Enlarged cavum septi pellucidi (CSP) is a neurodevelopmental anomaly that has been associated with schizophrenia. This study was designed to evaluate, in patients with schizophrenia, the relationship between the severity of this anomaly and measures of symptom and cognitive skills. Three groups were used: patients with large CSP (n=14), patients without large CSP (n=14), and healthy control subjects (n=14). In patients with large CSP, a significant, inverse relationship was found between size of CSP and measures of cognitive deficit. Thus, the greater the size of the anomaly, the greater the cognitive deficit. No relationship was found between severity of CSP and symptom measures.