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

                         ARIZONA PUBLIC SERVICE COMPANY

                                       TO

                            THE CHASE MANHATTAN BANK

                                     TRUSTEE

                          Fourth Supplemental Indenture

                           Dated as of August 1, 2000

                                       To

                                    Indenture

                          Dated as of January 15, 1998

                                   ----------

                              7 5/8% Notes Due 2005

                  ---------------------------------------------
<PAGE>
     FOURTH SUPPLEMENTAL INDENTURE,  dated as of August 1, 2000, between Arizona
Public Service Company, a corporation duly organized and existing under the laws
of the State of Arizona  (herein  called the  "Company"),  having its  principal
office  at 400  North  Fifth  Street,  Phoenix,  Arizona  85004,  and The  Chase
Manhattan  Bank, a New York banking  corporation,  as Trustee (herein called the
"Trustee")  under the Indenture dated as of January 15, 1998 between the Company
and the Trustee (the "Indenture").

                             RECITALS OF THE COMPANY

     The Company has  executed  and  delivered  the  Indenture to the Trustee to
provide for the issuance from time to time of its unsecured debentures, notes or
other evidences of indebtedness (the "Securities"), said Securities to be issued
in one or more series as in the Indenture provided.

     Pursuant to the terms of the Indenture,  the Company desires to provide for
the  establishment  of a new series of its  Securities to be known as its 7 5/8%
Notes Due 2005 (herein  called the "Notes Due 2005"),  the form and substance of
such Notes Due 2005 and the terms, provisions,  and conditions thereof to be set
forth as provided in the Indenture and this Fourth Supplemental Indenture.

     All things  necessary  to make this Fourth  Supplemental  Indenture a valid
agreement of the Company,  and to make the Notes Due 2005,  when executed by the
Company and authenticated and delivered by the Trustee, the valid obligations of
the Company, have been done.

         NOW, THEREFORE, THIS FOURTH SUPPLEMENTAL INDENTURE WITNESSETH:

     For and in  consideration of the premises and the purchase of the Notes Due
2005 by the Holders  thereof,  and for the purpose of setting forth, as provided
in the  Indenture,  the form and  substance of the Notes Due 2005 and the terms,
provisions,  and conditions  thereof,  it is mutually agreed,  for the equal and
proportionate benefit of all Holders of the Notes Due 2005, as follows:

                                   ARTICLE ONE

                         GENERAL TERMS AND CONDITIONS OF
                               THE NOTES DUE 2005

     SECTION 101. There shall be and is hereby authorized a series of Securities
designated the "7 5/8% Notes Due 2005" limited in aggregate  principal amount to
$300,000,000,  which amount  shall be as set forth in any Company  Order for the
authentication  and delivery of Notes Due 2005.  The Notes Due 2005 shall mature
and the principal shall be due and payable  together with all accrued and unpaid
interest  thereon  on  August  1,  2005,  and  shall  be  issued  in the form of
registered Notes Due 2005 without coupons.

     SECTION  102.  The Notes Due 2005  shall be  issued in  certificated  form,
except that the Notes Due 2005 shall be issued initially as a Global Security to
and  registered  in the name of Cede & Co., as nominee of The  Depository  Trust

                                        2
<PAGE>
Company, as Depositary therefor.  Any Notes Due 2005 to be issued or transferred
to, or to be held by, Cede & Co. (or any  successor  thereof)  for such  purpose
shall bear the depositary  legend in substantially the form set forth at the top
of the form of Note Due 2005 in Article Two hereof (in lieu of that set forth in
Section 204 of the  Indenture),  unless  otherwise  agreed by the Company,  such
agreement to be confirmed in writing to the Trustee. Such Global Security may be
exchanged in whole or in part for Notes Due 2005 registered, and any transfer of
such Global Security in whole or in part may be registered, in the name or names
of  Persons  other  than such  Depositary  or a nominee  thereof  only under the
circumstances  set forth in Clause (2) of the last  paragraph  of Section 305 of
the Indenture,  or such other  circumstances  in addition to or in lieu of those
set forth in Clause (2) of the last paragraph of Section 305 of the Indenture as
to which the Company shall agree,  such  agreement to be confirmed in writing to
the Trustee.  Principal  of, and premium,  if any, and interest on the Notes Due
2005 will be payable,  the  transfer of Notes Due 2005 will be  registrable  and
Notes Due 2005 will be exchangeable  for Notes Due 2005 bearing  identical terms
and  provisions,  at the  office or  agency of the  Company  in the  Borough  of
Manhattan,  The City and State of New York; PROVIDED,  HOWEVER,  that payment of
interest  may be made at the  option  of the  Company  by  check  mailed  to the
registered holder at such address as shall appear in the Security Register.

