In response to concerns that Gulf War veterans were experiencing increased morbidity resulting from wartime exposures in the Gulf War, the Department of Veterans Affairs and the Department of Defense (DoD) initiated clinical registries to provide systematic health evaluations for self-referred Gulf War veterans. The authors used Cox's proportional hazard modeling with data from all DoD hospitals to estimate the probability of hospitalization resulting from any cause, resulting from diagnosis in a major diagnostic category, and resulting from a specific diagnosis of interest. After adjusting for other risk factors, registry participants were 1.43 times more likely to have a postwar hospitalization than registry nonparticipants (95% confidence interval, 1.40-1.46). These findings support the hypothesis that registry participants were more likely to experience postwar morbidity than veterans who chose not to enroll in the health registries.