SUMMARY

This summary highlights selected information contained in this joint proxy statement/prospectus with respect to the merger and may not contain all of the information that is important to you. To understand the merger fully and for a more complete description of the legal terms of the merger agreement, you should carefully read this entire joint proxy statement/prospectus and the documents to which AGL Resources and Nicor refer you. A copy of the merger agreement is attached as Annex A to this joint proxy statement/prospectus and is incorporated by reference into this joint proxy statement/prospectus. See “Where You Can Find More Information” beginning on page 168. AGL Resources and Nicor have included in this summary references to other portions of this joint proxy statement/prospectus to direct you to a more complete description of the topics presented, which you should review carefully in their entirety.

The Companies Involved in the Merger (see page 39)

AGL Resources Inc.

Ten Peachtree Place, NE

Atlanta, Georgia 30309

(404) 584-3000

AGL Resources is an energy services holding company, headquartered in Atlanta, Georgia, whose principal business is the distribution of natural gas in six states: Florida, Georgia, Maryland, New Jersey, Tennessee and Virginia. AGL Resources operates six utilities which, combined, serve approximately 2.3 million end-use customers, making it the largest distributor of natural gas in the southeastern and mid-Atlantic regions of the United States based on customer count. AGL Resources is also involved in various related businesses, including retail natural gas marketing to end-use customers in Georgia, Ohio and Florida; natural gas asset management and related logistics activities for its own utilities as well as for other nonaffiliated companies; natural gas storage arbitrage and related activities; and the development and operation of high-deliverability underground natural gas storage assets.

Additional information about AGL Resources and its subsidiaries is included in documents incorporated by reference in this joint proxy statement/prospectus. See “Where You Can Find More Information” beginning on page 168.

Nicor Inc.

1844 Ferry Road

Naperville, Illinois 60563

(630) 305-9500

Nicor, an Illinois corporation formed in 1976, is a holding company and is a member of the Standard & Poor’s 500 Index. Its primary business is Nicor Gas, one of the nation’s largest natural gas distribution companies. Nicor also owns Tropical Shipping, a containerized shipping business serving the Caribbean region and the Bahamas. In addition, Nicor owns several energy-related businesses, including Nicor Services, Nicor Solutions and Nicor Advanced Energy, which provide energy-related products and services to retail markets, Nicor Enerchange, a wholesale natural gas marketing company and Central Valley, which is developing a natural gas storage facility. Nicor also has equity interests in a cargo container leasing business, a FERC-regulated natural gas pipeline and certain affordable housing investments. For more information, visit the Nicor website at www.nicor.com.

Additional information about Nicor and its subsidiaries is included in documents incorporated by reference in this joint proxy statement/prospectus. See “Where You Can Find More Information” beginning on page 168.

The Proposed Merger (see page 51)

Under the terms of the merger agreement, Apollo Acquisition Corp. (sometimes referred to as Merger Sub), a wholly owned subsidiary of AGL Resources formed for the purpose of the merger, will merge with and into Nicor. As a result, Nicor will survive the merger and will become a wholly owned subsidiary of AGL Resources upon completion of the merger. Immediately after the merger, Nicor will merge with and into Ottawa Acquisition LLC (sometimes referred to as Merger LLC or the surviving entity), a wholly owned subsidiary of AGL Resources formed for the purpose of the merger, and Merger LLC will continue to exist as a wholly owned subsidiary of AGL Resources (sometimes referred to as the subsequent merger). Merger Sub and Merger LLC are sometimes referred to as the acquisition subsidiaries and the two mergers are sometimes referred to as the transaction.

The merger will be completed only after the satisfaction or waiver of the conditions to the completion of the merger discussed below.

The merger agreement is attached as Annex A to this joint proxy statement/prospectus. AGL Resources and Nicor encourage you to read the merger agreement carefully and fully, as it is the legal document that governs the merger.

Effects of the Merger; Merger Consideration (see page 51)

Common Stock

Except as described below, subject to the terms and conditions of the merger agreement, at the effective time of the merger, each share of Nicor common stock issued and outstanding immediately prior to the effective time of the merger (other than dissenting shares) will be converted into the right to receive (i) $21.20 in cash and (ii) 0.8382 of a share of AGL Resources common stock, subject to adjustment for certain changes in AGL Resources common stock or Nicor common stock such as reclassifications or stock splits (sometimes referred to as the exchange ratio).

However, if the aggregate value of all shares of AGL Resources common stock that would be issued pursuant to the merger (sometimes referred to as the total stock consideration), calculated based on the price of AGL Resources common stock on the date the merger agreement was executed (which was $37.13), is less than 40% of the sum of the total stock consideration plus the total amount of cash paid to Nicor shareholders, including cash paid in lieu of fractional shares and deemed paid in respect of dissenting shares (which sum is sometimes referred to as the total merger consideration), then the exchange ratio will be increased, and the amount of cash paid per share of Nicor common stock will be correspondingly decreased, until the total stock consideration equals 40% of the total merger consideration. The adjustment will be made as follows: for each 0.0001 increase to the exchange ratio that is made, the amount of cash paid per share of Nicor common stock will be reduced by the product of 0.0001 multiplied by $37.13. For purposes of the adjustment described above, the cash deemed paid in respect of dissenting shares will be $53.00.

