BACKGROUND: During the 1991 Gulf War, some Allied troops were potentially exposed to chemical warfare agents as the result of the detonation of Iraqi munitions at Khamisiyah. METHODS: In 1999, we conducted a computer-assisted telephone survey of 2918 Gulf War veterans from Oregon, Washington, California, North Carolina, and Georgia to evaluate the prevalence of self-reported medical diagnoses and hospitalizations among this potentially exposed population and among comparison groups of veterans deployed and nondeployed to the Southwest Asia theater of operations. RESULTS: Troops reported to be within 50 kilometers of the Khamisiyah site did not differ from other deployed troops on reports of any medical conditions or hospitalizations in the 9 years following the Gulf War. Hospitalization rates among deployed and nondeployed troops did not differ. Deployed troops were significantly more likely to report diagnoses of high blood pressure (odds ratio [OR]=1.7); heart disease (OR=2.5); slipped disk or pinched nerve (OR=1.5); post-traumatic stress disorder (OR=14.9); hospitalization for depression (OR=5.1); and periodontal disease (OR=1.8) when compared to nondeployed troops. There was a trend for deployed veterans to report more diagnoses of any cancer (OR=3.0). CONCLUSIONS: These findings do not provide evidence of any long-term health effect associated with exposure to the detonation of chemical warfare agents, but support findings from other investigations of increased morbidity among deployed troops. The prevalence of cancer among this population of deployed troops merits ongoing attention.