Physiological studies reported from our laboratory over the past several years have been reviewed and support epidemiological reports indicating that hypertensive cardiac and vascular disease runs a more severe course in the black patient. Although comparison of systemic hemodynamics failed to demonstrate that, for any level of arterial pressure, the magnitude of total peripheral resistance (which is the hemodynamic hallmark of hypertensive disease) differed between black patients and white patients, there are more subtle differences that were ascertained. Thus, although intravascular (plasma) volume contracts as arterial pressure and total peripheral resistance increase in both racial groups, this relation may differ quantitatively. At least in some black patients (43%), intravascular volume may be more expanded; in these patients, this relation is less closely correlated with the renopressor system (i.e., plasma renin activity). Moreover, these studies indicated that, at any level of arterial pressure, cardiac (left ventricular mass and posterior wall thickness) and renal hemodynamic involvement is more severe in the black patient. These findings point to important differences that operate in black patients and white patients with essential hypertension. With further study, these findings may be translated into more specific antihypertensive therapeutic implications for patients of both racial groups with essential hypertension.