The adjustment mechanism referenced in the preceding paragraph is intended to ensure that the transaction satisfies the “continuity of interest” requirement for a “reorganization” within the meaning of Section 368(a) of the Internal Revenue Code. This requirement generally should be satisfied if the AGL Resources common stock issued in the transaction to Nicor shareholders represents at least 40% of the value of the total consideration received by Nicor shareholders in the transaction, as determined under applicable United States Treasury regulations. For a discussion of the United States federal income tax consequences of the merger, see “The Proposed Merger—Material United States Federal Income Tax Consequences of the Transaction” beginning on page 93 of this joint proxy statement/prospectus.

Should such adjustment to the exchange ratio be made, AGL Resources and Nicor will each disclose the adjustment on a current report on Form 8-K and in a press release. Additionally, AGL Resources will send a written notification of the change in the exchange ratio to each shareholder of Nicor whose shares are converted into the right to receive the merger consideration with the letter of transmittal that will be mailed to each of those shareholders immediately after the effective time of the merger.

AGL Resources will not issue any fractional shares in connection with the merger. Instead, each holder of Nicor common stock who would otherwise be entitled to receive a fraction of a share of AGL Resources common stock (after taking into account all shares of Nicor common stock owned by a holder at the effective time of the merger) will receive cash, without interest, rounded down to the nearest cent, in an amount equal to the fractional share to which such holder would otherwise be entitled multiplied by the average of the closing sale prices of AGL Resources common stock on the NYSE, as reported in The Wall Street Journal for each of the 20 consecutive trading days ending with the fifth complete trading day prior to the closing date.

The merger consideration represented a value of $53.00 based on the volume-weighted average price for AGL Resources common stock on the NYSE for the 20 trading days ended December 1, 2010. This represents a premium of approximately 22% to the closing stock price of Nicor on December 1, 2010, and an approximately 17% premium to the volume-weighted average stock price of Nicor over the last 20 trading days ending December 1, 2010. The value of the consideration to be received by Nicor shareholders will fluctuate with changes in the price of AGL Resources common stock. The merger consideration represented a value of $54.92 based on the closing price of AGL Resources common stock on the NYSE on April 25, 2011. This represents a premium of approximately 26% to the closing stock price of Nicor on December 1, 2010, and an approximately 21% premium to the volume-weighted average stock price of Nicor over the last 20 trading days ending December 1, 2010. AGL Resources and Nicor urge you to obtain current market quotations for AGL Resources and Nicor common stock.

Treasury Shares; Shares Owned by AGL Resources

Immediately prior to the effective time of the merger, each share of Nicor common stock (i) held as a treasury share by Nicor, (ii) owned of record by any subsidiary of Nicor, or (iii) owned of record by AGL Resources, Merger Sub or any of their respective wholly owned subsidiaries will, in each case, be canceled and cease to exist, and no consideration will be delivered in exchange for those shares.

AGL Resources Shareholders Will Not Have Dissenters’ Rights in Connection with the Merger

(see page 43)

Under Georgia law, AGL Resources shareholders are not entitled to dissenters’ rights in connection with the issuance of shares of AGL Resources common stock as contemplated by the merger agreement and the amendment to AGL Resources’ amended and restated articles of incorporation to increase the number of directors that may serve on the AGL Resources Board from 15 to 16 directors. It is anticipated that AGL Resources shares will continue to be traded on the NYSE during the pendency of and following the effectiveness of the merger, and AGL Resources is not one of the constituent corporations to the merger.

Nicor Shareholders Will Have Dissenters’ Rights in Connection with the Merger (see page 47)

Under Illinois law, Nicor shareholders have dissenters’ rights in connection with the merger. Therefore, a shareholder of Nicor may elect to be paid for such shareholder’s shares in accordance with the procedures set forth in the Illinois Business Corporation Act of 1983, as amended (sometimes referred to as the IBCA). The full text of Article 11 of the IBCA is reprinted in its entirety as Annex B to this joint proxy statement/prospectus. See “Information About the Nicor Special Meeting and Vote—Dissenters’ Rights” beginning on page 47.

Treatment of Nicor Stock Options, Restricted Stock, Restricted Stock Units and Stock Plans (see page 109)

Immediately prior to the effective time of the merger, each outstanding option to purchase Nicor common stock will be cancelled and in exchange therefor, former holders of Nicor stock options will be entitled to receive a cash payment in an amount equal to (i) the product of (A) the number of shares of Nicor common stock subject to the option and (B) the excess, if any, of (1) the value of the merger consideration, based on the volume-weighted average price of AGL Resources common stock on the business day immediately preceding the closing date of the merger over (2) the exercise price per share subject to the option, less (ii) withholding with respect to any applicable taxes.

