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                                                                   Exhibit 4.15







                               GUARANTEE AGREEMENT



                                KeySpan Trust __



                        Dated as of _________ ___, ______









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                             CROSS REFERENCE TABLE*

                                                                                                    
Section of Trust                                                                                         Section of
Indenture Act of                                                                                          Guarantee
1939, as amended                                                                                          Agreement
- ----------------                                                                                          ---------

310(a).......................................................................................................4.1(a)
310(b)..................................................................................................2.8; 4.1(c)
310(c).................................................................................................Inapplicable
311(a).......................................................................................................2.2(b)
311(b).......................................................................................................2.2(b)
311(c).................................................................................................Inapplicable
312(a)..................................................................................................2.2(a); 2.9
312(b)..................................................................................................2.2(b); 2.9
312(c)..........................................................................................................2.9
313(a)..........................................................................................................2.3
313(b)..........................................................................................................2.3
313(c)..........................................................................................................2.3
313(d)..........................................................................................................2.3
314(a)..........................................................................................................2.4
314(b).................................................................................................Inapplicable
314(c)..........................................................................................................2.5
314(d).................................................................................................Inapplicable
314(e)..........................................................................................................2.5
314(f).................................................................................................Inapplicable
315(a)...............................................................................................3.1(d); 3.2(a)
315(b).......................................................................................................2.7(a)
315(c).......................................................................................................3.1(c)
315(d).......................................................................................................3.1(d)
316(a)..................................................................................................2.6; 5.4(a)
316(b)......................................................................................................... 5.3
316(c)................................................................................................ Inapplicable
317(a).........................................................................................................2.10
317(b).................................................................................................Inapplicable
318(a).......................................................................................................2.1(b)

- --------
*This Cross-Reference Table does not
 constitute part of the Agreement and shall
 not have any bearing upon the interpretation
 of any of its terms or provisions.








                                Table of Contents

                                                                                                        
                                                                                                               Page

                                    ARTICLE I


                                            INTERPRETATION AND DEFINITIONS........................................1

  SECTION 1.1         Interpretation and Definitions..............................................................1

                                   ARTICLE II


                                                  TRUST INDENTURE ACT.............................................4

  SECTION 2.1         Trust Indenture Act; Application............................................................4
  SECTION 2.2         Lists of Holders of Securities..............................................................4
  SECTION 2.3         Reports by Guarantee Trustee................................................................5
  SECTION 2.4         Periodic Reports to Guarantee Trustee.......................................................5
  SECTION 2.5         Evidence of Compliance with Conditions Precedent............................................5
  SECTION 2.6         Guarantee Event of Default; Waiver..........................................................5
  SECTION 2.7         Guarantee Event of Default; Notice..........................................................5
  SECTION 2.8         Conflicting Interests.......................................................................6
  SECTION 2.9         Disclosure of Information...................................................................6
  SECTION 2.10        Guarantee Trustee May File Proofs of Claim..................................................6

                                   ARTICLE III


                                    POWERS, DUTIES AND RIGHTS OF GUARANTEE TRUSTEE................................6

  SECTION 3.1         Powers and Duties of Guarantee Trustee......................................................6
  SECTION 3.2         Certain Rights of Guarantee Trustee.........................................................8
  SECTION 3.3         Not Responsible for Recitals or Issuance of Guarantee.......................................9

                                   ARTICLE IV


                                                   GUARANTEE TRUSTEE..............................................9

  SECTION 4.1         Guarantee Trustee; Eligibility..............................................................9
  SECTION 4.2         Appointment, Removal and Resignation of Guarantee Trustee..................................10

                                    ARTICLE V


                                                       GUARANTEE.................................................11

  SECTION 5.1         Guarantee..................................................................................11
  SECTION 5.2         Waiver of Notice and Demand................................................................11
  SECTION 5.3         Obligations Not Affected...................................................................11
  SECTION 5.4         Rights of Holders..........................................................................12
  SECTION 5.5         Guarantee of Payment.......................................................................12
  SECTION 5.6         Subrogation................................................................................13
  SECTION 5.7         Independent Obligations....................................................................13

                                   ARTICLE VI


                                       LIMITATION OF TRANSACTIONS; SUBORDINATION.................................13

  SECTION 6.1         Limitation of Transactions.................................................................13
  SECTION 6.2         Ranking....................................................................................13
  SECTION 6.3         Subordination of Common Securities.........................................................14

                                   ARTICLE VII


                                                      TERMINATION................................................14

  SECTION 7.1         Termination................................................................................14

                                  ARTICLE VIII


                                                    INDEMNIFICATION..............................................14

  SECTION 8.1         Exculpation................................................................................14
  SECTION 8.2         Indemnification............................................................................14

                                   ARTICLE IX


                                                     MISCELLANEOUS...............................................15

  SECTION 9.1         Successors and Assigns.....................................................................15
  SECTION 9.2         Amendments.................................................................................15
  SECTION 9.3         Notices....................................................................................15
  SECTION 9.4         Benefit....................................................................................16
  SECTION 9.5         Governing Law..............................................................................16







                               GUARANTEE AGREEMENT

                  This GUARANTEE AGREEMENT (the "Guarantee"), dated as of
________ ___, _____, is executed and delivered by KeySpan Corporation, a New
York corporation (the "Guarantor"), and JPMorgan Chase Bank, as trustee (the
"Guarantee Trustee"), for the benefit of the Holders (as defined herein) from
time to time of the Securities (as defined herein) of KeySpan Trust __, a
Delaware statutory business trust (the "Trust").

                              W I T N E S S E T H :
                               - - - - - - - - - -

                  WHEREAS, pursuant to the Declaration (as defined herein), the
Trust is issuing on the date hereof $_____________ aggregate liquidation amount
of preferred securities, having a liquidation amount of $____ per security and
designated the ____% Preferred Securities of the Trust (the "Preferred
Securities") and $_____________ aggregate liquidation amount of common
securities, having a liquidation amount of $___ per security and designated the
____% Common Securities of the Trust (the "Common Securities" and, together with
the Preferred Securities, the "Securities");

                  WHEREAS, as incentive for the Holders to purchase the
Securities, the Guarantor desires irrevocably and unconditionally to agree, to
the extent set forth in this Guarantee, to pay to the Holders of the Securities
the Guarantee Payments (as defined herein) and to make certain other payments on
the terms and conditions set forth herein; and that if a Trust Enforcement Event
(as defined herein) has occurred and is continuing, the rights of holders of the
Common Securities to receive Guarantee Payments under this Guarantee are
subordinated to the rights of Holders of Preferred Securities to receive
Guarantee Payments under this Guarantee.

