Among the most striking epidemiologic characteristics of prostatic cancer in the United States is the sizeable excess in rates for the disease among blacks as compared with whites. This study attempted to determine whether the higher black rates might be explained by controlling for social class, using mortality data from Alameda County for the pericensal period 1968--1972 (n = 400), and the population-based series of cases for Alameda County included in the Third National Cancer Survey, 1969--1971 (n = 750). Reviewed first are previous studies addressed to the relationship of prostatic cancer and socioeconomic status (SES), most of which have been confined to whites. In the present study, each death or case was assigned to a socioeconomic class based on census tract of residence and rates by race and social class determined. Comparison of age-specific mortality and incidence rates by SES reveals no gradient for prostatic cancer in either whites or blacks.