PSI ENERGY, INC.

                                      AND

                               FIFTH THIRD BANK,
                                    Trustee



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

                          Sixth Supplemental Indenture

                           Dated as of April 30, 1999

                                       To

                                   Indenture

                         Dated as of November 15, 1996
                                ----------------



                          6.52% Senior Notes Due 2009













         SIXTH SUPPLEMENTAL  INDENTURE,  dated as of April 30, 1999, between PSI
Energy,  Inc., a corporation  duly  organized and existing under the laws of the
State of Indiana (herein called the "Company"),  having its principal  office at
1000 East Main Street, Plainfield,  Indiana 46168, and Fifth Third Bank, an Ohio
banking  corporation,  as  Trustee  (herein  called  the  "Trustee")  under  the
Indenture dated as of November 15, 1996 between the Company and the Trustee,  as
supplemented (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"),  to be issued in one or more
series as provided in the Indenture.

         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 6.52%
Senior  Notes  Due  2009  (herein  called  the  "Debentures"),   in  this  Sixth
Supplemental Indenture.

         All things necessary to make this Sixth Supplemental  Indenture a valid
agreement of the Company have been done.

         Now, Therefore, This Sixth Supplemental Indenture Witnesseth:

         For  and in  consideration  of the  premises  and the  purchase  of the
Debentures  by the Holders  thereof,  it is mutually  agreed,  for the equal and
proportionate benefit of all Holders of the Debentures, as follows:


                                   ARTICLE ONE

                             Terms of the Debentures

     Section 101. There is hereby  authorized a series of Securities  designated
the "6.52%  Senior  Notes Due 2009",  limited in aggregate  principal  amount to
$97,342,000  (except  as  provided  in  Section  301(2) of the  Indenture).  The
Debentures shall mature and the principal shall be due and payable together with
all accrued and unpaid interest thereon on March 15, 2009 and shall be issued in
the form of a registered Global Security without coupons, registered in the name
of Cede & Co., as nominee of the Depository Trust Company (the "Depositary").

     Section 102. The  provisions of Section 305 of the Indenture  applicable to
Global Securities shall apply to the Debentures.

     Section  103.   Interest  on  each  of  the  Debentures  shall  be  payable
semiannually  on March  15 and  September  15 in each  year  (each an  "Interest
Payment  Date"),  commencing  on  September  15,  1999,  at the rate  per  annum
specified in the form of Debentures, from and including, April 30, 1999, or from
the most recent  Interest  Payment Date to which  interest has been paid or duly
provided for. The interest so payable, and punctually paid or duly provided for,
on any  Interest  Payment  Date will be paid to the  Person  in whose  name such
Debenture (or one or more Predecessor  Securities) is registered at the close of
business on March 1 or September 1 next preceding the Interest Payment Date. The
amount of  interest  payable  for any period  will be computed on the basis of a
360-day year of twelve 30-day months.

     Section 104.  Subject to agreements  with or the rules of the Depositary or
any  successor  book-entry  security  system or similar  system with  respect to
Global  Securities,  payments  of interest  will be made by check  mailed to the
Holder of each  Debenture  at the address  shown in the Security  Register,  and
payments of the principal  amount of each  Debenture will be made at maturity by
check  against  presentation  of the  Debenture  at the  office or agency of the
Trustee.

     Section 105. The Debentures  shall be issued in  denominations of $1,000 or
any integral multiple of $1,000.

     Section 106.  Principal and interest on the Debentures  shall be payable in
the coin or currency  of the United  States of  America,  which,  at the time of
payment, is legal tender for public and private debts.

     Section 107. The  Debentures  shall be subject to  defeasance  and covenant
defeasance,  at the Company's  option, as provided for in Sections 1302 and 1303
of the Indenture.

         Section 108.  Subject to the terms of Article  Eleven of the Indenture,
the Company shall have the right to redeem the Debentures,  at any time in whole
or from time to time in part, until maturity,  (such  redemption,  a "Make-Whole
Redemption", and the date thereof, the "Redemption Date"), upon not less than 30
nor more than 60 days' notice to the holders, at a redemption price equal to the
sum of the principal  amount of the  Debentures  being redeemed plus accrued and
unpaid interest thereon to the Redemption  Date, and (ii) the Make-Whole  Amount
(as defined below), if any, with respect to the Debentures being redeemed.

