Seven cases of hypothalamic hamartomas with gelastic seizures are reported. A precocious puberty was found in 4 cases. The normal neurologic examination and lack of sign of intracranial hypertension were in contrast with the severity of the epileptic seizures, of the mental impairment and of the behavioral disorders. The fact that the presenting symptom may be gelastic seizures is stressed. CT scan is the best means to assess the diagnosis and to follow the evolution of these tumors. Except for the management of the precocious puberty, the treatment is disappointing and neurosurgical indications are quite exceptional.