Eighty patients with manifest or concealed Wolff-Parkinson-White (WPW) syndrome underwent catheter ablation of 86 accessory pathways (AP) using radiofrequency current. There are 65 AP located on the left side and 21 on the right side of the heart. The atrioventricular reciprocating tachycardia was previously documented in 77 patients and atrial fibrillation with a rapid ventricular response in 21 patients. Ablation was attempted via a catheter positioned at the atrial aspect of the tricuspid annulus in patients with a right-sided AP and via a catheter positioned in the left ventricle directly below the mitral annulus in patients with a left-sided AP. AP conduction was permanently abolished in 82 of the 86 pathways (95%). The number of radiofrequency current applications for these 82 successfully ablated AP was 7.6 +/- 0.9. Of the 65 left-sided and 21 right-sided AP, 62 (95%) and 20 AP (95%) were successfully ablated, respectively. The current application to the right-sided AP was 16.7 +/- 2.2, which was greater than that to the left-sided one (4.7 +/- 0.6, p < 0.001). No serious complication was observed in any case. Catheter ablation of AP using radiofrequency current is an effective and safe therapeutic modality for patients with symptomatic WPW syndrome.