A multi-centre general practitioner assessment of pindolol, a beta adrenergic blocking drug, was carried out in 464 patients with essential hypertension. The average daily dose was 21 mg and the average period of observation was 15 weeks. Pindolol was shown to be a safe, effective and well tolerated hypotensive agent. In 227 new cases of hypertension, 148 (65.2%) were controlled on pindolol alone, and in 237 previously treated cases of hypertension 91 (38.4%) were subsequently controlled on pindolol alone. In the remaining cases the addition of a diuretic or other antihypertensive agent was necessary to achieve satisfactory control. The mean blood pressure was lowered from 190/111 mmHg to 154/90 mmHg, a mean fall of 36/21 mmHg. Side-effects were not of a serious nature.