Exhibit 4(d)


                               GUARANTEE AGREEMENT


                                     Between

                         Minnesota Power & Light Company
                                  (as Guarantor)

                                       and

                               The Bank of New York
                                   (as Trustee)

                                   dated as of

                                  March 1, 1996






                                TABLE OF CONTENTS
                                                          
                                                                            Page

ARTICLE I              DEFINITIONS..........................................  1
         SECTION 1.01  Definitions..........................................  1

ARTICLE II             TRUST INDENTURE ACT..................................  4
         SECTION 2.01  Trust Indenture Act; Application.....................  4
         SECTION 2.02  Lists of Holders of Preferred Securities.............  4
         SECTION 2.03  Reports by the Guarantee Trustee.....................  4
         SECTION 2.04  Periodic Reports to Guarantee Trustee................  4
         SECTION 2.05  Evidence of Compliance with Conditions Precedent.....  5
         SECTION 2.06  Events of Default; Waiver............................  5
         SECTION 2.07  Event of Default; Notice.............................  5
         SECTION 2.08  Conflicting Interests................................  5

ARTICLE III            POWERS, DUTIES AND RIGHTS OF GUARANTEE TRUSTEE.......  5
         SECTION 3.01  Powers and Duties of the Guarantee Trustee...........  5
         SECTION 3.02  Certain Rights of Guarantee Trustee..................  7

ARTICLE IV             GUARANTEE TRUSTEE....................................  9
         SECTION 4.01  Guarantee Trustee; Eligibility.......................  9
         SECTION 4.02  Compensation and Reimbursement.......................  9
         SECTION 4.03  Appointment, Removal and Resignation of
                                   Guarantee Trustee........................ 10

ARTICLE V              GUARANTEE............................................ 11
         SECTION 5.01  Guarantee............................................ 11
         SECTION 5.02  Waiver of Notice and Demand.......................... 11
         SECTION 5.03  Obligations Not Affected............................. 12
         SECTION 5.04  Rights of Holders.................................... 12
         SECTION 5.05  Guarantee of Payment................................. 13
         SECTION 5.06  Subrogation.......................................... 13
         SECTION 5.07  Independent Obligations.............................. 13

ARTICLE VI             SUBORDINATION........................................ 13
         SECTION 6.01  Subordination........................................ 13

ARTICLE VII            TERMINATION.......................................... 14
         SECTION 7.01  Termination.......................................... 14

ARTICLE VIII           MISCELLANEOUS........................................ 14
         SECTION 8.01  Successors and Assigns............................... 14
         SECTION 8.02  Amendments........................................... 14
         SECTION 8.03  Notices.............................................. 14
         SECTION 8.04  Benefit.............................................. 15
         SECTION 8.05  Interpretation....................................... 16
         SECTION 8.06  Governing Law........................................ 16




                              CROSS-REFERENCE TABLE



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

310(a)....................................................... 4.01(a)
310(b)....................................................... 4.01(c), 2.08
310(c)....................................................... Inapplicable
311(a)....................................................... 2.02(b)
311(b)....................................................... 2.02(b)
311(c)....................................................... Inapplicable
312(a)....................................................... 2.02(a)
312(b)....................................................... 2.02(b)
313.......................................................... 2.03
314(a)....................................................... 2.04
314(b)....................................................... Inapplicable
314(c)....................................................... 2.05
314(d)....................................................... Inapplicable
314(e)....................................................... 1.01, 2.05, 3.02
314(f)....................................................... 2.01, 3.02
315(a)....................................................... 3.01(d)
315(b)....................................................... 2.07
315(c)....................................................... 3.01
315(d)....................................................... 3.01(d)
316(a)....................................................... 5.04(a), 2.06
316(b)....................................................... 5.03
316(c)....................................................... 2.02
317(a)....................................................... Inapplicable
317(b)....................................................... Inapplicable
318(a)....................................................... 2.01(b)
318(b)....................................................... 2.01
318(c)....................................................... 2.01(a)

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



                               GUARANTEE AGREEMENT

                  This GUARANTEE AGREEMENT ("Guarantee Agreement"),  dated as of
March 1, 1996, is executed and delivered by Minnesota  Power & Light Company,  a
Minnesota  corporation (the  "Guarantor"),  and The Bank of New York, as trustee
(the  "Guarantee  Trustee"),  for the benefit of the Holders (as defined herein)
from  time to time of the  Preferred  Securities  (as  defined  herein)  of MP&L
Capital I, a Delaware statutory business trust (the "Issuer").

