The 1991 Persian Gulf War was considered a brief and successful military operation with few injuries and deaths. A large number of returning veterans, however, soon began reporting health problems that they believed to be associated with their service in the gulf. Under a Congressional mandate, the Institute of Medicine (IOM) is reviewing a wide array of biologic, chemical, and physical agents to determine if exposure to these agents may be responsible for the veterans' health problems. In a 2000 report, Gulf War and Health, Volume 1: Depleted Uranium, Sarin, Pyridostigmine Bromide, and Vaccines, the IOM concluded that there was not enough evidence to draw conclusions as to whether long-term health problems are associated with exposure to depleted uranium, a component of some military munitions and armor. In response to veterans' ongoing concerns and recent publications in the literature, IOM updated its 2000 report. In this most recent report, Gulf War and Health: Updated Literature Review of Depleted Uranium, the committee concluded that there is still not enough evidence to determine whether exposure to depleted uranium is associated with long-term health problems. The report was sponsored by the U.S. Department of Veterans Affairs.