The effect of intravenous infusion of labetalol and of dihydralazine in increasing doses was compared in 12 women with severe hypertension in pregnancy. In 5 our of 6 women labetalol produced a smooth, progressive fall in blood pressure to normal levels with minimal side effects. In 2 our of 6 women on dihydralazine the blood pressure control was satisfactory but in the remaining 4 patients treatment had to by discontinued because of unpredictable, sudden falls in blood pressure. One of the 6 infants of mothers treated with labetalol manifested signs of adrenergic blockade. Continuous infusion of labetalol appears to offer significant advantages in the management of severe hypertension in pregnancy and merits further trial.