Verapamil is highly effective in terminating paroxysmal supraventricular tachycardia(PSVT) by its depressive action on the AV node. In other countries it is already the drug of choice if vagal manevers fail for conversion of PSVT. We evaluated therapeutic efficacy of intravenous verapamil in 30 patients with PSVT who visited Severance Hospital from november 1978 to November 1984. Twenty six of 30 patients(86.7%) had a restoration of normal sinus rhythm by intravenous verapamil without significant side effects. Thus intravenous verapamil is safe and extremely effective in terminating most PSVT.