                  NOW, THEREFORE, in consideration of the purchase by each
Holder of Securities, which purchase the Guarantor hereby agrees shall benefit
the Guarantor, the Guarantor executes and delivers this Guarantee for the
benefit of the Holders.

                                   ARTICLE I

                         INTERPRETATION AND DEFINITIONS

SECTION 1.1 Interpretation and Definitions. In this Guarantee, unless the
context otherwise requires:

     (a)  capitalized  terms  used in this  Guarantee  but  not  defined  in the
preamble  above have the  respective  meanings  assigned to them in this Section
1.1;

     (b) a term  defined  anywhere  in  this  Guarantee  has  the  same  meaning
throughout;

     (c) all  references  to "the  Guarantee"  or "this  Guarantee"  are to this
Guarantee as modified, supplemented or amended from time to time;

     (d) all references in this Guarantee to Articles, Sections and Recitals are
to  Articles,   Sections  and  Recitals  of  this  Guarantee,  unless  otherwise
specified;

     (e) unless otherwise defined in this Guarantee, a term defined in the Trust
Indenture Act has the same meaning when used in this Guarantee;

     (f) a reference  to the  singular  includes the plural and vice versa and a
reference to any  masculine  form of a term shall include the feminine form of a
term, as applicable; and

     (g) the following terms have the following meanings:

                  "Affiliate" has the same meaning as given to that term in Rule
405 of the Securities Act of 1933, as amended, or any successor rule thereunder.

                  "Business Day" has the meaning specified in the Declaration.

                  "Common Securities" has the meaning specified in the Recitals
hereto.

                  "Corporate Trust Office" means the principal office of the
Guarantee Trustee at which at any particular time its corporate trust business
shall be administered, which office at the date of execution of this Guarantee
is located at 450 West 33rd Street, New York, New York 10001.

                  "Covered Person" means a Holder or beneficial owner of
Securities.

                  "Debentures" means the series of subordinated deferrable
interest debentures to be issued by the Guarantor designated the ____%
Subordinated Deferrable Interest Debentures due 20__ held by the Property
Trustee (as defined in the Declaration) of the Trust.

                  "Declaration" means the Amended and Restated Declaration of
Trust, dated as of ____________ ___, _____, as amended, modified or supplemented
from time to time, among the trustees of the Trust named therein, the Guarantor,
as sponsor, and the Holders, from time to time, of undivided beneficial
ownership interests in the assets of the Trust.

                  "Global Security" means a fully registered, global Preferred
Security.

                  "Guarantee Event of Default" means a default by the Guarantor
on any of its payment or other obligations under this Guarantee.

                  "Guarantee Payments" means the following payments or
distributions, without duplication, with respect to the Securities, to the
extent not paid by or on behalf of the Trust: (i) any accumulated and unpaid
Distributions (as defined in the Declaration) that are required to be paid on
such Securities to the extent the Trust has sufficient funds available therefor
at the time, (ii) the redemption price, including all accumulated and unpaid
Distributions to the date of redemption, with respect to any Securities called
for redemption by the Trust, to the extent the Trust shall have sufficient funds
available therefor at the time or (iii) upon a voluntary or involuntary
dissolution, winding-up or termination of the Trust (other than in connection
with the distribution of Debentures to the Holders in exchange for Securities as
provided in the Declaration), the lesser of (a) the aggregate of the liquidation
amount and all accumulated and unpaid Distributions on the Securities to the
date of payment, to the extent the Trust has sufficient funds available therefor
and (b) the amount of assets of the Trust remaining available for distribution
to Holders in liquidation of the Trust (in either case, the "Liquidation
Distribution").

                  "Guarantee Trustee" means JPMorgan Chase Bank, until a
Successor Guarantee Trustee has been appointed and has accepted such appointment
pursuant to the terms of this Guarantee and thereafter means each such Successor
Guarantee Trustee.

                  "Holder" means any holder of Securities, as registered on the
books and records of the Trust; provided, however, that, in determining whether
the Holders of the requisite liquidation amount of Preferred Securities have
voted on any matter provided for in this Guarantee, then for the purpose of such
determination only (and not for any other purpose hereunder), if the Preferred
Securities remain in the form of one or more Global Certificates (as defined in
the Declaration), the term "Holders" shall mean the holder of the Global
Certificate acting at the direction of the Beneficial Owners (as defined in the
Declaration).

                  "Indemnified Person" means the Guarantee Trustee, any
Affiliate of the Guarantee Trustee, or any officers, directors, shareholders,
members, partners, employees, representatives, nominees, custodians or agents of
the Guarantee Trustee.

                  "Indenture" means the Indenture, dated as of [November 1,
2000][_________, 2002], between the Guarantor (the "Company") and JPMorgan Chase
Bank [(as successor to The Chase Manhattan Bank)], as trustee, as amended and
supplemented by any other indenture thereto pursuant to which the Debentures are
to be issued to the Property Trustee (as defined in the Declaration) of the
Trust.

                  "Majority in Liquidation Amount" means, except as provided in
the terms of the Preferred Securities or by the Trust Indenture Act, Holder(s)
of outstanding Securities, voting together as a single class, or, as the context
may require, Holders of outstanding Preferred Securities or Holders of
outstanding Common Securities, voting separately as a class, who are the record
owners of more than 50% of the aggregate liquidation amount (including the
stated amount that would be paid on redemption, liquidation or otherwise, plus
accumulated and unpaid Distributions to the date upon which the voting
percentages are determined) of all outstanding Securities of the relevant class.
In determining whether the Holders of the requisite amount of Securities have
voted, Securities which are owned by the Guarantor or any Affiliate of the
Guarantor or any other obligor on the Securities shall be disregarded for the
purpose of any such determination.

