Radiofrequency (RF) ablation has made a significant impact on the ability to treat arrhythmias in children.1-3 The success rate has been comparable to the surgical approach, while postablation morbidity has been greatly reduced. However, rare cases of procedure-related mortality have been reported.2,3 These reports, combined with the findings that most infants with supraventricular tachycardia (SVT) can be managed medically,4 have led to a reluctance to perform catheter ablation in infants. However, some infants have recurrent and/or incessant tachycardia that is unresponsive to any medication. 1,5,6 Frequent or incessant tachycardic episodes may also lead to ventricular dysfunction and symptoms of congestive heart failure, particularly when associated with congenital heart disease. This report describes 10 infants and children aged <18 months who underwent RF ablation for treatment of medically refractory or unstable SVT, and 1 other patient who underwent elective ablation before having an atrial septal defect closure that may have prevented access to an accessory pathway (AP). © 1994.