

                Section 4.3.   Allocations for Income Tax Purposes.  The
income, gains, losses, deductions and credits of the Partnership shall be
allocated in the same manner as the items entering into the computation of Net
Income and Net Loss were allocated under Sections 4.1 and 4.2; provided,
however, that solely for federal, state and local income and franchise tax
purposes and not for book or Capital Account purposes, income, gain, loss and
deduction with respect to any property properly carried on the Partnership's
books at a value other than the tax basis of such property shall be allocated
in a manner determined in the General Partner's discretion, so as to take into
account (consistently with Code Section 704(c) principles) the difference
between such property's book value and its tax basis.

                Section 4.4.   Withholding.  The Partnership shall comply with
withholding requirements under federal, state and local law and shall remit
amounts withheld to and file required forms with applicable jurisdictions.  To
the extent that the Partnership is required to





                                      -11-
<PAGE>   16
withhold and pay over any amounts to any authority with respect to
distributions or allocations to any  Partner, the amount withheld shall be
deemed to be a distribution in the amount of the withholding to the Partner.
In the event of any claimed over-withholding, Partners shall be limited to an
action against the applicable jurisdiction.  If the amount withheld was not
withheld from actual distributions, the Partnership may reduce subsequent
distributions by the amount of such withholding.  Each Partner agrees to
furnish the Partnership with any representations and forms as shall reasonably
be requested by the Partnership to assist it in determining the extent of, and
in fulfilling, its withholding obligations.


                                   ARTICLE V

                                   DIVIDENDS

                Section 5.1.   Dividends.  Limited Partners shall receive
periodic Dividends, if any, redemption payments and Liquidation Distributions
in accordance with the applicable terms of the Preferred Securities.  Subject
to the rights of the Preferred Securities, all remaining cash shall be
distributed to the General Partner at such time as the General Partner shall
determine.

                Section 5.2.   Limitations on Distributions.  Notwithstanding
any provision to the contrary contained in this Agreement, the Partnership
shall not make a distribution to any Partner on account of its interest in the
Partnership if such distribution would violate Section 17-607 of the Act or
other applicable law.


                                   ARTICLE VI

                        ISSUANCE OF PREFERRED SECURITIES

                Section 6.1.   General Provisions Regarding Preferred
Securities.

                (a)    The aggregate number of Preferred Securities which the
Partnership shall have authority to issue is unlimited.

                (b)    The designations, powers, rights, preferences,
privileges, limitations and other terms and provisions of the Preferred
Securities shall be as follows:

                    (i)        The payment of Dividends and payments on
        dissolution of the Partnership or on redemption in respect of Preferred
        Securities shall be guaranteed by Illinois Power pursuant to the
        Guarantee.  The Preferred Security Holders hereby authorize the General
        Partner to hold the Guarantee on behalf of the Preferred Security
        Holders.  In the event of the appointment of a Special Representative
        to, among other things, enforce the Guarantee, the Special
        Representative may take possession of the Guarantee for such purpose.
        If no Special Representative has been appointed to enforce the
        Guarantee, the General Partner has the right to enforce the Guarantee
        on behalf of the Preferred Security Holders.  The Holders of not less
        than 10% in liquidation preference of the Preferred Securities have the
        right to direct the time, method and place of conducting any proceeding
        for any remedy available in respect of the Guarantee including the
        giving of directions to the General Partner or the Special
        Representative, as the case may be.  If the General Partner or the
        Special Representative fails to enforce the Guarantee as above
        provided, a





                                      -12-
<PAGE>   17
        Preferred Security Holder may institute a legal proceeding directly
        against the Guarantor to enforce its rights under the Guarantee,
        without first instituting a legal proceeding against the Partnership or
        any other Person.  The Preferred Security Holders, by acceptance of
        such Preferred Securities, hereby agree to the subordination provisions
        and other terms of the Guarantee;

                   (ii)        The General Partner on behalf of the Partnership
        is authorized to issue from time to time limited partner interests in
        the Partnership (the "Preferred Securities") in one or more series
        having such designations, powers, rights, preferences, privileges,
        limitations and other terms and provisions as may from time to time be
        established in the written action or actions (each, an "Action") of the
        General Partner providing for the issue of that series.  In connection
        with the foregoing, the General Partner is expressly authorized, prior
        to issuance, to set forth in an Action or Actions providing for the
        issue of such series, the following:

                       (A)     the distinctive designation of such series which
                               shall distinguish it from other series;

                       (B)     the number of Preferred Securities included in
                such series, which number may be increased or decreased from
                time to time unless otherwise provided by the General Partner
                in creating the series;

                       (C)     the annual Dividend rate (or method of
                determining such rate) for Preferred Securities of such series
                and the date or dates upon which such Dividends shall be
                payable, provided, however, Dividends on any series of
                Preferred Securities shall be payable on a monthly basis to
                Holders of such series of Preferred Securities as of a record
                date in each month during which such series of Preferred
                Securities are outstanding;

                       (D)     whether Dividends on the Preferred Securities of
                such series shall be cumulative, and, in the case of Preferred
                Securities of any series having cumulative Dividend rights, the
                date or dates or method of determining the date or dates from
                which Dividends on the Preferred Securities of such series
                shall be cumulative;

                       (E)     the amount or amounts which shall be paid out of
                the assets of the Partnership to the Holders of the Preferred
                Securities of such series upon voluntary or involuntary
                dissolution, winding up or termination of the Partnership;

                       (F)     the price or prices at which, the period or
                periods within which and the terms and conditions upon which
                the Preferred Securities of such series may be redeemed or
                purchased, in whole or in part, at the option of the
                Partnership or the General Partner;

                       (G)     the obligation, if any, of the Partnership to
                purchase or redeem Preferred Securities of such series and the
                price or prices at which, the period or periods within which
                and the terms and conditions upon which the Preferred
                Securities of such series shall be purchased or redeemed, in
                whole or in part, pursuant to such obligation;





                                      -13-
<PAGE>   18
                       (H)     the voting rights, if any, of the Preferred
                Securities of such series in addition to those required by law,
                including the number of votes per Preferred Security and any
                requirement for the approval by the Holders of Preferred
                Securities, or of the Preferred Securities of one or more
                series, or of both, as a condition to specified action or
                amendments to this Agreement; and

                       (I)     any other relative rights, powers, preferences
                or limitations of the Preferred Securities of the series not
                inconsistent with this Agreement or with applicable law.

                       In connection with the foregoing and without limiting
        the generality thereof, the General Partner is hereby expressly
        authorized, without the vote or approval of any Preferred Security
        Holder, (i) to take any Action to create under the provisions of this
        Agreement a series of Preferred Securities that was not previously
        outstanding and (ii) to admit Preferred Security Holders as limited
        partners of the Partnership.  Without the vote or approval of any
        Preferred Security Holder, the General Partner may execute, swear to,
        acknowledge, deliver, file and record whatever documents may be
        required in connection with the issue from time to time of Preferred
        Securities in one or more series as shall be necessary, convenient or
        desirable to reflect the issue of such series.  The General Partner
        shall do all things it deems to be appropriate or necessary to comply
        with the Act and is authorized and directed to do all things it deems
        to be necessary or permissible in connection with any future issuance,
        including compliance with any statute, rule, regulation or guideline of
        any federal, state or other governmental agency or any securities
        exchange.

                       Any Action or Actions taken by the General Partner
        pursuant to the provisions of this paragraph (ii) shall be deemed an
        amendment and supplement to and part of this Agreement.

                  (iii)        The proceeds received by the Partnership from
        the issuance of any series of Preferred Securities, together with the
        proceeds of any capital contribution of the General Partner made at the
        time of such issuance, shall be invested by the Partnership in
        Subordinated Debentures with (A) an aggregate principal amount equal to
        such aggregate proceeds and (B) an interest rate equal to the Dividend
        rate of such series of Preferred Securities.

                   (iv)        So long as any series of Subordinated Debentures
        are held by the Partnership, the General Partner shall not (i) direct
        the time, method and place of conducting any proceeding for any remedy
        available to the Trustee, or exercising any trust or power conferred on
        the Trustee with respect to such series, (ii) waive any past default
        which is waivable under Section 6.06 of the Indenture, (iii) exercise
        any right to rescind or annul a declaration that the principal of all
        the Subordinated Debentures of such series shall be due and payable or
        (iv) consent to any amendment, modification or termination of the
        Indenture without, in each case, obtaining the prior approval of the
        Holders of at least 66-2/3% in liquidation preference of all series of
        Preferred Securities affected thereby, acting as a single class;
        provided, however, that where a consent under the Indenture would
        require the consent of each holder of Subordinated Debentures affected
        thereby, no such consent shall be given by the General Partner without
        the prior consent of each Holder of all series of Preferred Securities
        affected thereby.  The General Partner shall not revoke any action
        previously authorized or approved by a vote of any series of Preferred
        Securities affected thereby.  The General Partner shall notify all
        Holders of any series of Preferred Securities





                                      -14-
<PAGE>   19
        of any notice of default received from the Trustee with respect to the
        related series of Subordinated Debentures.