                  "Officers' Certificate" means, with respect to any Person, a
certificate signed on behalf of such Person by two Authorized Officers (as
defined in the Declaration) of such Person. Any Officers' Certificate delivered
with respect to compliance with a condition or covenant provided for in this
Guarantee shall include:

     (a) a statement  that each officer  signing the Officers'  Certificate  has
read the covenant or condition and the definitions relating thereto;

     (b) a brief  statement  of the  nature  and  scope  of the  examination  or
investigation  undertaken  by each officer on behalf of such Person in rendering
the Officers' Certificate;

     (c) a  statement  that  each such  officer  has made  such  examination  or
investigation as, in such officer's opinion, is necessary to enable such officer
on behalf of such  Person to  express an  informed  opinion as to whether or not
such covenant or condition has been complied with; and

     (d) a statement as to whether,  in the opinion of each such officer  acting
on behalf of such Person, such condition or covenant has been complied with.

                  "Person" means a legal person, including any individual,
corporation, estate, partnership, joint venture, association, joint stock
company, limited liability company, trust, unincorporated association, or
government or any agency or political subdivision thereof, or any other entity
of whatever nature.

                  "Preferred Securities" has the meaning specified in the
Recitals hereto.

                  "Redemption Price" has the meaning specified in the
Declaration.

                  "Responsible Officer" means, with respect to the Guarantee
Trustee, any officer with direct responsibility for the administration of this
Guarantee and also means, with respect to a particular corporate trust matter,
any other officer to whom such matter is referred because of that officer's
knowledge of and familiarity with the particular subject.

                  "Securities" has the meaning specified in the Recitals hereto.

                  "Successor Guarantee Trustee" means a successor Guarantee
Trustee possessing the qualifications to act as Guarantee Trustee under Section
4.1.

                  "Trust Enforcement Event" in respect of the Securities means
an Indenture Event of Default (as defined in the Indenture) has occurred and is
continuing in respect of the Debentures.

                  "Trust Indenture Act" means the Trust Indenture Act of 1939,
as amended from time to time, or any successor legislation.

                                   ARTICLE II

                               TRUST INDENTURE ACT

     SECTION 2.1 Trust Indenture Act; Application. (a) This Guarantee is subject
to the  provisions  of the Trust  Indenture  Act that are required to be part of
this  Guarantee  and  shall,  to the  extent  applicable,  be  governed  by such
provisions.

     (b) If and to the  extent  that any  provision  of this  Guarantee  limits,
qualifies  or  conflicts  with  the  duties  imposed  by  Sections  310 to  317,
inclusive, of the Trust Indenture Act, such imposed duties shall control.

     SECTION 2.2 Lists of Holders of Securities. (a) The Guarantor shall provide
the Guarantee Trustee (i) except while the Preferred  Securities are represented
by one or more Global Securities at least one Business Day prior to the date for
payment of  Distributions,  a list,  in such form as the  Guarantee  Trustee may
reasonably  require, of the names and addresses of the Holders of the Securities
("List of  Holders")  as of the  record  date  relating  to the  payment of such
Distributions,  and (ii) at any other  time,  within 30 days of  receipt  by the
Guarantor of a written request from the Guarantee  Trustee for a List of Holders
as of a date no more than 15 days  before  such List of  Holders is given to the
Guarantee Trustee; provided that the Guarantor shall not be obligated to provide
such List of Holders at any time the List of  Holders  does not differ  from the
most recent List of Holders given to the Guarantee Trustee by the Guarantor. The
Guarantee  Trustee  shall  preserve,  in as  current  a  form  as is  reasonably
practicable, all information contained in Lists of Holders given to it, provided
that the Guarantee  Trustee may destroy any List of Holders  previously given to
it on receipt of a new List of Holders.

     (b) The Guarantee  Trustee shall comply with its obligations under Sections
311(a), 311(b) and 312(b) of the Trust Indenture Act.

     SECTION 2.3 Reports by  Guarantee  Trustee.  Within 60 days after May 15 of
each year (commencing with the year of the first  anniversary of the issuance of
the  Securities),  the  Guarantee  Trustee  shall  provide to the Holders of the
Securities  such reports as are  required by Section 313 of the Trust  Indenture
Act (if any) in the form and in the manner  provided by Section 313 of the Trust
Indenture Act. The Guarantee  Trustee shall also comply with the requirements of
Section 313(d) of the Trust Indenture Act.

     SECTION 2.4 Periodic  Reports to Guarantee  Trustee.  The  Guarantor  shall
provide to the Guarantee  Trustee such  documents,  reports and  information  as
required  by  Section  314(a)  (if  any)  of the  Trust  Indenture  Act  and the
compliance  certificate required by Section 314(a) of the Trust Indenture Act in
the form, in the manner and at the times required by Section 314(a) of the Trust
Indenture Act.

     SECTION 2.5 Evidence of Compliance with Conditions Precedent. The Guarantor
shall  provide to the Guarantee  Trustee such  evidence of  compliance  with any
conditions precedent,  if any, provided for in this Guarantee that relate to any
of the  matters  set forth in Section  314(c) of the Trust  Indenture  Act.  Any
certificate  or opinion  required to be given by an officer  pursuant to Section
314(c)(1) may be given in the form of an Officers' Certificate.

     SECTION 2.6 Guarantee Event of Default;  Waiver.  The Holders of a Majority
in Liquidation  Amount of the  Securities  may, by vote or written  consent,  on
behalf of the Holders of all of the  Securities,  waive any past Guarantee Event
of Default and its consequences.  Upon such waiver,  any such Guarantee Event of
Default  shall  cease to  exist,  and any  Guarantee  Event of  Default  arising
therefrom  shall be  deemed  to have  been  cured,  for  every  purpose  of this
Guarantee, but no such waiver shall extend to any subsequent or other default or
Guarantee Event of Default or impair any right consequent thereon.

