Hemispherectomy for intractable unihemispheric epilepsy (IUE) has long been established in pediatric patients. This study reports the first series examining hemispherectomy exclusively in adult patients (>18 years old). Nine adults with IUE underwent hemispherectomy at the University of Minnesota. All patients had unilateral hemiplegia and visual field loss. Seven patients (77.8%) were Engel class I/II at last follow-up. Five (83.3%) of the six patients with >30 years of follow-up were seizure free. No surgery-related mortality, hydrocephalus, or superficial cerebral hemosiderosis occurred. Hemispherectomy is an effective procedure in appropriately selected adult patients, resulting in excellent long-term seizure control and no mortality. Ann Neurol 2007