This report describes the treatment of a completely edentulous, mentally retarded patient with epilepsy with an implant-retained overdenture, anchored by a locator system. The intractable epileptic condition of the patient with frequent grand mal seizures and complex partial seizures required a stable, well retained prosthesis, however the maxilla and the mandible were severely atrophied. The bone volume of the maxilla allowed the placement of only two implants it the region of the canines, compared with the generally required four. On long time recall, after one year, patient's chewing ability was satisfactory.