OBJECTIVE: This study compared morphometric analyses of brain regions in elderly subjects with early- or late-onset schizophrenia to identify structural abnormalities responsible for schizophrenia. METHOD: Quantitative analyses of magnetic resonance images of the brain were performed in 16 patients with DSM-III-R-diagnosed late-onset schizophrenia (i.e., onset after age 45), 14 patients with early-onset schizophrenia, and 28 normal comparison subjects, all of whom were over the age of 45. The three groups were similar in age, sex, education, and handedness. RESULTS: The groups differed significantly in ventricular and thalamic volumes. The patients with late-onset schizophrenia had significantly larger ventricles than the normal comparison subjects and significantly larger thalamic volumes than the patients with early-onset schizophrenia. There were no significant linear correlations between thalamic volume and age at onset, duration of illness, or mean current neuroleptic dose. CONCLUSIONS: Differences in thalamic volume may account for the putative disruption in thalamofrontal ciruitry in schizophrenia.Abstract Teaser