Beckwith-Wiedemann Syndrome (BWS) is the most common overgrowth syndrome in infancy. The characteristic findings are macroglossia, abdominal wall defects, and macrosomia. Genetic studies in infants with BWS demonstrate 3 major subgroups of patients: familial, sporadic, or chromosomally abnormal. Recognition in the neonatal period is important because of the high incidence of childhood malignant tumors associated with BWS. This article provides an overview of the syndrome and discusses its etiology, physical findings, and diagnostic evaluation. Management and clinical implications including family support will also be discussed.