                    (v)        The Partnership may not issue any limited
        partner interests in the Partnership, unless such series of Preferred
        Securities ranks pari passu with each other series of Preferred
        Securities then outstanding as regards (A) participation in profits and
        Dividends of the Partnership and (B) participation in the assets of the
        Partnership.  All Preferred Securities shall rank senior to the General
        Partner's Interest in respect of the right to receive Dividends and the
        right to receive payments out of the assets of the Partnership upon
        voluntary or involuntary dissolution, winding up or termination of the
        Partnership.  All Preferred Securities redeemed, purchased or otherwise
        acquired by the Partnership (including Preferred Securities surrendered
        for conversion or exchange) shall be canceled.

                   (vi)        No Holder of a Preferred Security shall be
        entitled as a matter of right to subscribe for or purchase, or have any
        preemptive right with respect to, any part of any new or additional
        issue of Preferred Securities of any class whatsoever, or of securities
        convertible into any Preferred Securities of any class whatsoever,
        whether now or hereafter authorized and whether issued for cash or
        other consideration or by way of a Dividend.

                Section 6.2.   Voting Rights.  If (i) the Partnership fails to
pay Dividends in full on the Preferred Securities for 18 consecutive monthly
Dividend periods, (ii) an event of default occurs and is continuing on the
Subordinated Debentures or (iii) Illinois Power is in default on any of its
payment or other obligations under the Guarantee, then the Holders of any
series of the Preferred Securities having the right to vote for the appointment
of a special representative of the Partnership and the Limited Partners (the
"Special Representative") in such event, acting as a single class, will be
entitled by the majority vote of such Holders to appoint and authorize a
Special Representative to enforce the Partnership's creditor rights under the
Subordinated Debentures, enforce the rights of the Preferred Security Holders
under the Guarantee and enforce the rights of the Preferred Security Holders to
receive Dividends on Preferred Securities.  Illinois Power agrees to execute
and deliver such documents as may be necessary, appropriate or convenient for
the Special Representative to enforce such rights and obligations.

                In furtherance of the foregoing, and without limiting the
powers of any Special Representative so appointed and for the avoidance of any
doubt concerning the powers of the Special Representative, any Special
Representative, in its own name and as Special Representative of the
Partnership, may institute a proceeding, including, without limitation, any
suit in equity, an action at law or other judicial or administrative
proceeding, to enforce the Partnership's rights directly against Illinois
Power, or any other obligor on behalf of the Partnership, and may prosecute
such proceeding to judgment or final decree, and enforce the same against
Illinois Power or any other obligor and collect, out of the property, wherever
situated, of Illinois Power or any such other obligor upon its obligations, the
monies adjudged or decreed to be payable in the manner provided by law.  The
Special Representative shall not be admitted as a Partner or otherwise be
deemed to be a Partner and shall have no liability for the debts, obligations
or liabilities of the Partnership.

                For purposes of determining whether the Partnership has failed
to pay Dividends in full for 18 consecutive monthly Dividend periods, Dividends
shall be deemed to remain in arrears, notwithstanding any payments in respect
thereof, until full cumulative Dividends have been or contemporaneously are
declared and paid with respect to all monthly Dividend periods terminating on
or prior to the date of payment of such full cumulative Dividends.  Not later
than





                                      -15-
<PAGE>   20
30 days after such right to appoint a Special Representative arises, the
General Partner will convene a meeting for the purpose of appointing a Special
Representative.  If the General Partner fails to convene such meeting within
such 30-day period, the Holders of 10% in liquidation preference of the
Preferred Securities will be entitled to convene such meeting.  The provisions
of Section 12.3 relating to the convening and conduct of meetings of the
Partners will apply with respect to any such meeting.  Any Special
Representative so appointed shall cease to be a representative of the
Partnership and the Limited Partners if the Partnership (or Illinois Power
pursuant to the Guarantee) shall have paid in full all accumulated and unpaid
Dividends on the Preferred Securities or such default or breach, as the case
may be, shall have been cured, and Illinois Power, as the General Partner, is
hereby authorized to and shall continue the business of the Partnership without
dissolution.  Notwithstanding the appointment of any such Special
Representative, Illinois Power retains all rights under the Indenture,
including the right to extend the interest payment period, and shall continue
to be a General Partner.

                If any proposed amendment of this Agreement provides for, or
the General Partner otherwise proposes to effect (pursuant to an Action or
otherwise), (x) any action which would adversely affect the powers, preferences
or special rights of the Preferred Securities, whether by way of amendment of
this Agreement or otherwise (including, without limitation, the authorization
or issuance of any interests ranking, as to participation in the profits and
Dividends or in the assets of the Partnership, senior or junior to the
Preferred Securities), or (y) the dissolution, winding up or termination of the
Partnership, other than (A) a dissolution, winding up or termination in
connection with which the Partnership distributes the Subordinated Debentures
to the Preferred Security Holders upon the occurrence of a Special Event or (B)
as described in Section 6.3 below, then the Preferred Security Holders will be
entitled to vote on such amendment or proposal of the General Partner (but not
on any other amendment or proposal) as a class with all other Holders of
Preferred Securities similarly affected, and such amendment or proposal shall
not be effective except with the approval of Holders of 66-2/3% in liquidation
preference of such Preferred Securities having a right to vote on the matter;
provided however, that no such approval shall be required if the dissolution,
winding up or termination of the Partnership is proposed or initiated pursuant
to Section 11.2 hereof or upon the initiation of proceedings, or after
proceedings have been initiated, for the dissolution, winding up or termination
of Illinois Power.

                The rights attached to the Preferred Securities will be deemed
not to be adversely affected by the creation or issue of, and no vote will be
required for the creation of, any further Preferred Securities ranking pari
passu with, the Preferred Securities with regard to participation in the
profits and Dividends or in the assets of the Partnership.

                Any required approval of Holders of Preferred Securities may be
given at a separate meeting of such Holders convened for such purpose, at a
meeting of all of the Partners or pursuant to written consent.  The Partnership
will cause a notice of any meeting at which Limited Partners holding Preferred
Securities are entitled to vote, or of any matter upon which action by written
consent of such Holders is to be taken, to be mailed to each Holder of
Preferred Securities.  Each such notice will include a statement setting forth
(i) the date of such meeting or the date by which such action is to be taken,
(ii) a description of any matter on which such Holders are entitled to vote or
upon which written consent is sought and (iii) instructions for the delivery of
proxies or consents.  No vote or consent of the Holders of Preferred Securities
will be required for the Partnership to redeem and cancel Preferred Securities
in accordance with this Agreement.

                Notwithstanding that Holders of Preferred Securities are
entitled to vote or consent under any of the circumstances described above, any
Preferred Securities that are owned by Illinois





                                      -16-
<PAGE>   21
Power or any entity owned more than 50% by Illinois Power, either directly or
indirectly, shall not be entitled to vote or consent and shall, for the
purposes of such vote or consent, be treated as if they were not outstanding.

                Section 6.3.   Mergers.  The Partnership shall not consolidate,
amalgamate, merge with or into, or be replaced by, or convey, transfer or lease
its properties and assets substantially as an entirety to any corporation or
other body, except as described below.  The Partnership may, without the
consent of the Holders of the Preferred Securities, consolidate, amalgamate,
merge with or into, or be replaced by a limited liability company, a limited
partnership or a trust organized as such under the laws of any state of the
United States; provided, that (i) such successor entity either (x) expressly
assumes all of the obligations of the Partnership under the Preferred
Securities or (y) substitutes for the Preferred Securities other securities
having substantially the same terms as the Preferred Securities (the "Successor
Securities") so long as the Successor Securities rank, with respect to
participation in the profits and Dividends or in the assets of the successor
entity, at least as high as the Preferred Securities rank with respect to
participation in the profits and Dividends or in the assets of the Partnership,
(ii) Illinois Power expressly acknowledges such successor entity as the Holder
of the Subordinated Debentures, (iii) the Preferred Securities or the Successor
Securities are listed, or will be listed on notification of issuance, on any
national securities exchange or other organization on which the Preferred
Securities are then listed, (iv) such merger, consolidation, amalgamation or
replacement does not cause the Preferred Securities to be downgraded by any
nationally recognized statistical rating organization, as that term is defined
by the Securities and Exchange Commission for purposes of Rule 436(g)(2) under
the Securities Act, or cause any Successor Securities to be rated lower than
the Preferred Securities immediately prior to such merger, consolidation,
amalgamation or replacement, (v) such merger, consolidation, amalgamation or
replacement does not adversely affect the powers, preferences and special
rights of Holders of Preferred Securities in any material respect, (vi) such
successor entity has a purpose substantially identical to that of the
Partnership and (vii) prior to such merger, consolidation, amalgamation or
replacement, Illinois Power has received an opinion of nationally recognized
independent counsel to the Partnership experienced in such matters to the
effect that (x) such successor entity will be treated as a partnership for
Federal income tax purposes, (y) following such merger, consolidation,
amalgamation or replacement, Illinois Power and such successor entity will be
in compliance with the 1940 Act without registering thereunder as an investment
company, and (z) such merger, consolidation, amalgamation or replacement will
not adversely affect the limited liability of Holders of Preferred Securities.