     SECTION  103.  Each Note Due 2005 will bear  interest at the rate of 7 5/8%
from  August  7,  2000 or  from  the  most  recent  Interest  Payment  Date  (as
hereinafter  defined) to which interest has been paid or duly provided for until
the principal thereof is paid or made available for payment, payable on February
1 and August 1 of each year (each, an "Interest  Payment  Date"),  commencing on
February  1,  2001,  to the  person  in  whose  name  such  Note Due 2005 or any
Predecessor  Security is registered,  at the close of business on the January 15
or July 15,  as the case may be,  whether  or not a  Business  Day,  immediately
preceding  the  Interest  Payment  Date.  Any  such  interest   installment  not
punctually  paid or duly provided for shall forthwith cease to be payable to the
registered holders on such regular record date, and may be paid to the person in
whose  name  the  Note  Due  2005  (or one or more  Predecessor  Securities)  is
registered at the close of business on a special  record date to be fixed by the
Trustee for the payment of such  defaulted  interest,  notice  whereof  shall be
given to the  registered  holders  of the  Notes  Due 2005 not less than 10 days
prior to such  special  record  date,  or may be paid at any  time in any  other
lawful manner not inconsistent with the requirements of any securities  exchange
on which  the  Notes  Due 2005 may be  listed,  and upon  such  notice as may be
required by such exchange, all as more fully provided in the Indenture.

     The amount of interest payable for any period will be computed on the basis
of a 360-day year of twelve 30-day  months.  Interest will accrue from August 7,
2000 to, but not  including,  the relevant  payment  date. In the event that any
date on which  interest is payable on the Notes Due 2005 is not a Business  Day,
then  payment  of  interest  payable  on such  date  will  be  made on the  next
succeeding  day which is a  Business  Day (and  without  any  interest  or other
payment  in  respect  of any such  delay),  in each case with the same force and
effect as if made on such date.  A "Business  Day" shall mean any day,  except a
Saturday,  a Sunday or a legal  holiday in The City of New York on which banking
institutions are authorized or required by law, regulation or executive order to
close.

                                        3
<PAGE>
     SECTION 104. The Company,  at its option,  may redeem all, or, from time to
time any part of the Notes Due 2005, upon notice as provided in the Indenture at
a Redemption Price equal to the greater of (a) the principal amount of the Notes
Due 2005 (or portion  thereof) to be redeemed  plus interest (if any) accrued to
the Redemption  Date or (b) the Make-Whole  Amount with respect to the Notes Due
2005 to be redeemed.

     For  purposes  of this  Section  104,  the  following  terms shall have the
following meanings:

          "MAKE-WHOLE AMOUNT" means the sum, as determined by a Quotation Agent,
of the  present  values  of the  principal  amount  of the  Notes Due 2005 to be
redeemed, together with scheduled payments of interest (exclusive of interest to
the  Redemption  Date) from the  Redemption  Date to the Stated  Maturity of the
Notes Due 2005, in each case  discounted to the Redemption Date on a semi-annual
basis,  assuming a 360-day  year  consisting  of twelve  30-day  months,  at the
Adjusted  Treasury Rate, plus accrued  interest (if any) on the principal amount
of the Notes Due 2005 being redeemed to the Redemption Date.

