Objectives. The aim of this study was to report the results and techniques of radiofrequency ablation for treatment of supraventricular arrhythmias in patients with congenital structural heart disease. Background. The management of patients with congenital and other structural heart disease may be complicated by serious arrhythmias due to Wolff-Parkinson-White syndrome or by atrial arrhythmias after cardiac surgery. Ablation techniques using radiofrequcncy current are revolutionizing the management of arrhythmias, but reports have included few with structural heart disease. Methods. Fifteen patients with significant heart disease underwent radiofrequency ablation: 11 with Wolff-Parkinson-White syndrome and 4 with intraatrial reentrant tachycardia after atrial surgery. Seven had Ebstein's anomaly, complex in two, and the rest had other defects. Coexistence of structural defects introduced significant technical difficulties to radiofrequency ablation in patients with the Wolff-Parkinson-White syndrome and was accomplished by adaptation of current techniques. Ablation of intraatrial reentrant tachycardia was performed by finding early atrial activation sites with electrogram fractionation for radiofrequency application. Results. Radiofrequency ablation was initially successful in 14 of 15 patients, with cure in 10 and clinical improvement in 14. Two patients subsequently underwent cardiac surgery without perioperative arrhythmias. Conclusions. Radiofrequency ablation in patients with congenital heart disease and arrhythmias is both safe and effective and may be the preferred approach to treatment in some patients. In patients who are to undergo surgical correction or palliation, preoperative radiofrequency ablation of the tachycardia substrate is effective and may be preferred to operative accessory pathway division. The ablation of intraatrial reentrant tachycardia shows promise in the management of patients who have undergone extensive atrial surgery, and it may eventually become the preferred approach, particularly when there are contraindications to the use of antiarrhythmic agents.