                                  ARTICLE VII

                     BOOKS OF ACCOUNT, RECORDS AND REPORTS

                Section 7.1.   Books and Records.

                (a)    Proper and complete records and books of account of the
Partnership shall be kept by the General Partner in which shall be entered
fully and accurately all transactions and other matters relative to the
Partnership's business as are usually entered into records and books of account
maintained by Persons engaged in businesses of a like character, including a
Capital Account for each Partner.  The books and records of the Partnership,
together with a copy of this Agreement and a certified copy of the Certificate,
shall at all times be maintained at the principal office of the Partnership and
shall be open to the inspection and examination of the Limited





                                      -17-
<PAGE>   22
Partners or their duly authorized representatives for any purpose reasonably
related to their Interests during reasonable business hours.

                (b)    Notwithstanding any other provision of this Agreement,
the General Partner may, to the maximum extent permitted by applicable law,
keep confidential from the Partners any information the disclosure of which the
General Partner reasonably believes is not in the best interests of the
Partnership or is adverse to the interests of the Partnership or which the
Partnership or the General Partner is required by law or by an agreement with
any Person to keep confidential.

                (c)    Within three months after the close of each Fiscal Year,
the General Partner shall transmit to each Partner, a statement indicating such
Partner's share of each item of Partnership income, gain, loss, deduction or
credit for such Fiscal Year for federal income tax purposes.

                Section 7.2.   Accounting Method.  For both financial and tax
reporting purposes and for purposes of determining profits and losses, the
books and records of the Partnership shall be kept on the accrual method of
accounting applied in a consistent manner and shall reflect all Partnership
transactions and be appropriate and adequate for the Partnership's business.


                                  ARTICLE VIII

                           POWERS, RIGHTS AND DUTIES
                            OF THE LIMITED PARTNERS

                Section 8.1.   Limitations.  The Limited Partners shall not
participate in the management or control of the Partnership's business,
property or other assets nor shall the Limited Partners transact any business
for the Partnership, nor shall the Limited Partners have the power to act for
or bind the Partnership, said powers being vested solely and exclusively in the
General partner.  The Limited Partners shall have such rights as are set forth
in this Agreement or in any Action, and as are set forth in the Guarantee and
the Indenture.  The Limited Partners shall have no interest in the properties
or assets of the General Partner, or any equity therein, or in any proceeds of
any sales thereof (which sales shall not be restricted in any respect), by
virtue of acquiring or owning an Interest.

                Section 8.2.   Liability.  Subject to the provisions of the
Act, no Limited Partner shall be liable for the repayment, satisfaction or
discharge of any debts or other obligations of the Partnership in excess of the
Capital Account balance of such Limited Partner.

                Section 8.3.   Priority.  No Limited Partner shall have
priority over any other Limited Partner as to Partnership allocations or
distributions.





                                      -18-
<PAGE>   23
                                   ARTICLE IX

                           POWERS, RIGHTS AND DUTIES
                             OF THE GENERAL PARTNER

                Section 9.1.   Authority.  Subject to the limitations provided
in this Agreement, the General Partner shall have exclusive and complete
authority and discretion to manage the operations and affairs of the
Partnership and to make all decisions regarding the business of the
Partnership.  Any action taken by the General Partner shall constitute the act
of and serve to bind the Partnership.  In dealing with the General Partner
acting on behalf of the Partnership, no Person shall be required to inquire
into the authority of the General Partner to bind the Partnership.  Persons
dealing with the Partnership are entitled to rely conclusively on the power and
authority of the General Partner as set forth in this Agreement.

                Section 9.2.   Powers and Duties of General Partner.  Except as
otherwise specifically provided herein, the General Partner shall have all
rights and powers of a general partner under the Act, and shall have all
authority, rights and powers in the management of the Partnership business to
do any and all other acts and things necessary, proper, convenient or advisable
to effectuate the purposes of this Agreement, including by way of illustration
but not by way of limitation, the following:

                (a)    to secure the necessary goods and services required in
performing the General Partner's duties for the Partnership;

                (b)    to exercise all powers of the Partnership, on behalf of
the Partnership, in connection with enforcing the Partnership's rights and
interest under the Subordinated Debentures and the Guarantee;

                (c)    to issue Preferred Securities, and series thereof, in
accordance with this Agreement;

                (d)    to establish a record date with respect to all actions
to be taken hereunder that require a record date be established, including with
respect to Dividends and voting rights and to make determinations as to the
payment of Dividends, and make all other required payments to Preferred
Security Holders and to the General Partner as the Partnership's paying agent;

                (e)    to open, maintain and close bank accounts and to draw
checks and other orders for the payment of money;

                (f)    to bring or defend, pay, collect, compromise, arbitrate,
resort to legal action, or otherwise adjust claims or demands of or against the
Partnership;

                (g)    to deposit, withdraw, invest, pay, retain and distribute
the Partnership's funds in a manner consistent with the provisions of this
Agreement;

                (h)    to take all action which may be necessary or appropriate
for the preservation and the continuation of the Partnership's valid existence,
rights, franchises and privileges as a limited partnership under the laws of
the State of Delaware and of each other jurisdiction in which such existence is
necessary to protect the limited liability of the Limited Partners or to enable
the Partnership to conduct the business in which it is engaged;





                                      -19-
<PAGE>   24
                (i)    to take all action not inconsistent with applicable law,
the Certificate or this Agreement as long as such action does not adversely
affect the interests of the Preferred Security Holders, necessary to conduct
its affairs and to operate the Partnership in such a way that (x) the
Partnership would not be deemed an "investment company" required to be
registered under the 1940 Act, (y) the Partnership will be taxed as a
partnership for federal income tax purposes, and (z) the Subordinated
Debentures will be treated as indebtedness of Illinois Power for federal income
tax purposes;

                (j)    to cause the Partnership to enter into and perform, on
behalf of the Partnership Underwriting Agreements and to cause the Partnership
to purchase the Subordinated Debentures without any further act, vote or
approval of any Partner; and

                (k)    to execute and deliver any and all documents or
instruments, perform all duties and powers and do all things for and on behalf
of the Partnership in all matters necessary or desirable or incidental to the
foregoing.

                Section 9.3.   Liability.  Except as expressly set forth in
this Agreement, (a) the General Partner shall not be personally liable for the
return of any portion of the capital contributions (or any return thereon) of
the Limited Partners; (b) the return of such capital contributions (or any
return thereon) shall be made solely from assets of the Partnership; and (c)
the General Partner shall not be required to pay to the Partnership or to any
Limited Partner any deficit in any Limited Partner's Capital Account upon
dissolution or otherwise.

                Section 9.4.   Exculpation.  (a)  No Indemnified Person shall
be liable, responsible or accountable in damages or otherwise to the
Partnership or any Covered Person for any loss, damage or claim incurred by
reason of any act or omission performed or omitted by such Indemnified Person
in good faith on behalf of the Partnership and in a manner reasonably believed
to be within the scope of the authority conferred on such Indemnified Person by
this Agreement or by law except that an Indemnified Person shall be liable for
any such loss, damage or claim incurred by reason of such Indemnified Person's
gross negligence or willful misconduct with respect to such acts or omissions.

                (b)    An Indemnified Person shall be fully protected in
relying in good faith upon the records of the Partnership and upon such
information, opinions, reports or statements presented to the Partnership by
any Person as to matters the Indemnified Person reasonably believes are within
such other Persons's professional or expert competence and who has been
selected with reasonable care by or on behalf of the Partnership, including
information, opinions, reports or statements as to the value and amount of the
assets, liabilities, profits, losses, or any other facts pertinent to the
existence and amount of assets from which distributions to Partners might
properly be paid.

                Section 9.5.   Fiduciary Duty.

                (a)    To the extent that, at law or in equity, an Indemnified
Person has duties (including fiduciary duties) and liabilities relating thereto
to the Partnership or to any other Covered Person, an Indemnified Person acting
under this Agreement shall not be liable to the Partnership or to any other
Covered Person for its good faith reliance on the provisions of this Agreement.
The provisions of this Agreement, to the extent that they restrict the duties
and liabilities of an Indemnified Person otherwise existing at law or in
equity, are agreed by the parties hereto to replace such other duties and
liabilities of such Indemnified Person.





