Exhibit 4.23

                           [FORM OF FACE OF DEBENTURE]

                               KEYSPAN CORPORATION

                       __% SUBORDINATED DEBENTURE DUE 20__


                                                              PRINCIPAL AMOUNT
REGISTERED                                                    $__________
                                                              CUSIP No.
No. R-__________                                              __________
                                                              ISIN No.
                                                              ----------


         [IF THE DEBENTURE IS TO BE A GLOBAL DEBENTURE, INSERT THE FOLLOWING:
THIS DEBENTURE IS A GLOBAL DEBENTURE WITHIN THE MEANING OF THE INDENTURE
HEREINAFTER REFERRED TO AND IS REGISTERED IN THE NAME OF A DEPOSITARY OR A
NOMINEE THEREOF. UNLESS AND UNTIL IT IS EXCHANGED IN WHOLE OR IN PART FOR
DEBENTURES IN CERTIFICATED FORM, THIS DEBENTURE MAY NOT BE TRANSFERRED EXCEPT AS
A WHOLE BY THE DEPOSITORY TRUST COMPANY (THE "DEPOSITARY") TO A NOMINEE OF THE
DEPOSITARY OR BY THE DEPOSITARY OR ANY SUCH NOMINEE TO A SUCCESSOR DEPOSITARY OR
A NOMINEE OF SUCH SUCCESSOR DEPOSITARY. UNLESS THIS DEBENTURE IS PRESENTED BY AN
AUTHORIZED REPRESENTATIVE OF THE DEPOSITARY TO THE COMPANY OR ITS AGENT FOR
REGISTRATION OF TRANSFER, EXCHANGE OR PAYMENT, AND ANY DEBENTURE ISSUED IS
REGISTERED IN THE NAME OF CEDE & CO. OR IN SUCH OTHER NAME AS IS REQUESTED BY AN
AUTHORIZED REPRESENTATIVE OF THE DEPOSITARY (AND ANY PAYMENT IS MADE TO CEDE &
CO. OR TO SUCH OTHER ENTITY AS IS REQUESTED BY AN AUTHORIZED REPRESENTATIVE OF
THE DEPOSITARY), 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.]

                  KEYSPAN CORPORATION, a New York corporation (the "Issuer" or
the "Company" which terms include any successor corporation under the Indenture
hereinafter referred to), for value received, hereby promises to pay to [If the
Debenture is held by KeySpan Trust __: JPMORGAN CHASE BANK, as Property Trustee
(the "Property Trustee") for KEYSPAN TRUST __ (the "Trust")] [If the Debenture
is not held by the Trust: _______________], the principal sum of
_________________ DOLLARS on __________ ___, 20__, and to pay interest thereon
(computed on the basis of a 360-day year of twelve 30-day months),
[semi-annually] [quarterly] (subject to deferral as set forth herein) on
____________ ___, ____________ ___, ___________ ___ and ___________ ___ (the
"Interest Payment Dates") of each year, commencing on ___________ ___, 200_, at
the rate per annum specified in the title of this Debenture from ____________
__, 200_ or the most recent Interest Payment Date to which interest had been
paid or duly provided for.

                  The interest so payable and punctually paid or duly provided
for on any Interest Payment Date will, as provided in the Indenture, be paid to
the Person in whose name this Debenture (or one or more Predecessor Securities,
as defined in said Indenture) is registered at [If the Debentures are held only
by the Property Trustee or if this is a Global Debenture: the close of business
on the Business Day prior to the relevant Interest Payment Date] [Otherwise: the
___________ prior to the relevant Interest Payment Date] (each a "Regular Record
Date"). Payment of the principal of (and premium, if any) and interest on this
Debenture will be made at the office or agency of the Company maintained by the
Company for such purpose in the Borough of Manhattan, The City of New York, in
such coin or currency of the United States of America as at the time of payment
is legal tender for payment of public and private debts.

