Syncope is a brief sudden loss of consciousness and muscle tone secondary to cerebral ischaemia, inadequate oxygen or glucose delivery to the brain. The causes of syncope may be benign and require very little in the way of evaluation or treatment. However, syncope may be the harbinger of sudden death, and extensive evaluation, monitoring and detailed recommendations regarding advisability of participating in sports should be reviewed with the patient. The history is the most important clue when attempting to identify which patient with syncope is at risk for sudden death. A careful cardiac and neurological examination should be performed in any patient presenting with syncope. Selective use of laboratory testing and cardiac monitoring may assist the practitioner in making the diagnosis. Most often patients with syncope will have a benign cause such as vaso-vagal events, hyperventilation or orthostatic hypotension. Patients with a cardiac condition causing their syncope are at increased risk for sudden death. The ominous, cardiac-related causes of syncope in the younger population include hypertrophic cardiomyopathy, aberrant coronary arteries and aortic dissection secondary to Marfan's syndrome. In the older athletic population, coronary atherosclerosis may present with syncope. Dysrhythmias may be the cause of syncope in both populations.