Each share of Nicor restricted stock outstanding immediately prior to the merger will vest in full and all restrictions will lapse and, as of the effective time of the merger, will entitle the holder to receive the merger consideration, less withholding with respect to applicable taxes.

Each restricted stock unit of Nicor outstanding immediately prior to the merger will be cancelled and, in exchange therefor, former holders of Nicor restricted stock units will be entitled to receive a cash payment in an amount equal to the value of the merger consideration, based on the volume-weighted average price of AGL Resources common stock on the business day immediately preceding the closing date of the merger multiplied by the number of shares of Nicor common stock subject to such restricted stock unit, less withholding with respect to applicable taxes. Such cash will be payable in accordance with the terms of the restricted stock unit.

After the effective time of the merger, all Nicor equity plans will be terminated and no further options, restricted stock or restricted stock units or other rights with respect to shares of Nicor common stock will be granted pursuant to such equity plans.

Dividends (see page 134)

During 2010, AGL Resources declared quarterly cash dividends of $0.44 per share of common stock, or $1.76 annually, and Nicor declared quarterly cash dividends of $0.465 per share of common stock, or $1.86 annually. On February 8, 2011, AGL Resources increased its dividend rate to $0.45 per share of common stock quarterly, or $1.80 annually, effective for the dividend payable March 1, 2011. Under the terms of the merger agreement, AGL Resources and Nicor have agreed to coordinate the declaration and payment of dividends in respect of each party’s common stock including the record dates and payment dates relating thereto. It is the intent of AGL Resources and Nicor that no shareholder of either company will receive two dividends, or fail to receive one dividend, for any single calendar quarter (or portion thereof) with respect to its shares of AGL Resources common stock and/or Nicor common stock. AGL Resources and Nicor intend that the first quarterly dividend paid to the holders of AGL Resources common stock (including former holders of Nicor common stock) following the effective time of the merger will be paid in accordance with AGL Resources’ dividend policy, and in no event later than the first record date for the payment of dividends after the closing date of the merger. This would represent an anticipated dividend accretion of approximately 35% for Nicor’s shareholders.

Material United States Federal Income Tax Consequences of the Transaction (see page 93)

AGL Resources and Nicor expect that the merger and the subsequent merger, taken together as a single integrated transaction, will qualify as a “reorganization” for United States federal income tax purposes within the meaning of Section 368(a) of the Internal Revenue Code and that each of AGL Resources and Nicor will be a party to the “reorganization,” and it is a condition to the consummation of the merger that each of AGL Resources and Nicor receive an opinion from legal counsel to that effect. If the transaction qualifies as a “reorganization,” a Nicor shareholder generally will recognize gain (but not loss), determined separately for each identifiable block of shares of Nicor common stock (generally, Nicor common stock acquired at different prices or at different times) that is exchanged in the transaction, in an amount equal to the lesser of (i) the amount of

cash received in the transaction with respect to such block, excluding any cash received in lieu of a fractional share of AGL Resources common stock and (ii) the excess, if any, of (a) the sum of the amount of such cash and the fair market value of the AGL Resources common stock received in the transaction with respect to such block over (b) the Nicor shareholder’s tax basis in its shares of Nicor common stock in such block.

A Nicor shareholder generally will recognize gain or loss with respect to cash received in lieu of a fractional share of AGL Resources common stock in the transaction measured by the difference, if any, between the amount of cash received and the tax basis in such fractional share.

Nicor shareholders are urged to read the discussion in the section entitled “The Proposed Merger—Material United States Federal Income Tax Consequences of the Transaction” beginning on page 93 of this joint proxy statement/prospectus and to consult their tax advisors as to the United States federal income tax consequences of the transaction, as well as the effects of state, local and non-United States tax laws.

Approvals Required by AGL Resources and Nicor Shareholders to Complete the Merger (see pages 42 and 46)

A shareholder will be deemed “present” at the special meeting by proxy if the shareholder has returned a proxy by mail, by telephone, or via the Internet (even if the proxy contains no instructions as to voting, abstains from voting, or constitutes a broker “non-vote”). If you do not return your proxy card or submit your proxy by telephone, via the Internet or vote in person at the AGL Resources special meeting or Nicor special meeting, your vote will not be counted and it will be less likely that a quorum to conduct business at the AGL Resources special meeting or Nicor special meeting will be obtained and that the vote necessary for approval of the proposals will be obtained.

