The hemodynamic effects of Sunitang, an ancient Chinese remedy for general weakness, weak pulse, and cold extremities, were studied. In study, 1, 10 patients with left ventricular failure received Sunitang in single oral doses of 250, 500, and 1000 mg in a double-blind manner. Sunitang showed dose-related positive inotropic, chronotropic, and vasodilator effects. The effects reached their maximum within 30 to 60 minutes and lasted for 6 hours. In study 2, 77 patients with left ventricular failure who had not been treated satisfactorily by the conventional methods entered a controlled (parallel design), double-blind study for 1 month. When they entered the study they were in steady states. They continued their original medications throughout the month. Sunitang showed additional positive inotropic, chronotropic, and vasodilator effects. In this study no apparent adverse effects of Sunitang were noted. We conclude from these results that Sunitang may be useful in heart failure and bradycardia.