Concerns about the health of veterans of recent military conflicts have given rise to broader questions regarding the health consequences of service in any major military engagement. The Veterans Program Enhancement Act of 1998 directed the Secretary of Veterans Affairs to enter into an agreement with the National Academy of Sciences to help develop a plan for establishing’ a national center (or centers) for the study of war-related illnesses and postdeployment health issues. In response to this legislation, the Department of Veterans Affairs (VA) asked the Institute of Medicine (IOM) to convene a committee of experts. The charge to the committee was to (1) assist the VA in developing a plan for establishing a national center (or centers) for the study of war-related illnesses and postdeployment health issues, and (2) assess preliminary VA plans and make recommendations regarding such efforts.