• Within a prospective, longitudinal study of offspring of schizophrenic mothers, computed tomographic scan—derived measurements of ventricular size were evaluated for a subsample consisting of schizophrenics, borderline schizophrenics (DSM-III schizotypal), and mentally healthy individuals. Schizophrenics exhibited larger ventricular sizes and borderline schizophrenics smaller ventricular sizes than mentally healthy individuals. Ventricular size correlated with premorbidly obtained obstetric data. These results are interpreted as being consistent with the hypothesis that neurological insult may decompensate schizotypal individuals toward florid schizophrenia.