Exhibit 4.2


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
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.


UNLESS AND UNTIL THIS CERTIFICATE IS EXCHANGED IN WHOLE
OR IN PART FOR NOTES IN CERTIFICATED FORM, THIS CERTIFICATE MAY NOT BE
TRANSFERRED EXCEPT AS A WHOLE BY DTC TO A NOMINEE THEREOF OR BY A NOMINEE
THEREOF TO DTC OR ANOTHER NOMINEE OF DTC OR BY DTC OR ANY SUCH NOMINEE TO A
SUCCESSOR OF DTC OR A NOMINEE OF SUCH SUCCESSOR.


	
  REGISTERED

  	
   

  	
  REGISTERED

  
	
  NO. 001

  	
   

  	
  PRINCIPAL
  AMOUNT

  
	
   

  	
   

  	
   

  
	
  CUSIP No. 26884A AW3

  	
   

  	
  $350,000,000

  



 


ERP
OPERATING LIMITED PARTNERSHIP


5.50% Notes
due October 1, 2012


ERP Operating Limited Partnership, an Illinois limited
partnership (the “Issuer,” which term includes any successor 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
Fifty Million Dollars on October 1, 2012 (the “Maturity Date”), and to pay
interest thereon from June 4, 2007 (or from the most recent Interest Payment
Date to which interest has been paid or duly provided for), semi-annually
in arrears on January 15 and July 15 of each year (each, an “Interest Payment
Date”), commencing on January 15, 2008, and on the Maturity Date, at the rate
of 5.50% per annum, until payment of said principal sum has been made or duly
provided for.


The interest so payable and punctually paid or duly
provided for on any Interest Payment Date and on the Maturity Date will be paid
to the Holder in whose name this Note (or one or more predecessor Notes) is
registered at the close of business on the “Record Date” for such payment,
which will be the January 1 or July 1 next preceding such payment date or the
Maturity Date, as the case may be. Any interest not so punctually paid or duly
provided for shall forthwith cease to be payable to the Holder on such Record
Date, and shall be paid to the Holder in whose name this Note (or one or more
predecessor Notes) is registered at the close of business on a subsequent
record date for the payment of such defaulted interest (which shall be not less
than five Business Days (as defined below) prior to the date of the payment of
such defaulted interest) established by notice given by mail by or on behalf of
the Issuer to the Holders of the Notes not less than 15 days preceding such
subsequent record date. Interest on this Note will be computed on the basis of
a 360-day year of twelve 30-day months.


The principal of this Note payable on the Maturity Date
will be paid against presentation and surrender of this Note at the office or
agency of the Issuer maintained for that purpose in The Borough of Manhattan,
The City of New York. The Issuer hereby initially designates the Corporate
Trust Office of the Trustee in The City of New York as the office to be
maintained by it where Notes may be presented for payment, registration of
transfer, or exchange and where notices or demands to or upon the Issuer in
respect of the Notes or the Indenture referred to on the reverse hereof may be
served.


Interest payable on this Note on any Interest Payment
Date and on the Maturity Date, as the case may be, will be the amount of
interest accrued from and including the immediately preceding Interest Payment
Date (or from and including June 4, 2007, in the case of the initial Interest
Payment Date) to but excluding the applicable Interest Payment Date or the
Maturity Date, as the case may be. If any Interest Payment Date other than the
Maturity Date would otherwise be a day that is not a Business Day (as defined
below), such Interest Payment Date will be postponed to the 













succeeding Business Day. If the Maturity Date falls on a day that is
not a Business Day, principal and interest payable on the Maturity Date will be
paid on the succeeding Business Day with the same force and effect as if it
were paid on the date such payment was due, and no interest will accrue on the
amount so payable for the period from and after the Maturity Date. “Business
Day” means any day, other than a Saturday or a Sunday on which banking
institutions in The City of New York are not required or authorized by law or
executive order to close.


Payments of principal and interest in respect of this
Note will be made by wire transfer of immediately available funds in such coin
or currency as at the time of payment is legal tender for the payment of public
and private debts.


Reference is made to the further provisions of this Note
set forth on the reverse hereof. Such further provisions shall for all purposes
have the same effect as though fully set forth at this place.


This Note shall not be entitled to the benefits of the
Indenture referred to on the reverse hereof or be valid or become obligatory
for any purpose until the certificate of authentication hereon shall have been
signed by the Trustee under such Indenture.