                  WHEREAS,  pursuant to an Amended and Restated Trust  Agreement
(the "Trust  Agreement"),  dated as of March 1, 1996 between the Trustees of the
Issuer named therein,  Minnesota  Power & Light Company,  as Depositor,  and the
several Holders (as defined therein) the Issuer is issuing as of the date hereof
$75,000,000  aggregate  liquidation  amount  of its 8.05%  Cumulative  Quarterly
Income Preferred Securities (the "Preferred Securities")  representing preferred
undivided  beneficial ownership interests in the Issuer and having the terms set
forth in the Trust Agreement;

                  WHEREAS, the Preferred Securities are to be issued for sale by
the Issuer and the proceeds are to be invested in $77,500,000  principal  amount
of Debentures (as defined in the Trust Agreement); and

                  WHEREAS,  in  order to  enhance  the  value  of the  Preferred
Securities,  the Guarantor desires to irrevocably and unconditionally  agree, to
the extent set forth herein,  to pay to the Holders the  Guarantee  Payments (as
defined  herein) and to make certain other  payments on the terms and conditions
set forth herein;

                  NOW,   THEREFORE,   in   consideration   of  the  purchase  of
Debentures,  which  purchase  the  Guarantor  hereby  agrees  shall  benefit the
Guarantor,  the Guarantor executes and delivers this Guarantee Agreement for the
benefit of the Holders from time to time.


                                    ARTICLE I

                                   DEFINITIONS

                  SECTION 1.01 Definitions. As used in this Guarantee Agreement,
the terms set forth below shall, unless the context otherwise requires, have the
following  meanings.  Capitalized  or  otherwise  defined  terms  used  but  not
otherwise  defined herein shall have the meanings  assigned to such terms in the
Trust Agreement as in effect on the date hereof.

                  "Affiliate"  of any  specified  Person  means any other Person
directly or indirectly  controlling or controlled by or under direct or indirect
common control with such specified Person.  For the purposes of this definition,
"control"  when used with  respect to any  specified  Person  means the power to
direct the  management  and  policies of such  Person, 



directly or indirectly,  whether through the ownership of voting securities,  by
contract  or  otherwise;  and the  terms  "controlling"  and  "controlled"  have
meanings correlative to the foregoing.

                  "Common  Securities" means the securities  representing common
undivided beneficial ownership interests in the assets of the Issuer.

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

                  "Guarantee  Payments"  shall mean the  following  payments  or
distributions, without duplication, with respect to the Preferred Securities, to
the extent not paid or made by or on behalf of the  Issuer:  (i) any accrued and
unpaid  Distributions that are required to be paid on such Preferred  Securities
but only if and to the extent that the  Property  Trustee has  available  in the
Payment Account funds sufficient to make such payment, (ii) the redemption price
(the "Redemption  Price"),  and all accrued and unpaid Distributions to the date
of redemption, with respect to the Preferred Securities called for redemption by
the Issuer but only if and to the extent that the Property Trustee has available
in the Payment  Account  funds  sufficient  to make such  payment,  (iii) upon a
voluntary or  involuntary  dissolution,  winding-up or termination of the Issuer
(other than in connection with a redemption of all of the Preferred Securities),
the lesser of (a) the  aggregate of the  Liquidation  Amount and all accrued and
unpaid Distributions on the Preferred Securities to the date of payment, and (b)
the amount of assets of the  Issuer  remaining  available  for  distribution  to
Holders  in  liquidation  of  the  Issuer  (in  either  case,  the  "Liquidation
Distribution").

                  "Guarantee  Trustee"  means  The  Bank  of New  York  until  a
Successor Guarantee Trustee has been appointed and has accepted such appointment
pursuant to the terms of this Guarantee Agreement and thereafter means each such
Successor Guarantee Trustee.

                  "Holder" shall mean any holder, as registered on the books and
records of the Issuer, of any Preferred  Securities then outstanding;  provided,
however,  that in determining whether the holders of the requisite percentage of
Preferred  Securities  have  given  any  request,   notice,  consent  or  waiver
hereunder,  "Holder"  shall not include the  Guarantor  or any  Affiliate of the
Guarantor.

                  "Indenture"  means the  Indenture  dated as of March 1,  1996,
among the  Guarantor  (the  "Debenture  Issuer")  and The Bank of New  York,  as
trustee, pursuant to which the Debentures are issued.