          "ADJUSTED  TREASURY RATE" means,  with respect to any Redemption Date,
(i)  the  yield,  under  the  heading  which  represents  the  average  for  the
immediately preceding week, appearing in the most recently published statistical
release designated "H.15 (519)" or any successor  publication which is published
weekly  by the  Board of  Governors  of the  Federal  Reserve  System  and which
establishes yields on actively traded United States Treasury securities adjusted
to constant maturity under the caption "Treasury  Constant  Maturities," for the
maturity  corresponding  to the  Comparable  Treasury  Issue (if no  maturity is
within three months  before or after the  remaining  term of the Notes Due 2005,
yields  for the two  published  maturities  most  closely  corresponding  to the
Comparable  Treasury  Issue shall be determined  and the Adjusted  Treasury Rate
shall be interpolated or extrapolated from such yields on a straight line basis,
rounding  to the  nearest  month)  or  (ii) if such  release  (or any  successor
release) is not published during the week preceding the calculation date or does
not contain such yields,  the rate per year equal to the semi-annual  equivalent
yield to maturity of the Comparable Treasury Issue, calculated using a price for
the  Comparable  Treasury  Issue  (expressed  as a percentage  of its  principal
amount) equal to the Comparable Treasury Price for such Redemption Date, in each
case calculated on the third Business Day preceding the Redemption Date, plus in
each case 0.35%.

          "COMPARABLE  TREASURY ISSUE" means the United States Treasury security
selected by the Quotation Agent as having a maturity comparable to the remaining
term from the Redemption  Date to the Stated Maturity of the Notes Due 2005 that
would be utilized,  at the time of selection  and in accordance  with  customary
financial  practice,  in pricing  new issues of  corporate  debt  securities  of
comparable maturity to the remaining term of the Notes Due 2005.

          "QUOTATION AGENT" means the Reference  Treasury Dealer selected by the

Trustee after consultation with the Company.

          "REFERENCE TREASURY DEALER" means a primary U.S. Government securities
dealer selected by the Company.

                                        4
<PAGE>
          "COMPARABLE  TREASURY  PRICE"  means,  with respect to any  Redemption
Date, if clause (ii) of the definition of Adjusted  Treasury Rate is applicable,
the  average of three,  or such lesser  number as is  obtained  by the  Trustee,
Reference Treasury Dealer Quotations for such Redemption Date.

          "REFERENCE  TREASURY DEALER  QUOTATIONS"  means,  with respect to each
Reference Treasury Dealer and any Redemption Date, the average, as determined by
the Trustee,  of the bid and asked  prices for the  Comparable  Treasury  Issue,
expressed  in each  case as a  percentage  of its  principal  amount,  quoted in
writing to the Trustee by such Reference  Treasury Dealer at 5:00 p.m., New York
City time, on the third Business Day preceding such Redemption Date.

     The  Trustee  shall be  under no duty to  inquire  into,  may  conclusively
presume  the  correctness  of, and shall be fully  protected  in acting upon the
Company's calculation of any Redemption Price, including any Make-Whole Amount.

     The Company shall give the Trustee written notice of the Redemption  Price,
promptly after the calculation thereof.

     Notwithstanding  Section 1104 of the  Indenture,  any notice of  redemption
given pursuant to said Section with respect to the foregoing redemption need not
set forth the Redemption Price but only the manner of calculation thereof.

     SECTION  105.  The Notes Due 2005 shall be  defeasible  pursuant to Section
1302 or 1303 of the Indenture.

