Corpus callosotomy is a well established procedure for the treatment of intractable epilepsy. However, this is the first clinical report of surgical division of the corpus callosum in Japan. Four patients with refractory seizures suffering from Lennox-Gastaut syndrome underwent anterior partial corpus callosotomy. Their seizures consisted of absences, tonic, atonic, tonic-clonic attacks and were characterized by frequent falls. Electroencephalograms showed paroxysms of bilateral synchrony of slow spike and wave complexes. Postoperative follow-up during 12-27 months showed that partial callosotomy reduced the frequency and severity of seizures in all the patients, although they still require antiepileptic medication. This procedure was effective even in patients with mixed cerebral dominance and also in a patient with low intelligence quotient. Postoperatively, disconnection syndrome developed in three patients, which was transient in one and lasting in two.