Abstract: Heart rhythm disturbances were precipitated in about 80.9% of normal rabbits 0～10 minutes after the intravenous injection of pyquiton at the dosage of 35～45 mg/kg, and sustained for 1～21 minutes. Prior to cardiac arrhythmia, bradycardia was observed in 84.1% of the rabbits. Among the tested antiarrhythmic agents, phenoxybenzamine (dibenzyline) at the dosage of 3 mg/kg exhibited the most dramatic antiarrhythmic action on pyquiton-induced arrhythmia; chlorpromazine hydrochloride (5mg/kg), isoptinum (0.3～0.5 mg/kg), promethazine hydrochloridum(3～5 mg/kg) and phenytoine sodium (50 mg/kg) could also abolish arrhythmia; lidocaine hydrochloride, quinidine, isopreanline sulfate, and atropine sulfate etc. showed partial and/ or incomplete antiarrhymic action; while proctolol and shangrolin were ineffective. Preadministration of phenytoine sodium (50 mg/kg), chlorpromazine hydrochloride (5 mg/kg) etc. were demonstrated to be effective in preventing the pyquitoninduced arrhythmia.