For AGL Resources Shareholders

AGL Resources’ directors and executive officers beneficially owned 405,532 shares of AGL Resources common stock on April 18, 2011, the record date for the special meeting. These shares represent in total 0.5% of the total voting power of AGL Resources’ voting securities outstanding and entitled to vote as of the record date. AGL Resources currently expects that AGL Resources’ directors and executive officers will vote their shares in favor of all the proposals to be voted on at the special meeting, although none of them has entered into any agreements obligating them to do so.

AGL Resources cannot complete the merger unless AGL Resources shareholders approve both the proposal to approve the issuance of shares of AGL Resources common stock as contemplated by the merger agreement and the proposal to approve the amendment to AGL Resources’ amended and restated articles of incorporation to increase the number of directors that may serve on the AGL Resources Board from 15 to 16 directors. In the event that AGL Resources shareholders do not approve the amendment, AGL Resources and Nicor may agree to waive the requirement that this approval be obtained and nonetheless proceed with the merger, however, there can be no assurance that AGL Resources and Nicor would agree to waive this condition.

For Nicor Shareholders

Nicor’s directors and executive officers beneficially owned 1,005,723 shares of Nicor common stock on April 18, 2011, the record date for the special meeting. These shares represent in total 2.2% of the total voting power of Nicor’s voting securities outstanding and entitled to vote as of the record date. Nicor currently expects that Nicor’s directors and executive officers will vote their shares in favor of all the proposals to be voted on at the special meeting, although none of them has entered into any agreements obligating them to do so.

Nicor cannot complete the merger unless Nicor shareholders approve the proposal to adopt the merger agreement.

Recommendations of the AGL Resources Board (see page 62)

The AGL Resources Board has reviewed and considered the terms of the merger and the merger agreement and has unanimously determined that the merger, including the issuance of shares of AGL Resources common stock and the increase in the number of directors on the AGL Resources Board, as contemplated by the merger agreement, is fair to and in the best interests of AGL Resources and its shareholders and unanimously recommends that AGL Resources shareholders vote FOR the proposal to approve the issuance of shares of AGL Resources common stock as contemplated by the merger agreement, FOR the proposal to amend AGL Resources’ amended and restated articles of incorporation to increase the number of directors that may serve on the AGL Resources Board from 15 to 16 directors and FOR the proposal to adjourn AGL Resources’ special meeting if necessary to permit further solicitation of proxies in the event there are not sufficient votes at the time of the special meeting to approve the issuance of shares and/or the amendment to AGL Resources’ amended and restated articles of incorporation.

Recommendations of the Nicor Board (see page 75)

The board of directors of Nicor (sometimes referred to as the Nicor Board) has reviewed and considered the terms of the merger and the merger agreement and the directors present unanimously determined that the merger agreement and the transactions contemplated thereby, including the merger, are advisable and in the best interests of Nicor’s shareholders and recommend that Nicor shareholders vote FOR the proposal to approve the merger agreement and thereby approve the merger. The Nicor Board also recommends that you vote FOR the proposal to adjourn the special meeting if necessary to permit further solicitation of proxies in the event there are not sufficient votes at the time of the special meeting to approve the merger agreement.

Opinion of AGL Resources’ Financial Advisor (see page 67)

Goldman, Sachs & Co. (sometimes referred to as Goldman Sachs) delivered its opinion to the AGL Resources Board that, as of December 6, 2010 and based upon and subject to the factors and assumptions set forth therein, the $21.20 in cash and 0.8382 of a share of AGL Resources common stock to be paid by AGL Resources in respect of each share of Nicor common stock pursuant to the merger agreement was fair from a financial point of view to AGL Resources.

The full text of the written opinion of Goldman Sachs, dated as of December 6, 2010, which sets forth assumptions made, procedures followed, matters considered and limitations on the review undertaken in connection with the opinion, is attached as Annex D to this joint proxy statement/prospectus. Goldman Sachs provided its opinion for the information and assistance of the AGL Resources Board in connection with its consideration of the transaction contemplated by the merger agreement. The Goldman Sachs opinion is not a recommendation as to how any holder of AGL Resources common stock should vote with respect to the transaction contemplated by the merger agreement or any other matter. Pursuant to an engagement letter between AGL Resources and Goldman Sachs, AGL Resources has agreed to pay Goldman Sachs a transaction fee of $16.0 million, a significant portion of which is contingent upon consummation of the transaction contemplated by the merger agreement.

Opinion of Nicor’s Financial Advisor (see page 80)

At the meeting of the Nicor Board on December 6, 2010, J.P. Morgan Securities LLC (sometimes referred to as J.P. Morgan), rendered its oral opinion, subsequently confirmed in writing, to the Nicor Board that, as of such date, and based upon and subject to the factors, procedures, assumptions, qualifications and limitations set forth in its opinion, the merger consideration to be paid to the holders of shares of Nicor common stock in the merger was fair, from a financial point of view, to such holders.

