Prospectively collected data on the incidence of treated hypertensive end-stage renal disease (HT-ESRD) were analyzed to investigate whether the higher rate of HT-ESRD in blacks compared with whites is due to differences in putative ESRD risk factors. The overall age-adjusted relative risks of HT-ESRD for black compared with white residents in the Maryland Regional ESRD Registry (Network 31) Catchment Area were 7.4 (95% confidence interval, 5.9 to 9.4) and 9.9 (95% confidence interval, 7.4 to 13.1) for men and women, respectively. In a population level analysis, race-specific HT-ESRD incidence rates in the black and white populations of 13 regions in Network 31 were related to the prevalence of putative ESRD risk factors in those populations. The latter were estimated from the 1981-1982 Maryland Statewide Household Hypertension Survey. Black populations had a 5.6-fold (95% confidence interval, 3.9 to 8.1) higher unadjusted incidence of HT-ESRD than white populations. The HT-ESRD incidence in a population was also directly related to that population's prevalence of hypertension, severe hypertension, and diabetes mellitus and inversely related to measures of socioeconomic status and mean age at diagnosis of hypertension. When adjusted simultaneously for age, prevalence of hypertension, severe hypertension, diabetes, and level of education, the risk of HT-ESRD was still 4.5 (95% confidence interval, 3.2 to 6.2) times higher for black compared with white populations. Our findings failed to support the hypothesis that race-related differences in the prevalence, severity, or age at onset of hypertension, in the prevalence of diabetes or in socioeconomic status, explain the well-recognized black-white differences in the HT-ESRD incidence.