1. One hundred patients with severe essential hypertension have been treated with minoxidil for a mean period of 8·4 months in a study involving eleven European centres. Seventy-two males and twenty-eight females were included in the group; the mean age was 55 years and the initial supine systolic and diastolic pressures averaged 212 (range 150–270) and 125 (range 90–150) mmHg respectively. 2. Reduction of supine diastolic pressure to less than 100 mmHg occurred in 94% of patients within 4 weeks. After the average follow-up period of 8·4 months the mean pressures were 151/91 mmHg. Concomitant therapy with β-receptor-blocking agents and diuretics resulted in satisfactory control of heart rate and weight gain. 3. Side effects included increased hair growth, nausea, fatigue, rash and darkening of the skin. ECG showed mainly T-wave changes and echocardiographic examination indicated improved ventricular emptying.