SENIOR NOTE This Security is a Book-Entry Security within the meaning of the Indenture hereinafter referred to and is registered in the name of a Depository or a nominee of a Depository. This Security is exchangeable for Securities registered in the name of a Person other than the Depository or its nominee only in the limited circumstances described in the Indenture, and no transfer of this Security (other than a transfer of this Security as a whole by the Depository to a nominee of the Depository or by a nominee of the Depository to the Depository or another nominee of the Depository) may be registered except in such limited circumstances. UNLESS THIS CERTIFICATE IS PRESENTED BY AN AUTHORIZED REPRESENTATIVE OF THE DEPOSITORY TRUST COMPANY, A NEW YORK CORPORATION ("DTC"), TO THE COMPANY OR ITS AGENT FOR REGISTRATION OF TRANSFER, EXCHANGE, OR PAYMENT, AND ANY CERTIFICATE ISSUED IS REGISTERED IN THE NAME OF CEDE & CO. OR IN SUCH OTHER NAME AS IS REQUESTED BY AN AUTHORIZED REPRESENTATIVE OF DTC (AND ANY PAYMENT IS MADE TO CEDE & CO. OR TO SUCH OTHER ENTITY AS IS REQUESTED BY AN AUTHORIZED REPRESENTATIVE OF DTC), ANY TRANSFER, PLEDGE, OR OTHER USE HEREOF FOR VALUE OR OTHERWISE BY OR TO ANY PERSON IS WRONGFUL INASMUCH AS THE REGISTERED OWNER HEREOF, CEDE & CO., HAS AN INTEREST HEREIN. DYNEGY HOLDINGS INC. 8.125% Senior Notes due March 15, 2005 No. R-005 CUSIP 26816L AC 6 Dynegy Holdings Inc., a corporation duly organized and existing under the laws of the State of Delaware (herein called the "Company," which term includes any successor Person under the Indenture referred to on the reverse hereof), for value received, hereby promises to pay to Cede & Co. or registered assigns, the principal sum of $300,000,000 on March 15, 2005 and to pay interest thereon from March 20, 2000 or from the most recent Interest Payment Date to which interest has been paid or duly provided for, semi-annually in arrears on March 15 and September 15 in each year, commencing September 15, 2000, at the rate of 8.125% per annum, until the principal hereof is paid or made available for payment. The interest so payable, and punctually paid or duly provided for, on any Interest Payment Date will, as provided in such Indenture, be paid to the Person in whose name this Security (or one or more Predecessor Securities) is registered at the close of business on the Regular Record Date for such interest, which shall be the March 1 or September 1 (whether or not a Business Day), as the case may be, next preceding such Interest Payment Date. Except as otherwise provided in the Indenture, any such interest not so punctually paid or duly provided for will forthwith cease to be payable to the Holder on such Regular Record Date and may either be paid to the Person in whose name this Security (or one or more Predecessor Securities) is registered at the close of business on a Special Record Date for the payment of such Defaulted Interest to be fixed by the Trustee, notice whereof shall be given to Holders of Securities of this series not less than 10 days prior to such Special Record Date, or be paid at any time in any other lawful manner not inconsistent with the requirements of any securities exchange on which the Securities of this series may be listed, and upon such notice as may be required by such exchange, all as more fully provided in the Indenture. Payment of the principal of and interest on this Security will be made at the Corporate Trust Office of the Trustee, or such other office or agency of the Company as may be designated by it for such purpose in such coin or currency of the United States of America as at the time of payment shall be legal tender for the payment of public and private debts; provided, however, that at the option of the Company payment of interest may be made by check mailed to the address of the Person entitled thereto as such address shall appear in the Security Register. Reference is hereby made to the further provisions of this Security set forth on the reverse hereof, which further provisions shall for all purposes have the same effect as if set forth at this place. Unless the certificate of authentication hereon has been executed by the Trustee referred to on the reverse hereof, directly or through an Authenticating Agent, by manual signature of an authorized signatory, this Security shall not be entitled to any benefit under the Indenture or be valid or obligatory for any purpose. IN WITNESS WHEREOF, the Company has caused this instrument to be signed in its name by its Chairman of the Board, President, Treasurer or Chief Financial Officer, manually or by a facsimile of his signature, and its corporate seal (or a facsimile thereof) to be hereunto affixed and the same to be attested by its Secretary or an Assistant Secretary, all either manually or in facsimile. Dated: