A cross-sectional study of all Black and Caucasian enlisted males in the U.S. Navy between 1974 and 1979 was conducted to determine if there were any significant racial group differences in disease incidence. First hospitalization rates for sixteen ICDA-8 diagnostic categories and selected diagnoses were examined and compared on the basis of race, age, year hospitalized, education and occupation. Results indicated that total disease incidence among Black males has declined in the past decade, with a reduction in total first hospitalizations from 1652 per 10,000 men in 1974 to 1088 per 10,000 men in 1979. Total incidence rates for Caucasian males in the same period declined from 1347 per 10,000 men to 1100 per 10,000 men. However, Blacks were found to be at significant risk for: mental disorders; diseases of the genitourinary system; diseases of the circulatory system; diseases of the digestive system; diseases of the blood and blood-forming organs; symptoms and ill-defined conditions; supplementary classifications; and diseases of the musculoskeletal system. Caucasians had significant higher incidence rates for diseases of the skin and subcutaneous tissue, and accidents, poisonings and violence. Nevertheless, the study results indicated that the populations of Blacks and Caucasians in the Navy are not uniform with respect to disease incidence. There exist numerous subgroups within either racial group, defined on the basis of certain demographic and social characteristics, which are at risk for particular diseases. In addition, the relationship between race and disease is mediated by several factors, including genetic predisposition, socioeconomic status and cultural patterns of belief and behavior. No single factor can account for the excess risk for all diseases among all members of either racial group.