Complete hemispherectomies were performed throughout the 1950's and early 1960's for the treatment of medically refractory seizures associated with hemiplegia. In 1964 a study published by Laine, Pruvet and Ossen reported a late post operative complication; superficial cerebral hemosiderosis. This, with its associated neurological deterioration, hydrocephalus, and at times death, led to disfavor with the procedure. It was replaced by the subtotal hemispherectomy which effectively eliminated the late complication of superficial cerebral hemosiderosis but was less successful in controlling seizures. Results decreased from 85% showing improved seizure tendency to 68%. Dissatisfied with these results, a hybrid operation was designed by Dr. Rasmussen and Dr. Villemure known as functional hemispherectomy. Removing less cortical tissue but disconnecting the remaining tissue provided a functionally complete but anatomically incomplete removal. Patients, having undergone this surgery, have obtained the same degree of seizure reduction without any of the late complications of the complete hemispherectomy. Our presentation will discuss the preoperative, operative and post-operative course of these patients. Criteria for surgery will be reviewed. A description of the surgical procedure will be included so that one can understand why the complications of aseptic meningitis, hydrocephalus, cerebral hemosiderosis and altered motor function will or will not occur postoperatively. Concerns of family and patient will be addressed throughout the presentation.