March 20, 2000 DYNEGY HOLDINGS INC. By: ------------------------------------- Name: John U. Clarke Title: Executive Vice President and Chief Financial Officer Attest: - ----------------------------- Secretary TRUSTEE'S CERTIFICATE OF AUTHENTICATION This is one of the Securities of the series designated therein referred to in the within-mentioned Indenture. BANK ONE TRUST COMPANY, N.A., as Trustee By: ------------------------------ Authorized Officer Reverse of Senior Note This Senior Note is one of a duly authorized issue of securities of the Company (herein called the "Securities"), issued and to be issued in one or more series under an Indenture, dated as of September 26, 1996, and as amended and restated on March 23, 1998 (herein called the "Indenture"), among the Company and Bank One Trust Company, NA (formerly The First National Bank of Chicago), as Trustee (herein called the "Trustee," which term includes any successor trustee under the Indenture), to which Indenture and all indentures supplemental thereto reference is hereby made for a statement of the respective rights, limitations of rights, duties and immunities thereunder of the Company, the Trustee and the Holders of the Securities and of the terms upon which the Securities are, and are to be, authenticated and delivered. This Security is one of the series designated on the face hereof, limited in aggregate principal amount of $300,000,000. The Securities of this series are not subject to any sinking fund. The Securities of this series shall be redeemable, at the option of the Company, in whole at any time or in part from time to time, on at least 30 days but not more than 60 days prior notice mailed to the registered address of each holder of Securities to be so redeemed, at a redemption price equal to the greater of (i) 100% of the principal amount of the Securities to be so redeemed plus accrued interest thereon to the date of redemption, and (ii) the sum of the present values of the remaining scheduled payments of principal of the Securities to be so redeemed and interest thereon discounted to the date of redemption, on a semiannual basis (assuming 360-day year consisting of twelve 30-day months), at the Treasury Rate (as defined below) plus 25 basis points plus accrued interest thereon to the date of redemption. "Comparable Treasury Issue" means the United States Treasury security selected by an Independent Investment Banker as having a maturity comparable to the remaining term of the Securities to be redeemed that would be utilized, at the time of selection and in accordance with customary financial practice, in pricing new issues of corporate debt securities of comparable maturity to the remaining term of such Securities. "Independent Investment Banker" means one of the Reference Treasury Dealers. "Treasury Rate" means, with respect to any redemption date, the rate per annum equal to the semiannual equivalent yield to maturity of the Comparable Treasury Issue, assuming a price for the Comparable Treasury Issue (expressed as a percentage of its principal amount) equal to the Comparable Treasury Price for such redemption date. "Comparable Treasury Price" means, with respect to any redemption date, (i) the average of the bid and asked prices for the Comparable Treasury Issue (expressed in each case as a percentage of its principal amount) on the third business day preceding such redemption date, as set forth in the daily statistical release (or any successor release) published by the Federal Reserve Bank of New York and designated "Composite 3:30 p.m. Quotations for U.S. Government Securities" or (ii) if such release (or any successor release) is not published or does not contain such prices on such business day, the average of the Reference Treasury Dealer Quotations for such redemption date. "Reference Treasury Dealer Quotations" means, with respect to the Reference Treasury Dealer and any redemption date, the average, as determined by the Trustee, of the bid and asked prices for the Comparable Treasury Issue (expressed in each case as a percentage of its principal amount) quoted in writing to the Trustee by the Reference Treasury Dealer at 5:00 p.m. on the third business day preceding such redemption date. "Reference Treasury Dealer" means Banc of America Securities LLC or Lehman Brothers Inc. and their respective successors; provided however, that if either party shall cease to be a primary U.S. Government securities dealer in New York City (a "Primary Treasury Dealer"), the Company shall substitute therefor another Primary Treasury Dealer. The Indenture contains provisions for defeasance of (a) the entire indebtedness of the Company on this Security and (b) certain restrictive covenants upon compliance by the Company with certain conditions set forth therein which provisions apply to