     SECTION 2.7 Guarantee Event of Default;  Notice.  (a) The Guarantee Trustee
shall,  within 90 days after the  occurrence  of a  Guarantee  Event of Default,
transmit by mail, first class postage prepaid, to the Holders of the Securities,
notices of all  Guarantee  Events of  Default  actually  known to a  Responsible
Officer of the  Guarantee  Trustee,  unless such defaults have been cured before
the  giving  of such  notice;  provided,  that the  Guarantee  Trustee  shall be
protected in withholding such notice if and so long as a Responsible  Officer of
the Guarantee  Trustee in good faith  determines  that the  withholding  of such
notice is in the interests of the Holders of the Securities.

     (b) The  Guarantee  Trustee  shall not be deemed to have  knowledge  of any
Guarantee  Event of Default  unless the  Guarantee  Trustee  shall have received
written notice thereof or a Responsible Officer of the Guarantee Trustee charged
with the  administration of the Declaration shall have obtained actual knowledge
thereof.

     SECTION 2.8 Conflicting  Interests.  The Declaration  shall be deemed to be
specifically  described in this  Guarantee for the purposes of clause (i) of the
first  proviso  contained  in  Section  310(b) of the Trust  Indenture  Act.  In
determining whether the Guarantee Trustee has a conflicting  interest as defined
in Section  310(b) of the Trust  Indenture Act with respect to the Securities of
any  series,  there shall be excluded  [(i)] all series of  securities  issuable
under the Indenture,  dated as of [November 1,  2000][__________,  2002],  among
KeySpan  Corporation,  as issuer,  and JPMorgan Chase Bank [(as successor to The
Chase  Manhattan  Bank)],  as trustee[,  including the 7.25% Notes due 2005, the
7.625% Notes due 2010, the 8.00% Notes due 2030 and the 6.15% Notes due 2006 and
(ii) all series of securities issuable under the Indenture, dated as of December
1, 1999,  among the KeySpan Gas East  Corporation,  as issuer,  the Company,  as
guarantor,  and JPMorgan Chase Bank (as successor to The Chase Manhattan  Bank),
as trustee, including the 7.875% Notes due 2010 issued thereunder].

     SECTION 2.9 Disclosure of Information.  The disclosure of information as to
the names and  addresses of the Holders of the  Securities  in  accordance  with
Section 312 of the Trust Indenture Act, regardless of the source from which such
information  was derived,  shall not be deemed to be a violation of any existing
law, or any law hereafter  enacted which does not specifically  refer to Section
312 of the  Trust  Indenture  Act,  nor  shall  the  Guarantee  Trustee  be held
accountable  by reason of mailing any material  pursuant to a request made under
Section 312(b) of the Trust Indenture Act.

     SECTION  2.10  Guarantee  Trustee  May  File  Proofs  of  Claim.  Upon  the
occurrence  of a Guarantee  Event of Default,  the  Guarantee  Trustee is hereby
authorized to (a) recover judgment, in its own name and as trustee of an express
trust,  against the  Guarantor  for the whole amount of any  Guarantee  Payments
remaining unpaid and (b) file such proofs of claim and other papers or documents
as may be  necessary  or  advisable in order to have its claims and those of the
Holders of the Securities  allowed in any judicial  proceedings  relative to the
Guarantor, its creditors or its property.

                                  ARTICLE III

                          POWERS, DUTIES AND RIGHTS OF
                                GUARANTEE TRUSTEE

     SECTION  3.1 Powers and Duties of  Guarantee  Trustee.  (a) This  Guarantee
shall be held by the Guarantee Trustee on behalf of the Trust for the benefit of
the Holders of the Securities, and the Guarantee Trustee shall not transfer this
Guarantee  to any Person  except a Holder of  Securities  exercising  his or her
rights  pursuant  to  Section  5.4(b) or to a  Successor  Guarantee  Trustee  on
acceptance by such  Successor  Guarantee  Trustee of its  appointment  to act as
Successor  Guarantee  Trustee.  The right,  title and interest of the  Guarantee
Trustee  in and to this  Guarantee  shall  automatically  vest in any  Successor
Guarantee  Trustee,  and such vesting and succession of title shall be effective
whether or not conveyance documents have been executed and delivered pursuant to
the appointment of such Successor Guarantee Trustee.

     (b) If a Guarantee Event of Default actually known to a Responsible Officer
of the Guarantee  Trustee has occurred and is continuing,  the Guarantee Trustee
shall enforce this Guarantee for the benefit of the Holders of the Securities.

     (c) The Guarantee Trustee,  before the occurrence of any Guarantee Event of
Default and after the curing of all  Guarantee  Events of Default  that may have
occurred,  shall undertake to perform only such duties as are  specifically  set
forth in this  Guarantee,  and no  implied  covenants  shall be read  into  this
Guarantee  against the Guarantee  Trustee.  In case a Guarantee Event of Default
has occurred (that has not been cured or waived  pursuant to Section 2.6) and is
actually known to a Responsible Officer of the Guarantee Trustee,  the Guarantee
Trustee  shall  exercise  such of the  rights  and  powers  vested in it by this
Guarantee, and use the same degree of care and skill in its exercise thereof, as
a prudent person would exercise or use under the circumstances in the conduct of
his or her own affairs.

     (d) No  provision  of this  Guarantee  shall be  construed  to relieve  the
Guarantee Trustee from liability for its own negligent action, its own negligent
failure to act, or its own willful misconduct, except that:

     (i) prior to the occurrence of any Guarantee Event of Default and after the
curing  or  waiving  of all  such  Guarantee  Events  of  Default  that may have
occurred:

          (A) the duties  and  obligations  of the  Guarantee  Trustee  shall be
     determined  solely by the express  provisions  of this  Guarantee,  and the
     Guarantee  Trustee shall not be liable except for the  performance  of such
     duties and obligations as are specifically set forth in this Guarantee, and
     no  implied  covenants  or  obligations  shall be read into this  Guarantee
     against the Guarantee Trustee; and

          (B) in the absence of bad faith on the part of the Guarantee  Trustee,
     the  Guarantee  Trustee  may  conclusively  rely,  as to the  truth  of the
     statements and the correctness of the opinions expressed therein,  upon any
     certificates or opinions  furnished to the Guarantee Trustee and conforming
     to  the  requirements  of  this  Guarantee;  but in the  case  of any  such
     certificates  or opinions  that by any  provision  hereof are  specifically
     required to be furnished to the Guarantee  Trustee,  the Guarantee  Trustee
     shall be under a duty to examine the same to determine  whether or not they
     conform to the requirements of this Guarantee;

