The electrophysiologic and hemodynamic effects and the pharmacokinetics of a single oral administration of pirmenol were evaluated in 20 patients with supraventricular tachycardia (SVT). Pirmenol, at 1hr after administration, significantly shortened sinus cycle length and sinoatrial conduction time. HV interval (46±10msec to 54±11msec, P<0.01), refractory period of the right atrium and the right ventricle were significantly prolonged. Furthermore, anterograde refractory period of accessory pathway and retrograde refractory period of AV node and accessory pathway were prolonged. Hemodynamic study revealed increased systemic and pulmonary vascular resistance and decreased stroke volume index. Induction of SVT was suppressed in 11 out of 16 patients. Among 5 patients who were not suppressed at 1hr, 2 patients resulted in noninducible at 2hr after administration. Plasma concentration of pirmenol at 1hr after administration was 1.0±0.4μg/ml in effective cases and was 0.4±0.5μg/ml in failed cases (P<0.05). Pharmacokinetics of single oral pirmenol were, t_max of 2.9hr, C_max of 1.4μg/ml, t_1/2 of 6.8hr and AUC of 18.7μg·hr/ml. In conclusion, a single oral administration of pirmenol was highly effective in suppression of induction of SVT with sufficient hemodynamic tolerance.