Aconitum plants (Ranunculaceae family) are as extremely dangerous plant that contains various toxic di-ester di-terpene type Aconitum alkaloids, such as aconitines (aconitine, mesaconitine, hypaconitine and jesaconitine), primarily concentrated in the roots. Aconitines are well known for acute and highly toxicity in the causation of severe arrhythmias leading to death. We documented life-threatening intoxication in thirteen patients after accidental aconite poisoning. All patients developed characteristic symptoms of aconite poisoning within 15-30 minutes after intake of roots or leaves. These patients revealed arrhythmia including a ventricular tachycardia (VT) and ventricular fibrillation (VF) and 1 patient of them died. We examined relationship between serum aconitines concentration and disappearance of arrhythmia in five patients of thirteen patients. Serum concentration of aconitines at the time of disappearance of arrhythmia in these patients was within 0.5-1.5 ng/mL, despite the fact that time required for the disappearance exhibited large interindividual variability (5.5-16 h). It suggests that serum concentration of aconitines is important for treatment to arrhythmia of aconite poisoning patient. Therefore, our results seem to be the useful information in the future treatment for the patient of aconite poisoning.