     (ii) the  Guarantee  Trustee  shall not be liable for any error of judgment
made in good faith by a Responsible Officer of the Guarantee Trustee,  unless it
shall be proved that the  Guarantee  Trustee was negligent in  ascertaining  the
pertinent facts upon which such judgment was made;

     (iii) the Guarantee  Trustee shall not be liable with respect to any action
taken  or  omitted  to be  taken  by it in good  faith  in  accordance  with the
direction  of the Holders of not less than a Majority in  Liquidation  Amount of
the  Securities  relating  to the  time,  method  and  place of  conducting  any
proceeding for any remedy available to the Guarantee Trustee,  or exercising any
trust or power conferred upon the Guarantee Trustee under this Guarantee; and

     (iv) no provision of this Guarantee shall require the Guarantee  Trustee to
expend or risk its own funds or otherwise incur personal financial  liability in
the  performance of any of its duties or in the exercise of any of its rights or
powers,  if the Guarantee  Trustee shall have  reasonable  grounds for believing
that the  repayment of such funds or liability is not  reasonably  assured to it
under  the  terms of this  Guarantee  or if the  Guarantee  Trustee  shall  have
reasonable grounds for believing that an indemnity,  reasonably  satisfactory to
the Guarantee Trustee,  against such risk or liability is not reasonably assured
to it under the terms of this Guarantee.

     SECTION  3.2  Certain  Rights of  Guarantee  Trustee.  (a)  Subject  to the
provisions of Section 3.1:

     (i) The  Guarantee  Trustee  may  conclusively  rely,  and  shall  be fully
protected in acting or refraining from acting upon, any resolution, certificate,
statement,  instrument,  opinion, report, notice, request,  direction,  consent,
order, bond,  debenture,  note, other evidence of indebtedness or other paper or
document believed by it to be genuine and to have been signed, sent or presented
by the proper party or parties;

     (ii) Any direction or act of the Guarantor  contemplated  by this Guarantee
shall be sufficiently evidenced by an Officers' Certificate;

     (iii) Whenever,  in the  administration  of this  Guarantee,  the Guarantee
Trustee shall deem it desirable  that a matter be proved or  established  before
taking,  suffering  or omitting  any action  hereunder,  the  Guarantee  Trustee
(unless other evidence is herein specifically prescribed) may, in the absence of
bad  faith  on its  part,  request  and  conclusively  rely  upon  an  Officers'
Certificate which, upon receipt of such request,  shall be promptly delivered by
the Guarantor;

     (iv) The  Guarantee  Trustee  shall  have no duty to see to any  recording,
filing or  registration  or any  instrument  (or any  rerecording,  refiling  or
re-registration thereof);

     (v) The  Guarantee  Trustee may  consult  with  counsel,  and the advice or
opinion of such counsel with respect to legal matters shall be full and complete
authorization and protection in respect of any action taken, suffered or omitted
by it  hereunder  in good faith and in  accordance  with such advice or opinion.
Such counsel may be counsel to the  Guarantor or any of its  Affiliates  and may
include any of its employees.  The Guarantee Trustee shall have the right at any
time to seek instructions  concerning the  administration of this Guarantee from
any court of competent jurisdiction;

     (vi) The Guarantee  Trustee shall be under no obligation to exercise any of
the rights or powers vested in it by this  Guarantee at the request or direction
of any Holder,  unless such Holder shall have provided to the Guarantee  Trustee
such security and indemnity,  reasonably  satisfactory to the Guarantee Trustee,
against the costs,  expenses  (including  attorneys'  fees and  expenses and the
expenses  of  the  Guarantee  Trustee's  agents,  nominees  or  custodians)  and
liabilities  that might be  incurred  by it in  complying  with such  request or
direction,  including  such  reasonable  advances  as  may be  requested  by the
Guarantee Trustee;  provided,  that nothing contained in this Section 3.2(a)(vi)
shall be taken to  relieve  the  Guarantee  Trustee,  upon the  occurrence  of a
Guarantee Event of Default,  of its obligation to exercise the rights and powers
vested in it by this Guarantee;

     (vii) The Guarantee  Trustee  shall not be bound to make any  investigation
into the facts or  matters  stated in any  resolution,  certificate,  statement,
instrument,  opinion, report, notice, request, direction,  consent, order, bond,
debenture,  note, other evidence of indebtedness or other paper or document, but
the  Guarantee  Trustee,  in its  discretion,  may make such further  inquiry or
investigation into such facts or matters as it may see fit;

     (viii)  The  Guarantee  Trustee  may  execute  any of the  trusts or powers
hereunder  or perform  any duties  hereunder  either  directly  or by or through
agents,  nominees,  custodians or attorneys, and the Guarantee Trustee shall not
be  responsible  for any  misconduct  or  negligence on the part of any agent or
attorney appointed with due care by it hereunder;

     (ix) Any action  taken by the  Guarantee  Trustee  or its agents  hereunder
shall bind the Holders, and the signature of the Guarantee Trustee or its agents
alone shall be  sufficient  and  effective to perform any such action.  No third
party shall be required to inquire as to the authority of the Guarantee  Trustee
to so act or as to its  compliance  with any of the terms and provisions of this
Guarantee,  both of  which  shall be  conclusively  evidenced  by the  Guarantee
Trustee's or its agent's taking such action; and

     (x) Whenever in the  administration of this Guarantee the Guarantee Trustee
shall deem it desirable to receive  instructions  with respect to enforcing  any
remedy or right or taking any other action hereunder,  the Guarantee Trustee (i)
may request written  instructions  from the Holders of a Majority in Liquidation
Amount of the  Securities,  (ii) may refrain from enforcing such remedy or right
or taking such other  action until such  written  instructions  are received and
(iii) shall be protected in conclusively relying on or acting in accordance with
such written instructions.

     (b) No  provision of this  Guarantee  shall be deemed to impose any duty or
obligation on the  Guarantee  Trustee to perform any act or acts or exercise any
right, power, duty or obligation  conferred or imposed on it in any jurisdiction
in which it  shall be  illegal,  or in  which  the  Guarantee  Trustee  shall be
unqualified or incompetent to act in accordance  with applicable law, to perform
any such act or acts or to exercise any such right,  power,  duty or obligation.
No permissive  power or authority  available to the  Guarantee  Trustee shall be
construed to be a duty.

