Our understanding of pediatric arrhythmias continues to evolve through natural history studies of paroxysmal supraventricular tachycardia, the congenital long QT syndrome, and postoperative atrial and ventricular tachyarrhythmias. The influence of the autonomic nervous system on cardiovascular function may play a role in the sudden infant death syndrome, pallid breath-holding spells, and neurally mediated syncope; much work is necessary to understand these entities better. Therapeutic approaches to pediatric arrhythmias are extending beyond newer antiarrhythmic drugs and now include ablative therapy for many supraventricular tachyarrhythmias, both surgical and transcatheter. Advances in pacemaker therapy include novel implantation sites, down-sizing of devices, and the application of antitachycardia and rate-adaptive technologies.