Syncope is a common presentation to the emergency room. Unlike in the adult population, most pediatric syncope has non-life-threatening causes, and minimal evaluation in the emergency department is appropriate with parental reassurance. Despite this benign prognosis, care must be made to find uncommon and potentially fatal causes. The primary purpose of evaluation of the patient with syncope is to determine whether the patient is at increased risk for death and needs either admission to the hospital or an expedited outpatient evaluation. This article reviews some of the most dangerous causes of syncope in the pediatric patient.