                                   ARTICLE TWO

                             FORM OF NOTES DUE 2005

     SECTION  201.  The  Notes  Due  2005  and  the  Trustee's   certificate  of
authentication  to be endorsed  thereon are to be substantially in the following
forms:

Form of Face of Security:

UNLESS THIS  CERTIFICATE  IS PRESENTED BY AN  AUTHORIZED  REPRESENTATIVE  OF THE
DEPOSITORY  TRUST COMPANY,  A NEW YORK  CORPORATION  ("DTC"),  TO ARIZONA PUBLIC
SERVICE COMPANY OR ITS AGENT FOR REGISTRATION OF TRANSFER, EXCHANGE, OR PAYMENT,
AND ANY  CERTIFICATE  ISSUED IS  REGISTERED IN THE NAME OF CEDE & CO. OR IN SUCH
OTHER  NAME AS IS  REQUESTED  BY AN  AUTHORIZED  REPRESENTATIVE  OF DTC (AND ANY
PAYMENT  IS MADE TO CEDE & CO. OR TO SUCH  OTHER  ENTITY AS IS  REQUESTED  BY AN
AUTHORIZED REPRESENTATIVE OF DTC), ANY TRANSFER, PLEDGE, OR OTHER USE HEREOF FOR
VALUE OR  OTHERWISE BY OR TO ANY PERSON IS WRONGFUL  INASMUCH AS THE  REGISTERED
OWNER HEREOF, CEDE & CO., HAS AN INTEREST HEREIN.

                                        5
<PAGE>
                         ARIZONA PUBLIC SERVICE COMPANY

                              7 5/8% Note Due 2005

No. _________                                                       $300,000,000
                                                           CUSIP No. 040555 CA O

     Arizona Public Service  Company,  a corporation duly organized and existing
under the laws of Arizona (herein called the "Company",  which term includes any
successor  Person  under  the  Indenture  hereinafter  referred  to),  for value
received,  hereby  promises to pay to Cede & Co.,  or  registered  assigns,  the
principal sum of Three  Hundred  Million  Dollars on August 1, 2005,  and to pay
interest  thereon from August 7, 2000 or from the most recent  Interest  Payment
Date to which  interest has been paid or duly  provided  for,  semi-annually  in
arrears on February 1 and August 1 in each year, commencing February 1, 2001, at
the rate of 7 5/8%,  until the  principal  hereof is paid or made  available for
payment.

     The interest so payable,  and punctually  paid or duly provided for, on any
Interest Payment Date will, as provided in such Indenture, be paid to the Person
in  whose  name  this  Security  (or  one or  more  Predecessor  Securities)  is
registered  at the  close  of  business  on the  Regular  Record  Date  for such
interest,  which  shall  be the  January  15 or July  15,  as the  case  may be,
immediately preceding the Interest Payment Date (whether or not a Business Day).
Any such  interest not so punctually  paid or duly  provided for will  forthwith
cease to be payable to the Holder on such Regular  Record Date and may either be
paid to the  Person in whose  name  this  Security  (or one or more  Predecessor
Securities)  is registered at the close of business on a Special Record Date for
the  payment  of such  Defaulted  Interest  to be fixed by the  Trustee,  notice
whereof  shall be given to Holders of Securities of this series not less than 10
days  prior to such  Special  Record  Date,  or be paid at any time in any other
lawful manner not inconsistent with the requirements of any securities  exchange
on which the  Securities  of this series may be listed,  and upon such notice as
may be required by such exchange, all as more fully provided in said Indenture.

     Payment of the principal of (and premium,  if any) and any interest on this
Security will be made at the office or agency of the Company maintained for that
purpose in The City of New York,  in such coin or currency of the United  States
of America as at the time of payment is legal  tender for  payment of public and
private debts;  provided,  however, that at the option of the Company payment of
interest  may be made by check  mailed to the  address  of the  Person  entitled
thereto as such address shall appear in the Security Register.

     Reference  is hereby made to the further  provisions  of this  Security set
forth on the reverse  hereof,  which further  provisions  shall for all purposes
have the same effect as if set forth at this place.

                                        6
<PAGE>
     Unless the  certificate of  authentication  hereon has been executed by the
Trustee  referred to on the reverse  hereof by manual  signature,  this Security
shall  not be  entitled  to any  benefit  under  the  Indenture  or be  valid or
obligatory for any purpose.

