A previous report that the presence of a cavum septum pellucidum was significantly more common in schizophrenic patients than in control subjects (DeGreef et al., 1992) stimulated the present study of an independent but similar population of first admission schizophrenic patients. A high prevalence of this developmental anomaly (44.8%) was found in the patients (n = 85), although it could also be detected in 29.8% of similarly aged control subjects (n = 47). This finding was not associated with corpus callosum, ventricular, or temporal lobe size or asymmetries.