In this report, we evaluate and synthesize the published literature on diagnosis of, and medical and nonmedical interventions for treatment-resistant epilepsy. This report was commissioned upon the request of the Centers for Disease Control and Prevention and the Social Security Administration. Epilepsy is a common, serious neurologic condition. An International League Against Epilepsy (ILAE) Commission Report from 1997 estimated the prevalence of active epilepsy as 40 to 100 in 10,000 and the incidence of unprovoked seizures as 2 to 7 per 10,000. However, precise estimates of prevalence and incidence are complicated by differences in the way investigators define epileptic and nonepileptic seizures (NES), and by the fact that prevalence is typically estimated using retrospective methods. In addition to the immediate, debilitating effects of seizures, epilepsy also interferes with daily activities, and persons with epilepsy may have to contend with the increased possibility of accidental injury and even death. Psychiatric disorders may also be more common in people with epilepsy. Persons with epilepsy often have impaired physical, psychological, and social functioning, which may lead to economic loss and diminished quality of life. A survey of 1,023 people with epilepsy published in 2000 showed that compared to U.S. Census Bureau norms, respondents received less education, were less likely to be employed, and were more likely to be members of low-income households. (See Volume 2 for Evidence Tables).