Using a retrospective cohort approach and data from Department of Defense hospitals, this study examines whether 547,076 Persian Gulf War veterans (PGWVs) were at increased risk for hospitalization (RH) after the war, as compared with 618,335 veterans from the same era who did not go to the Persian Gulf. Multivariate logistic regression models were used to analyze risk factors both overall and in 14 broad diagnostic categories in each of 3 postwar periods (1991, 1992, and 1993). In 16 of the 45 comparisons involving specific diagnoses, the RH among PGWVs differed from the other veterans. PGWVs were at higher risk in 5 disorders: neoplasms and genitourinary system diseases during 1991, diseases of the blood and blood forming organs during 1992, and mental disorders during both 1992 and 1993. The differences were not consistent over time and could be accounted for by deferred care, postwar pregnancies, and postwar stress.