OBJECTIVE AND CLINICAL IMPORTANCE: We report a patient with a hypothalamic hamartoma treated by stereotactic radiofrequency thermocoagulation. CLINICAL PRESENTATION: A 15-year-old girl presented with a hypothalamic hamartoma associated with intractable gelastic and tonic seizures. There were no clinical signs of precocious puberty. Magnetic resonance imaging revealed an isointense suprasellar mass, about 1 cm in diameter. TECHNIQUE: A depth electrode was placed into the hamartoma using a computed tomography-compatible stereotactic frame. Depth electroencephalographic studies allowed us to record the seizure onset from the lesion, and stereotactic radiofrequency thermocoagulation produced seizure remission. CONCLUSION: These findings suggest that hypothalamic hamartoma itself has intrinsic epileptogenicity. We believe that this surgical treatment is effective for the relatively small hypothalamic hamartoma associated with intractable gelastic seizures.