                                      -20-
<PAGE>   25
                (b)    Unless otherwise expressly provided herein, (i) whenever
a conflict of interest exists or arises between Covered Persons, or (ii)
whenever this Agreement or any other agreement contemplated herein or therein
provides that an Indemnified Person shall act in a manner that is, or provides
terms that are, fair and reasonable to the Partnership or any Partner, the
Indemnified Person shall resolve such conflict of interest, take such action or
provide such terms, considering in each case the relative interest of each
party (including its own interest) to such conflict, agreement, transaction or
situation and the benefits and burdens relating to such interests, any
customary or accepted industry practices, and any applicable generally accepted
accounting practices or principles.  In the absence of bad faith by the
Indemnified Person, the resolution, action or term so made, taken or provided
by the Indemnified Person shall not constitute a breach of this Agreement or
any other agreement contemplated herein or of any duty or obligation of the
Indemnified Person at law or in equity or otherwise.

                (c)    Whenever in this Agreement an Indemnified Person is
permitted or required to make a decision (i) in its "discretion" or under a
grant of similar authority, the Indemnified Person shall be entitled to
consider only such interests and factors as it desires, including its own
interests, and shall have no duty or obligation to give any consideration to
any interest of or factors affecting the Partnership or any other Person, or
(ii) in its "good faith" or under another express standard, the Indemnified
Person shall act under such express standard and shall not be subject to any
other or different standard imposed by this Agreement or other applicable law.

                Section 9.6.   Indemnification.

                (a)    To the fullest extent permitted by applicable law, the
Partnership shall indemnify and hold harmless each Indemnified Person from and
against any loss, damage or claim incurred by such Indemnified Person by reason
of any act or omission performed or omitted by such Indemnified Person in good
faith on behalf of the Partnership and in a manner reasonably believed to be
within the scope of authority conferred on such Indemnified Person by this
Agreement, except that no Indemnified Person shall be entitled to be
indemnified in respect of any loss, damage or claim incurred by such
Indemnified Person by reason of gross negligence or willful misconduct with
respect to such acts or omissions; provided, however, that any indemnity under
this Section 9.6 shall be provided out of and to the extent of Partnership
assets only, and no Covered Person shall have any personal liability on account
thereof.

                (b)    To the fullest extent permitted by applicable law,
expenses (including legal fees) incurred by an Indemnified Person in defending
any claim, demand, action, suit or proceeding shall, from time to time, be
advanced by the Partnership prior to the final disposition of such claim,
demand, action, suit or proceeding upon receipt by the Partnership of an
undertaking by or on behalf of the Indemnified Person to repay such amount if
it shall be determined that the Indemnified Person is not entitled to be
indemnified as authorized in Section 9.6(a).

                Section 9.7.   Outside Businesses.  Any Covered Person may
engage in or possess an interest in other business ventures of any nature of
description, independently or with others, similar or dissimilar to the
business of the Partnership, and the Partnership and the Partners shall have no
rights by virtue of this Agreement in and to such independent ventures or the
income or profits derived therefrom and the pursuit of any such venture, even
if competitive with the business of the Partnership, shall not be deemed
wrongful or improper.  No Covered Person shall be obligated to present any
particular investment opportunity to the Partnership even if such opportunity
is of a character that, if presented to the Partnership, could be taken by the
Partnership,





                                      -21-
<PAGE>   26
and any Covered Person shall have the right to take for its own account
(individually or as a partner or fiduciary) or to recommend to others any such
particular investment opportunity.

                Section 9.8.   Limits on General Partner's Powers.  Anything in
this Agreement to the contrary notwithstanding, the General Partner shall not
cause or permit the Partnership to

                (a)    acquire any assets other than as expressly provided
herein,

                (b)    possess Partnership property for other than a
Partnership purpose;

                (c)    admit a Person as a Partner, except as expressly
provided in this Agreement;

                (d)    make any loans to the General Partner or its Affiliates,
other than loans represented by the Subordinated Debentures or other similar
debt instruments of Illinois Power;

                (e)    perform any act that would subject any Limited Partner
to liability as a general partner in any jurisdiction;

                (f)    engage in any activity that is not consistent with the
purposes of the Partnership, as set forth in Section 1.3;

                (g)    confess a judgment against the Partnership;

                (h)    without the written consent of 66-2/3% in liquidation
preference of the Preferred Securities have an order for relief entered with
respect to the Partnership or commence a voluntary case under any applicable
bankruptcy, insolvency or other similar law now or hereafter in effect, or
consent to the entry of an order for relief in an involuntary case under any
such law, or consent to the appointment of or taking possession by a receiver,
trustee or other custodian for all or a substantial part of the Partnership's
property, or make any assignment for the benefit of creditors of the
Partnership; it being understood that nothing in this paragraph (h) is to
effect the ability of the Partnership to dissolve pursuant to this Agreement;
or

                (i)    subject to Section 1.3, borrow money or become liable
for the borrowings of any third party or to engage in any financial or other
trade or business.

                Section 9.9.   Tax Matters Partner.  (a)  For purposes of Code
Section 6231(a)(7), the "Tax Matters Partner" shall be Illinois Power as long
as it remains the general partner of the Partnership.  The Tax Matters Partner
shall keep the Limited Partners fully informed of any inquiry, examination or
proceeding involving any taxing authority.

                (b)    The General Partner shall not make an election in 
accordance with Section 754 of the Code.

                (c)    The General Partner and the Preferred Security Holders
acknowledge that they intend, for United States federal income tax purposes,
that the Partnership shall be treated as a partnership and that the General
Partner and the Preferred Security Holders shall be treated as Partners of such
Partnership for such purposes.

                Section 9.10.  Expenses.  The General Partner shall pay for
all, and the Partnership shall not be obligated to pay, directly or indirectly,
for any, costs and expenses of the Partnership





                                      -22-
<PAGE>   27
(including, but not limited to, costs and expenses relating to the organization
of, and offering of limited partner interests in, the Partnership and costs and
expenses relating to the operation of the Partnership, including without
limitation, costs and expenses of accountants, attorneys, statistical or
bookkeeping services and computing or accounting equipment, paying agent(s),
registrar(s), transfer agent(s), duplicating, travel and telephone and costs
and expenses incurred in connection with the acquisition, financing, and
disposition of Partnership assets).


                                   ARTICLE X

                       TRANSFERS OF INTERESTS BY PARTNERS

                Section 10.1.  Transfer of Interests.  (a)  Preferred
Securities shall be freely transferable by a Preferred Security Holder.

                (b)    The General Partner may not assign its interest in the
Partnership in whole or in part under any circumstances except to a successor
of Illinois Power by virtue of operation of law and, even then, only to the
extent permitted by the Indenture.  The admission of such successor as a
general partner of the Partnership shall be effective upon the filing of an
amendment to the Certificate with the Secretary of State of the State of
Delaware which indicates that such successor has been admitted as a general
partner in the Partnership.  If the General Partner assigns its entire Interest
to a successor of Illinois Power in accordance with this Agreement, the General
Partner shall cease to be a general partner in the Partnership simultaneously
with the admission of the successor as a general partner in the Partnership.
Any such successor general partner in the Partnership is hereby authorized to
and shall continue the business of the Partnership without dissolution.

                (c)    No Interest shall be transferred, in whole or in part,
except in accordance with the terms and conditions set forth in this Agreement.
Any transfer or purported transfer of any Interest not made in accordance with
this Agreement shall be null and void.

                Section 10.2.  Transfer of LP Certificates.  The General
Partner shall provide for the registration of LP Certificates and of transfers
of LP Certificates.  Upon surrender for registration of transfer of any LP
Certificate, the General Partner shall cause one or more new LP Certificates to
be issued in the name of the designated transferee or transferees.  Every LP
Certificate surrendered for registration of transfer shall be accompanied by a
written instrument of transfer in form satisfactory to the General Partner duly
executed by the Preferred Security Holder or his or her attorney duly
authorized in writing.  Each LP Certificate surrendered for registration of
transfer shall be canceled by the General Partner.  A transferee of an LP
Certificate shall be admitted to the Partnership as a Limited Partner and shall
be entitled to the rights and subject to the obligations of a Preferred
Security Holder hereunder upon the receipt by a transferee of an LP
Certificate.  By acceptance of an LP Certificate, each transferee shall be
deemed to have requested admission as a Limited Partner and to have agreed to
be bound by this Agreement.  The transferor of an LP Certificate, in whole,
shall cease to be a Limited Partner at the time that the transferee of such LP
Certificate is admitted to the Partnership as a Limited Partner in accordance
with this Section 10.2.

                Section 10.3.  Persons Deemed Preferred Security Holders.  The
Partnership may treat the Person in whose name any LP Certificate shall be
registered on the books and records of the Partnership as the sole holder of
such LP Certificate and of the Preferred Securities represented





                                      -23-
<PAGE>   28
by such LP Certificate (the "Preferred Security Holder") for purposes of
receiving Dividends and for all other purposes whatsoever and, accordingly,
shall not be bound to recognize any equitable or other claim to or interest in
such LP Certificate or in the Preferred Securities represented by such LP
Certificate on the part of any other Person, whether or not the Partnership
shall have actual or other notice thereof.

