A case is reported of intractable epilepsy associated with a hypothalamic hamartoma in an 18 year old man. The patient underwent a two-third anterior callsotomy and, subsequently, removal of the hamartoma. Callosotomy did not affect the generalized seizure pattern. The authors believe this to be the first documented case of hypothalamic hamartoma in which callosotomy for seizure control was attempted. The poor response to callosotomy suggests the extracallosal diffusion of the generalized seizures from hypothalamic hamartomas.