                  "Majority in liquidation  amount of the Preferred  Securities"
means a vote by Holders,  voting  separately as a class, of more than 50% of the
aggregate liquidation amount of all Preferred Securities.

                                   -2-


                  "Officers'  Certificate"  means a  certificate  signed  by the
Chairman of the Board,  a Vice  Chairman of the Board,  the  President or a Vice
President,  and by the Treasurer,  an Assistant  Treasurer,  the Secretary or an
Assistant Secretary,  of the Guarantor,  and delivered to the Guarantee Trustee.
Any Officers'  Certificate delivered with respect to compliance with a condition
or covenant provided for in this Guarantee Agreement 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 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 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, such condition or covenant has been complied with.

                  "Person" means any individual, corporation, partnership, joint
venture,  trust,  unincorporated  organization  or  government  or any agency or
political subdivision thereof.

                  "Responsible  Officer"  means,  with respect to the  Guarantee
Trustee, any vice-president,  any assistant  vice-president,  the secretary, any
assistant secretary,  the treasurer,  any assistant treasurer, any trust officer
or  assistant  trust  officer  or  any  other  officer  of the  Corporate  Trust
Department of the Guarantee Trustee customarily  performing functions similar to
those  performed by any of the above  designated  officers 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.

                  "Successor  Guarantee  Trustee"  means a  successor  Guarantee
Trustee  possessing the qualifications to act as Guarantee Trustee under Section
4.01.

                  "Trust Indenture Act" means the Trust Indenture Act of 1939, 
as amended.

                                   -3-

                                ARTICLE II

                            TRUST INDENTURE ACT

                  SECTION 2.01  Trust Indenture Act; Application.

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

                  (b) if and to the extent that any provision of this  Guarantee
Agreement 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 2.02 Lists of Holders of Preferred Securities.

                  (a) The  Guarantor  shall  furnish or cause to be furnished to
the Guarantee Trustee (a)  semiannually,  not later than December 31 and June 30
in each year,  a list,  in such form as the  Guarantee  Trustee  may  reasonably
require,  of the names and addresses of the Holders  ("List of Holders") as of a
date not more than 15 days prior to the delivery thereof,  and (b) at such other
times as the Guarantee Trustee may request in writing,  within 30 days after the
receipt by the Guarantor of any such request, a List of Holders as of a date not
more than 15 days prior to the time such list is furnished;  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 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 Section 311(a) of the Trust  Indenture  Act,  subject to the provisions of
Section 311(b) and Section 312(b) of the Trust Indenture Act.

                  SECTION 2.03 Reports by the Guarantee Trustee.  Within 60 days
after  December 31 of each year,  commencing  December 31, 1996,  the  Guarantee
Trustee shall  provide to the Holders such  reports,  if any, as are required by
Section 313(a) of the Trust Indenture Act in the form and in the manner provided
by Section 313(a) of the Trust  Indenture Act. The Guarantee  Trustee shall also
comply  with the  requirements  of  Sections  313(b),  (c) and (d) of the  Trust
Indenture Act.

                  SECTION  2.04  Periodic  Reports  to  Guarantee  Trustee.  The
Guarantor  shall provide to the Guarantee  Trustee such  documents,  reports and
information as required by Section 314 (if any) and the  compliance  certificate
required by Section 314 of the Trust  Indenture  Act in the form,  in the manner
and at the times required by Section 314 of the Trust Indenture Act.

                                   -4-


                  SECTION 2.05 Evidence of Compliance with Conditions Precedent.
The Guarantor shall provide to the Guarantee Trustee such evidence of compliance
with any conditions precedent provided for in this Guarantee Agreement as and to
the  extent  required  by  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)  of the Trust  Indenture  Act may be given in the form of an Officers'
Certificate.

                  SECTION  2.06  Events of  Default;  Waiver.  The  Holders of a
Majority in liquidation  amount of Preferred  Securities may, by vote, on behalf
of all of the  Holders,  waive any past Event of Default  and its  consequences.
Upon such waiver,  any such Event of Default shall cease to exist, and any Event
of  Default  arising  therefrom  shall be deemed to have been  cured,  for every
purpose of this  Guarantee  Agreement,  but no such waiver  shall  extend to any
subsequent or other  default or Event of Default or impair any right  consequent
thereon.

                  SECTION 2.07 Event of Default; Notice.

