Sudden unexpected death accounts for a substantial portion of deaths among epileptics. The incidence of this phenomenon is probably 1 in 370 to 1 in 1,110 in the general epileptic population but may be even higher in the 20- to 40-year age group, and still higher if epileptics with symptomatic epilepsy are selected. Sudden unexpected death in epileptics has been observed at least once weekly by the Office of the Medical Examiner of Cook County (Chicago), Illinois, for many years. A year-long prospective study revealed that victims of this complication of epilepsy are most commonly black males averaging 35 years of age who have infrequent generalized seizures and usually have some structural lesion in the brain responsible for their seizures. They tend to abuse alcohol and have poor compliance with anticonvulsant medication. The electroencephalograms display considerable variability from record to record. At autopsy the heart, lung, and liver weights were heavier and the brain weights were lighter than expected. The mechanisms involved in sudden unexpected death in epileptics may include autonomically mediated cardiac arrhythmia alone or in combination with sudden "neurogenic" pulmonary edema and "backward" cardiac failure.