Ten young patients with a median age of 10.5 (range: 6 to 31) years suffering from the permanent form of junctional reciprocating tachycardia (PJRT; n = 7) and ectopic atrial tachycardia (AET; n = 3) were treated by transcatheter radiofrequency current application. Indications for interventional therapy were failure of medical therapy after a median of 3 antiarrhythmic drugs in all patients, syncope in 1, and impaired left ventricular function in 4 patients (PJRT n = 3, AET n = 1). The intervention was primarily successful in all patients. Median fluoroscopy time during the ablation procedure was 17 (10 to 70) minutes. A median of 3 (1 to 14) radiofrequency (500 kHz) pulses was delivered at a target temperature of 70 degrees C or with 30 W for 30 s. One patient had a recurrence of PJRT and was successfully treated by a repeat ablation. After a median follow-up of 14 (2 to 61) months, all patients are free of drug treatment and in normal sinus rhythm. Left ventricular function has normalized in patients with follow-up > 6 months. Radiofrequency catheter ablation was a safe and effective therapy in young patients with drug-resistant forms of chronic-permanent supraventricular tachycardia.