The authors report the case of a 35-year old woman with normal heart who voluntarily poisoned herself by swallowing 6 grams of naftidrofuryl. She developed disorders of atrioventricular conduction and a ventricular-like arrhythmia with collapse which resolves after mechanical ventilation. Data from the literature indicate that naftidrofuryl possesses class I electrophysiological properties which must not be ignored and which account for the cardiac effects observed in this particular case and in cases of parenteral overdosage already reported. By analogy with class I antiarrhythmic agents, treatment of naftidrofuryl poisoning with disorders of conduction could include the administration of molar sodium lactate.