Patients with syncope were accrued from the emergency room, the inpatient services and the ambulatory clinics of the Presbyterian University Hospital of Pittsburgh. All patients underwent a basic standardized evaluation consisting of a history, physical examination, baseline laboratory tests, electrocardiogram, prolonged electrocardiographic monitoring, and special diagnostic tests as necessary. Diagnosis of a cause of syncope was assigned by standardized criteria. Follow-up information regarding sudden death and mortality was obtained at three-month intervals until the end of the study. Causes of death were assigned in a standardized manner.