The full text of the written opinion of J.P. Morgan dated as of December 6, 2010, which sets forth, among other things, the assumptions made, procedures followed, matters considered, and qualifications and limitations on the review undertaken in connection with its opinion, is included as Annex E to this proxy statement/prospectus and is incorporated herein by reference. J.P. Morgan provided its opinion for the information of the Nicor Board in connection with and for the purposes of its evaluation of the transactions contemplated by the merger agreement. J.P. Morgan’s written opinion addresses only the consideration to be paid to the holders of shares of Nicor common stock in the merger, and does not address any other matter. J.P. Morgan’s opinion does not constitute a recommendation to any shareholder of Nicor as to how such shareholder should vote with respect to the merger or any other matter. J.P. Morgan has acted as financial advisor to Nicor with respect to the proposed merger and will receive a fee of approximately $13 million for its services, a principal portion of which is contingent upon completion of the merger. For a more complete description of J.P. Morgan’s opinion, see “The Proposed Merger—Opinion of Nicor’s Financial Advisor” beginning on page 80. See also Annex E to this joint proxy statement/prospectus.

Debt Financing (see page 160)

In connection with the transactions contemplated by the merger agreement, AGL Capital Corporation, a Nevada corporation and a wholly owned subsidiary of AGL Resources (sometimes referred to as the borrower), entered into a Bridge Term Loan Credit Agreement (sometimes referred to as the Bridge Facility) on December 21, 2010, among the borrower, AGL Resources, as guarantor, Goldman Sachs Bank USA (sometimes referred to as GS Bank), as agent and the lenders party thereto (sometimes referred to as the lenders), pursuant to which, subject to certain conditions and limitations, the lenders agreed to provide loans to the borrower in an aggregate principal amount of $1.05 billion. In connection with the borrower’s issuance of senior notes in the aggregate principal amount of $500 million and pursuant to the terms of the Bridge Facility, the aggregate principal amount of the Bridge Facility has been reduced to approximately $852 million. If AGL Capital Corporation chooses to borrow under the Bridge Facility, it is expected that the proceeds of the Bridge Facility

(or an allowable replacement financing thereof), will be used to fund the cash consideration for the transaction and to pay the fees and expenses incurred in connection with the Bridge Facility. AGL Resources and/or AGL Capital Corporation may issue debt securities, preferred stock, common equity, or other securities; bank loans; or other debt financings in lieu of all or a portion of the drawing under the Bridge Facility.

Completion of the Merger is Subject to Regulatory Clearance (see page 96)

To complete the merger, AGL Resources and Nicor must receive approval from and/or make filings with various federal and state regulatory authorities. The required statutory approvals include, among others: (i) the filing of notification and report forms with the Department of Justice (sometimes referred to as the DOJ) and the Federal Trade Commission (sometimes referred to as the FTC) under the Hart-Scott-Rodino Antitrust Improvements Act of 1976, as amended (sometimes referred to as the HSR Act), and expiration or early termination of any applicable waiting periods under the HSR Act; (ii) compliance with any applicable requirements of the Illinois Public Utilities Act, the Illinois Gas Storage Act, the Illinois Gas Pipeline Safety Act and the Illinois Gas Transmission Facilities Act (sometimes collectively referred to as the Illinois Statutes) including notice to and approval of, the Illinois Commerce Commission (sometimes referred to as the ICC); (iii) the approval of the California Public Utilities Commission (sometimes referred to as the CPUC) of a change in control over Central Valley Gas Storage, LLC (sometimes referred to as Central Valley); and (iv) approval of the Federal Communications Commission (sometimes referred to as the FCC) for the transfer of control over the FCC licenses of Northern Illinois Gas Company (sometimes referred to as Nicor Gas). See “The Proposed Merger—Regulatory Matters Relating to the Merger” beginning on page 96 of this joint proxy statement/prospectus for a discussion of the status of the regulatory approval process.

AGL Resources’ Articles Will Be Amended Following Completion of the Merger (see page 134)

AGL Resources is proposing to amend its amended and restated articles of incorporation to increase the number of directors that may serve on the AGL Resources Board from 15 to 16 directors, subject to shareholder approval. You should read the complete text of the amendment to AGL Resources’ amended and restated articles of incorporation substantially in the form to become effective upon completion of the merger, which is attached as Annex C to this joint proxy statement/prospectus in conjunction with this summary.

Interests of AGL Resources Directors (see page 102)

AGL Resources shareholders should be aware that AGL Resources directors may have interests in the merger that are different from, or in addition to, AGL Resources shareholders’ interests when they consider their board of directors’ recommendation that they vote (i) to approve the issuance of shares of AGL Resources common stock as contemplated by the merger agreement, (ii) to approve an amendment to AGL Resources’ amended and restated articles of incorporation to increase the number of directors that may serve on the AGL Resources Board from 15 to 16 directors and (iii) to adjourn AGL Resources’ special meeting if necessary to permit further solicitation of proxies in the event there are not sufficient votes at the time of the special meeting to approve the issuance of shares and/or the amendment to AGL Resources’ amended and restated articles of incorporation. Those interests include, among other things, the continuation of the 12 current AGL Resources directors (or others designated by AGL Resources) on the board of directors of the combined company.