     IN WITNESS  WHEREOF,  the  Company has caused  this  instrument  to be duly
executed under its corporate seal.

                                        ARIZONA PUBLIC SERVICE COMPANY


                                        By
                                           -------------------------------------
                                           Vice President, Finance

Attest:


------------------------------
Vice President and Secretary
Form of Reverse of Security.

     This  Security  is one of a duly  authorized  issue  of  securities  of the
Company (herein called the "Securities"), issued and to be issued in one or more
series  under an  Indenture,  dated as of January  15, 1998  (herein  called the
"Indenture",  which  term  shall  have  the  meaning  assigned  to  it  in  such
instrument),  between  the  Company  and The Chase  Manhattan  Bank,  as Trustee
(herein  called the "Trustee",  which term includes any successor  trustee under
the Indenture), and reference is hereby made to the Indenture for a statement of
the respective rights,  limitations of rights,  duties and immunities thereunder
of the Company,  the Trustee and the Holders of the  Securities and of the terms
upon which the Securities are, and are to be, authenticated and delivered.  This
Security  is  one of the  series  designated  on the  face  hereof,  limited  in
aggregate principal amount to $300,000,000.

     The Securities of this series are subject to redemption  upon not less than
30 days' notice by mail at the option of the Company,  in whole or in part, from
time to time at a  Redemption  Price equal to the  greater of (a) the  principal
amount of the Securities (or portion thereof) of this series to be redeemed plus
interest (if any) accrued to the Redemption  Date or (b) the  Make-Whole  Amount
(as defined  below) with respect to the Securities of this series to be redeemed
(the "Redemption Price").

     If notice has been given as  provided  in the  Indenture  and funds for the
redemption of any  Securities  (or any portion  thereof)  called for  redemption
shall  have been made  available  on the  Redemption  Date  referred  to in such
notice,  such Securities (or any portion thereof) will cease to bear interest on
the date fixed for such  redemption  specified in such notice and the only right
of the Holders of such  Securities  will be to receive payment of the Redemption
Price.

     Notice of any  optional  redemption  of  Securities  of this series (or any
portion  thereof) will be given to Holders at their  addresses,  as shown in the
Security  Register for such  Securities,  not more than 60 nor less than 30 days
prior to the date fixed for  redemption.  The notice of redemption will specify,

                                        7
<PAGE>
among other items,  the Redemption  Price or, if not  then known,  the manner of
calculation  thereof,  and the principal amount of the Securities of this series
held by such Holder to be redeemed.  If less than all of the  Securities of this
series  are to be  redeemed  at the option of the  Company,  the  Trustee  shall
select,  in such  manner as it shall deem fair and  appropriate,  the portion of
such Securities to be redeemed in whole or in part.

     As used herein:

         "MAKE-WHOLE  AMOUNT" means the sum, as determined by a Quotation Agent,
of the present  values of the principal  amount of the Securities of this series
to be redeemed,  together  with  scheduled  payments of interest  (exclusive  of
interest to the Redemption Date) from the Redemption Date to the Stated Maturity
of the Securities of this series, in each case discounted to the Redemption Date
on a  semi-annual  basis,  assuming a 360-day year  consisting  of twelve 30-day
months,  at the Adjusted  Treasury Rate,  plus accrued  interest (if any) on the
principal  tamount  of the  Securities  of this  series  being  redeemed  to the
Redemption Date.

