Two patients with schizophrenia had markedly abnormal neuroimaging studies; one was found to have a large, cystic cavum vergae, while the other demonstrated complete agenesis of the septum pellucidum with a monoventricular system. The increased prevalence of developmental abnormalities of midline forebrain structure in patients with schizophrenia suggests that dysgenesis of these structures may be contributory to the neurobiology of schizophrenia and other psychotic disorders.