                  Reference is hereby made to the further provisions of this
Debenture 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 or on behalf of JPMorgan Chase Bank, the Trustee for this Debenture
under the Indenture, or its successor thereunder, by the manual signature of one
of its authorized officers, this Debenture 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 duly executed, manually or in facsimile, and an imprint or facsimile of its
corporate seal to be imprinted hereon.



Dated: ________ __, 2001



                                            KEYSPAN CORPORATION


                                            By:______________________________
                                               Name:
                                               Title:



[SEAL]

                                            Attest:


                                            By:______________________________
                                               Name:
                                               Title:



CERTIFICATE OF AUTHENTICATION

This is one of the Securities of the series designated therein described in the
within-mentioned Indenture.

JPMORGAN CHASE BANK,
    as Trustee


By:______________________________
     Authorized Officer










                         [FORM OF REVERSE OF DEBENTURE]

                             (Reverse of Debenture)

                               KEYSPAN CORPORATION

                       __% SUBORDINATED DEBENTURE DUE 20__

                  This Debenture is one of a duly authorized issue of Securities
of the Company designated as the __% Subordinated Debentures Due 20__ (the
"Debentures"). The Debentures are one of an indefinite number of series of debt
securities of the Company (the "Securities"), issued or issuable under and
pursuant to an indenture (the "Indenture") dated as of __________, 2002, between
the Company and JPMorgan Chase Bank (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 thereunder of the Company, the Trustee and the Holders of the
Debentures and the terms upon which the Debentures are to be authenticated and
delivered. This Debenture is one of a series designated on the face hereof as
limited (except as provided in the Indenture) in aggregate principal amount to
$__________. The terms of other series of Securities issued under the Indenture
may vary with respect to interest rates or interest rate formulas, issue dates,
maturity, redemption, repayment, currency of payment and otherwise as provided
in the Indenture. The Indenture further provides that Securities of a single
series may be issued at various times, with different maturity dates and may
bear interest at different rates.

                  This Debenture is not subject to any sinking fund.

                  Payment of the principal of and interest on this Debenture is,
to the extent provided in the Indenture, subordinated and subject in right of
payment to the prior payment in full when due of the principal of (and premium,
if any) and interest, if any, on all Senior Indebtedness, as defined in the
Indenture, of the Company, and this Debenture is issued subject to the
provisions of the Indenture with respect thereto. Each Holder of this Debenture,
by accepting the same, (a) agrees to and shall be bound by such provisions, (b)
authorizes and expressly directs the Trustee on his or her behalf to take such
action as may be necessary or appropriate to effectuate the subordination so
provided and (c) appoints the Trustee as his or her attorney-in-fact for any and
all such purposes. Each Holder hereof, by his or her acceptance hereof, hereby
waives all notice of the acceptance of the subordination provisions contained
herein and in the Indenture by each Holder of Senior Indebtedness, whether now
outstanding or hereafter incurred, and waives reliance by each such Holder upon
said provisions.

                  Subject to Article 14 of the Indenture, at any time on or
after _________ __, ____, and prior to maturity, the Company shall have the
right to redeem this Debenture at the option of the Company, in whole or in
part, at the Redemption Prices (expressed as a percentage of the principal
amount of such Debentures) set forth below, plus any accrued but unpaid
interest, to the Redemption Date, if redeemed during the twelve-month period
beginning on the ________ __ of the years indicated below:

Year                                                                 Percentage
- ----                                                                 ----------
20__......................................................                 %
20__......................................................                 %
20__......................................................                 %
20__......................................................                 %
20__......................................................                 %
20__......................................................                 %
20__......................................................                 %
20__......................................................                 %
20__......................................................                 %
20__......................................................                 %
20__......................................................                 %
and thereafter............................................              100%


