Brachial artery hemodynamics including brachial artery diameter (D) and local blood flow velocity (V) was studied in 15 normotensive subjects (NT) and 19 age-matched hypertensive patients (HT) at rest using a bidimensional pulsed Doppler system during a 2-min period of distal circulatory occlusion and during reactive hyperemia. Kinetics of changes in V and D were determined during successive and reproducible maneuvers. V and D decreased significantly during distal circulatory occlusion in both groups. During reactive hyperemia, V reached similar maximum values in both groups, and D increased significantly in NT and HT. Changes in D during reactive hyperemia were positively and significantly correlated with changes in V recorded at the same level. No significant difference was found between the two groups. These results demonstrate noninvasively that there are velocity-dependent variations in the diameter of a large artery in humans and suggest that velocity-dependent vasodilation of the brachial artery is not impaired in essential hypertension.