     SECTION 3.3 Not  Responsible  for  Recitals or Issuance of  Guarantee.  The
recitals  contained in this  Guarantee  shall be taken as the  statements of the
Guarantor,  and the  Guarantee  Trustee does not assume any  responsibility  for
their  correctness.  The Guarantee  Trustee makes no  representations  as to the
validity or sufficiency of this Guarantee.

                                   ARTICLE IV

                                GUARANTEE TRUSTEE

     SECTION 4.1 Guarantee Trustee; Eligibility. (a) There shall be at all times
a Guarantee Trustee which shall:

     (i) not be an Affiliate of the Guarantor; and

     (ii) be a corporation  organized and doing  business  under the laws of the
United States of America or any state or territory thereof or of the District of
Columbia,  or a  corporation  or other Person  permitted by the  Securities  and
Exchange Commission to act as an institutional trustee under the Trust Indenture
Act,  authorized  under such laws to exercise  corporate trust powers,  having a
combined capital and surplus of at least 50 million U.S. dollars  ($50,000,000),
and subject to  supervision or  examination  by federal,  state,  territorial or
District  of  Columbia  authority.  If such  corporation  publishes  reports  of
condition  at least  annually,  pursuant  to law or to the  requirements  of the
supervising or examining  authority referred to above, then, for the purposes of
this Section  4.1(a)(ii),  the combined  capital and surplus of such corporation
shall be deemed to be its combined  capital and surplus as set forth in its most
recent report of condition so published.

     (b) If at any time the  Guarantee  Trustee shall cease to be eligible to so
act under Section 4.1(a),  the Guarantee Trustee shall immediately resign in the
manner and with the effect set out in Section 4.2(c).

     (c)  If the  Guarantee  Trustee  has  or  shall  acquire  any  "conflicting
interest"  within the meaning of Section 310(b) of the Trust  Indenture Act, the
Guarantee Trustee and Guarantor shall in all respects comply with the provisions
of Section 310(b) of the Trust Indenture Act.

     SECTION 4.2 Appointment,  Removal and Resignation of Guarantee Trustee. (a)
Subject to  Section  4.2(b),  unless a  Guarantee  Event of  Default  shall have
occurred and be  continuing,  the Guarantee  Trustee may be appointed or removed
with or without cause at any time by the Guarantor.

     (b) The Guarantee  Trustee shall not be removed in accordance  with Section
4.2(a) until a Successor  Guarantee  Trustee has been appointed and has accepted
such  appointment by written  instrument  executed by such  Successor  Guarantee
Trustee and delivered to the Guarantor.

     (c) The Guarantee  Trustee appointed to office shall hold such office until
a Successor  Guarantee Trustee shall have been appointed or until its removal or
resignation.  The  Guarantee  Trustee may resign from office  (without  need for
prior or subsequent  accounting)  by an  instrument  in writing  executed by the
Guarantee  Trustee and delivered to the Guarantor,  which  resignation shall not
take effect  until a Successor  Guarantee  Trustee  has been  appointed  and has
accepted such  appointment  by instrument in writing  executed by such Successor
Guarantee  Trustee and delivered to the  Guarantor  and the resigning  Guarantee
Trustee.

     (d) If no  Successor  Guarantee  Trustee  shall  have  been  appointed  and
accepted  appointment  as  provided  in this  Section  4.2  within 30 days after
delivery  to the  Guarantor  of an  instrument  of removal or  resignation,  the
removed or  resigning  Guarantee  Trustee may  petition  any court of  competent
jurisdiction for appointment of a Successor  Guarantee  Trustee.  Such court may
thereupon, after prescribing such notice, if any, as it may deem proper, appoint
a Successor Guarantee Trustee.

     (e) No Guarantee  Trustee  shall be liable for the acts or omissions to act
of any Successor Guarantee Trustee.

     (f) Upon  termination  of this  Guarantee or removal or  resignation of the
Guarantee  Trustee  pursuant to this Section 4.2, the Guarantor shall pay to the
Guarantee Trustee all amounts owing for fees and reimbursement of expenses which
have accrued to the date of such termination, removal or resignation.

                                   ARTICLE V

                                    GUARANTEE

     SECTION 5.1 Guarantee. The Guarantor irrevocably and unconditionally agrees
to pay in full to the Holders the Guarantee  Payments  (without  duplication  of
amounts  theretofore  paid by the  Trust),  as and when due,  regardless  of any
defense, right of set-off or counterclaim that the Trust may have or assert. The
Guarantor's  obligation  to make a Guarantee  Payment may be satisfied by direct
payment of the  required  amounts by the  Guarantor to the Holders or by causing
the Trust to pay such  amounts to the Holders.  Notwithstanding  anything to the
contrary herein,  the Guarantor retains all of its rights under the Indenture to
(i) extend the interest payment period on the Debentures and the Guarantor shall
not be obligated  hereunder to make any Guarantee  Payments during any Extension
Period (as defined in the certificate evidencing the Debentures) with respect to
the  Distributions  (as defined in the  Declaration)  on the Securities and (ii)
change  the  maturity  date of the  Debentures  to the extent  permitted  by the
Indenture.

     SECTION 5.2 Waiver of Notice and Demand. The Guarantor hereby waives notice
of acceptance of this  Guarantee and of any liability to which it applies or may
apply, presentment,  demand for payment, any right to require a proceeding first
against the Trust or any other Person before  proceeding  against the Guarantor,
protest, notice of nonpayment,  notice of dishonor, notice of redemption and all
other notices and demands.

