Malignant or accelerated hypertension is a life-threatening disease whose complications may be prevented by rapid reduction of the blood pressure. Diazoxide is presently regarded as the preferred therapeutic agent, but drugs such as trimethaphan, sodium nitroprusside, phenoxybenzamine and hydralazine may be useful in particular situations. Treatment is best carried out in an intensive care unit, where appropriate monitoring and study of the patient can be done. Since the introduction of antihypertensive agents the life expectancy of these patients, even those with renal insufficiency, has increased.