This Institute of Medicine report examines the long-term health effects of participation in Project SHAD (Shipboard Hazard and Defense), which involved some 5,800 US Navy and Marine personnel participating, often unknowingly, in a series of tests of US warship vulnerability to biological and chemical warfare agents during 1962- 1973. Having received responses from about 60 percent of Project SHAD participants and 47 percent of controls, the study primarily assesses general health, physically and mentally. The study finds no difference in all-cause mortality between participants and controls, although participants had a significantly higher risk of death due to heart disease.