     SECTION  5.3  Obligations  Not  Affected.   The   obligations,   covenants,
agreements and duties of the Guarantor  under this  Guarantee  shall be absolute
and  unconditional  and shall  remain in full force and effect  until the entire
liquidation  amount of all outstanding  Securities shall have been paid and such
obligation  shall in no way be affected  or impaired by reason of the  happening
from time to time of any event,  including  without  limitation,  the following,
whether or not with notice to, or the consent of, the Guarantor:

     (a) The  release  or  waiver,  by  operation  of law or  otherwise,  of the
performance  or  observance  by the Trust of any  express or implied  agreement,
covenant,  term or  condition  relating to the  Securities  to be  performed  or
observed by the Trust;

     (b) The  extension  of time  for the  payment  by the  Trust  of all or any
portion of the Distributions,  Redemption Price, Liquidation Distribution or any
other sums payable  under the terms of the  Securities  or the extension of time
for the  performance  of any  other  obligation  under,  arising  out of,  or in
connection  with the Securities  (other than an extension of time for payment of
Distributions,  Redemption Price,  Liquidation Distribution or other sum payable
that results from the extension of any interest payment period on the Debentures
or  any  change  to  the  maturity  date  of  the  Debentures  permitted  by the
Indenture);

     (c) Any  failure,  omission,  delay or lack of diligence on the part of the
Property  Trustee  or the  Holders to  enforce,  assert or  exercise  any right,
privilege,  power or remedy  conferred  on the  Property  Trustee or the Holders
pursuant to the terms of the Securities,  or any action on the part of the Trust
granting indulgence or extension of any kind;

     (d) The  voluntary or  involuntary  liquidation,  dissolution,  sale of any
collateral, receivership,  insolvency, bankruptcy, assignment for the benefit of
creditors, reorganization,  arrangement, composition or readjustment of debt of,
or other similar  proceedings  affecting,  the Trust or any of the assets of the
Trust;

     (e) Any invalidity of, or defect or deficiency in, the Securities;

     (f) The  settlement or compromise of any  obligation  guaranteed  hereby or
hereby incurred; or

     (g) Any other  circumstance  whatsoever that might  otherwise  constitute a
legal or equitable  discharge or defense of a guarantor,  it being the intent of
this  Section  5.3 that the  obligations  of the  Guarantor  hereunder  shall be
absolute and unconditional under any and all circumstances.

                  There shall be no obligation of the Guarantee Trustee or the
Holders to give notice to, or obtain consent of the Guarantor or any other
Person with respect to the happening of any of the foregoing.

                  No setoff, counterclaim, reduction or diminution of any
obligation, or any defense of any kind or nature that the Guarantor has or may
have against any Holder shall be available hereunder to the Guarantor against
such Holder to reduce the payments to it under this Guarantee.

     SECTION  5.4 Rights of  Holders.  (a) The Holders of at least a Majority in
Liquidation  Amount of the Securities have the right to direct the time,  method
and place of conducting any proceeding for any remedy available to the Guarantee
Trustee in respect of this  Guarantee  or to direct the exercise of any trust or
power conferred upon the Guarantee Trustee under this Guarantee.

     (b) If the  Guarantee  Trustee  fails to enforce this  Guarantee,  then any
Holder of Securities  may,  subject to the  subordination  provisions of Section
6.2, institute a legal proceeding  directly against the Guarantor to enforce the
Guarantee  Trustee's  rights under this  Guarantee  without first  instituting a
legal proceeding against the Trust, the Guarantee Trustee or any other person or
entity. In addition,  if the Guarantor has failed to make a Guarantee Payment, a
Holder of Securities  may,  subject to the  subordination  provisions of Section
6.2,  directly  institute a proceeding  against the Guarantor for enforcement of
the Guarantee for such payment to the Holder of the  Securities of the principal
of or interest on the Debentures on or after the respective due dates  specified
in the  Debentures,  and the amount of the payment will be based on the Holder's
pro rata  share  of the  amount  due and  owing  on all of the  Securities.  The
Guarantor  hereby  waives any right or remedy to require that any action on this
Guarantee  be  brought  first  against  the Trust or any other  person or entity
before proceeding directly against the Guarantor.

     SECTION 5.5  Guarantee of Payment.  This  Guarantee  creates a guarantee of
payment and not of collection.

     SECTION 5.6 Subrogation.  The Guarantor shall be subrogated to all (if any)
rights of the Holders of Securities  against the Trust in respect of any amounts
paid to such Holders by the Guarantor under this Guarantee;  provided,  however,
that the  Guarantor  shall not  (except  to the  extent  required  by  mandatory
provisions  of law) be  entitled  to enforce or  exercise  any right that it may
acquire  by  way  of  subrogation  or  any  indemnity,  reimbursement  or  other
agreement,  in all cases as a result of payment under this Guarantee,  if at the
time of any such payment,  any amounts are due and unpaid under this  Guarantee.
If any amount  shall be paid to the  Guarantor  in  violation  of the  preceding
sentence,  the Guarantor agrees to hold such amount in trust for the Holders and
to pay over such amount to the Guarantee Trustee for the benefit of the Holders.

     SECTION 5.7 Independent  Obligations.  The Guarantor  acknowledges that its
obligations  hereunder  are  independent  of the  obligations  of the Trust with
respect to the  Securities,  and that the Guarantor shall be liable as principal
and as debtor hereunder to make Guarantee Payments pursuant to the terms of this
Guarantee notwithstanding the occurrence of any event referred to in subsections
5.3(a) through 5.3(g), inclusive, hereof.

                                   ARTICLE VI

                    LIMITATION OF TRANSACTIONS; SUBORDINATION

     SECTION 6.1 Limitation of  Transactions.  So long as any Securities  remain
outstanding,  if (i) there  shall have  occurred  an event of default  under the
Indenture with respect to the Debentures,  (ii) there shall be a Guarantee Event
of Default or (iii) the Guarantor  shall have given notice of its election of an
Extension  Period as provided in the  certificate  evidencing the Debentures and
shall not have rescinded such notice,  or such Extension Period or any extension
thereof shall be continuing,  then the Guarantor shall not, and shall not permit
any  subsidiary  of the  Guarantor,  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 Guarantor'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  Guarantor  that  rank on a parity  with or  junior  in
interest to the  Debentures or make any  guarantee  payments with respect to any
guarantee  by the  Guarantor of the debt  securities  of any  subsidiary  of the
Guarantor if such guarantee  ranks on a parity with or junior in interest to the
Debentures  (other than (a)  dividends or  distributions  in common stock of the
Guarantor,  (b) payments under this Guarantee, (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
Guarantor's benefit plans).

