Hypertensive emergencies present a difficult problem of management. Although many treatment regimens have been described over the years, their application has presented problems of adverse effects and all have required detailed and intensive supervision of patients. After favourable results obtained in a preliminary study using a combination of parenteral chlorpromazine and frusemide, a 5-year prospective study was conducted using this treatment to produce rapid reduction in blood pressure in patients with acute onset severe hypertension (blood pressure greater than 225/130 mmHg). The patients involved covered a wide range from 22 to 74 years (mean 47 years) and, on subsequent or previous investigation, were all considered to have essential hypertension. Twenty-seven patients were treated successfully with a single administration of the regimen. Two women required a second treatment before adequate control of blood pressure was achieved and 1 man died of extensive dissecting abdominal aortic aneurysm before the effects of the therapy could be fully assessed. The reduction in blood pressure was gradual but progressive over 4 hours and the pattern of response was uniform. No significant adverse effects related to the treatment were found. Only basic measurement of pulse and blood pressure was considered necessary and so this regimen of therapy is suitable for general use even when sophisticated monitoring facilities are not available and staff levels are limited.