                  (a) The  Guarantee  Trustee  shall,  within 90 days  after the
occurrence  of an Event  of  Default,  transmit  by mail,  first  class  postage
prepaid, to the Holders, notices of all Events of Default known to 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 the board of directors,  the executive committee,  or a
trust committee of directors or Responsible Officers of the Guarantee Trustee in
good faith determines that the withholding of such notice is in the interests of
the Holders.

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

                  SECTION 2.08  Conflicting  Interests.  The Trust Agreement and
the Indenture  shall be deemed to be  specifically  described in this  Guarantee
Agreement  for the  purposes  of clause (i) of the first  proviso  contained  in
Section 310(b) of the Trust Indenture Act.


                                ARTICLE III
  
              POWERS, DUTIES AND RIGHTS OF GUARANTEE TRUSTEE

                  SECTION 3.01 Powers and Duties of the Guarantee Trustee.

                  (a) This  Guarantee  Agreement  shall be held by the Guarantee
Trustee for the benefit of the  Holders,  and the  Guarantee  Trustee  shall not
transfer this Guarantee 

                                   -5-


Agreement or any rights  hereunder to any Person except a Holder  exercising his
or her rights  pursuant to Section 5.04 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 shall  automatically vest in any Successor  Guarantee Trustee,  and such
vesting and  cessation of title shall be effective  whether or not  conveyancing
documents have been executed and delivered  pursuant to the  appointment of such
Successor Guarantee Trustee.

                  (b) The  Guarantee  Trustee,  prior to the  occurrence  of any
Event of Default  and after the  curing of all  Events of Default  that may have
occurred,  shall undertake to perform only such duties as are  specifically  set
forth in this Guarantee Agreement, and no implied covenants or obligations shall
be read into this Guarantee  Agreement against the Guarantee Trustee. In case an
Event of Default  has  occurred  (that has not been cured or waived  pursuant to
Section  2.06),  the  Guarantee  Trustee  shall  exercise such of the rights and
powers vested in it by this Guarantee Agreement, 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.

                  (c)  No  provision  of  this  Guarantee   Agreement  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 Event of Default
                  and after the curing or waiving of all such  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  Agreement,  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  Agreement;
                           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 Agreement;  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 Agreement;

                           (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 

                                   -6-

                  it shall be proved that the  Guarantee  Trustee or such  
                  Responsible  Officer 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
                  a Majority in liquidation  amount of the Preferred  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 Agreement; and

                         (iv) no provision  of this  Guarantee  Agreement  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  Agreement  or  adequate  indemnity
                  against such risk or liability  is not  reasonably  assured to
                  it.

                  SECTION  3.02 Certain Rights of Guarantee Trustee.

                  (a)  Subject to the provisions of Section 3.01:

                           (i) the Guarantee Trustee may 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  reasonably  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 Agreement shall be sufficiently
                  evidenced by an Officers' Certificate;

                           (iii)  whenever,   in  the   administration  of  this
                  Guarantee  Agreement,  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 rely  upon an  Officers'  Certificate
                  which,  upon  receipt  of  such  request,  shall  be  promptly
                  delivered by the Guarantor;

                                   -7-


                           (iv) the  Guarantee  Trustee may consult with counsel
                  of its  choice,  and the  written  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  Agreement from any court of
                  competent jurisdiction;

                           (v)  the   Guarantee   Trustee   shall  be  under  no
                  obligation  to exercise any of the rights or powers  vested in
                  it by this Guarantee  Agreement at the request or direction of
                  any  Holder,  unless such  Holder  shall have  provided to the
                  Guarantee  Trustee such  adequate  security  and  indemnity as
                  would  satisfy  a  reasonable  person in the  position  of the
                  Guarantee  Trustee,  against  the costs,  expenses  (including
                  attorneys'  fees and expenses) 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  3.02(a)(v)  shall be taken to relieve  the  Guarantee
                  Trustee,  upon the  occurrence of an Event of Default,  of its
                  obligation  to exercise the rights and powers  vested in it by
                  this Guarantee Agreement;

                           (vi) 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 reasonably  believed by it to be genuine,  but the
                  Guarantee  Trustee,  in its discretion,  may make such further
                  inquiry or investigation  into such facts or matters as it may
                  see fit;

                           (vii) the  Guarantee  Trustee  may execute any of the
                  trusts or powers  hereunder  or perform  any duties  hereunder
                  either directly or by or through agents 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;

                           (viii)  whenever  in  the   administration   of  this
                  Guarantee  Agreement  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  (1)  may  request  instructions  from  the
                  Holders,  (2) may refrain from  enforcing such remedy or right
                  or taking  such  other  action  until  such  instructions  are
                  received,  and (3) shall be protected in acting in  accordance
                  with such instructions; and

                                   -8-

                           (ix) the  Guarantee  Trustee  shall not be liable for
                  any  action  taken,  suffered  or omitted to be taken by it in
                  good faith and  reasonably  believed by it to be authorized or
                  within the discretion or rights or powers conferred upon it by
                  this Guarantee.

