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Exhibit 31.1 CERTIFICATION
OF
CHIEF EXECUTIVE OFFICER
PURSUANT TO SECTION 302 OF THE SARBANES-OXLEY ACT OF 2002 I, Jeffrey L. McWaters, Chairman and Chief Executive Officer of AMERIGROUP Corporation, certify
that:  1.
    I have reviewed this Quarterly Report on Form 10-Q for the three-month period ended March 31,
2005 of AMERIGROUP Corporation;2.
    Based on my knowledge, this report does not contain any untrue statement of a material fact or
omit to state a material fact necessary to make the statements made, in light of the circumstances
under which such statements were made, not misleading with respect to the period covered by this
report;3.
    Based on my knowledge, the financial statements, and other financial information included in
this report, fairly present in all material respects the financial condition, results of operations
and cash flows of the registrant as of, and for, the periods presented in this report;4.
    The registrants other certifying officer and I are responsible for establishing and maintaining
disclosure controls and procedures (as defined in Exchange Act Rules 13a-15(e) and 15d-15(e)) and
internal control over financial reporting (as defined in Exchange Act Rules 13a-15(f) and
15d-15(f)) for the registrant and have:  (a)
    Designed such disclosure controls and procedures, or caused such disclosure
controls and procedures to be designed under our supervision, to ensure that material
information relating to the registrant, including its consolidated subsidiaries, is
made known to us by others within those entities, particularly during the period in
which this report is being prepared;(b)
    Designed such internal control over financial reporting, or caused such
internal control over financial reporting to be designed under our supervision, to
provide reasonable assurance regarding the reliability of financial reporting and the
preparation of financial statements for external purposes in accordance with generally
accepted accounting principles;(c)
    Evaluated the effectiveness of the registrants disclosure controls and
procedures and presented in this report our conclusions about the effectiveness of the
disclosure controls and procedures, as of the end of the period covered by this report
based on such evaluation; and(d)
    Disclosed in this report any change in the registrants internal control over
financial reporting that occurred during the registrants most recent fiscal




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quarter that has materially affected, or is reasonably likely to materially
affect, the registrants internal control over financial reporting; and  5.
    The registrants other certifying officer and I have disclosed, based on our most recent
evaluation of internal control over financial reporting, to the registrants auditors and the audit
committee of the registrants board of directors (or persons performing the equivalent functions):  (a)
    All significant deficiencies and material weaknesses in the design or operation
of internal control over financial reporting which are reasonably likely to adversely
affect the registrants ability to record, process, summarize and report financial
information; and(b)
    Any fraud, whether or not material, that involves management or other employees
who have a significant role in the registrants internal control over financial
reporting. Date: May 6, 2005
    /s/ Jeffrey L. McWatersJeffrey L. McWatersChairman and Chief Executive Officer