                  If an Investment Company Event (as defined in the Amended and
Restated Declaration of Trust of the Trust, dated ___________ ___, 20__, among
the Company, as Sponsor, the Trust, and the trustees of the Trust named thereto
(the "Declaration") shall occur and be continuing, the Company may, at any time
within 90 days following the occurrence of such Investment Company Event, redeem
the Debentures, in whole but not in part, at a Redemption Price equal to 100% of
the principal amount thereof, plus accrued and unpaid interest thereon to the
Redemption Date. Subject to certain conditions described in the Indenture, in
the event of the occurrence and continuation of a Tax Event (as defined in the
Declaration), in certain circumstances the Company may redeem the Debentures, in
whole but not in part, at any time within 90 days following the occurrence of a
Tax Event at a Redemption Price equal to 100% of the aggregate principal amount
thereof, plus accrued and unpaid interest thereon to the Redemption Date. Any
redemption pursuant to this paragraph shall be made upon not less than 30 nor
more than 60 days' notice to the Trustee and Holders of the Debentures. If less
than all the Debentures are to be redeemed by the Company, the Debentures to be
redeemed will be selected by lot or by such other method as the Trustee shall
deem fair and appropriate.

                  In the event of redemption of this Debenture in part only, a
new Debenture or Debentures of this series for the unredeemed portion hereof
will be issued in the name of the Holder hereof upon the surrender hereof at a
Place of Payment.

                  In case an Event of Default with respect to the Debentures
shall have occurred and be continuing, the principal hereof may be declared, and
upon such declaration shall become, due and payable, in the manner, with the
effect and subject to the conditions provided in the Indenture. The omission by
the Company to pay interest during an Extension Period (as defined below) as
permitted hereby shall not constitute an Event of Default under Section 501 of
the Indenture. An "Event of Default" means any of those events set forth in
Section 501 of the Indenture, and the event that, when the Property Trustee is
the Holder of the Debentures, the Trust shall have voluntarily or involuntarily
dissolved, wound-up its business or otherwise terminated its existence except in
connection with the (i) distribution of Debentures to holders of Preferred
Securities and Common Securities (each, as defined in the Declaration) in
liquidation of their interests in the Trust, (ii) the redemption of all of the
outstanding Preferred Securities and Common Securities, or (iii) certain
mergers, consolidations or amalgamation, each as permitted by the Declaration.

                  The Company shall have the right at any time, on one or more
occasions, so long as an Event of Default has not occurred and is not continuing
under the Indenture, to extend any interest payment period on this Debenture for
a period (an "Extension Period") not to exceed [ten] [twenty] consecutive
[semi-annual] [quarterly] interest payment periods; provided that the date on
which such Extension Period ends must be on an Interest Payment Date and must be
no later than ___________ __, ____ or any date on which any Debentures are fixed
for redemption, and, as a consequence, the [semi-annual] [quarterly] interest
payment on the Debentures would be deferred (but would continue to accrue with
interest thereon compounded [semi-annually] [quarterly] at the rate of interest
on the Debentures, except to the extent payment of such interest is prohibited
by law) during any such Extension Period. On the Interest Payment Date at the
end of each Extension Period, the Company shall pay all interest then accrued
and unpaid (compounded [semi-annually] [quarterly], at the rate of interest on
the Debentures, except to the extent payment of such interest is prohibited by
law) to the date of payment, to the persons in whose name the Debentures are
registered on the Regular Record Date immediately preceding the Interest Payment
Date at the end of such Extension Period. The Company shall give written notice
to the Regular Trustees (as defined in the Declaration), the Property Trustee
and the Trustee of its election of such Extension Period one Business Day before
the earlier of (i) the next succeeding date on which distributions on the
Preferred Securities of the Trust are payable or (ii) the date the Trust is
required to give notice of the record date or the date such distributions are
payable to the New York Stock Exchange or other applicable self-regulatory
organization or to holders of the Preferred Securities issued by the Trust, but
in any event at least one Business Day before such record date. During any
Extension Period, the Company may continue to extend the interest payment period
by extending the Extension Period, on one or more occasions by giving notice as
aforesaid; provided that such Extension Period, as extended, must end on an
Interest Payment Date and in no event shall the aggregate Extension Period, as
extended, exceed [ten] [twenty] consecutive [semi-annual] [quarterly] interest
payment periods or extend beyond ___________ __, ____ or any date on which any
of the Debentures are fixed for redemption. No interest shall be due and payable
on the Debentures during an Extension Period except at the end thereof.

