Seizures in patients with Lennox-Gastaut syndrome are very resistant to drug therapy. Division of the anterior half of the corpus callosum was performed in two patients with Lennox-Gastaut syndrome incapacitated by frequent atonic seizures leading to sudden falls. Postoperatively, the atonic seizures were completely eliminated and their mental reactivities remarkably improved. It is clear that they have benefited from a lower frequency of seizures and reduced dosages of anticonvulsant medication, which outweight the acquired disabilities.