SIXTH AMENDMENT

Exhibit 10.3

SIXTH AMENDMENT

This Sixth Amendment (this “Amendment”) is made and entered into as of May 1,2003 by and between 10 & 30 SOUTH WACKER, L.L.C., a Delaware limited liability company (“Landlord”) and CHICAGO MERCANTILE EXCHANGE INC., a Delaware corporation (“Tenant”).

RECITALS:

Landlord and Tenant (each as a successor in interest by assignment and/or operation of law) are parties to a certain Lease dated as of March 31, 1988 between American National Bank as Trustee under Trust Agreement dated June 2, 1981 and known as Trust No. 51234 and Chicago Mercantile Exchange, an Illinois not-for-profit corporation, as amended by amendments dated November 1, 1999, January 2, 2002, May 3, 2002, August 22, 2002 and October 1, 2002 (the “Lease”). The parties desire to amend the Lease as hereinafter provided. Therefore, the parties agree as follows:

1. Defined Terms. Except as defined in this Amendment, the capitalized defined terms used in this Amendment shall have the meanings ascribed to such terms in the Lease. References to “Section” refer to sections and subsections of the Lease. References to “Exhibit” or “Exhibits” are to exhibits to this Amendment unless otherwise indicated. For the purposes of this Amendment, the following terms shall have the following meaning:

“18th Floor Space” means the space located on the 18^th floor of the 30 South Wacker Building consisting of 26,616 rentable square feet and depicted on Exhibit A.

2. Addition of 18th Floor Space.

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3. Base Rent. Base Rent for the 18th Floor Space shall be as follows:

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4. Allowance. Section 12 of the Fifth Amendment is amended and restated in its entirety to provide as follows:

Landlord will provide Tenant with a cash allowance of $2,332,700 (the “Allowance”) which Tenant may use, at its discretion, for remodeling, upgrades, alterations, equipment or other costs related to the Premises. The Allowance, the Relocation Allowance and the 19^th Floor Expansion Allowance are collectively referred to as the “Allowances”. Disbursements of any portion of the Allowances for Alterations shall be paid to Tenant in periodic disbursements within 30 days after receipt of the following documentation: (i) an application for payment and sworn statement of contractor substantially in the form of AIA Document G-702 covering all work for which disbursement is to be made to a date specified therein; (ii) a certification from an AIA architect substantially in the form of the Architect’s Certificate for Payment which is located on AIA Document G702, Application and Certificate of Payment; and (iii) Contractor’s, subcontractor’s and material supplier’s waivers of liens which shall cover all Alterations for which disbursement is being requested. Disbursements of any portion of the Allowances for items other than Alterations shall be paid to Tenant within 30 days after receipt of invoices for the cost incurred by Tenant. If Landlord fails to timely pay the Allowances or any portion thereof, Tenant’s obligation to pay Base Rent and Rent Adjustments (without interest or late charge) shall be deferred until the applicable portion of the Allowances is paid. Tenant shall pay Landlord any Base Rent and Rent Adjustments so deferred within

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thirty (30) days after the applicable portion of the Allowances is paid to Tenant. Notwithstanding the foregoing, the amount of Base Rent and Rent Adjustments that Tenant is entitled to defer shall be limited to the amount of the Allowances that is not timely paid by Landlord.

5. Expansion Option. Section 48, as amended by Section 19 of the Fifth Amendment, is amended and restated in its entirety to provide as follows:

48. Expansion Option. Tenant shall have the option (the “Expansion Option”) to lease 14,094 rentable square feet on the 19^th floor of the 30 South Wacker Building as depicted on Exhibit B (the “19^th Floor Expansion Space”). Such Expansion Option shall be exercised by notice to Landlord on or before September 30, 2004, provided that such notice will not be effective if any uncured default then exists and applicable grace periods with respect thereto have then expired. If such Expansion Option is timely exercised, the 19^th Floor Expansion Space shall be delivered to Tenant and added to the Premises on July 1, 2005 and Tenant’s Proportion for the 30 South Wacker Building shall be appropriately adjusted. Base Rent for the 19^th Floor Expansion Space shall be based upon the base rental rates applicable to the other Office Premises (including all subsequent adjustments thereto). Tenant shall be entitled to receive a cash allowance of $132,362.00 (the “19^th Floor Expansion Allowance”) which Tenant may use, at its discretion, for remodeling, upgrades, alterations, equipment or other costs related to the 19^th Floor Expansion Space. The 19^th Floor Expansion Allowance shall be disbursed in the manner described in Section 4 of this Amendment with respect to the Allowance.

6. 12^lh Floor Space. Tenant acknowledges that Landlord desires to lease the 12^th floor of the 10 South Wacker Building to itself, the managing or leasing agent for the Building or one or more of their respective affiliated entities (the “Landlord Related Entities”); provided that such space shall be used by the Landlord Related Entity(ies) as a management and/or leasing office. Tenant agrees that its Right of First Offer on all or any portion of the 12^th floor of the 10 South Wacker Building to be subject and subordinate to Landlord’s right to lease such space to itself or any of the Landlord Related Entities and that such right of

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Landlord shall be considered to be a “Superior Right” as defined in Section 50.B; provided that a sublease or assignment of any portion of the 12^th floor space to a party other than a Landlord Related Entity shall be subject to Tenant’s Right of First Offer.