     SECTION 6.2 Ranking. This Guarantee will constitute an unsecured obligation
of the Guarantor and will rank (i) subordinate and junior in right of payment to
all other  liabilities of the  Guarantor,  (ii) on a parity with the most senior
preferred or preference  stock now or hereafter issued by the Guarantor and with
any guarantee  now or hereafter  entered into by the Guarantor in respect of any
preferred  securities  of any Affiliate of the Guarantor and (iii) senior to the
Guarantor's  common stock. In addition,  at all times such  obligations  will be
structurally  subordinated to the liabilities and obligations of the Guarantor's
subsidiaries.

     SECTION 6.3  Subordination  of Common  Securities.  If a Trust  Enforcement
Event has occurred and is continuing  under the  Declaration,  the rights of the
holders of the Common Securities to receive Guarantee  Payments  hereunder shall
be  subordinated  to the rights of the Holders of the  Preferred  Securities  to
receive Guarantee Payments under this Guarantee.

                                  ARTICLE VII

                                   TERMINATION

     SECTION 7.1  Termination.  This  Guarantee  shall  terminate  upon (i) full
payment of the Redemption  Price of all  Securities,  (ii)  distribution  of the
Debentures  to the Holders of all the  Securities  or (iii) full  payment of the
amounts  payable in accordance  with the  Declaration  upon  liquidation  of the
Trust.  Notwithstanding  the  foregoing,  this  Guarantee  will  continue  to be
effective or will be  reinstated,  as the case may be, if at any time any Holder
of  Securities  must restore  payment of any sums paid under the  Securities  or
under this Guarantee.

                                  ARTICLE VIII

                                 INDEMNIFICATION

     SECTION  8.1  Exculpation.  (a) No  Indemnified  Person  shall  be  liable,
responsible  or  accountable  in damages or  otherwise  to the  Guarantor or any
Covered  Person for any loss,  damage,  liability,  expense or claim incurred by
reason of any act or omission performed or omitted by such Indemnified Person in
good  faith  in  accordance  with  this  Guarantee  and in a  manner  that  such
Indemnified  Person reasonably  believed to be within the scope of the authority
conferred on such Indemnified Person by this Guarantee 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  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 Guarantor and upon such information,  opinions,  reports
or  statements  presented  to the  Guarantor  by any  Person as to  matters  the
Indemnified   Person   reasonably   believes  are  within  such  other  Person's
professional or expert competence and who has been selected with reasonable care
by or on behalf of the Guarantor,  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 Holders of Securities might properly be paid. SECTION 8.2
Indemnification.  The Guarantor agrees to indemnify each Indemnified Person for,
and to hold each  Indemnified  Person  harmless  against any loss,  liability or
expense incurred without  negligence or bad faith on its part, arising out of or
in  connection  with the  acceptance  or  administration  of the trust or trusts
hereunder, including the costs and expenses (including reasonable legal fees and
expenses) of defending itself against, or investigating,  any claim or liability
in connection  with the exercise or  performance  of any of its powers or duties
hereunder.  The  obligation  to indemnify as set forth in this Section 8.2 shall
survive the termination of this Guarantee.

                                   ARTICLE IX

                                  MISCELLANEOUS

     SECTION 9.1 Successors and Assigns. All guarantees and agreements contained
in this Guarantee shall bind the successors,  assigns,  receivers,  trustees and
representatives  of the  Guarantor and shall inure to the benefit of the Holders
of the Securities then outstanding.

     SECTION  9.2  Amendments.  Except with  respect to any changes  that do not
materially  adversely affect the rights of the Holders (in which case no consent
of the Holders will be required),  this Guarantee may not be amended without the
prior  approval  of the  Holders  of not  less  than  66-2/3%  of the  aggregate
liquidation  amount of the  Securities.  The  provisions  of Section 11.2 of the
Declaration  with respect to meetings of, and action by written  consent of, the
Holders of the Securities apply to the giving of such approval.

     SECTION 9.3 Notices. All notices provided for in this Guarantee shall be in
writing,  duly signed by the party giving such notice, and shall be delivered by
hand, telecopied or mailed by registered or certified mail, as follows:

     (a) If given to the Guarantee Trustee,  at the Guarantee  Trustee's mailing
address set forth below (or such other address as the Guarantee Trustee may give
notice of to the Guarantor and the Holders of the Securities):


                   JPMorgan Chase Bank
                   450 West 33rd Street
                   New York, New York  10001
                   Attention:________________
                   Telecopy no.: (212) 946-8161

     (b) If given to the Guarantor,  at the  Guarantor's  mailing  addresses set
forth below (or such other  address as the  Guarantor  may give notice of to the
Guarantee Trustee and the Holders of the Securities):


                   KeySpan Corporation
                   One Metrotech Center
                   Brooklyn, New York  11201
                   Attention: Corporate Counsel
                   Telecopy no.: _____________

     (c) If given to any Holder of  Securities,  at the address set forth on the
books and records of the Trust.

                  All such notices shall be deemed to have been given when
received in person, telecopied with receipt confirmed, or mailed by first class
mail, postage prepaid, except that if a notice or other document is refused
delivery or cannot be delivered because of a changed address of which no notice
was given, such notice or other document shall be deemed to have been delivered
on the date of such refusal or inability to deliver.

     SECTION  9.4  Benefit.  This  Guarantee  is solely  for the  benefit of the
Holders of the  Securities  and,  subject to Section  3.1(a),  is not separately
transferable from the Securities.

     SECTION  9.5  Governing  Law.  THIS  GUARANTEE  SHALL BE  GOVERNED  BY, AND
CONSTRUED AND INTERPRETED IN ACCORDANCE WITH, THE LAWS OF THE STATE OF NEW YORK.









                  IN WITNESS WHEREOF, this Guarantee is executed as of the day
and year first above written.

                                  KEYSPAN CORPORATION,
                                  as Guarantor


                                  By:
                                    --------------------------------------
                                    Name:
                                    Title:


                                  JPMORGAN CHASE BANK,
                                  as Guarantee Trustee


                                  By:
                                    --------------------------------------
                                    Name:
                                    Title: