SUMMARY Sixteen untreated black patients with mild-to-moderate hypertension and no evidence of target organ damage were matched for age, sex, casual blood pressure (BP), and socioeconomic status with 16 white hypertensives. All patients were studied under standardized conditions in the hospital where they underwent continuous intraarterial ambulatory monitoring of BP and assessment of BP control mechanisms. BP characteristics over prolonged periods of recording were similar for both groups, as were sinoaortic baroreflex activity and pressor response to isometric and dynamic exercise and to cold. Fasting cholesterol and triglyceride levels in both groups were similar. Resting plasma renin activity (PRA) was significantly lower in blacks, but no difference was observed in resting plasma norepinephrine levels. Urinary excretion of Na + and K + was also similar in both groups. Thus, results showed that casual BPs matched for black and whites, and recorded over a prolonged period, were similar in pattern, variability, and response to pressor stimuli. It appears that, if BP contributes to the different patterns of morbidity in blacks and whites, it is more likely to be the actual level of BP rather than differences in BP characteristics. (Hypertension 4: 817-820, 1982) KEY WORDS • ambulatory blood pressure • reflex cardiac control * atheroma T HE observation that the black population in North America has a higher blood pressure (BP) than the white population 1 2 has excited much interest. Associated with the higher BP is an increased incidence of target organ damage in blacks manifested as left ventricular hypertrophy (LVH), 3 cerebrovascular accidents/ and changes in optic fundi.
5The pathophysiological basis for raised BP in blacks and whites may differ, and reduced levels of plasma renin activity (PRA), 6 resting heart rate (HR), 7 and dopamine beta-hydroxylase (DBH) 8 could reflect differences in activity of the central nervous system. In addition, pathological studies have shown a different distribution of atheroma in the arteries of blacks and whites, 9 ' l0 the former having an increased deposition in the cerebral arteries, but conversely the coronary arteries are relatively spared, and this might be related to different BP characteristics and control between the groups.The purpose of this report is to compare the responses of matched black and white hypertensive pa-