                Section 10.4.  Book Entry Interests.  The LP Certificates, on
original issuance, will be issued in the form of a global LP Certificate or LP
Certificates representing the Book Entry Interests, to be delivered to DTC, the
initial Clearing Agency, by, or on behalf of, the Partnership.  Such LP
Certificate or LP Certificates shall initially be registered on the books and
records of the Partnership in the name of Cede & Co., the nominee of DTC, and
no Preferred Security Owner will receive a definitive LP Certificate
representing such Preferred Security Owner's interests in such LP Certificate,
except as provided in Section 10.7.  Unless and until definitive, fully
registered LP Certificates (the "Definitive LP Certificates") have been issued
to the Preferred Security Owners pursuant to Section 10.7:

                   (i)        The provisions of this Section shall be in full 
        force and effect;

                   (ii)       The Partnership and the General Partner shall be
        entitled to deal with the Clearing Agency for all purposes of this
        Agreement (including the payment of Dividends on the LP Certificates
        and receiving approvals, votes or consents hereunder) as the Preferred
        Security Holder and the sole holder of the LP Certificates and shall
        have no obligation to the Preferred Security Owners;

                  (iii)       To the extent that the provisions of this
        Section conflict with any other provisions of this Agreement, the
        provisions of this Section shall control; and

                   (iv)       The rights of the Preferred Security Owners
        shall be exercised only through the Clearing Agency and shall be
        limited to those established by law and agreements between such
        Preferred Security Owners and the Clearing Agency and/or the Clearing
        Agency Participants.  DTC will make book entry transfers among the
        Clearing Agency Participants and receive and transmit payments of
        Dividends on the LP Certificates to such Clearing Agency Participants.

                Section 10.5.  Notices to Clearing Agency.  Whenever a notice
or other communication to the Preferred Security Holders is required under this
Agreement, unless and until Definitive LP Certificates shall have been issued
to the Preferred Security Owners pursuant to Section 10.7, the General Partner
shall give all such notices and communications specified herein to be given to
the Preferred Security Holders to the Clearing Agency, and shall have no
obligations to the Preferred Security Owners.

                Section 10.6.  Appointment of Successor Clearing Agency.  If
any Clearing Agency elects to discontinue its services as securities depository
with respect to the Preferred Securities, the General Partner may, in its sole
discretion, appoint a successor Clearing Agency with respect to the Preferred
Securities.

                Section 10.7.  Definitive LP Certificates; Appointment of
Paying Agent(s).  If (i) a Clearing Agency elects to discontinue its services
as securities depository with respect to the Preferred Securities and a
successor Clearing Agency is not appointed within 90 days after such
discontinuance pursuant to Section 10.6 or (ii) the Partnership elects to
terminate the book entry





                                      -24-
<PAGE>   29
system through the Clearing Agency, then (a) Definitive LP Certificates shall
be prepared by the Partnership and (b) the General Partner shall authorize one
or more Persons (each, a "Paying Agent") to pay Dividends, redemption payments
or liquidation payments on behalf of the Partnership with respect to the
Preferred Securities.  Upon surrender of the global LP Certificate or LP
Certificates representing the Book Entry Interests by the Clearing Agency,
accompanied by registration instructions, the General Partner shall cause
Definitive LP Certificates to be delivered to Preferred Security Owners in
accordance with the instructions of the Clearing Agency.  Neither the General
Partner nor the Partnership shall be liable for any delay in delivery of such
instructions and may conclusively rely on, and shall be protected in relying
on, such instructions.  Any Person receiving a Definitive LP Certificate in
accordance with this Article X shall be admitted to the Partnership as a
Limited Partner upon receipt of such Definitive LP Certificate and shall be
registered on the books and records of the Partnership as a Preferred Security
Holder.  The Clearing Agency or the nominee of the Clearing Agency, as the case
may be, shall cease to be a Limited Partner under this Section 10.7 at the time
that at least one additional Person is admitted to the Partnership as a Limited
Partner in accordance with this Section 10.7.  The Definitive LP Certificates
shall be printed, lithographed or engraved or may be produced in any other
manner as is reasonably acceptable to the General Partner, as evidenced by its
execution thereof.


                                   ARTICLE XI

                            WITHDRAWAL; DISSOLUTION;
                     LIQUIDATION AND DISTRIBUTION OF ASSETS

                Section 11.1.  Withdrawal of Partners.  Subject to the further
provisions of this Section 11.1 and except as provided in Article X, no Partner
shall at any time withdraw from the Partnership.  Any Partner withdrawing in
contravention of this Section 11.1, shall indemnify, defend and hold harmless
the Partnership and the other Partners from and against any losses, expenses,
judgments, fines, settlements or damages suffered or incurred by the
Partnership or such other Partners arising out of or resulting from such
withdrawal.  No permitted transfer of all or any portion of a Partner's
Interest in the Partnership in accordance with Article X shall constitute a
withdrawal in violation of this Section 11.1.  Further, the withdrawal of a
Holder in connection with the redemption of its entire Interest in the
Partnership, in accordance with the terms hereof, or of an Action, shall not
constitute a violation of this Section 11.1.

                Section 11.2.  Dissolution of the Partnership.

                (a)     The Partnership shall not be dissolved by the admission
of additional or successor Partners in accordance with the terms of this
Agreement.  The death, withdrawal, bankruptcy or dissolution of a Limited
Partner, or the occurrence of any other event which terminates the Interest of
a Limited Partner in the Partnership, shall not, in and of itself, cause the
Partnership to be dissolved and its affairs wound up.  To the fullest extent
permitted by applicable law, upon the occurrence of such event, the General
Partner may, without any further act, vote or approval of any Partner, admit
any Person to the Partnership as an additional or substitute limited partner in
the Partnership, which admission shall be effective as of the date of the
occurrence of such event, and the business of the Partnership shall be
continued without dissolution.

                (b)    The Partnership shall be dissolved and its affairs shall
be wound up upon the occurrence of any of the following events:





                                      -25-
<PAGE>   30
                    (i)        The expiration of the term of the Partnership,
        as provided in Section 1.4 hereof;

                   (ii)        Upon the bankruptcy or withdrawal of the General
        Partner;

                  (iii)        Upon the assignment by the General Partner of
        its entire interest in the Partnership when the assignee is not
        admitted to the Partnership as a general partner of the Partnership in
        accordance with Section 10.1, or the filing of a certificate of
        dissolution or its equivalent with respect to the General Partner, or
        the revocation of the General Partner's charter and the expiration of
        90 days after the date of notice to the General Partner of revocation
        without a reinstatement of its charter, or any other event occurs which
        causes the General Partner to cease to be a general partner of the
        Partnership under the Act, unless the business of the Partnership is
        continued in accordance with the Act (any remaining general partner of
        the Partnership is hereby authorized to and shall continue the business
        of the Partnership without dissolution);

                   (iv)        In accordance with any Action;

                    (v)        the entry of a decree of judicial dissolution
        under Section 17-802 of the Act; or

                   (vi)        the written consent of all Partners.

                (c)    Upon dissolution of the Partnership, the Liquidator (as
defined below) shall promptly notify the Partners of such dissolution.

                Section 11.3.  Liquidation.  (a)   In the event of the
dissolution of the Partnership for any reason, the General Partner (or, if the
Partnership is dissolved pursuant to Section 11.2(b)(ii) or (iii), then a
liquidating trustee appointed by 66 2/3% in liquidation preference of the
Preferred Securities (the General Partner or such Person so appointed is
hereinafter referred to as the "Liquidator")), shall commence to wind up the
affairs of the Partnership and to liquidate the Partnership's assets; provided,
however, that a reasonable time shall be allowed for the orderly liquidation of
the assets of the Partnership and the satisfaction of liabilities to creditors
so as to enable the Partners to minimize the normal losses attendant upon
liquidation.  The Partners shall continue to share all income, losses and
distributions during the period of liquidation in accordance with Articles IV
and V.  Subject to the provisions of this Article XI, the Liquidator shall have
full right and unlimited discretion to determine the time, manner and terms of
any sale or sales of Partnership property pursuant to such liquidation, giving
due regard to the activity and condition of the relevant market and general
financial and economic conditions.

                (b)    The Liquidator shall have all of the rights and powers
with respect to the assets and liabilities of the Partnership in connection
with the liquidation and termination of the Partnership that the General
Partner would have with respect to the assets and liabilities of the
Partnership during the term of the Partnership, and the Liquidator is hereby
expressly authorized and empowered to execute any and all documents necessary
or desirable to effectuate the liquidation and termination of the Partnership
and the transfer of any assets.

                (c)     Notwithstanding the foregoing, a Liquidator which is
not the General Partner shall not be deemed a Partner in the Partnership and
shall not have any of the economic interests in the Partnership of a Partner;
and such Liquidator may be compensated for its services to the





                                      -26-
<PAGE>   31
Partnership at normal, customary and competitive rates for its services to the
Partnership as reasonably determined by a majority in liquidation  preference
of the Preferred Securities.