                  The Company hereby covenants that, so long as any Preferred
Securities and Common Securities of the Trust remain outstanding, if (i) there
shall have occurred any Event of Default under the Indenture with respect to the
Debentures, (ii) the Company shall be in default with respect to its payment of
any obligations under its Guarantee (as defined in the Declaration) with respect
to the Trust or (iii) the Company shall have given notice of its election of an
Extension Period as provided herein and shall not have rescinded such notice, or
such Extension Period or any extension thereof shall be continuing, then the
Company will not, and will not permit any Subsidiary to (x) declare or pay any
dividends or distributions on, or redeem, purchase, acquire or make a
liquidation payment with respect to, any of the Company's capital stock or (y)
make any payment of principal, interest or premium, if any, on or repay,
repurchase or redeem any debt securities of the Company that rank on a parity
with or junior in interest to this Debenture or make any guarantee payments with
respect to any guarantee by the Company of the debt securities of any Subsidiary
of the Company if such guarantee ranks on a parity with or junior in interest to
this Debenture (other than (a) dividends or distributions in common stock of the
Company, (b) payments under the Guarantee made by the Company in respect of the
Preferred Securities and Common Securities of the Trust, (c) any declaration of
a dividend in connection with the implementation of a shareholders' rights plan,
or the issuance of stock under any such plan in the future, or the redemption or
repurchase of any such rights pursuant thereto, and (d) purchases of common
stock related to the issuance of common stock or rights under any of the
Company's benefit plans).

                  The Indenture permits, with certain exceptions as therein
provided, the Company and the Trustee with the consent of the Holders of more
than 66-"% in principal amount of the Securities at the time Outstanding of each
series issued under the Indenture to be affected thereby, to execute
supplemental indentures for the purpose of adding any provisions to or changing
in any manner or eliminating any of the provisions of the Indenture or of
modifying in any manner the rights of the Holders of the Securities of such
series; provided, however, that no such supplemental indenture shall, among
other things, (i) change the Stated Maturity of the principal of, or any
installment of principal of or interest on, any Security, or reduce the
principal amount thereof or interest thereon, if any, or any premium payable
upon redemption thereof, or amend the Indenture to modify its provisions
relating to the subordination of each Security in a manner adverse to the Holder
thereof, or (ii) change the Place of Payment on any Security or the currency or
currency unit in which any Security or the principal or interest thereon is
payable; impair the right to institute suit for the enforcement of any such
payment on or after the Stated Maturity thereof; or reduce or alter the method
of computation of any amount payable upon redemption, repayment or purchase of
any Securities by the Company (or the time when such redemption, repayment or
purchase may be made); or reduce the percentage in principal amount of the
Securities, the Holders of which are required to consent to any supplemental
indenture, without the consent of the Holder of each Security affected thereby.
The Indenture also contains provisions permitting the Holders of more than 66-"%
in principal amount of the Securities of each series at the time outstanding, on
behalf of the Holders of all the Securities of that series, to waive compliance
by the Company with certain provisions of the Indenture and certain past
defaults under the Indenture and their consequences with respect to such series,
except a default in the payment of principal of or interest, if any, on any
Security of that series or a default with respect to a covenant or provision of
the Indenture which cannot be amended without the consent of such Holder.

                  The Debentures are issuable only in registered form without
coupons in denominations of $1,000 and integral multiples thereof. As provided
in the Indenture and subject to certain limitations therein set forth, the
Debentures are exchangeable for a like aggregate principal amount of Debentures
as requested by the Holder surrendering the same. [If Debentures are distributed
to holders of trust preferred securities: If (x) the Depositary is at any time
unwilling or unable to continue as depository and a successor depository is not
appointed by the Company within 90 days after the Company receives such notice
or becomes aware of such ineligibility, (y) the Company delivers to the Trustee
a Company Order to the effect that this Debenture shall be exchangeable or (z)
an Event of Default has occurred and is continuing with respect to the
Debentures, this Debenture shall be exchangeable for Debentures in definitive
form and in an equal aggregate principal amount. Such definitive Debentures
shall be registered in such name or names as the Depositary shall instruct the
Trustee.]

