1 Six previously untreated emergency admissions to hospital with severe hypertension were given oral treatment with labetalol. 2 Pre-treatment diastolic BP exceeded 130 mmHg, and clinical evidence of either accelerated hypertension or encephalopathy was present. 3 Hypotensive response after treatment followed two patterns. 4 Quick-responders (n = 3) showed a sharp fall in BP to normal levels within 2 h, which was subsequently sustained for 10 or more hours. The daily dose of labetalol eventually required to achieve good BP control in this group was relatively low: 600--1200 mg. 5 Slow-responders (n = 3) showed a gradual, less marked fall in BP, which was sustained for many hours. These patients required further doses of labetalol to reduce BP to normal. The eventual daily dose of labetalol that ensured good BP control was high: 1200--2400 mg. 6 Heart rate was little changed by treatment. 7 Complications or side-effects were not observed.