                Section 11.4.  Distribution in Liquidation.

                (a) Upon the winding up of the Partnership, the assets of the
        Partnership shall be distributed in the following order of priority:

                (i)    to creditors of the Partnership, including Preferred
        Security Holders who are creditors, to the extent permitted by law, in
        satisfaction of the liabilities of the Partnership (whether by payment
        or the making of reasonable provision for payment thereof); and

                (ii)   to the Partners in proportion to the Partners' positive
        Capital Account balances.

                Section 11.5.  Rights of Limited Partners.  Each Limited
Partner shall look solely to the assets of the Partnership for all
distributions with respect to the Partnership and such Partner's capital
contribution (including return thereof), and such Partner's share of profits or
losses thereof, and shall have no recourse therefor (upon dissolution or
otherwise) against the General Partner.  No Partner shall have any right to
demand or receive property other than cash upon dissolution and termination of
the Partnership.

                Section 11.6.  Termination.  The Partnership shall terminate
when all of the assets of the Partnership shall have been disposed of and the
assets shall have been distributed as provided in Section 11.4, and the
Liquidator has executed and caused to be filed a certificate of cancellation of
the Certificate.


                                  ARTICLE XII

                            AMENDMENTS AND MEETINGS

                Section 12.1.  Amendments.  Except as otherwise provided in
this Agreement or by any applicable terms of any Action establishing a series
of Preferred Securities, this Agreement may be amended by, and only by, a
written instrument executed by the General Partner; provided, however, that (i)
no amendment shall be made, and any such purported amendment shall be void and
ineffective, to the extent the result thereof would be to cause the Partnership
to be treated as anything other than a partnership for purposes of United
States income taxation and (ii) any amendment which would adversely affect the
powers, preferences or special rights of any series of Preferred Securities may
be effected only as permitted by the terms of such series of Preferred
Securities.

                Section 12.2.  Amendment of Certificate.  In the event this
Agreement shall be amended pursuant to Section 12.1, the General Partner shall
amend the Certificate to reflect such change if it deems such amendment of the
Certificate to be necessary or appropriate.

                Section 12.3.  Meetings of the Partners.

                (a)    Meetings of the Limited Partners who are Holders of any
series or, in the case of a class vote, of multiple series of Preferred
Securities may be called at any time by the





                                      -27-
<PAGE>   32
General Partner (or as provided in any Action establishing a series of
Preferred Securities) to consider and act on any matter on which Limited
Partners are entitled to act under the terms of this Agreement or the Act.  The
General Partner shall call a meeting of Holders of any series or, in the case
of a class vote, multiple series, if directed to do so by Holders of not less
than 10% in liquidation preference of the Preferred Securities of that series
entitled to vote at the meeting.  Such direction shall be given by delivering
to the General Partner one or more calls in writing stating that the signing
Limited Partners wish to call a meeting and indicating the general or specific
purpose for which the meeting is to be called.  Any Limited Partner calling a
meeting shall specify in a writing the LP Certificates held by the Limited
Partners exercising the right to call a meeting and only those specified
Interests shall be counted for purposes of determining whether the required
percentage set forth in the proceeding sentence has been met.  Except to the
extent otherwise provided in any such Action, the following provisions shall
apply to meetings of Partners.

                (b)    Notice of any such meeting shall be given to all Limited
Partners having a right to vote thereat not less than seven Business Days nor
more than 60 days prior to the date of such meeting. Whenever a vote, consent
or approval of Limited Partners is permitted or required under this Agreement,
such vote, consent or approval may be given at a meeting of Limited Partners.
Further, any action that may be taken at a meeting of the Limited Partners may
be taken without a meeting if a consent in writing setting forth the action so
taken is signed by Limited Partners owning not less than the minimum Interests
that would be necessary to authorize or take such action at a meeting at which
all Limited Partners having a right to vote thereon were present and voting.
Prompt notice of the taking of action without a meeting shall be given to the
Limited Partners entitled to vote who have not consented in writing.  The
General Partner may specify that any written ballot submitted to the Limited
Partners for the purpose of taking any action without a meeting shall be
returned to the Partnership within the time specified by the General Partner.

                (c)    Each Limited Partner may authorize any Person to act for
it by proxy on all matters in which a Limited Partner is entitled to
participate, including waiving notice of any meeting, or voting or
participating at a meeting.  No proxy shall be valid after the expiration of 11
months from the date thereof unless otherwise provided in the proxy.  Every
proxy shall be revocable at the pleasure of the Limited Partner executing it.
Except as otherwise provided herein, in any Action or pursuant to Section
12.3(e), all matters relating to the giving, voting or validity of proxies
shall be governed by the General Corporation Law of the State of Delaware
relating to proxies, and judicial interpretations thereunder, as if the
Partnership were a Delaware corporation and the Limited Partners were
stockholders of a Delaware corporation.

                (d)    Each meeting of Partners shall be conducted by the
General Partner or by such other Person that the General Partner may designate.

                (e)    The General Partner, in its sole discretion, shall
establish all other provisions relating to meetings of Limited Partners,
including notice of the time, place or purpose of any meeting at which any
matter is to be voted on by any Limited Partners, waiver of any such notice,
action by consent without a meeting, the establishment of a record date, quorum
requirements, voting in person or by proxy or any other matter with respect to
the exercise of any such right to vote.





                                      -28-
<PAGE>   33
                                  ARTICLE XIII

                                 MISCELLANEOUS

                Section 13.1.  Notices.  All notices provided for in this
Agreement shall be in writing, duly signed by the party giving such notice, and
shall be delivered, telecopied or mailed by registered or certified mail, as
follows:

                (a)    if given to the Partnership, in care of the General
      Partner at the Partnership's mailing address set forth below:


                (b)    if given to the General Partner, at its mailing address
      set forth below:

                                       Illinois Power Company
                                       500 South 27th Street
                                       Decatur, Illinois   62525
                                       Attention:  President

                (c)    if given to any other Partner at the address for such
      Partner set forth on the books and records of the Partnership.

                All such notices shall be deemed to have been given when sent.

                Section 13.2.  Entire Agreement.  This Agreement constitutes
the entire agreement among the parties.  It supersedes any prior agreement or
understandings among them, and it may not be modified or amended in any manner
other than as set forth herein.

                Section 13.3.  Governing Law.  This Agreement and the rights of
the parties hereunder shall be governed by and interpreted in accordance with
the law of the State of Delaware and all rights and remedies shall be governed
by such laws without regard to principles of conflict of laws.

                Section 13.4.  Effect.  Except as herein otherwise specifically
provided, this Agreement shall be binding upon and inure to the benefit of the
parties and their legal representatives, successors and assigns.

                Section 13.5.  Pronouns and Number.  Wherever from the context
it appears appropriate, each term stated in either the singular or the plural
shall include the singular and the plural, and pronouns stated in either the
masculine, feminine or neuter shall include the masculine, feminine and neuter.

                Section 13.6.  Captions.  Captions contained in this Agreement
are inserted only as a matter of convenience and in no way define, limit or
extend the scope or intent of this Agreement or any provision hereof.

                Section 13.7.  Partial Enforceability.  If any provision of
this Agreement, or the application of such provision to any Person or
circumstance, shall be held invalid, the remainder of this Agreement, or the
application of such provision to Persons or circumstances other than those to
which it is held invalid, shall not be affected thereby.





                                      -29-
<PAGE>   34
                Section 13.8.  Counterparts.  This Agreement may contain more
than one counterpart of the signature page and this Agreement may be executed
by the affixing of the signature of each of the Partners to one of such
counterpart signature pages.  All of such counterpart signatures pages shall be
read as though one, and they shall have the same force and effect as though all
of the signers had signed a single signature page.

                Section 13.9.  Waiver of Partition.  Each Partner hereby
irrevocably waives any and all rights (if any) that such Partner may have to
maintain any action for partition of any of the Partnership's property.

                Section 13.10. Remedies.  The failure of any party to seek
redress for violation of, or to insist upon the strict performance of, any
provision of this Agreement shall not prevent a subsequent act, which would
have originally constituted a violation, from having the effect of an original
violation.  The rights and remedies provided by this Agreement are cumulative
and the use of any one right or remedy by any party shall not preclude or waive
its right to use any or all other remedies.  Said rights and remedies are given
in addition to any other rights the parties may have by law, statute, ordinance
or otherwise.

                IN WITNESS WHEREOF, the parties hereto have executed this
Agreement as of the date first above stated.

                                               General Partner:

                                               ILLINOIS POWER COMPANY,
                                               an Illinois corporation


                                               By:______________________
                                                   Name:
                                                   Title:


                                               Initial Limited Partner:


                                               ILLINOVA CORPORATION,
                                               an Illinois corporation



                                               By:_______________________
                                                   Name:
                                                   Title:





                                      -30-
<PAGE>   35
                                                                         Annex A


Certificate Number

        R-1

                                                                       CUSIP NO.



