Syncope is a common medical problem with up to 30 percent of normal individuals reporting one or more syncopal episodes. Thus, physicians of all specialties are frequently confronted by patients with syncope. The spectrum of diseases which may cause syncope is broad, ranging from common benign problems to severe life-threatening disorders. Because of the complexity of the clinical situation when an obvious cause for syncope is not found, patients may be subjected to a significant period of hospitalization and a large number of diagnostic tests. Retrospective and prospective studies have shown that many diagnostic tests are frequently employed but are infrequently diagnostic of a cause of syncope. Thus, studies have shown that when a cause is established or suggested, the majority of diagnoses are assigned based on initial history and physical examination. An initial electrocardiogram is helpful in assigning a cause of syncope in only approximately five percent of additional patients. In a prior study prolonged electrocardiographic monitoring was helpful in assigning a cause of syncope in approximately fifteen percent of patients. Other studies of prolonged electrocardiographic monitoring in patients with syncope reveal that arrhythmias as a potential cause of syncope are found in eleven to sixty-four percent of patients. Diagnostic procedures such as EEG, head CT scan, brain scan, cerebral angiography, echocardiography, and cardiac catheterization rarely establish a cause of syncope but are useful when employed selectively for diagnosis of specific etiologies of syncope.