Yohimbine was studied for its effect on aconitine induced cardiac arrhythmias in rats. Aconitine was infused intravenously and the time of onset of initial arrhythmias and ventricular tachycardia was noted in yohimbine (1.25, 2.5 and 5.0 mg kg-1) and quinidine (5.0 mg kg-1) treated rats. Yohimbine like the antiarrhythmic agent quinidine, showed significant antiarrhythmic activity, and delayed the onset of the arrhythmic stages produced by aconitine.