Congenital cardiac lesions, whether unrepaired or postoperative, are among the most common diagnoses associated with sudden death in the 1- to 20-year-old range. In the general population, myocarditis, hypertrophic cardiomyopathy, and coronary artery anomalies are common causes of sudden cardiac death. Within the subset of pediatric cardiology patients who have not undergone operation, patients at greatest risk of sudden death are those with hypertrophic cardiomyopathy, Eisenmenger syndrome, and tetralogy of Fallot.