Using mortality and incidence data from Alameda County, California, this study attempted to determine whether the higher occurrence rate of prostatic cancer among black men as compared with whites in the United States might be explained by racial differences in factors associated with socioeconomic status. Each death or case of prostatic cancer was assigned to a social class based on census tract of residence, and rates by race and socioeconomic status were computed. Comparison of age-specific mortality and incidence rates by socioeconomic status reveals no gradient in either whites or blacks. The higher risk for blacks holds up at almost every age and socioeconomic level. However, the racial differences are less pronounced for incidence than for mortality. Racial differences in the occurrrence of deaths appearing in Part II of the death certificate are also examined.