Abstract: Tetrandrineis an alkaloid isolated from the Chinese medicinal herb, Stephania tetrandra S. Moore. It has been shown clinically to be an effective antihypertensive drug. Its effects to dilate the coronary vasculature, to reduce the toxicity of cardiac glycosides and to correct cardiac arrhythmias have been demonstrated in the laboratory.This paper presents results of an experimental study of the influence of Tetrandrine on the left ventricular function and peripheral blood vessels in anesthetized openchest dogs.Tetrandrine given intravenously (10mg/kg and 15mg/kg) lowered the systemic blood pressure, decreased LVP and dp/dt max. The decreased LVP and dp/dt max recovered more rapidly than the systemic blood pressure. It is suggested that this cardiac inhibitory effect contributed at least in-part to the early hypotensive effect.Concomitant with its hypotensive effect, Tetrandrine caused a decrease of heart rate and a prolongation of P-R interval.The drug produced a marked reduction of the peripheral resistance which paralleled its effect on blood pressure. In addition, the pulse pressure was increased because the amount of decrease Of diastolic blood pressure was larger than that of the systolic. It may be concluded that this drug depresses blood pressure mainly by its dilatatory action on the resistant blood vessels.