                  Certificate Evidencing Preferred Securities

                                       of

                         Illinois Power Capital, L.P.*

________________ Monthly Income Preferred Securities, Series _______ 
(liquidation preference $25 per Preferred Security)


                Illinois Power Capital, L.P., a limited partnership formed
under the laws of the State of Delaware (the "Partnership"), hereby certifies
that __________ (the "Holder") is the registered owner of _______ (          ) 
preferred securities of the Partnership representing limited partner interests 
in the Partnership of a series designated the ______________ Monthly Income 
Preferred Securities, Series _____ (liquidation preference $25 per Preferred 
Security) (the "Preferred Securities").  The Preferred Securities are fully 
paid and nonassessable limited partner interests in the Partnership, as to 
which the limited partners in the Partnership who hold the Preferred Securities
(the "Preferred Security Holders"), as limited partners in the Partnership, 
will, assuming such Preferred Security Holders do not participate in the 
control of the business of the Partnership, have no liability in excess of their
obligations to make payments provided for in the Limited Partnership Agreement
(as defined below) and their share of the Partnership's assets and
undistributed profits (subject to the obligation of a Preferred Security Holder
to repay any funds wrongfully distributed to it) and are transferable on the
books and records of the Partnership, in person or by a duly authorized
attorney, upon surrender of this certificate duly endorsed and in proper form
for transfer. The powers, preferences and special rights and limitations of the
Preferred Securities are set forth in, and this certificate and the Preferred
Securities represented hereby are issued and shall in all respects be subject
to the terms and provisions of, the Amended and Restated Agreement of Limited
Partnership of the Partnership dated as of __________ 1994, as the same may be
amended from time to time (the "Limited Partnership Agreement"), and the Action
of the General Partner taken pursuant thereto authorizing the issuance of the
Preferred Securities and determining the designations, powers, rights,
preferences, privileges, limitations and other terms and provisions, regarding
Dividends, voting, return of capital and otherwise, and other matters relating
to the Preferred Securities. Capitalized terms used herein but not defined
shall have the meaning given them in the Limited Partnership Agreement or the
Action. The Holder is entitled to the benefits of the Guarantee Agreement of
Illinois Power Company, an Illinois corporation ("Illinois Power"), dated as of
____________________, 1994 (the "Guarantee"), and the Subordinated Debentures
of Illinois Power issued pursuant to the Indenture dated as of ______________,
1994





                                  
________________________
     *The form of this Certificate may be modified to reflect the specific
terms and provisions of a particular series of Preferred Securities.
<PAGE>   36
between Illinois Power and The First National Bank of Chicago, as Trustee (the
"Indenture"), in each case to the extent provided therein.  The Partnership
will furnish a copy of the Limited Partnership Agreement, the Action, the
Guarantee and the Subordinated Debentures to the Holder without charge upon
written request to the Partnership at its principal place of business or
registered office.

                The Holder, by accepting this certificate, is deemed to have
agreed that (i) the Subordinated Debentures acquired by the Partnership with
the proceeds from the issuance of the Preferred Securities are subordinate and
junior in right of payment to all Senior Indebtedness of Illinois Power as and
to the extent provided in the Indenture, and (ii) the Guarantee ranks
subordinate and junior in right of payment to all liabilities of Illinois
Power, pari passu with the most senior preferred or preference stock now or
hereafter issued by Illinois Power and with any guarantee now or hereafter
issued by Illinois Power in respect of any preferred or preference stock of any
Affiliate of Illinois Power, and senior to Illinois Power's common stock, as
and to the extent provided in the Guarantee.  Upon receipt of this certificate,
the Holder is admitted to the Partnership as a Limited Partner, is bound by the
Limited Partnership Agreement and the Action and is entitled to the benefits
thereunder.

                IN WITNESS WHEREOF, the Partnership has executed this 
certificate this day of ___________, 199__



                                               ILLINOIS POWER CAPITAL, L.P.

                                               By:     ILLINOIS POWER COMPANY,
                                                        its General Partner

                                               By: __________________________





                                      -2-

<PAGE>   1
                                                                    EXHIBIT 4(D)

                           ACTION OF GENERAL PARTNER


      ILLINOIS POWER COMPANY, an Illinois corporation ("Illinois Power"), as
General Partner of Illinois Power Capital, L.P., a Delaware limited partnership
(the "Partnership"), in accordance with Section 6.1(b)(ii) of the Amended and
Restated Agreement of Limited Partnership of the Partnership dated as of
_________________, 1994 (the "Partnership Agreement"), does hereby establish a
new series of Preferred Securities having the following designation, powers,
rights, preferences, privileges, limitations and other terms and provisions
(capitalized terms used herein without definition having the meanings specified
in the Partnership Agreement):

      (a)    Designation.  __________ (_____________)  Preferred Securities,
with a liquidation preference of $25 per Preferred Security, are hereby
designated as ["_____% Cumulative Monthly Income Preferred Securities, Series
A"] ["Cumulative Adjustable Rate Monthly Income Preferred Securities, Series
A"] (the "Series A Preferred Securities").

      (b)    Dividends.  (i)  The Limited Partners who hold the Series A
Preferred Securities shall be entitled to receive, when, as and if available
and determined to be so distributed by the General Partner (the General
Partner's discretion to be subject to (b)(ii) below), cumulative dividends at a
[rate per annum of ____% of the liquidation preference of $25 per Preferred
Security, calculated on the basis of a 360-day year of twelve 30-day months,]
[rate per annum of ___% from the date of initial issuance to  , 1994, and
thereafter at the Applicable Rate (as defined in the Prospectus Supplement
relating to the offering of the Series A Preferred Securities) from time to
time in effect], and payable in United States dollars monthly in arrears on the
last day of each calendar month of each year, commencing  , 1994.  Such
Dividends will accumulate and be cumulative whether or not they have been
determined to be made and whether or not there are funds of the Partnership
legally available for the payment of Dividends.  Dividends on the Series A
Preferred Securities shall be cumulative from the date of original issue, and
the cumulative portion from such date to _______________ , 1994 shall be 
payable on , 1994.  In the event that any date on which Dividends are payable 
on the Series A Preferred Securities is not a Business Day, then payment of the
Dividends payable on such date will be made on the next succeeding day which is
a Business Day (and without any interest or other payment in respect of any such
delay) except that, if such Business Day is in the next succeeding calendar
year, such payment shall be made on the immediately preceding Business Day, in
each case with the same force and effect as if made on such date.  Dividends in
arrears for more than one month will bear interest thereon at the rate per
annum of ____% thereof.

             (ii)   Dividends on the Series A Preferred Securities must be paid
on the date such Dividends are payable to the extent that the Partnership has,
on the date such Dividends are payable, (x) funds legally available for the
payment of such Dividends and (y) cash on hand sufficient to permit such
payments.  Dividends will be payable to the Preferred Security Holders as they
appear on the books and records of the Partnership on the relevant record
dates, which, as long as the Series A Preferred Securities remain in
book-entry-only form, will be one Business Day prior to the relevant payment
dates.  In the event the Series A Preferred Securities shall not continue to
remain in book-entry-only form, the General Partner shall have the right to
select relevant record dates which shall be more than one Business Day prior to
the relevant payment dates.
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             (iii)  The Partnership shall not:

                    (A)    pay, or set aside for payment, any Dividends with
respect to any other Preferred Securities, unless the amount of any Dividends
paid or set aside on such other Preferred Securities is paid or set aside on
such other Preferred Securities and the Series A Preferred Securities on a pro
rata basis on the date such dividends are paid or set aside on such other
Preferred Securities, so that

                           (x)    the aggregate amount of Dividends paid on the
                    Series A Preferred Securities bears to the aggregate amount
                    of Dividends paid on such other Preferred Securities the
                    same ratio as

                           (y)    the aggregate of all accumulated and unpaid
                    Dividends in respect of the Series A Preferred Securities
                    bears to the aggregate of all accumulated and unpaid
                    Dividends in respect of such other Preferred Securities; or

                    (B)    redeem, purchase or otherwise acquire any other
Preferred Securities;

until, in each case, such time as all accumulated and unpaid Dividends on the
Series A Preferred Securities shall have been paid in full for all Dividend
periods terminating on or prior to, in the case of clause (A), such payment
and, in the case of clause (B), the date of such redemption, purchase or
acquisition.

      (c)    Redemption.  (i) The Series A Preferred Securities are redeemable,
at the option of the Partnership, in whole or in part from time to time, on or
after _____, 1999, upon not less than 30 nor more than 60 days' notice, at the
Redemption Price (as hereinafter defined); provided, however, that prior to
giving any such notice, the Partnership shall have received from Illinois Power
a notice of redemption of Series A Subordinated Debentures in an aggregate
principal amount equal to the aggregate liquidation preference of the Series A
Preferred Securities to be redeemed.  If a partial redemption would result in a
delisting of the Series A Preferred Securities, the Partnership may only redeem
the Series A Preferred Securities in whole.