7. Temporary Space. Section 23 of the Fifth Amendment amended and restated Section 2 of the Fourth Amendment dated August 22, 2002 in its entirety. Section 23 of the Fifth Amendment is hereby amended and restated in its entirety to provide as follows:

Commencing on January 1, 2003 (or such earlier date as Landlord may permit) through November 30, 2003 (“Temporary Space Term”), Tenant shall be permitted to occupy Suite 1818 at the 30 South Wacker Building (“Suite 1818”) consisting of 16,434 rentable square feet, which space is depicted on Exhibit I of the Fifth Amendment (the “Temporary Space”). No Base Rent or Rent Adjustment shall be payable with respect to the Temporary Space during the Temporary Space Term. Temporary Space shall be governed by the terms of the Lease. Landlord shall provide Tenant with an allowance of $250,000 (the “Relocation Allowance”) to be applied toward the cost of relocating into the Temporary Space and, at Tenant’s discretion, for remodeling, upgrades, alterations, equipment or other costs related to the Premises. The Relocation Allowance shall be disbursed in the same manner as the Allowance. If all or any portion of the Relocation Allowance is not used on or before November 30, 2003, Tenant may use all or any portion of such unused amount as a credit against Base Rent and Rent Adjustment.

8. Sublease of Suite 2020. Landlord hereby grants its consent to a subletting of all or any portion of Suite 2020 of the 30 South Wacker Building by Reuters, as sublessor, to Tenant, as sublessee.

9. Configuration of Elevator Banks. The low mid-rise elevator bank for the 30 South Wacker Building currently serves floors 11-21. Landlord shall have the right at anytime to switch the service of floor 21 from the low mid-rise elevator bank to the high mid-rise elevator bank. Regardless of whether Landlord reconfigures the elevator bank for the 21^st floor, Landlord agrees that it will not reduce the number of

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elevator cars serving any floor in the low mid-rise elevator bank below its current number of seven (7) at any time prior to November 30, 2006. If less than 63,500 rentable square feet in the low mid-rise elevator bank is unleased on November 30, 2006, Landlord agrees that it will not reduce the number of elevator cars serving the low mid-rise elevator bank at any time prior to November 30, 2008.

10. Miscellaneous.

(a) This Amendment sets forth the entire agreement between the parties with respect to the matters set forth herein. There have been no additional oral or written representation or agreement.

(b) Except as herein modified or amended, the provisions, conditions and terms of the Lease shall remain unchanged and in full force and effect.

(c) In the case of any inconsistency between the provision of the Lease and this Amendment, the provision of this Amendment shall govern and control.

(d) Neither party shall be bound by this Amendment until both parties have executed and delivered the same to the other.

(e) Tenant hereby represents to Landlord that Tenant has dealt with no broker in connection with this Amendment except for The Levy Organization (“Broker”). Tenant agrees to indemnify and hold Landlord Related Parties harmless from all claims of any brokers other than Broker claiming to have represented Tenant in connection with this Amendment. Landlord hereby

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represents to Tenant that Landlord has dealt with no broker in connection with this Amendment. Landlord agrees to indemnify and hold Tenant Related Parties harmless from all claims of any brokers claiming to have represented Landlord in connection with this Amendment.

(f) Each exhibit attached hereto is hereby made a part hereof.

(g) Each signatory of this Amendment represents hereby that he or she has the authority to execute and deliver the same on behalf of the party hereto for which such signatory is acting.

[The next page is the signature page.]

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IN WITNESS WHEREOF, Landlord and Tenant have duly executed this Amendment as of the day and year first above written.

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SEVENTH AMENDMENT

THIS SEVENTH AMENDMENT (the “Amendment”) is made and entered into as of the 20 day of April, 2004, by and between 10 & 30 SOUTH WACKER, L.L.C., a Delaware limited liability company (“Landlord”), and CHICAGO MERCANTILE EXCHANGE, INC., a Delaware corporation (“Tenant”).

RECITALS

NOW, THEREFORE, in consideration of the mutual covenants and agreements herein contained and other good and valuable consideration, the receipt and sufficiency of which are hereby acknowledged, Landlord and Tenant agree as follows:

All such Base Rent shall be payable by Tenant in accordance with the terms of the Lease.

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IN WITNESS WHEREOF, Landlord and Tenant have duly executed this Seventh Amendment as of the day and year first above written.

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EIGHTH AMENDMENT

THIS EIGHTH AMENDMENT (the “Amendment”) is made and entered into as of October 29, 2004, by and between 10 & 30 SOUTH WACKER, L.L.C., a Delaware limited liability company (“Landlord”), and CHICAGO MERCANTILE EXCHANGE INC., a Delaware corporation (“Tenant”).

RECITALS

   NOW, THEREFORE, in consideration of the above recitals, which by this reference are incorporated herein, the mutual covenants and conditions contained herein and other valuable consideration, the receipt and sufficiency of which are hereby acknowledged, Landlord and Tenant agree as follows:

  All such Base Rent shall be payable by Tenant in accordance with the terms of the Lease.

Expansion Option. The Expansion Option, as it appears in Section 5 of the Sixth Amendment, is deleted and shall be of no further force or effect.

that may have been provided Tenant in connection with entering into the Lease, unless specifically set forth in this Amendment. Tenant agrees that neither Tenant nor its agents or any other parties acting on behalf of Tenant shall disclose any matters set forth in this Amendment or disseminate or distribute any information concerning the terms, details or conditions hereof to any person, firm or entity without obtaining the express written consent of Landlord.

IN WITNESS WHEREOF, Landlord and Tenant have duly executed this Amendment as of the day and year first above written.