         "ADJUSTED  TREASURY RATE" means,  with respect to any Redemption  Date,
(i)  the  yield,  under  the  heading  which  represents  the  average  for  the
immediately preceding week, appearing in the most recently published statistical
release designated "H.15 (519)" or any successor  publication which is published
weekly  by the  Board of  Governors  of the  Federal  Reserve  System  and which
establishes yields on actively traded United States Treasury securities adjusted
to constant maturity under the caption "Treasury  Constant  Maturities," for the
maturity  corresponding  to the  Comparable  Treasury  Issue (if no  maturity is
within three months before or after the remaining term of the Securities of this
series,  yields for the two published  maturities most closely  corresponding to
the Comparable Treasury Issue shall be determined and the Adjusted Treasury Rate
shall be interpolated or extrapolated from such yields on a straight line basis,
rounding  to the  nearest  month)  or  (ii) if such  release  (or any  successor
release) is not published during the week preceding the calculation date or does
not contain such yields,  the rate per year equal to the semi-annual  equivalent
yield to maturity of the Comparable Treasury Issue, calculated using a price for
the  Comparable  Treasury  Issue  (expressed  as a percentage  of its  principal
amount) equal to the Comparable Treasury Price for such Redemption Date, in each
case calculated on the third Business Day preceding the Redemption Date, plus in
each case 0.35%.

          "COMPARABLE  TREASURY ISSUE" means the United States Treasury security
selected by the Quotation Agent as having a maturity comparable to the remaining
term from the Redemption  Date to the Stated  Maturity of the Securities of this
series that would be utilized,  at the time of selection and in accordance  with
customary financial practice, in pricing new issues of corporate debt securities
of comparable maturity to the remaining term of the Securities of this series.

          "QUOTATION AGENT" means the Reference  Treasury Dealer selected by the
Trustee after consultation with the Company.

          "REFERENCE TREASURY DEALER" means a primary U.S. Government securities
dealer selected by the Company.

                                        8
<PAGE>
          "COMPARABLE  TREASURY  PRICE"  means,  with respect to any  Redemption
Date, if clause (ii) of the definition of Adjusted  Treasury Rate is applicable,
the  average of three,  or such lesser  number as is  obtained  by the  Trustee,
Reference Treasury Dealer Quotations for such Redemption Date.

          "REFERENCE  TREASURY DEALER  QUOTATIONS"  means,  with respect to each
Reference Treasury Dealer and any Redemption Date, the average, as determined by
the Trustee,  of the bid and asked  prices for the  Comparable  Treasury  Issue,
expressed  in each  case as a  percentage  of its  principal  amount,  quoted in
writing to the Trustee by such Reference  Treasury Dealer at 5:00 p.m., New York
City time, on the third Business Day preceding such Redemption Date.

     The Securities of this series will not be subject to any sinking fund.

     In the event of redemption of this Security in part only, a new Security or
Securities of this series and of like tenor for the  unredeemed  portion  hereof
will be issued in the name of the Holder hereof upon the cancellation hereof.

     The Indenture contains  provisions for defeasance at any time of the entire
indebtedness  of the  Security or certain  restrictive  covenants  and Events of
Default with respect to this Security, in each case upon compliance with certain
conditions set forth in the Indenture.

     If an Event of Default  with  respect to  Securities  of this series  shall
occur and be  continuing,  the principal of the Securities of this series may be
declared  due and  payable in the manner  and with the  effect  provided  in the
Indenture.

     The Indenture  permits,  with certain  exceptions as therein provided,  the
amendment  thereof and the  modification  of the rights and  obligations  of the
Company  and the rights of the  Holders of the  Securities  of each series to be
affected under the Indenture at any time by the Company and the Trustee  without
the consent of such Holders in certain limited circumstances or with the consent
of the  Holders of 66-2/3% in  principal  amount of the  Securities  at the time
Outstanding  of  each  series  to  be  affected.  The  Indenture  also  contains
provisions  permitting the Holders of specified  percentages in principal amount
of the  Securities  of each  series  at the time  Outstanding,  on behalf of the
Holders of all  Securities  of such series,  to waive  compliance by the Company
with certain  provisions of the  Indenture  and certain past defaults  under the
Indenture  and their  consequences.  Any such consent or waiver by the Holder of
this  Security  shall be  conclusive  and binding  upon such Holder and upon all
future Holders of this Security and of any Security issued upon the registration
of transfer  hereof or in  exchange  herefor or in lieu  hereof,  whether or not
notation of such consent or waiver is made upon this Security.

