1. Six weeks' treatment with labetalol (600 mg/day) significantly reduced systolic and diastolic blood pressures in 24 patients with essential hypertension. There was a small but not significant decrease in heart rate.
2. After 6 weeks of therapy mean digital arterial blood flow at rest and during reactive hyperaemia had increased by 26%.
3. In nine essential hypertensive patients intravenous administration of 100 mg of labetalol caused prompt and striking reductions of systolic and diastolic blood pressures without significant changes in heart rate. There was a consistent and significant increase in peripheral blood flow by 32% 5 min after administration of the drug.
4. Antagonism of α-receptors in addition to β-receptors might improve peripheral arterial blood flow while achieving antihypertensive control. Thus labetalol, owing to its favourable haemodynamic effects, may have advantages over conventional pure β-receptor-blocking agents.