OBJECTIVE: Ebstein's anomaly is the most common pathology associated with the accessory conduction pathways. METHODS: From January 1990 to August 1999 48 patients underwent surgical repair of Ebstein's anomaly by various plastic techniques. The pathways were identified and characterized at preoperative electrophysiologic mapping in 17 (34.5%) patients. There were seven males and ten females. The patients age ranged 6-35 years (mean 12.7+/-2.1 years). Five patients were in NYHA class II and were in 12 in NYHA class III. The cardiothoracic ratio ranged from 0.59 to 0.69 (mean 0.65+/-0.08). Tachycardia was present in 15 patients with Wolf-Parkinson-White (WPW) syndrome. Atrial septal defect was present in 12 patients (70. 6%). Accessory conduction pathways were in the right posterior septal area in seven patients, in right posterior septal area and free wall in seven patients and in right free wall in three. The pathways were successfully ablated in all patients during cardiopulmonary bypass. RESULTS: There were no deaths, no relapses. Follow-up ranged from 4 months to 7 years (mean 4.7+/-1.1 years). There were no late deaths, but one patient required successful tricuspid valve replacement because of severe tricuspid insufficiency. At follow-up 57.8% of patients were in NYHA class I. CONCLUSIONS: Preoperative electrophysiologic study allows to identify the accessory conduction pathways in patients with Ebstein's anomaly. The combined approach of tricuspid valve repair and surgical ablation of accessory atrioventricular connections has been proved safe and effective. This operative procedure allows to improve functional results in patients with Ebstein's malformation and concomitant accessory conduction pathways.