SUMMARY Differences in blood pressure between blacks and whites in the United States are now well documented. The causes of these differences remain speculative. Genetic factors, personal characteristics, renal physiology, endocrine factors, autonomic nervous system function, cardiac function and various environmental factors are examined in the present review as potential determinants of racial blood pressure differences. Racial differences in renal physiology and environmental influences such as socioeconomic status seem to be likely candidates for important contributions to blood pressure differences. Further research aimed specifically at black-white blood pressure differences is of great importance to a fundamental understanding of the etiology and prevention of essential hypertension.