Dobutamine, a derivative of dopamine, was infused at a rate of 10 mug/kg per min in 15 patients with severe congestive heart failure. Cardiac output increased from an average of 3.1 to 5.6 liters/min (P less than 0.001) with no change in mean arterial pressure (93.3 to 98.2 mm Hg) and only a slight increase in heart rate (98.5 to 105.2 beats/min) (P less than 0.02). Pulmonary wedge pressure was decreased from an average of 27.4 to 21.1 mm Hg (P less than 0.001). In seven patients a dose of 5 mug/kg per min also produced a significant increase in cardiac output but the effect was less than with the 10 mug/kg per min dose. No side effects were observed during the infusion. Dobutamine therefore is a potent inotropic drug with limited chronotropic and peripheral vascular effects and deserves therapeutic trial in the short-term management of low output heart failure.