Abstract: The antiarrhythmic actions of 3,6 - dimethylamino - dibenzopyridoniumedetate ( IHC-72), lidocaine (Lid) and verapamil (Ver) on several models Werecompared at equitoxic doses (equal fraction of LD₅₀) . The action of IHC- 72 againstaconitine induced arrhythmia was similar to that of Lid but stronger than that of Ver inanesthetized rats. The effect of IHC- 72 on ouabain induced arrhythmia was also similarto that of Lid, but weaker than that of Ver in anesthetized guinea pigs. The activity ofIHC- 72 to raise electrical ventricular fibrillation thresholds (VFT) was weaker than thatof Lid and Ver. The effects of IHC-72 in decreasing the incidence of ventricular prema-ture beat(VP B), ventricular tachycardia (VT), ventricular fibrillation (VF) andshotenning the duration of VT yielded by reperfusion were similar to those of Lidanf Ver in vivo.