             (ii)   Upon repayment of the Series A Subordinated Debentures at
maturity or earlier, the proceeds from such repayment shall be applied to
redeem the Series A Preferred Securities, in whole, at the redemption price of
$25 per Preferred Security plus accumulated and unpaid Dividends (whether or
not declared) to the date fixed for redemption (the "Redemption Price") upon
not less than 30 nor more than 60 days' notice.

             (iii)  Except as provided in the next succeeding sentence, if a
Special Event shall occur and be continuing, the General Partner shall elect to
either (A) cause the Partnership to redeem the Series A Preferred Securities in
whole (and not in part), upon not less than 30 or more than 60 days' notice at
the Redemption Price within 90 days following the occurrence of such Special
Event; provided, that if at the time there is available to the General Partner
the opportunity to eliminate, within such 90-day period, the Special Event by
taking some ministerial action, such as filing a form or making an election, or
pursuing some other similar reasonable measure which





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has no adverse effect on the Partnership or the General Partner, the General
Partner will pursue such measure in lieu of redemption, or (B) dissolve the
Partnership and, after satisfaction of liabilities of creditors as required by
the Partnership Act, cause to be distributed to Series A Preferred Security
Holders in liquidation of the Partnership, within 90 days following the
occurrence of such Special Event, Series A Subordinated Debentures having a
principal amount equal to the aggregate liquidation preference of the
outstanding Series A Preferred Securities.  In the case of a Tax Event, the
General Partner may also elect to cause the Series A Preferred Securities to
remain outstanding.

      In the event of a distribution of Series A Subordinated Debentures as
described in (B) above, each holder of Series A Preferred Securities would
receive Series A Subordinated Debentures in an aggregate principal amount equal
to the aggregate liquidation preference of $25 per Series A Preferred Security
on the Series A Preferred Securities held by it, with such Series A
Subordinated Debentures bearing interest at a rate per annum equal to the
dividend rate per annum on such Series A Preferred Securities from the last
date on which dividends were paid.  After the date fixed for any distribution
of Series A Subordinated Debentures upon dissolution of the Partnership, (i)
the Series A Preferred Securities will no longer be deemed to be outstanding,
(ii) DTC or its nominee, as the record Holder of the Series A Preferred
Securities, will receive a registered global certificate or certificates
representing the Series A Subordinated Debentures to be delivered upon such
distribution, and (iii) any certificates representing Series A Preferred
Securities not held by DTC or its nominee will be deemed to represent Series A
Subordinated Debentures having a principal amount equal to the aggregate
liquidation preference of such Series A Preferred Securities until such
certificates are presented to the General Partner or its agent for transfer or
reissuance.

      (d)    Redemption Procedures.  (i) Notice of any redemption (a "Notice of
Redemption") of the Series A Preferred Securities will be given by the
Partnership by mail to each record Holder to be redeemed not fewer than 30 nor
more than 60 days prior to the date fixed for redemption thereof.  For purposes
of the calculation of the date of redemption and the dates on which notices are
given pursuant to this paragraph (d)(i), a Notice of Redemption shall be deemed
to be given on the day such notice is first mailed by first-class mail, postage
prepaid, to Preferred Security Holders who hold Series A Preferred Securities.
Each Notice of Redemption shall be addressed to the Preferred Security Holders
who hold Series A Preferred Securities at the address of the Holder appearing
in the books and records of the Partnership.  No defect in the Notice of
Redemption or in the mailing thereof or publication of its contents shall
affect the validity of the redemption proceedings.

             (ii)   In the event that fewer than all the outstanding Series A
Preferred Securities are to be redeemed in the case of a redemption pursuant to
paragraph (c)(i) above, the Series A Preferred Securities to be redeemed will
be selected in accordance with paragraph (d)(iv) below.  The Partnership may
not redeem fewer than all the outstanding Series A Preferred Securities unless
all accumulated and unpaid Dividends have been paid on all Series A Preferred
Securities for all monthly Dividend periods terminating on or prior to the date
of redemption.

             (iii)  If the Partnership gives a Notice of Redemption in respect
of Series A Preferred Securities, then, (A) by 12:00 noon, New York time, on
the redemption date in the case of Clauses (I) and (II) below, or (B) prior to
the close of business on the Business Day immediately preceding the redemption
date in the case of Clause (III) below, the Partnership will irrevocably





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deposit with (I) DTC, as long as DTC is the Clearing Agency on the date such
Notice of Redemption is given, (II) such other Person which is the Clearing
Agency on the date such Notice of Redemption is given, or (III) if there is no
Clearing Agency with respect to the Series A Preferred Securities on the date
such Notice of Redemption is given, the Paying Agent or Paying Agents appointed
by the General Partner pursuant to Section 10.7 of the Partnership Agreement,
funds sufficient to pay the applicable Redemption Price and will give DTC, such
other Clearing Agency or the Paying Agent or Paying Agents, as the case may be,
irrevocable instructions and authority to pay the Redemption Price to the
Holders of the Series A Preferred Securities.  If Notice of Redemption shall
have been given and funds deposited as required, then upon the date of such
deposit, all rights of the Preferred Security Holders who hold such Series A
Preferred Securities so called for redemption will cease, except the right of
the Holders of such securities to receive the Redemption Price, but without
interest on such Redemption Price.  In the event that any date fixed for
redemption of Series A Preferred Securities is not a Business Day, then payment
of the Redemption Price payable on such date will be made on the next
succeeding day which is a Business Day (and without interest or other payment
in respect of any such delay), except that, if such Business Day falls in the
next calendar year, such payment will be made on the immediately preceding
Business Day.  In the event that payment of the Redemption Price in respect of
Series A Preferred Securities is improperly withheld or refused and not paid
either by the Partnership or by Illinois Power pursuant to the Guarantee,
Dividends on such Series A Preferred Securities will continue to accumulate at
the then applicable rate, from the original redemption date to the date of
payment, in which case the actual payment date will be considered the date
fixed for redemption for purposes of calculating the Redemption Price.

             (iv)   Notices of Redemption shall be sent to (A) Cede & Co. or
any successor nominee of DTC, in either case so long as DTC is the Clearing
Agency, (B) the nominee of any Clearing Agency other than DTC or (C) any Paying
Agent or Paying Agents appointed by the General Partner pursuant to Section
10.7 of the Partnership Agreement.  If less than all the Series A Preferred
Securities are being redeemed, interests to be redeemed shall be determined as
follows: (x) in accordance with DTC's practice, as long as DTC is the Clearing
Agency, (y) in accordance with the practice of any other Clearing Agency or (z)
if, at the time such Notice of Redemption is sent, there is no Clearing Agency,
the Paying Agent or Paying Agents shall select, by lot or in such other manner
as the Paying Agent or Paying Agents shall deem appropriate and fair, in their
discretion, the Series A Preferred Securities to be redeemed.

      (e)    Liquidation Distribution.  In the event of any voluntary or
involuntary dissolution, winding up or termination of the Partnership,
Preferred Security Holders who hold the Series A Preferred Securities at the
time will be entitled to receive out of the assets of the Partnership available
for distribution to Partners, after satisfaction of liabilities of creditors as
required by the Partnership Act, before any distribution of assets is made to
the General Partner, but together with the Holders of every other series of
Preferred Securities outstanding, if any, an amount equal to, in the case of
Holders of Series A Preferred Securities, the aggregate of the liquidation
preference of $25 per Preferred Security and accumulated and unpaid Dividends
thereon (whether or not declared) to the date of payment (the "Liquidation
Distribution"), unless in connection with such dissolution, winding up or
termination, Series A Subordinated Debentures in an aggregate principal amount
equal to $25 per Series A Preferred Security have been distributed on a pro
rata basis to the Holders of the Series A Preferred Securities.





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      If, upon any such dissolution, the Liquidation Distribution can be paid
only in part because the Partnership has insufficient assets available to pay
in full the aggregate Liquidation Distribution and the aggregate maximum
liquidation distributions on any other series of Preferred Securities, then the
amounts payable directly by the Partnership on the Series A Preferred
Securities and on such other series of Preferred Securities shall be paid on a
pro rata basis, so that

             (i)    the aggregate amount paid in respect of the Liquidation
      Distribution bears to the aggregate amount paid as liquidation
      distributions on such other series of Preferred Securities the same ratio
      as

             (ii)   the aggregate Liquidation Distribution bears to the
      aggregate maximum liquidation distributions on such other series of
      Preferred Securities.

                                   *  *  *  *


      This written Action of General Partner shall constitute an Action within
the meaning of Section 6.1(b)(ii) of the Partnership Agreement.

      IN WITNESS WHEREOF, the undersigned has executed this Action of General
Partner this ____ day of ___________, 1994.

                                         GENERAL PARTNER

                                         Illinois Power Company



                                        By: ___________________________
                                         Name:
                                         Title:





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