                  (b) No provision of this Guarantee  Agreement  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 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.


                                ARTICLE IV

                             GUARANTEE TRUSTEE

                  4.01 Guarantee Trustee; Eligibility.

                  (a)  There shall at all times be 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 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 4.01(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  4.01(a),   the  Guarantee  Trustee  shall
immediately resign in the manner and with the effect set out in Section 4.03(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 

                                   -9-


Guarantor  shall in all respects comply with the provisions of Section 310(b) of
the Trust Indenture Act.

                  SECTION 4.02 Compensation and Reimbursement.

                  The Guarantor agrees:

                  (a) to pay the  Guarantee  Trustee  from  time  to  time  such
reasonable  compensation  as the Guarantor and the Guarantee  Trustee shall from
time to time agree in writing for all services  rendered by it hereunder  (which
compensation  shall  not be  limited  by any  provision  of law in regard to the
compensation of a trustee of an express trust);

                  (b)  except  as  otherwise   expressly   provided  herein,  to
reimburse the Guarantee  Trustee upon its request for all  reasonable  expenses,
disbursements  and  advances  incurred  or  made  by the  Guarantee  Trustee  in
accordance  with the  provisions of this  Guarantee  (including  the  reasonable
compensation  and expenses of its agents and counsel),  except any such expense,
disbursement  or advance as may be  attributable to its negligence or bad faith;
and

                  (c)  to  indemnify  each  of the  Guarantee  Trustee  and  any
predecessor Guarantee Trustee for, and to hold it harmless from and against, any
and all loss, damage, claim,  liability or expense,  including taxes (other than
taxes  based  upon  the  income  of  the  Guarantee  Trustee)  incurred  without
negligence or bad faith on its part,  arising out of or in  connection  with the
acceptance of the  administration  of this  Guarantee  Agreement,  including the
costs and  expenses  of  defending  itself  against  any claim or  liability  in
connection  with  the  exercise  or  performance  of any its  powers  or  duties
hereunder.

                  As security  for the  performance  of the  obligations  of the
Guarantor under this Section,  the Guarantee  Trustee shall have a lien prior to
the  Preferred  Securities  upon all the property and funds held or collected by
the  Guarantee  Trustee as such,  except  funds held in trust for the payment of
principal of, and premium (if any) or interest on, particular obligations of the
Guarantor under this Guarantee Agreement.

                  The  provisions of this Section shall survive the  termination
of this Guarantee Agreement.

                  SECTION 4.03 Appointment, Removal and Resignation of Guarantee
Trustee.

                  (a)  Subject  to Section  4.03(b),  unless an Event of Default
shall have occurred and be continuing, the Guarantee Trustee may be appointed or
removed without cause at any time by the Guarantor.

                                   -10-


                  (b)  The  Guarantee  Trustee  shall  not be  removed  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
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 4.03 within 60
days after  delivery to the  Guarantor  of an  instrument  of  resignation,  the
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) The Guarantor  shall give notice of each  resignation  and
each  removal of the  Guarantee  Trustee  and each  appointment  of a  successor
Guarantee  Trustee to all Holders in the manner provided in Section 8.03 hereof.
Each notice shall  include the name of the successor  Guarantee  Trustee and the
address of its Corporate Trust Office.


                               ARTICLE V

                               GUARANTEE

                  SECTION  5.01   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 Issuer),  as and when
due,  regardless  of any  defense,  right of set-off or  counterclaim  which the
Issuer  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 Issuer to pay such  amounts to the
Holders.

                  SECTION 5.02 Waiver of Notice and Demand. The Guarantor hereby
waives notice of acceptance of this Guarantee  Agreement and of any liability to
which it applies or may apply,  presentment,  demand for  payment,  any right to
require a  proceeding  first  against  the  Issuer 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.

