Abstract: Harris tow- stage left anterior coronary ligation was performed in anesthetizeddogs.After twenty hours,severe ventricular arrhythmias were recorded under conscious state.Cumu-lative intravenous injections of guanfu base A,a new alkaloid isolated from the tuber of Aconitumcoreanum in China,from 1 0 to 4 0 mg· kg^-1produced remarkable antiarrhythmic effect lasting over30 min and a moderate reduction of heart rate. The P-R interval,QRS complex and Q-Tinterval ofthe sinus rhythm were not significantly altered.The antiarrhythmic potency of guanfu base A in thismodel was found to be about one third that of quinidine.