Sudden unexpected death represents a significant cause of mortality in people with epilepsy. It derives this significance not because it is the most frequent cause of death but because it is apparently a direct consequence of a seizure. The implication is that epilepsy is an inherently lethal disorder. Seven patients who were studied in an epilepsy surgery program died a sudden unexpected death. This incidence of sudden unexpected death was five times higher than the 1-2/1,000 per year reported in the general epilepsy population. Sudden unexpected death shares some of the characteristics associated with sudden cardiac death, which kills 300,000 people in the United States each year. A cardiac arrhythmia, usually ventricular fibrillation, is the most common terminal event for sudden cardiac death and is the leading candidate as the mechanism for sudden unexpected death. Despite this knowledge, little is known on how to identify a high-risk group of patients for sudden death or how these deaths might be prevented.