*    *   
*    *    *



 2
 









IN WITNESS WHEREOF, the Issuer
has caused this instrument to be signed manually or by facsimile by its duly
authorized officers.


	
  Dated: June 4, 2007

  	
   

  	
  ERP OPERATING LIMITED PARTNERSHIP, as Issuer

  	
   

  
	
   

  	
   

  	
   

  	
   

  	
   

  
	
   

  	
   

  	
  By:

  	
  EQUITY RESIDENTIAL,

  	
   

  
	
   

  	
   

  	
   

  	
  not individually but as General Partner

  	
   

  
	
   

  	
   

  	
   

  	
   

  	
   

  
	
   

  	
   

  	
   

  	
   

  	
   

  
	
   

  	
   

  	
  By:

  	
   

  	
   

  
	
   

  	
   

  	
   

  	
  Donna Brandin

  	
   

  
	
   

  	
   

  	
  Its:

  	
  Executive Vice President and Chief Financial Officer

  
	
   

  	
   

  	
   

  	
   

  	
   

  
	
   

  	
   

  	
  By:

  	
   

  	
   

  
	
   

  	
   

  	
   

  	
  David J. Neithercut

  	
   

  
	
   

  	
   

  	
  Its:

  	
  President and Chief Executive Officer

  	
   

  
							



 


TRUSTEE’S
CERTIFICATE OF AUTHENTICATION


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


	
  

  	
   

  	
  THE BANK OF NEW YORK TRUST COMPANY, N.A., as Trustee
  

  	 

	
   

  	
   

  	
   

  	 

	
   

  	
   

  	
   

  	 

	
   

  	
   

  	
   

  	 

	
   

  	
   

  	
  By:

  	
   

  
	
   

  	
   

  	
  Authorized Officer

  	 




 



 3
 









[REVERSE OF
NOTE]


ERP OPERATING
LIMITED PARTNERSHIP


5.50% Notes
due October 1, 2012


This security is one of a duly authorized issue of
debentures, notes, bonds, or other evidences of indebtedness of the Issuer
(hereinafter called the “Securities”) of the series hereinafter specified, all
issued or to be issued under and pursuant to (i) an Indenture dated as of
October 1, 1994 as supplemented from time to time (herein called the “Indenture”),
duly executed and delivered by the Issuer to The Bank of New York Trust
Company, N.A. (as successor in interest to J.P. Morgan Trust Company, National
Association, as successor in interest to Bank One Trust Company, N.A.,
successor to The First National Bank of Chicago) as Trustee (herein called the “Trustee,”
which term includes any successor trustee under the Indenture with respect to
the series of Securities of which this Note is a part), and (ii) an Officers’
Certificate dated the date hereof (the “Officers’ Certificate”), duly executed
by authorized officers of the Issuer, pursuant to Section 301 of the Indenture
to which Officers’ Certificate and Indenture and all Indentures supplemental
thereto reference is hereby made for a description of the rights, limitations
of rights, obligations, duties, and immunities thereunder of the Trustee, the
Issuer, and the Holders of the Securities, and of the terms upon which the
Securities are, and are to be, authenticated and delivered. The Securities may
be issued in one or more series, which different series may be issued in
various aggregate principal amounts, may mature at different times, may bear
interest (if any) at different rates, may be subject to different redemption
provisions (if any), and may otherwise vary as provided in the Indenture. This
Security is one of a series designated as the 5.50% Notes due October 1, 2012
of the Issuer, limited in aggregate principal amount to $350,000,000.


In case an Event of Default with respect to the 5.50%
Notes due October 1, 2012 have occurred and be continuing, the principal hereof
and Make-Whole Amount (if any) may be declared, and upon such declaration shall
become, due and payable, in the manner, with the effect, and subject to the
conditions provided in the Indenture.


The Issuer may redeem the Securities, at any time in
whole or from time to time in part, at the election of the Issuer, at a
redemption price equal to the sum of (i) the principal amount of the Securities
being redeemed plus accrued interest thereon to the Redemption Date and (ii) the
Make-Whole Amount, if any, with respect to such Securities (the “Redemption
Price”). For purposes of the Notes, the Reinvestment Rate will be determined
using 0.15% as specified in the Officers’ Certificate in lieu of the percentage
contained in the Indenture. Notice of any optional redemption of any Securities
will be given to Holders at their addresses, as shown in the Security Register,
not more than 60 nor less than 30 days prior to the date fixed for redemption. The
notice of redemption will specify, among other items, the Redemption Price and
the principal amount of the Securities held by such Holder to be redeemed.


