Eight patients with severe tetanus experienced episodes of marked cardiovascular instability. During these unstable periods, cardiac output and vascular resistance varied independently. Beta blocking and low doses of ganglionic blocking agents failed to control cardiovascular instability even when combined. High doses of ganglionic blockers stabilized hemodynamics for a short period, but caused the elevation of transaminases. After unsuccessful treatment with cardiovascular drugs, continuous spinal anesthesia (CSA) was applied to five patients. For 5 to 23 days circulation was regulated artificially under complete blockade of the autonomic nervous system by infusing isotonic 0.5% bupivacaine intrathecally. Catecholamine was added intravenously to maintain adequate blood pressure. Before the introduction of CSA, three patients died of circulatory failure. In contrast, CSA dramatically suppressed the cardiovascular instabilities, and all five treated patients survived. This suggests that both sympathetic and parasympathetic nervous systems need to be blocked to stabilize hemodynamics in severe tetanus.