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| UNITED STATES                                                                                                                                                                     |
| SECURITIES AND EXCHANGE COMMISSION                                                                                                                                                |
| Washington, D.C.  20549                                                                                                                                                      |
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| FORM 8-K                                                                                                                                                                          |
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| CURRENT REPORT                                                                                                                                                                    |
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| PURSUANT TO SECTION 13 OR 15(d) OF                                                                                                                                                |
| THE SECURITIES EXCHANGE ACT OF 1934                                                                                                                                               |
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| Date of Report (Date of earliest event reported): December 9, 2011                                                                                                                |
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| NORTHERN ILLINOIS GAS COMPANY(doing business as NICOR GAS COMPANY)                                                                                                                |
| (Exact name of registrant as specified in its charter)                                                                                                                            |
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| Illinois                                                                                                                                                                          | 1-7296 | 36-2863847 |
| (State or other jurisdiction of incorporation)                                                                                                                                    | (Commission File Number) | (IRS Employer Identification No.) |
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| 1844 Ferry RoadNaperville, Illinois 60563-9600                                                                                                                                    |
| (Address of principal executive offices) (Zip Code)                                                                                                                     |
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| (630) 983-8888                                                                                                                                                                    |
| (Registrant’s telephone number, including area code)                                                                                                                        |
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| Not Applicable                                                                                                                                                                    |
| (Former name or former address, if changed since last report)                                                                                                                     |
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| Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy  the filing obligation of the registrant under any of the following provisions: |
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|  ̈  Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425)                                                                                |
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|  ̈  Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a-12)                                                                               |
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|  ̈  Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b))                                                               |
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|  ̈  Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c))                                                               |

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| Introductory Note |
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| Exhibit No. | Description                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    |
|-------------|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
|        |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           |
| 3.1         | Amended and Restated By-Laws of Nicor Gas Company, as amended on December 9, 2011.                                                                                                                                                                                                                                                                                                                                                                                                                                                             |
|        |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           |
|   10.1 |   Credit Facility, dated as of December 15, 2011 among Northern Illinois Gas Company, an Illinois corporation, as borrower, the several banks and other financial institutions or entities from time to time parties to this Agreement, as lenders, SunTrust Bank, as administrative agent and lender, Wells Fargo Bank, National Association and The Bank of Tokyo-Mitsubishi UFJ, Ltd., as co-syndication agents and lenders, and JPMorgan Chase Bank, N.A. and U.S. Bank National Association, as co-documentation agents and lenders. |
|        |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           |
| 16.1        | Letter from Deloitte & Touche LLP to the Securities and Exchange Commission, dated December 15, 2011.                                                                                                                                                                                                                                                                                                                                                                                                                                      |

| 99.1 | Press Release of AGL Resources Inc., dated December 9, 2011. |
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|                         | NORTHERN ILLINOIS GAS COMPANY                                                                                                                                                                                                                                                                                                                           |
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|                         | (Registrant)                                                                                                                                                                                                                                                                                                                                       |
| Date: December 15, 2011 | /s/ Paul R. Shlanta                                                       |
|                         | Name: Paul R. ShlantaTitle: Executive Vice President andGeneral Counsel                                                                                                                                                                                                                                                                                 |

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| Exhibit No. | Description                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    |
|-------------|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
|        |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           |
| 3.1         | Amended and Restated By-Laws of Nicor Gas Company, as amended on December 9, 2011.                                                                                                                                                                                                                                                                                                                                                                                                                                                             |
|        |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           |
|   10.1 |   Credit Facility, dated as of December 15, 2011 among Northern Illinois Gas Company, an Illinois corporation, as borrower, the several banks and other financial institutions or entities from time to time parties to this Agreement, as lenders, SunTrust Bank, as administrative agent and lender, Wells Fargo Bank, National Association and The Bank of Tokyo-Mitsubishi UFJ, Ltd., as co-syndication agents and lenders, and JPMorgan Chase Bank, N.A. and U.S. Bank National Association, as co-documentation agents and lenders. |
|        |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           |
| 16.1        | Letter from Deloitte & Touche LLP to the Securities and Exchange Commission, dated December 15, 2011.                                                                                                                                                                                                                                                                                                                                                                                                                                      |
|        |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           |
| 99.1        | Press Release of AGL Resources Inc., dated December 9, 2011.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |

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