Ten years after the end of the Gulf War, questions continue to be raised about the health of U.S. service personnel who fought in that war. A primary concern is whether Gulf War veterans are receiving effective treatments for their health problems. Section 105 of the Veterans Program Enhancement Act of 1998 mandates that the Department of Veterans Affairs (VA) ask the Institute of Medicine (IOM) to convene a committee that would identify a method for assessing treatment effectiveness and describe already-validated treatments for Gulf War veterans'' health problems, including the problem of medically unexplained symptoms. The specific charge to the committee is to (1) identify and describe approaches for assessing treatment effectiveness; (2) identify illnesses and conditions among veterans of the Gulf War, using data obtained from the VA and the Department of Defense (DoD) Gulf War Registries, as well as information in published articles; and (3) for these identified conditions and illnesses, identify validated models of treatment (to the extent that such treatments exist), or identify new approaches, theories, or research on the management of patients with these conditions if validated treatment models are not available.