Hypothalamic hamartoma[HH] is an unusual nonneoplastic developmental lesion associated with gelastic epilepsy and precocious puberty, mostly found in children. Although open surgery has been attempted when antiepileptic medication failed to control seizures, its deep location and surrounding vital structures often rendered surgery unsuccessful. We describe the outcome of gamma knife radiosurgery in three children with a HH associated with gelastic epilepsy and reviewed the literature for a possible therapeutic mechanism.