Sixty uncomplicated hypertensive patients (30 stable and 30 borderline) were studied, by strain gauge plethysmography, in comparison with 25 normotensive subjects, in order to evaluate the arterial hemodynamics of the lower limbs in essential hypertension and to verify the different pattern in borderline and in stable hypertensives. Resting blood flow, even if slightly decreased in hypertensive groups, did not show significant differences in its mean values; peak flow, instead, was reduced proportionally to the severity of hypertension in all the hypertensive patients, but only in the stable hypertensives was it statistically significant. Minimal vascular resistance showed a similar behavior: it was significantly increased only in the stable hypertensives, whereas basal vascular resistance was raised in all hypertensive patients and also in the borderline group. Finally, the half-time and the total hyperemic response time, which indicate vascular reactivity, were significantly decreased in all the hypertensives. These results suggest that the stable hypertensive patients develop principally arterial structural changes, while the borderline hypertensive patients have only functional modi fications, such as a reduced compliance and a hyperdynamic condition.