The effects of complete and partial corpus callosotomy in 6 patients are reported. Only the 2 cases undergoing total callosotomy showed evidence of impaired interhemispheric sensory transfer, related to sectioning of the splenium. Only mild long-lasting neuropsychological deficits were detected. Post-commissurotomy mutism and akinesia appeared in 4 cases, 2 with total, and 2 with partial anterior callosotomy. The short-and long-term effects of corpus callosotomy appear to be related to the extent of the section the creation of lesions during the surgical procedure, and a peculiar organization of cognitive functions in chronic epileptic patients.