                                   -11-


                  SECTION 5.03  Obligations Not Affected.  The obligation of the
Guarantor to make the Guarantee Payments under this Guarantee Agreement shall in
no way be affected or impaired by reason of the  happening  from time to time of
any of the following:

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

                  (b) the extension of time for the payment by the Issuer of all
         or any  portion of the  Distributions,  Redemption  Price,  Liquidation
         Distribution or any other sums payable under the terms of the Preferred
         Securities  or the extension of time for the  performance  of any other
         obligation under,  arising out of, or in connection with, the Preferred
         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 permitted by the Indenture);

                  (c) any failure,  omission,  delay or lack of diligence on the
         part  of  the  Holders  to  enforce,  assert  or  exercise  any  right,
         privilege,  power or remedy  conferred  on the Holders  pursuant to the
         terms of the  Preferred  Securities,  or any  action on the part of the
         Issuer 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 Issuer or any of the assets of the Issuer;

                  (e)  any invalidity of, or defect or deficiency in, the 
         Preferred 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  5.03  that the  obligations  of the
         Guarantor  hereunder shall be absolute and unconditional  under any and
         all circumstances.

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

                  SECTION  5.04  Rights  of  Holders.  The  Guarantor  expressly
acknowledges  that:  (i) this  Guarantee  Agreement  will be deposited  with the
Guarantee Trustee to be held for the benefit of the Holders;  (ii) the Guarantee
Trustee  has the right to  enforce  this  

                                   -12-


Guarantee Agreement on behalf of the Holders; (iii) the Holders of a Majority in
liquidation  amount of the  Preferred  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  Agreement or exercising any
trust or power  conferred  upon  the  Guarantee  Trustee  under  this  Guarantee
Agreement; and (iv) any Holder may institute a legal proceeding directly against
the Guarantor to enforce its rights under this Guarantee Agreement without first
instituting a legal proceeding against the Issuer or any other person or entity.

                  SECTION 5.05 Guarantee of Payment.  This  Guarantee  Agreement
creates a guarantee of payment and not of collection.  This Guarantee  Agreement
will not be  discharged  except by payment  of the  Guarantee  Payments  in full
(without duplication).

                  SECTION 5.06 Subrogation. The Guarantor shall be subrogated to
all (if any) rights of the Holders  against the Issuer in respect of any amounts
paid to the Holders by the Guarantor under this Guarantee  Agreement;  provided,
however,  that the  Guarantor  shall  not  (except  to the  extent  required  by
mandatory provisions of law) be entitled to enforce or exercise any rights which
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  Agreement,
if, at the time of any such payment,  any amounts of Guarantee  Payments are due
and unpaid under this  Guarantee  Agreement.  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 Holders.

                  SECTION   5.07   Independent   Obligations.    The   Guarantor
acknowledges  that its obligations  hereunder are independent of the obligations
of the Issuer with respect to the  Preferred  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 Agreement notwithstanding the occurrence
of any event referred to in subsections (a) through (g),  inclusive,  of Section
5.03.


                                  ARTICLE VI

                                SUBORDINATION

                  SECTION 6.01  Subordination.  This  Guarantee  Agreement  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, including the Debentures, except those made pari passu or subordinate
by their terms,  (ii) pari passu 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  or
preference  stock of any  Affiliate  of the  Guarantor,  and (iii) senior to all
common  stock of the  Guarantor.  Nothing in

                                   -13-


this  Section  6.01 shall  apply to claims  of, or  payments  to, the  Guarantee
Trustee under or pursuant to Section 4.02 hereof.


                                   ARTICLE VII

                                   TERMINATION

                  SECTION  7.01  Termination.  This  Guarantee  Agreement  shall
terminate  and be of no further  force and effect upon:  (i) full payment of the
Redemption  Price  of all  Preferred  Securities,  and all  accrued  and  unpaid
Distributions to the date of redemption,  (ii) the distribution of Debentures to
Holders in exchange for all of the Preferred Securities or (iii) full payment of
the amounts payable in accordance  with the Trust Agreement upon  liquidation of
the  Issuer.  Notwithstanding  the  foregoing,  this  Guarantee  Agreement  will
continue to be  effective or will be  reinstated,  as the case may be, if at any
time any  Holder  must  restore  payment  of any sums paid with  respect  to the
Preferred Securities or under this Guarantee Agreement.


