The relationship between family history of psychosis and cortical sulcal widening on CT scans was investigated. Forty-two schizophrenic subjects with a positive family history were individually matched to 42 schizophrenics with no documented family history and 42 healthy controls. Abnormally wide sulci, as defined on the basis of the normal control data, were significantly more common in the family history negative group (9/42) than in the family history positive group (1/42) or the controls (2/36). No significant correlation was found between cerebral cortical ratings and ventricular size.