The cardiovascular instability in some cases of severe tetanus is due to increased circulating catecholamines. In 15 patients with this complication of tetanus, labetalol, a drug with alpha- and beta-peripheral adrenergic blocking properties, was used in management. The drug was administered orally, by i.v. bolus or by continuous infusion. Wide variation in dosage was needed both from case to case and in the same patient during the course of his disease. In most cases the pulse and blood pressure were reduced by labetalol, although their variability was not much improved. The effect on the cardiac output and systemic vascular resistance ranged from modest reduction in both, to marked effect on cardiac output without any change in systemic vascular resistance. The alpha-adrenergic blockage of labetalol is known to be less powerful than the beta-blocking effect, and this property could be a disadvantage in the management of sympathetic overactivity in tetanus.