         "Make-Whole Amount" means, in connection with any Make-Whole Redemption
of any  Debentures,  the  excess,  if any, of (i) the sum,  as  determined  by a
Quotation Agent (as defined herein) of the present value of the principal amount
of such  Debentures,  together  with  scheduled  payments of  interest  from the
Redemption  Date  to  the  Stated  Maturity  of the  Debentures,  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 (as
defined  herein) over (ii) 100% of the principal  amount of the Debentures to be
redeemed.

         "Adjusted Treasury Rate" means, with respect to any Redemption Date for
a Make-Whole Redemption,  the rate per annum 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,
calculated on the third business day preceding the Redemption Date, plus in each
case 0.20% (20 basis points).

         "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  Debentures  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 Debentures.

     "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.

         "Comparable  Treasury Price" means,  with respect to the any Redemption
Date for a  Make-Whole  Redemption,  (i) the average of the bid and asked prices
for the Comparable Treasury Issue (expressed in each case as a percentage of its
principal  amount) on the third business day preceding such Redemption  Date, as
set forth in the daily statistical  release  designated "H.15" (or any successor
release)  published by the Board of Governors of the Federal  Reserve  System or
(ii) if such  release (or any  successor  release) is not  published or does not
contain  such prices on such  business  day,  (A) the  average of the  Reference
Treasury Dealer Quotations for such Redemption Date, after excluding the highest
and lowest such  Reference  Treasury  Dealer  Quotations,  or (B) if the Trustee
obtains fewer than three such Reference Treasury Dealer Quotations,  the average
of such Quotations.

         "Reference  Treasury  Dealer  Quotations"  means,  with respect to each
Reference  Treasury Dealer and any Redemption Date for a Make-Whole  Redemption,
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.








                                   ARTICLE TWO

                             Form of the Debentures

     Section 201. The Debentures are to be  substantially  in the following form
and shall include  substantially  the legend shown so long as the Debentures are
Global Securities:


                           (FORM OF FACE OF DEBENTURE)


No. R-1                                                              $97,342,000

CUSIP No.  693627AL 5

                                PSI ENERGY, INC.

                           6.52% SENIOR NOTES DUE 2009


UNLESS THIS  CERTIFICATE  IS PRESENTED BY AN  AUTHORIZED  REPRESENTATIVE  OF THE
DEPOSITORY TRUST COMPANY, A NEW YORK CORPORATION ("DTC"), TO ISSUER OR ITS AGENT
FOR REGISTRATION OF TRANSFER,  EXCHANGE,  OR PAYMENT AND SUCH 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.

         PSI ENERGY,  INC., a corporation  duly organized and existing under the
laws of the State of Indiana  (herein called the "Company",  which term includes
any  successor  Person under the  Indenture  hereafter  referred  to), for value
received,  hereby  promises to pay to CEDE & CO.,  or  registered  assigns,  the
principal  sum of Ninety  Seven  Million  Three  Hundred  Forty Two Thousand and
No/100 Dollars  ($97,342,000.00)  on March 15, 2009, and to pay interest thereon
from, and  including,  April 30, 1999 or from the most recent  Interest  Payment
Date to which  interest has been paid or duly  provided  for,  semiannually,  on
March 15 and September 15, in each year,  commencing  September 15, 1999, at the
rate of 6.52% per annum,  until the principal  hereof is paid or made  available
for payment.  The amount of interest  payable on any Interest Payment Date shall
be computed on the basis of a 360-day year of twelve 30-day months. The interest
so payable,  and punctually  paid or duly provided for, on any Interest  Payment
Date will,  as  provided in the  Indenture,  be paid to the Person in whose name
this Security (or one or more Predecessor Securities) is registered at the close
of business on the March 1 or September 1 next preceding  such Interest  Payment
Date.  Any  such  interest  not so  punctually  paid or duly  provided  for will
forthwith  cease to be payable to the Holder on such Regular Record Date and may
either  be paid to the  Person  in  whose  name  this  Security  (or one or more
Predecessor  Securities)  is  registered  at the close of  business on a Special
Record  Date  for the  payment  of such  Defaulted  Interest  to be fixed by the
Trustee,  notice  whereof shall be given to Holders of Securities of this series
not less than 10 days prior to such Special  Record Date, or be paid at any time
in any  other  lawful  manner  not  inconsistent  with the  requirements  of any
securities  exchange on which the  Securities of this series may be listed,  and
upon such notice as may be required by such exchange, all as more fully provided
in the Indenture.

         Payment of the principal of (and premium,  if any) and interest on this
Security  will be made at the corporate  trust office of the Trustee  maintained
for that  purpose in the City of  Cincinnati,  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.