     As provided in and subject to the provisions of the  Indenture,  the Holder
of this  Security  shall not have the right to  institute  any  proceeding  with
respect to the Indenture or for the  appointment of a receiver or trustee or for
any other remedy thereunder,  unless such Holder shall have previously given the
Trustee  written  notice of a  continuing  Event of Default  with respect to the
Securities of this series,  the Holders of not less than 25% in principal amount

                                        9
<PAGE>
of the Securities of this series at the time Outstanding shall have made written
request to the  Trustee  to  institute  proceedings  in respect of such Event of
Default as Trustee and offered the Trustee reasonable indemnity, and the Trustee
shall not have  received  from the Holders of a majority in principal  amount of
Securities of this series at the time Outstanding a direction  inconsistent with
such  request,  and shall have failed to institute any such  proceeding,  for 60
days after receipt of such notice, request and offer of indemnity. The foregoing
shall not apply to any suit  instituted  by the Holder of this  Security for the
enforcement of any payment of principal hereof or any premium or interest hereon
on or after the respective due dates expressed herein.

     No reference  herein to the  Indenture and no provision of this Security or
of the Indenture  shall alter or impair the obligation of the Company,  which is
absolute and unconditional, to pay the principal of and any premium and interest
on this  Security  at the times,  place and rate,  and in the coin or  currency,
herein prescribed.

     As provided in the Indenture and subject to certain limitations therein set
forth,  the transfer of this Security is registrable  in the Security  Register,
upon  surrender of this Security for  registration  of transfer at the office or
agency of the  Company in any place where the  principal  of and any premium and
interest on this  Security are payable,  duly endorsed by, or  accompanied  by a
written  instrument  of  transfer  in form  satisfactory  to the Company and the
Security  Registrar  duly  executed by, the Holder  hereof or his attorney  duly
authorized in writing,  and thereupon one or more new  Securities of this series
and of like  tenor,  of  authorized  denominations  and for the  same  aggregate
principal amount, will be issued to the designated transferee or transferees.

     The Securities of this series are issuable only in registered  form without
coupons  in  denominations  of $1,000  and any  integral  multiple  thereof.  As
provided in the Indenture and subject to certain  limitations therein set forth,
Securities of this series are exchangeable for a like aggregate principal amount
of  Securities  of this  series  and of like  tenor  of a  different  authorized
denomination, as requested by the Holder surrendering the same.

     No service  charge shall be made for any such  registration  of transfer or
exchange,  but the Company may require  payment of a sum sufficient to cover any
tax or other governmental charge payable in connection therewith.

     Prior to due presentment of this Security for registration of transfer, the
Company,  the  Trustee and any agent of the Company or the Trustee may treat the
Person in whose name this  Security is  registered  as the owner  hereof for all
purposes,  whether or not this Security be overdue, and neither the Company, the
Trustee nor any such agent shall be affected by notice to the contrary.

     All terms used in this Security  which are defined in the  Indenture  shall
have the meanings assigned to them in the Indenture.

Form of Trustee's Certificate of Authentication.

                                       10
<PAGE>
                          CERTIFICATE OF AUTHENTICATION

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

Dated:                                 THE CHASE MANHATTAN BANK
      ----------------------------                                    AS TRUSTEE


                                        By
                                           -------------------------------------
                                                              AUTHORIZED OFFICER


                                  ARTICLE THREE

                        ORIGINAL ISSUE OF NOTES DUE 2005

     SECTION  301.  Notes  Due  2005  in  the  aggregate   principal  amount  of
$300,000,000 may, upon execution of this Fourth Supplemental  Indenture, or from
time to time thereafter, be executed by the Company and delivered to the Trustee
for  authentication,  and the Trustee shall thereupon  authenticate  and deliver
said Notes Due 2005 in accordance  with a Company Order delivered to the Trustee
by the Company, without any further action by the Company.

                                  ARTICLE FOUR

                           PAYING AGENT AND REGISTRAR

     SECTION 401. The Chase Manhattan Bank will be the Paying Agent and Security
Registrar for the Notes Due 2005.

