Bepridil (10mg ? kg-1) iv elevated the threshold dose of ouabain (15ug ? min-1 iv) in guinea-pig and aconitine (10?g ? kg-1 ? min-1 iv) in rat induced ventricular extrasystole, ventricular tachycardia, ventricular fibrillation and cardiac arrest. It shortened the duration of arrhythmia elicitde by Adr (50ug ? Kg-1 iv) in conscious rabbits and by BaCl2 (3mg ? kg-1 iv) in rats. It is also effective in preventing reperfusion-induced arrhythmias in aneasthetized rats.