The Indenture contains provisions for defeasance of (i) the
entire indebtedness of the 5.50% Notes due October 1, 2012 or (ii) certain
covenants and events of default with respect to the Notes, in each case upon
compliance with certain conditions set forth in the Indenture, which provisions
apply to these Notes.


The Indenture contains provisions permitting the Issuer
and the Trustee, with the consent of the Holders of not less than a majority of
the aggregate principal amount of the Securities at the time Outstanding of all
series to be affected (voting as one class), evidenced as provided in the
Indenture, to execute supplemental Indentures adding any provisions to or
changing in any manner or eliminating any of the provisions of the Indenture or
of any supplemental Indenture or modifying in any manner the rights of the
Holders of the Securities of each series; provided, however, that no such
supplemental Indenture shall, without the consent of the Holder of each
Security so affected, (i) change the final maturity of any Security, or reduce
the principal amount thereof or any premium thereon, or reduce the rate or
extend the time of payment of any interest thereon, or impair or affect the
rights of any Holder to institute suit for the payment on any Security, or (ii)
reduce the aforesaid percentage of Securities, the Holders of which are
required to consent to any such supplemental Indenture, or (iii) reduce the
percentage of Securities, the Holders of which are required to consent to any
waiver of compliance with certain provisions of the Indenture or any waiver of
certain defaults thereunder. It is also provided in the Indenture that, with
respect to certain defaults or Events of Default regarding the Securities of
any series, the Holders of a majority in aggregate principal amount outstanding
of the Securities of such series (or, in the case of certain defaults or Events
of Default, all series of Securities) may on behalf of the Holders of all the Securities
of such series (or all of the Securities, as the case may be) waive any such
past default or Event of Default and its consequences, 



 4
 









prior to any declaration accelerating the maturity of such Securities;
or, subject to certain conditions, may rescind a declaration of acceleration
and its consequences with respect to such Securities. Any such consent or
waiver by the Holder of this security (unless revoked as provided in the
Indenture) shall be conclusive and binding upon such Holder and upon all future
Holders and owners of this security and any securities that may be issued in
exchange or substitution herefor, irrespective of whether or not any notation
thereof is made upon this security or such other securities.


No reference herein to the Indenture and no provision of
this security or of the Indenture shall alter or impair the obligation of the
Issuer, which is absolute and unconditional, to pay the principal of and any
Make-Whole Amount and interest on this security in the manner, at the respective
times, at the rate and in the coin or currency herein prescribed.


This security is issuable only in registered form
without coupons in denominations of $1,000 and integral multiples thereof. Securities
may be exchanged for a like aggregate principal amount of securities of this
series of other authorized denominations at the office or agency of the Issuer
in The Borough of Manhattan, The City of New York, in the manner and subject to
the limitations provided in the Indenture, but without the payment of any
service charge except for any tax or other governmental charge imposed in
connection therewith.


Upon due presentment for registration of transfer of
Securities at the office or agency of the Issuer in The Borough of Manhattan,
The City of New York, a new Security or Securities of the same series of
authorized denominations in an equal aggregate principal amount will be issued
to the transferee in exchange therefor, subject to the limitations provided in
the Indenture, without charge except for any tax or other governmental charge
imposed in connection therewith.


The Issuer, the Trustee, and any authorized agent of the
Issuer or the Trustee may deem and treat the Person in whose name this Security
is registered as the absolute owner of this Security (whether or not this
security shall be overdue and notwithstanding any notation of ownership or
other writing hereon), for the purpose of receiving payment of, or on account
of, the principal hereof and Make-Whole Amount, if any, and subject to the
provisions on the face hereof, interest hereon, and for all other purposes, and
neither the Issuer nor the Trustee nor any authorized agent of the Issuer or
the Trustee shall be affected by any notice to the contrary.


The Indenture and each Security shall be deemed to be a
contract under the laws of the State of New York, and for all purposes shall be
construed in accordance with the laws of such state, except as may otherwise be
required by mandatory provisions of law.


Terms used herein that are defined in the Indenture or
in the Officers’ Certificate shall have the respective meanings assigned
thereto in the Indenture or the Officers’ Certificate, as the case may be.



 5