Abstract: Intravenous injections of changrolin followed by or concomitant with injections of aconitine could retard the onset of aconitineinduced arrhythmia. If changrolin was given after the onset of arrhythmia, the antiarrhythmic effect of changrolin would be weaker. Neither bilateral vagotomy nor intravenous injections of hexamethonium modified the antiarrhythmic effect of changrolin. The dose thresholds for ventricular premature beats, ventricular tachycardia and ventricular fibrillation during intravenous infusion of aconitine at constant rate were all raised by a premedication of changrolin, and further augmented by a previous reserpinization. Administrations of changrolin into the lateral cerebral ventricle also retarded the onset of arrhythmia induced by a subsequent intracerebral introduction of aconitine.On the sciatic nerves of rats changrolin manifestated only a very mild local anaesthetic action, which was obviously different from that of lidocaine.