                                  ARTICLE VIII

                                  MISCELLANEOUS

                  SECTION  8.01  Successors  and  Assigns.  All  guarantees  and
agreements  contained in this  Guarantee  Agreement  shall bind the  successors,
assigns,  receivers,  trustees and  representatives  of the  Guarantor and shall
inure  to  the  benefit  of  the  Holders  of  the  Preferred   Securities  then
outstanding. Except in connection with a consolidation, merger or sale involving
the Guarantor  that is permitted  under  Article  Eleven of the  Indenture,  the
Guarantor shall not assign its obligations hereunder.

                  SECTION  8.02  Amendments.  This  Guarantee  Agreement  may be
amended only by an instrument  in writing  entered into by the Guarantor and the
Guarantee  Trustee.  Except with respect to any changes which do not  materially
adversely affect the rights of Holders (in which case no consent of Holders will
be  required),  this  Guarantee  Agreement  may only be  amended  with the prior
approval of the Holders of not less than 66 2/3% in aggregate liquidation amount
of all the outstanding Preferred Securities. The provisions of Article VI of the
Trust Agreement concerning meetings of Holders shall apply to the giving of such
approval. Nothing herein contained shall be deemed to require that the Guarantee
Trustee enter into any amendment of this Guarantee Agreement.

                  SECTION   8.03   Notices.   Any   notice,   request  or  other
communication  required or permitted to be given  hereunder shall be in writing,
duly signed by the party giving such notice, and delivered, telecopied or mailed
by first class mail as follows:

                                   -14-


                  (a) if given to the Guarantor,  to the address set forth below
         or such  other  address  as the  Guarantor  may give  notice  of to the
         Holders of the Preferred Securities:

                                    Minnesota Power & Light Company
                                    30 West Superior Street
                                    Duluth, Minnesota  55802
                                    Facsimile No:  (218) 723-3912
                                    Attention:  James K. Vizanko

                  (b) if  given  to the  Issuer,  in care of the  Administrative
         Trustees,  at the Issuer's (and the  Administrative  Trustee's) address
         set forth below or such other address as the Administrative Trustees on
         behalf of the Issuer may give notice of to the Holders:

                                    MP&L Capital I
                                    c/o Minnesota Power & Light Company
                                    30 West Superior Street
                                    Duluth, Minnesota  55802
                                    Facsimile No:  (218) 723-3912
                                    Attention:  Administrative Trustees

                  (c) if given to the  Guarantee  Trustee,  to the  address  set
         forth  below or such other  address as the  Guarantee  Trustee may give
         notice of to the Holders of the Preferred Securities:

                                    The Bank of New York
                                    101 Barclay Street, 21 West
                                    New York, New York 10286

                                    Facsimile No: (212) 815-5915
                                    Attention: Corporate Trust Administration

                  (d)  if given to any Holder, at the address set forth on the 
         books and records of the Issuer.

                  All notices  hereunder 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.

                                   -15-


                  SECTION 8.04 Benefit.  This Guarantee  Agreement is solely for
the benefit of the Holders and,  subject to Section  3.01(a),  is not separately
transferable from the Preferred Securities.

                  SECTION  8.05  Interpretation.  In this  Guarantee  Agreement,
unless the context otherwise requires:

                  (a) Capitalized terms used in this Guarantee Agreement but not
         defined in the preamble hereto have the respective meanings assigned to
         them in Section 1.01;

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

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

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

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

                  (f)  a reference to the singular includes the plural and vice 
         versa; and

                  (g) the  masculine,  feminine  or neuter  genders  used herein
         shall include the masculine, feminine and neuter genders.

                  SECTION 8.06 Governing Law. This Guarantee  Agreement shall be
governed by and construed  and  interpreted  in accordance  with the laws of the
State of New York.

                  This instrument may be executed in any number of counterparts,
each of which  so  executed  shall be  deemed  to be an  original,  but all such
counterparts shall together constitute but one and the same instrument.

                                   -16-


                  THIS  GUARANTEE  AGREEMENT  is executed as of the day and year
first above written.

                                      Minnesota Power & Light Company

                                      By:  D. G. Gartzke
                                         ---------------------------------------
                                           Name: David G. Gartzke
                                           Title: Senior Vice President-Finance
                                                  and Chief Financial Officer


                                      The Bank of New York,
                                      as Guarantee Trustee

                                      By:  Helen M. Cotiaux
                                         ---------------------------------------
                                           Name: Helen M. Cotiaux
                                           Title: Vice President



                                   -17-