We report the identical monozygotic twin cases of agenesis of the corpus callosum that demonstrated schizophrenic disorder. Patients were 26-year-old twin brothers and both cases were diagnosed as having schizophrenia using DSM-III-R diagnostic criteria. On magnetic resonance imagings both cases demonstrated the total agenesis of the corpus callosum and the anterior commissure was hypertrophic. We speculated that the developmental disturbance of the corpus callosum might be related to the cause of the psychiatric disorders in the present cases.