         Any payment on this Security due on any day which is not a Business Day
in the City of New York  need  not be made on such  day,  but may be made on the
next  succeeding  Business  Day with the same force and effect as if made on the
due date and no interest  shall  accrue for the period from and after such date,
unless such payment is a payment at maturity or upon  redemption,  in which case
interest shall accrue thereon at the stated rate for such additional days.

         As used herein,  "Business Day" means any day, other than a Saturday or
Sunday,  or a day on  which  banking  institutions  in New  York,  New  York are
authorized or obligated by law or executive order to be closed.

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

         Unless the  certificate of  authentication  hereon has been executed by
the Trustee referred to on the reverse hereof 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.

                                PSI ENERGY, INC.



                                 By.............




                          CERTIFICATE OF AUTHENTICATION

Dated:

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

                                        FIFTH THIRD BANK,
                                            as Trustee

                                        By...............
                                       Authorized Signatory




                                 (FORM OF REVERSE OF DEBENTURE)


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  November  15,  1996  (herein  called  the
"Indenture",  which  term  shall  have  the  meaning  assigned  to  it  in  such
instrument), between the Company and Fifth Third 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 $97,342,000.

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

The Securities of this series are subject to optional  redemption at any time in
whole  or from  time to  time in  part,  until  maturity,  (such  redemption,  a
"Make-Whole Redemption",  and the date thereof, the "Redemption Date"), upon not
less than 30 nor more than 60 days' notice to the holders, at a redemption price
equal to the sum of the principal  amount of the Debentures  being redeemed plus
accrued  and  unpaid  interest  thereon  to the  Redemption  Date,  and (ii) the
Make-Whole  Amount (as defined  below),  if any, with respect to the  Debentures
being redeemed.

"Make-Whole  Amount" means, in connection with any Make-Whole  Redemption of any
Debentures,  the excess,  if any, of (i) the sum, as  determined  by a Quotation
Agent (as defined  herein) of the present value of the principal  amount of such
Debentures,  together with  scheduled  payments of interest from the  Redemption
Date to the Stated  Maturity of the  Debentures,  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 (as defined  herein) over
(ii) 100% of the principal amount of the Debentures to be redeemed.

"Adjusted  Treasury  Rate"  means,  with  respect to any  Redemption  Date for a
Make-Whole  Redemption,  the rate per annum 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,
calculated on the third business day preceding the Redemption Date, plus in each
case 0.20% (20 basis points).

"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 Debentures 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 Debentures.

"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.

"Comparable Treasury Price" means, with respect to the any Redemption Date for a
Make-Whole  Redemption,  (i) the  average  of the bid and asked  prices  for the
Comparable  Treasury  Issue  (expressed  in  each  case as a  percentage  of its
principal  amount) on the third business day preceding such Redemption  Date, as
set forth in the daily statistical  release  designated "H.15" (or any successor
release)  published by the Board of Governors of the Federal  Reserve  System or
(ii) if such  release (or any  successor  release) is not  published or does not
contain  such prices on such  business  day,  (A) the  average of the  Reference
Treasury Dealer Quotations for such Redemption Date, after excluding the highest
and lowest such  Reference  Treasury  Dealer  Quotations,  or (B) if the Trustee
obtains fewer than three such Reference Treasury Dealer Quotations,  the average
of such Quotations.

"Reference  Treasury Dealer  Quotations"  means,  with respect to each Reference
Treasury  Dealer  and any  Redemption  Date  for a  Make-Whole  Redemption,  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.

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 with the
consent of the Holders of a majority in principal  amount of the  Securities  at
the time outstanding of each series to be affected.  The Indenture also contains
provisions  permitting  the  Holders of a majority  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 35% in principal amount
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  reasonably  satisfactory  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.

                                  ARTICLE THREE

                          Original Issue of Debentures

     Section 301.  Debentures in the aggregate  principal amount of $97,342,000,
may, upon execution of this Sixth 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
Debentures upon a Company Order without any further action by the Company.


                                  ARTICLE FOUR

                       Paying Agent and Security Registrar

     Section  401.  Fifth  Third  Bank will be the  Paying  Agent  and  Security
Registrar for the Debentures.


                                  ARTICLE FIVE

                                Sundry Provisions

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

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

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








         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.

         In  Witness  Whereof,   the  parties  hereto  have  caused  this  Sixth
Supplemental  Indenture  to be duly  executed as of the day and year first above
written.

                                        PSI ENERGY, INC.



                                                 By                            
                                                         William L. Sheafer
                                                    Vice President and Treasurer






                                  FIFTH THIRD BANK, as Trustee




                                                 By                           
                                                             Kerry Byrne
                                                            Vice President