                  As provided in the Indenture and subject to certain
limitations set forth therein and above, the transfer of this Debenture may be
registered on the Security Register of the Company, upon surrender of this
Debenture for registration of transfer at the office or agency of the Company in
the Borough of Manhattan, The City of New York, duly endorsed by, or accompanied
by a written instrument of transfer in form satisfactory to the Company duly
executed by, the Holder hereof or by his attorney duly authorized in writing,
and thereupon one or more new Debentures of authorized denominations and for the
same aggregate principal amount will be issued to the designated transferee or
transferees.

                  No reference herein to the Indenture and no provisions of this
Debenture or of the Indenture shall alter or impair the obligations of the
Company, which is absolute and unconditional, to pay the principal of this
Debenture at the place, at the time and in the coin or currency herein
prescribed.

                  Prior to due presentment of this Debenture 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 Debenture is registered as the owner
hereof for all purposes, whether or not this Debenture be overdue, and neither
the Company, the Trustee nor any such agent shall be affected by notice to the
contrary.

                  Certain of the Company's obligations under the Indenture with
respect to Debentures, may be terminated if the Company irrevocably deposits
with the Trustee money or Government Obligations sufficient to pay and discharge
the entire indebtedness on all Debentures, as provided in the Indenture.

                  No recourse shall be had for the payment of the principal of
(and premium, if any), or the interest, if any, on this Debenture, or for any
claim based thereon, or upon any obligation, covenant or agreement of the
Company in the Indenture, against the any incorporator, stockholder, officer or
director, as such, past, present of future, of the Company or of any successor
corporation, whether by virtue of any constitution, statute or rule of law or by
the enforcement of any assessment of penalty or otherwise; and all such personal
liability is expressly released and waived as a condition of, and as part of the
consideration for, the issuance of this Debenture.

                  The Indenture and the Debentures shall be governed by and
construed in accordance with the laws of the State of New York.

                  Except as specified, all terms used in this Debenture which
are defined in the Indenture shall have the meanings assigned to them in the
Indenture.







                     --------------------------------------

                  The following abbreviations, when used in the inscription on
the face of the within Debenture, shall be construed as though they were written
out in full according to applicable laws or regulations:

                  TEN COM       -   as tenants in common

                  TEN ENT       -   as tenants by their entireties

                  JT TEN        -   as joint tenants with right of survivorship
                                    and not as tenants in common


                  UNIF GIFT MIN ACT - ___________ Custodian __________
                                         (Cut)               (Minor)

                  under Uniform Gifts to Minors Act__________________
                                                          (State)

                  Additional abbreviations may also be used though not in the
above list.
                     --------------------------------------












                            ASSIGNMENT/TRANSFER FORM



                  FOR VALUE RECEIVED the undersigned registered Holder hereby
sell(s), assign(s) and transfer(s) unto (insert Taxpayer Identification No.)
______________________________________________________________________________

______________________________________________________________________________
(Please print or typewrite name and address including postal zip code of
assignee)
______________________________________________________________________________
the within Debenture and all rights thereunder, hereby irrevocably constituting
and appointing ________________________________________ attorney to transfer
said Debenture on the books of the Company with full power of substitution in
the premises.



                  Date: ________________________
     _____________________________________________________NOTICE: The signature
of the registered Holder to this assignment must correspond with the name as
written upon the face of the within instrument in every particular, without
alteration or enlargement or any change whatsoever.

                                  Signature(s) Guaranteed:_____________________



                  THE SIGNATURE(S) SHOULD BE GUARANTEED BY AN ELIGIBLE GUARANTOR
INSTITUTION (BANKS, STOCKBROKERS, SAVINGS AND LOAN ASSOCIATIONS AND CREDIT
UNIONS WITH MEMBERSHIP IN AN APPROVED MEDALLION SIGNATURE GUARANTEE PROGRAM),
PURSUANT TO S.E.C. RULE 17Ad-15.