Twenty-six patients in late refractory septic shock were studied to evaluate the role of beta blockade. Following aggressive treatment 11 patients remained in shock and were treated with the beta-adrenergic blocking agent, propranolol hydrochloride. In all patients there was an increase in the arterial pressure, arterial oxygen pressure, urinary output, and total peripheral resistance, and a decrease in the central venous pressure, cardiac output, and heart rate. Survival resulted in the eight who had a normal or increased cardiac output (hyperdynamic shock). Beta blockade also appears to be effective in hypodynamic shock of various causations if the shock is primarily due to microcirculatory failure and if the cardiac output is not significantly decreased by beta blockade.