this Security. If an Event of Default with respect to the Securities of this series shall occur and be continuing, the principal hereof may be declared due and payable in the manner and with the effect provided in the Indenture. The Indenture permits, with certain exceptions as therein provided, the amendment thereof and the modification of the rights and obligations of the Company and the rights of the Holders of the Securities of each series to be affected under the Indenture at any time by the Company and the Trustee with the consent of the Holders of a majority in principal amount of the Securities at the time Outstanding of each series to be affected. The Indenture also contains provisions permitting the Holders of specified percentages in aggregate principal amount of the Securities of each series at the time Outstanding, on behalf of the Holders of all Securities of such series, to waive compliance by the Company with certain provisions of the Indenture and certain past defaults under the Indenture and their consequences. Any such consent or waiver by the Holder of this Security shall be conclusive and binding upon such Holder and upon all future Holders of this Security and of any Security issued upon the registration of transfer hereof or in exchange herefor or in lieu hereof, whether or not notation of such consent or waiver is made upon this Security. As set forth in, and subject to, the provisions of the Indenture, no Holder of any Security of this series will have any right to institute any proceeding with respect to the Indenture or for any remedy thereunder, unless such Holder shall have previously given to the Trustee written notice of a continuing Event of Default with respect to this series, the Holders of not less than 25% in principal amount of the Outstanding Securities of this series shall have made written request, and offered reasonable indemnity, to the Trustee to institute such proceeding as trustee, and the Trustee shall not have received from the Holders of a majority in principal amount of the Outstanding Securities of this series a direction inconsistent with such request and shall have failed to institute such proceeding within 60 days; provided, however, that such limitations do not apply to a suit instituted by the Holder hereof for the enforcement of payment of the principal of or interest on this Security on or after the respective due dates expressed herein. No reference herein to the Indenture and no provision of this Security or of the Indenture shall alter or impair the obligation of the Company, which is absolute and unconditional, to pay the principal of and interest on this Security at the times, place and rate, and in the coin or currency herein, prescribed. As provided in the Indenture and subject to certain limitations therein set forth, the transfer of this Security is registrable in the Security Register, upon surrender of this Security for registration of transfer at the office or agency of the Company in any place where the principal of and interest on this Security are payable, duly endorsed by, or accompanied by a written instrument of transfer in form satisfactory to the Company and the Security Registrar duly executed by, the Holder hereof or his attorney duly authorized in writing, and thereupon one or more new Securities of this series and of like tenor, of authorized denominations and for the same aggregate principal amount, will be issued to the designated transferee or transferees. The Securities of this series are issuable only in registered form, without coupons, in denominations of $1,000 and any integral multiple thereof. As provided in the Indenture and subject to certain limitations therein set forth, Securities of this series are exchangeable for a like aggregate principal amount of Securities of this series and of like tenor of a different authorized denomination, as requested by the Holder surrendering the same. No service charge shall be made for any such registration of transfer or exchange, but the Company may require payment of a sum sufficient to cover any tax or other governmental charge payable in connection therewith. Prior to due presentment of this Security for registration of transfer, the Company, the Trustee and any agent of the Company or the Trustee may treat the Person in whose name this Security is registered as the owner hereof for all purposes, whether or not this Security is overdue, and none of the Company, the Trustee or any agent shall be affected by notice to the contrary. The Indenture and this Security shall be governed by and construed in accordance with the laws of the State of New York, without regard to principles of conflicts of laws. All terms used in this Security which are defined in the Indenture shall have the same meanings assigned to them in the Indenture.