A case of a 38 year old male with WPW syndrome and frequently recurrent antidromic atrio-ventricular sustained tachycardias is presented. In his ecg recordings delta wave depolarizations indicated right free wall accessory pathway. This was proved during electrophysiologic study. The effective refractory period of this pathway was short in both directions-below 200 ms. There was a wide zone of sustained antidromic tachycardia 236-247/min induction. Intravenous injection of flecainide terminated antidromic tachycardia but a wide zone of sustained orthodromic tachycardia 150/min induction appeared. Dissection of the right free wall accessory pathway was performed using Sealy technique (Cox modification). During the intraoperation electrophysiologic study an orthodromic tachycardia with retrograde conduction through an antero-septal accessory pathway was induced. After dissection of that second pathway abnormal atrioventricular conduction was abolished. The patients has been free from episodes of tachycardia during one year follow-up period.