Local capillary blood flow in subcutaneous tissue and muscle was measured by tissue clearance of Na <sup>131</sup>I at rest and during vasomotor reactions in 33 patients with essential hypertension and in an age-matched control group, before and after application of guanethidine and propranolol. Capillary blood flow in the subcutaneous tissue of the hand and leg as well as in the calf musculature was significantly lower in hypertensive than in normotensive subjects, whereas capillary blood flow in forearm muscles was greater in hypertensives than in controls. Guanethidine returned the values of capillary blood flow in hypertensive patients to the values characteristic of normotensive controls before drug administration. Propranolol produced a significant decrease of capillary blood flow in subcutaneous tissue of the hand and leg, as well as in both forearm and calf muscles.