Head circumference, body weight, body length, and shoulder circumference at birth were studied in 70 RDC schizophrenic patients and 70 demographically matched controls from the same delivery series, using information recorded in the medical records at the time of birth. With preterm babies removed from both samples, only head circumference among preschizophrenic infants was significantly smaller than that of controls. Preschizophrenic infants also had a disproportionately smaller head circumference in relation to body length than did controls. Among the former, a small head circumference was systematically related to an absence of family history of psychosis, but was not related to season of birth or recorded pregnancy complications. The findings were strongest for females. The results suggest there is an unidentified non-genetic factor in schizophrenia that disturbs prenatal cerebral development.