The hemodynamic effect of oral TA-064 (20 mg), a newly synthesized inotropic agent, was compared with that of intravenous dobutamine (5 micrograms/kg/min) in eight patients with congestive heart failure who had been treated with intravenous dobutamine, digitalis, diuretics, and prazosin. Hemodynamics was measured using a Swan-Ganz catheter during the pre-dobutamine control period, during dobutamine infusion period, during the pre-TA-064 control period and at 90 minutes after oral administration of TA-064. Stroke work index was increased and mean pulmonary capillary wedge pressure was decreased with TA-064 or dobutamine. Cardiac index and stroke index was increased by each drug, and pulmonary and systemic vascular resistances were decreased. Mean systemic arterial pressure, heart rate and pressure-rate product did not significantly change in comparison with the control level. In conclusion, TA-064 has a hemodynamic effect similar to that of dobutamine and may be useful as an oral substitute for dobutamine in patients with congestive heart failure after temporary management with dobutamine.