As a result, the directors of AGL Resources may be more likely to recommend the approval of the proposals to be voted upon at the special meeting than if they did not have these interests.

Please see the section entitled “Additional Interests of AGL Resources’ and Nicor’s Directors and Executive Officers in the Merger” beginning on page 102.

Interests of Nicor Directors and Executive Officers (see page 103)

Nicor shareholders should be aware that Nicor’s directors and executive officers have interests in the merger that are in addition to those of Nicor shareholders generally. As a result, the directors and executive officers of Nicor may be more likely to recommend the approval of the proposals to be voted upon at the special meeting than if they did not have these interests. The Nicor Board was aware of and considered these potential interests, among other matters, in evaluating the merger agreement and the merger, and in recommending to you that you approve the merger agreement. Nicor’s shareholders should be aware of these interests when they consider the Nicor Board’s recommendation that they vote to approve the merger agreement and, thereby, the merger, and should refer to the section entitled “Additional Interests of AGL Resources’ and Nicor’s Directors and Executive Officers in the Merger” beginning on page  102.

Completion of the Merger is Subject to the Satisfaction of a Number of Conditions (see page 126)

Completion of the merger depends upon the satisfaction or waiver of a number of conditions, including, among others, the following:

How the Merger Agreement May Be Terminated by AGL Resources and/or Nicor (see page 129)

Termination

The merger agreement may be terminated in accordance with its terms at any time prior to the effective time of the merger, whether before or after the Nicor shareholder approval or the AGL Resources shareholder approval:

Termination Fees and Expenses May Be Payable Under Some Circumstances (see page 131)

Termination Fee

Under the terms of the merger agreement, Nicor must pay AGL Resources a termination fee equal to $67 million in the event that:

Under the terms of the merger agreement, AGL Resources must pay Nicor a termination fee equal to $67 million in the event that:

Further, under the terms of the merger agreement, AGL Resources must pay Nicor a financing failure fee equal to $115 million in the event that the merger agreement is properly terminated by either party because either the financing and any alternative financing are not available, or AGL Resources and/or Merger Sub have not received the proceeds of the financing or any alternative financing.

Expenses

Except as described below, each party will bear its own expenses in connection with the merger, except that AGL Resources and Nicor will share all costs and expenses incurred in connection with the printing, filing and mailing of this joint proxy statement/prospectus. AGL Resources will pay all fees and expenses incurred in connection with filings pursuant to the HSR Act.

In the event that either AGL Resources or Nicor terminates the merger agreement because (i) the Nicor shareholder approval is not obtained at the meeting of Nicor shareholders, then Nicor will reimburse AGL Resources for all documented out-of-pocket fees and expenses incurred by AGL Resources in connection with the merger or the subsequent merger (including all fees and expenses of counsel, financial advisors, accountants, experts and consultants reasonably retained by AGL Resources) or (ii) the AGL Resources shareholder approval is not obtained at the meeting of AGL Resources shareholders, then AGL Resources will reimburse Nicor for all documented out-of-pocket fees and expenses incurred by Nicor in connection with the merger or the subsequent merger (including all fees and expenses of counsel, financial advisors, accountants, experts and consultants reasonably retained by Nicor).

In the event that AGL Resources terminates the merger agreement because of a material breach of Nicor’s non-solicitation covenant in the merger agreement, Nicor will reimburse AGL Resources for all documented out-of-pocket fees and expenses incurred by AGL Resources in connection with the merger or the subsequent merger (including all fees and expenses of counsel, financial advisors, accountants, experts and consultants reasonably retained by AGL Resources).

In the event that Nicor terminates the merger agreement because of a material breach of AGL Resources’ non-solicitation covenant or covenant that it will not effect a change of board recommendation in the merger agreement, AGL Resources will reimburse Nicor for all documented out-of-pocket fees and expenses incurred by Nicor in connection with the merger or the subsequent merger (including all fees and expenses of counsel, financial advisors, accountants, experts and consultants reasonably retained by Nicor).

In the event that either party is required to reimburse expenses and also pay a termination fee, the amount of the termination fee will be reduced by the amount of the expenses so reimbursed.

AGL Resources Common Stock Will Continue to be Listed on the New York Stock Exchange (see page 100)

Shares of AGL Resources common stock will continue to be traded on the NYSE under the symbol “AGL”.

