Syncope is a transient and abrupt loss of consciousness with complete return to preexisting neurologic function. It is classified as neurally mediated (i.e., carotid sinus hypersensitivity, situational, or vasovagal), cardiac, orthostatic, or neurogenic. Older adults are more likely to have orthostatic, carotid sinus hypersensitivity, or cardiac syncope, whereas younger adults are more likely to have vasovagal syncope. Common nonsyncopal syndromes with similar presentations include seizures, metabolic and psychogenic disorders, and acute intoxication. Patients presenting with syncope (other than neurally mediated and orthostatic syncope) are at increased risk of death from any cause. Useful clinical rules to assess the short-term risk of death and the need for immediate hospitalization include the San Francisco Syncope Rule and the Risk Stratification of Syncope in the Emergency Department rule. Guidelines suggest an algorithmic approach to the evaluation of syncope that begins with the history and physical examination. All patients presenting with syncope require electrocardiography, orthostatic vital signs, and QT interval monitoring. Patients with cardiovascular disease, abnormal electrocardiography, or family history of sudden death, and those presenting with unexplained syncope should be hospitalized for further diagnostic evaluation. Patients with neurally mediated or orthostatic syncope usually require no additional testing. In cases of unexplained syncope, further testing such as echocardiography, grade exercise testing, electrocardiographic monitoring, and electrophysiologic studies may be required. Although a subset of patients will have unexplained syncope despite undergoing a comprehensive evaluation, those with multiple episodes compared with an isolated event are more likely to have a serious underlying disorder.