                                  ARTICLE FIVE

                                SUNDRY PROVISIONS

     SECTION  501.  Except  as  otherwise  expressly  provided  in  this  Fourth
Supplemental  Indenture  or in the form of Notes Due 2005 or  otherwise  clearly
required by the context hereof or thereof, all terms used herein or in said form
of Notes Due 2005 that are  defined  in the  Indenture  shall  have the  several
meanings respectively assigned to them thereby.

     SECTION 502. The Indenture,  as heretofore supplemented and amended, and as
supplemented by this Fourth Supplemental  Indenture, is in all respects ratified
and confirmed,  and this Fourth  Supplemental  Indenture shall be deemed part of
the Indenture in the manner and to the extent herein and therein provided.

                                       11
<PAGE>
     SECTION  503.  The  Trustee  hereby  accepts  the trusts  herein  declared,
provided, created,  supplemented, or amended and agrees to perform the same upon
the terms and conditions herein and in the Indenture, as heretofore supplemented
and amended, set forth and upon the following terms and conditions:

     The Trustee shall not be  responsible  in any manner  whatsoever  for or in
respect of the validity or sufficiency of this Fourth Supplemental  Indenture or
for or in respect of the recitals  contained  herein,  all of which recitals are
made by the  Company  solely.  In  general,  each and every  term and  condition
contained in Article Six of the Indenture shall apply to and form a part of this
Fourth Supplemental Indenture with the same force and effect as if the same were
herein set forth in full with such omissions,  variations,  and  insertions,  if
any, as may be  appropriate  to make the same conform to the  provisions of this
Fourth Supplemental Indenture.

     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.

                                       12
<PAGE>
     IN WITNESS WHEREOF, the parties hereto have caused this Fourth Supplemental
Indenture  to be duly  executed,  and  their  respective  corporate  seals to be
hereunto affixed and attested, all as of the day and year first above written.


                                        ARIZONA PUBLIC SERVICE COMPANY


                                        By: Barbara M. Gomez
                                            ------------------------------------
                                            Barbara M. Gomez
                                            Treasurer

Attest:

Faye Widenmann
------------------------------------
Faye Widenmann
Vice President and Secretary


                                        THE CHASE MANHATTAN BANK, as Trustee


                                        By: P. Morabito
                                            ------------------------------------
                                            P. Morabito
                                            Vice President

Attest:

R. Lorenzen
------------------------------------
R. Lorenzen
Senior Trust Officer

                                       13
<PAGE>
STATE OF ARIZONA     )
                     ) ss.:
COUNTY OF MARICOPA   )

     On the 4th day of August, 2000, before me personally came Barbara M. Gomez,
to me known,  who,  being by me duly  sworn,  did depose and say that she is the
Treasurer of Arizona Public Service Company,  one of the corporations  described
in and which executed the foregoing instrument;  that she knows the seal of said
corporation;  that the seal affixed to said  instrument is such corporate  seal;
that  it was so  affixed  by  authority  of  the  Board  of  Directors  of  said
corporation; and that she signed her name thereto by like authority.

                                        Kris Fenex
                                        ----------------------------------------
                                        Notary Public

My Commission Expires:

August 16, 2002
----------------------


STATE OF NEW YORK    )
                     ) ss.:
COUNTY OF NEW YORK   )

     On the 4th day of August,  2000, before me personally came P. Morabito,  to
me known,  who,  being by me duly  sworn,  did depose and say that she is a Vice
President of The Chase Manhattan Bank, one of the corporations  described in and
which  executed  the  foregoing  instrument;  that  she  knows  the seal of said
corporation;  that the seal affixed to said  instrument is such corporate  seal;
that  it was so  affixed  by  authority  of  the  Board  of  Directors  of  said
corporation; and that she signed her name thereto by like authority.

                                        Emily Fayan
                                        ----------------------------------------
                                        Notary Public

My Commission Expires:

December 31, 2001
----------------------

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