Nicor Shareholders Will Hold Approximately 33% of the Outstanding Shares of AGL Resources Common Stock Following Completion of the Merger (see pages 32 and 100)

Upon completion of the merger, AGL Resources will issue up to approximately 38.7 million shares of AGL Resources common stock to Nicor shareholders as contemplated by the merger agreement. Immediately following completion of the merger, it is expected that there will be approximately 116.1 million shares of AGL Resources common stock issued and outstanding on a fully diluted basis. The shares of AGL Resources common stock to be issued to Nicor shareholders will represent approximately 33% of the outstanding AGL Resources common stock after the merger on a fully diluted basis. This information is based on the number of AGL Resources and Nicor shares outstanding and Nicor equity-based awards on April 18, 2011.

Differences Exist Between the Rights of AGL Resources Shareholders and Nicor Shareholders (see page 142)

The rights of AGL Resources’ and Nicor’s shareholders under their respective business corporation laws are different. There are additional differences in the rights of AGL Resources shareholders and Nicor shareholders as a result of the provisions of the articles of incorporation, bylaws and other corporate documents of each company. See “Comparison of Shareholders’ Rights” beginning on page 142 of this joint proxy statement/prospectus.

The Merger and the Performance of the Combined Company are Subject to a Number of Risks (see page 27)

There are a number of risks relating to the merger and to the businesses of AGL Resources, Nicor and the combined company following the merger. See “Risk Factors” beginning on page 27 of this joint proxy statement/prospectus for a discussion of these and other risks and see also the documents that AGL Resources and Nicor have filed with the SEC and which the companies have incorporated by reference into this joint proxy statement/prospectus.

Post-Merger Governance and Management (see page 134)

Upon completion of the merger, AGL Resources will maintain its corporate headquarters in Atlanta, Georgia and locate the headquarters of its newly expanded gas distribution operations in Naperville, Illinois.

As provided in the merger agreement, upon completion of the merger, the board of directors of the combined company will be composed of the four directors designated by Nicor (sometimes referred to as the Nicor designees), subject to the approval of AGL Resources, not to be unreasonably withheld or delayed, and the 12 current AGL Resources directors (or others designated by AGL Resources). John W. Somerhalder II will serve as Chairman, President and Chief Executive Officer of the combined company. See “Post-Merger Governance and Management” beginning on page 134 and “Additional Interests of AGL Resources’ and Nicor’s Directors and Executive Officers in the Merger” beginning on page 102 for further information.

Litigation Relating to the Merger (see page 100)

Nicor, the Nicor Board, AGL Resources, one or both of AGL Resources’ acquisition subsidiaries and, in one instance, Nicor’s Executive Vice President and Chief Financial Officer, have been named as defendants in six putative class action lawsuits (sometimes referred to as the shareholder actions) brought by purported Nicor shareholders challenging Nicor’s proposed merger with AGL Resources, two of which, including the lawsuit that named Nicor’s Executive Vice President and Chief Financial Officer as a defendant, have subsequently been voluntarily dismissed. The shareholder actions variously allege, among other things, that: (a) the Nicor Board breached its fiduciary duties to Nicor and its shareholders by (i) approving the sale of Nicor to AGL Resources at an inadequate purchase price (and thus failing to maximize value to Nicor shareholders), (ii) conducting an inadequate sale process by agreeing to preclusive deal protection provisions in the merger agreement and (iii) failing to disclose material information regarding the proposed merger to Nicor shareholders; and (b) AGL Resources and Nicor aided and abetted these alleged breaches of fiduciary duty. One of the shareholder actions, filed in federal court, also asserts claims under the federal securities laws, alleging, among other things, that (i) Nicor and the Nicor Board violated Section 14(a) of the Exchange Act and Rule 14a-9 promulgated thereunder by issuing a materially incomplete Registration Statement in connection with the proposed merger and (ii) the Nicor Board violated Section 20(a) of the Exchange Act by virtue of its control over the content and dissemination of the Registration Statement. The shareholder actions seek, among other things, damages and declaratory and injunctive relief, including orders enjoining the defendants from consummating the proposed merger. Nicor and AGL Resources believe the claims asserted in each lawsuit to be without merit and intend to vigorously defend against them.

Selected Historical Consolidated Financial Data of AGL Resources

The selected historical consolidated financial data of AGL Resources for each of the years ended December 31, 2010, 2009 and 2008, and as of December 31, 2010 and 2009 have been derived from AGL Resources’ audited consolidated financial statements and related notes contained in its Annual Report on Form 10-K for the year ended December 31, 2010, which is incorporated by reference in this joint proxy statement/prospectus. The selected historical consolidated financial data for the years ended December 31, 2007 and 2006 and as of December 31, 2008, 2007, and 2006 have been derived from AGL Resources’ audited consolidated financial statements, which have not been incorporated by reference in this joint proxy statement/prospectus. The information set forth below is only a summary and is not necessarily indicative of the results of future operations of AGL Resources or the combined company, and you should read the following information together with AGL Resources’ audited consolidated financial statements, the related notes and the section entitled “Management’s Discussion and Analysis of Financial Condition and Results of Operations” contained in AGL Resources’ Annual Report on Form 10-K for the year ended December 31, 2010, which is incorporated by reference in this joint proxy statement/prospectus. For more information, see the section entitled “Where You Can Find More Information” beginning on page 168.

