Congenital heart disease complicates the management of most accessory pathway-mediated tachycardias and also increases the challenge of radiofrequency ablation. Since 1990, radiofrequency ablation of accessory atrioventricular (AV) pathways has been attempted in 10 patients (age range 3.5 months to 30 years) with congenital heart disease: Ebstein's anomaly (n = 5), heterotaxy with AV discordance (n = 3), tetralogy of Fallot (n = 1) and total anomalous pulmonary venous return (n = 1). Eight patients had manifest Wolff-Parkinson-White syndrome and 2 had concealed pathways. Five patients had multiple pathways including 4 of the 5 with Ebstein's anomaly. Of 16 pathways total, 15 were associated with the tricuspid valve including all pathways in the patients with Ebstein's anomaly and heterotaxy. The His bundle area was identified in all patients and involved an anterior AV node in 2 of 3 with heterotaxy. Ablation was performed on the atrial side of the AV ring in all cases. No instance of AV block was encountered. Complete success was achieved in 6 patients including the 3 with heterotaxy. In 2 patients, manifest preexcitation was eliminated and clinical symptoms were greatly modified. The procedure was transiently successful in 1 patient who later had surgical interruption of the accessory pathway during tetralogy of Fallot repair. Ablation was unsuccessful in 1 patient. Thus, the overall success was 80%.