Electrical ablation of a posteroseptal accessory pathway by delivery of direct current electrical energy at the coronary sinus ostium was attempted in six patients. As a result of 12 procedures in these six patients, the posteroseptal accessory pathway was successfully ablated in one patient. Retrograde conduction only was affected in a further three patients, abolishing paroxysmal supraventricular tachycardia in two and reducing the tachycardia rate in one. One of the six patients developed coronary sinus perforation requiring prompt pericardial aspiration. The procedure is complicated, time consuming, of limited efficacy and coronary sinus perforation is a significant risk. Surgery remains the preferred option as a curative procedure for arrhythmias due to posteroseptal accessory pathway.