Selected Historical Consolidated Financial Data of Nicor

The selected historical consolidated financial data of Nicor for each of the years ended December 31, 2010, 2009 and 2008, and as of December 31, 2010 and 2009 have been derived from Nicor’s audited consolidated financial statements and related notes contained in its Annual Report on Form 10-K for the year ended December 31, 2010, which is incorporated by reference in this joint proxy statement/prospectus. The selected historical consolidated financial data for the years ended December 31, 2007 and 2006 and as of December 31, 2008, 2007 and 2006 have been derived from Nicor’s audited consolidated financial statements, which have not been incorporated by reference in this joint proxy statement/prospectus. The information set forth below is only a summary and is not necessarily indicative of the results of future operations of Nicor or the combined company, and you should read the following information together with Nicor’s audited consolidated financial statements, the related notes and the section entitled “Management’s Discussion and Analysis of Financial Condition and Results of Operations” contained in Nicor’s Annual Report on Form 10-K for the year ended December 31, 2010, which is incorporated by reference in this joint proxy statement/prospectus. For more information, see the section entitled “Where You Can Find More Information” beginning on page 168.

Selected Unaudited Pro Forma Condensed Combined Consolidated Financial Information

The following selected Unaudited Pro Forma Condensed Combined Consolidated Statement of Income data of AGL Resources for the year ended December 31, 2010, has been prepared to give effect to the merger as if the merger was completed on January 1, 2010. The Unaudited Pro Forma Condensed Combined Consolidated Statement of Financial Position of AGL Resources as of December 31, 2010, has been prepared to give effect to the merger as if the merger was completed on December 31, 2010.

The following selected Unaudited Pro Forma Condensed Combined Consolidated Financial Information is for illustrative and informational purposes only and is not necessarily indicative of the results that might have occurred had the merger taken place on January 1, 2010 for statement of income purposes, and on December 31, 2010 for statement of financial position purposes, and is not intended to be a projection of future results. Future results may vary significantly from the results reflected because of various factors, including those discussed in the section entitled “Risk Factors” beginning on page 27. The following selected Unaudited Pro Forma Condensed Combined Consolidated Financial Information should be read in conjunction with the section entitled “Unaudited Pro Forma Condensed Combined Consolidated Financial Information” and related notes included in this joint proxy statement/prospectus beginning on page 135.

Comparative Historical and Unaudited Pro Forma Combined Per Share Information

The following table summarizes unaudited per share data for (i) AGL Resources and Nicor on a historical basis, (ii) AGL Resources on a pro forma combined basis giving effect to the merger and (iii) Nicor on a pro forma equivalent basis based on the exchange ratio of 0.8382 of a share of AGL Resources common stock per share of Nicor common stock. It has been assumed for purposes of the pro forma combined financial information provided below that the merger was completed on January 1, 2010 for earnings per share purposes, and on December 31, 2010 for book value per share purposes. The following information should be read in conjunction with the section entitled “Unaudited Pro Forma Condensed Combined Consolidated Financial Information” and related notes included in this joint proxy statement/prospectus beginning on page 135.

Comparative Per Share Market Price and Dividend Information

AGL Resources common stock and Nicor common stock are each listed on the NYSE. AGL Resources’ trading symbol is “AGL” and Nicor’s trading symbol is “GAS”.

The following table sets forth the high, low and closing prices for AGL Resources common stock and Nicor common stock as reported on the NYSE on December 6, 2010, the last trading day before AGL Resources and Nicor announced the merger, and April 25, 2011. The table also includes the value of Nicor common stock on an equivalent price per share basis, as determined by reference to the value of merger consideration to be received in respect of each share of Nicor common stock in the merger (including the cash consideration of $21.20 per share). These equivalent prices per share reflect the fluctuating value of AGL Resources common stock that Nicor shareholders would receive in exchange for each share of Nicor common stock (together with the amount of cash to be paid per share of Nicor common stock) if the merger was completed on either of these dates, applying the exchange ratio of 0.8382 of a share of AGL Resources common stock for each share of Nicor common stock.

The following table shows, for the calendar quarters indicated, based on published financial sources: (i) the high and low sale prices of shares of AGL Resources and Nicor common stock as reported on the NYSE and (ii) the cash dividends paid per share of AGL Resources and Nicor common stock.

Nicor shareholders are encouraged to obtain current market quotations for AGL Resources common stock prior to making any decision with respect to the merger. No assurance can be given concerning the market price for AGL Resources common stock before or after the date on which the merger is consummated. The market price for AGL Resources common stock will fluctuate between the date of this joint proxy statement/prospectus and the date on which the merger is consummated and thereafter.