UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 8-K

CURRENT REPORT

Pursuant to Section 13 or 15(d) of the

Securities Exchange Act of 1934

Date of Report (Date of earliest event reported): October 3, 2012

AMERIGROUP CORPORATION

(Exact name of registrant as specified in charter)

(757) 490-6900

Registrant’s telephone number, including area code

Not Applicable

Former name or former address, if changed since last report

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:

On October 3, 2012, Amerigroup Corporation (“Amerigroup”) issued a press release announcing that Institutional Shareholder Services Inc. and Glass Lewis & Co., each recommend that Amerigroup stockholders vote “FOR” adoption of the merger agreement pursuant to which WellPoint, Inc. (“WellPoint”) will acquire Amerigroup (the “transaction”). Additionally, the press release indicated that the State of Tennessee Department of Commerce and Insurance approved WellPoint’s filings with the State related to the transaction and that Amerigroup would not issue a press release or host an earnings call for its third quarter 2012 financial results. The full text of the press release is attached hereto as Exhibit 99.1 and is incorporated herein in its entirety by reference.

Cautionary Statement Regarding Forward-Looking Statements

This communication contains certain “forward-looking” statements as that term is defined by Section 27A of the Securities Act of 1933, as amended, and Section 21E of the Securities Exchange Act of 1934, as amended. Statements that are predictive in nature, that depend on or relate to future events or conditions, or that include words such as “believes”, “anticipates”, “expects”, “may”, “will”, “should”, “estimates”, “intends”, “plans” and other similar expressions are forward-looking statements. Forward-looking statements involve known and unknown risks and uncertainties that may cause our actual results in future periods to differ materially from those projected or contemplated in the forward-looking statements as a result of, but not limited to, the following factors: the failure to obtain regulatory approval or consummate the sale of Amerigroup Virginia, Inc., the failure to receive, on a timely basis or otherwise, the required approvals by Amerigroup’s stockholders and government or regulatory agencies related to its transaction with WellPoint; the risk that a condition to closing of the proposed transaction may not be satisfied; Amerigroup’s and WellPoint’s ability to consummate the merger; the failure by WellPoint to obtain the necessary debt financing arrangements set forth in the commitment letter received in connection with the merger; operating costs and business disruption may be greater than expected; the ability of Amerigroup to retain and hire key personnel and maintain relationships with providers or other business partners pending the consummation of the transaction; and the impact of legislative, regulatory and competitive changes and other risk factors relating to the industries in which Amerigroup and WellPoint operate, as detailed from time to time in each of Amerigroup’s and WellPoint’s reports filed with the Securities and Exchange Commission (the “SEC”). There can be no assurance that the proposed transaction will in fact be consummated.

Additional information about these factors and about the material factors or assumptions underlying such forward-looking statements may be found under Item 1.A in Amerigroup’s Annual Report on Form 10-K for the fiscal year ended December 31, 2011, and Item 1.A in Amerigroup’s Quarterly Report on Form 10-Q for the quarter ended June 30, 2012, as amended. Amerigroup cautions that the foregoing list of important factors that may affect future results is not exhaustive. When relying on forward-looking statements to make decisions with respect to the proposed transaction, stockholders and others should carefully consider the foregoing factors and other uncertainties and potential events. All subsequent written and oral forward-looking statements concerning the proposed transaction or other matters attributable to Amerigroup or any other person acting on their behalf are expressly qualified in their entirety by the cautionary statements referenced above. The forward-looking statements contained herein speak only as of the date of this communication. Amerigroup undertakes no obligation to update or revise any forward-looking statements for any reason, even if new information becomes available or other events occur in the future, except as may be required by law.

Additional Information and Where to Find It

This communication is being made in respect of the proposed transaction involving Amerigroup and WellPoint. The proposed transaction will be submitted to the stockholders of Amerigroup for their consideration. In connection with the proposed transaction, Amerigroup filed a definitive proxy statement and supplement to the definitive proxy statement with the SEC on August 30, 2012 and October 3, 2012, respectively. Amerigroup and WellPoint may file with the SEC other documents regarding the proposed transaction. STOCKHOLDERS ARE URGED TO READ THE DEFINITIVE PROXY STATEMENT AND SUPPLEMENT TO THE DEFINITIVE PROXY STATEMENT REGARDING THE PROPOSED TRANSACTION IN THEIR ENTIRETY AND TO READ ANY OTHER RELEVANT DOCUMENTS CAREFULLY AND IN THEIR ENTIRETY WHEN THEY BECOME AVAILABLE BECAUSE THEY WILL CONTAIN IMPORTANT INFORMATION ABOUT THE PROPOSED TRANSACTION. The definitive proxy statement was mailed to Amerigroup’s stockholders beginning on or about August 31, 2012. The supplement to the definitive proxy statement will be mailed to Amerigroup’s stockholders beginning on or about October 4, 2012. You may obtain copies of all documents filed with the SEC concerning the proposed transaction, free of charge, at the SEC’s website at www.sec.gov. In addition, stockholders may obtain free copies of the documents filed with the SEC by Amerigroup by going to Amerigroup’s Investor Relations website page by clicking the “Investors” link at www.amerigroup.com or by sending a written request to Amerigroup’s Secretary at Amerigroup Corporation, 4425 Corporation Lane, Virginia Beach, Virginia 23462, or by calling the Secretary at (757) 490-6900.

Interests of Participants

Amerigroup and WellPoint and each of their respective directors and executive officers may be deemed to be participants in the solicitation of proxies from the stockholders of Amerigroup in connection with the proposed transaction. Information regarding Amerigroup’s directors and executive officers is set forth in Amerigroup’s proxy statement for its 2012 annual meeting of stockholders and its Annual Report on Form 10-K for the fiscal year ended December 31, 2011, which were filed with the SEC on April 27, 2012 and February 24, 2012, respectively. Information regarding WellPoint’s directors and executive officers is set forth in WellPoint’s proxy statement for its 2012 annual meeting of shareholders and its Annual Report on Form 10-K for the fiscal year ended December 31, 2011, which were filed with the SEC on April 2, 2012 and February 22, 2012, respectively. Additional information regarding persons who may be deemed to be participants in the solicitation of proxies in respect of the proposed transaction is contained in the definitive proxy statement and supplement to the definitive proxy statement filed by Amerigroup with the SEC on August 30, 2012 and October 3, 2012, respectively.

SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, the Registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized.

Date: October 4, 2012