OBJECTIVE To compare progressive changes in lateral ventricular size in chronic schizophrenia patients with good and poor outcomes. BACKGROUND Several longitudinal studies associated excessive ventricular enlargement with poor outcome early in the course of schizophrenia. Changes in its chronic phase have not been as well ascertained. METHODS We used MRI to evaluate progression of the lateral ventricular size in 49 chronic schizophrenia patients (26 with poor outcome, 23 with good outcome) and 16 healthy comparison participants, scanned twice 4 years apart. RESULTS In comparison with healthy participants, schizophrenia patients displayed significantly enlarged body, and anterior and posterior horns of the lateral ventricles at baseline and follow-up, but no between-group differences in their longitudinal expansion were observed. Progressive enlargement of the posterior horn in the poor-outcome (Kraepelinian) group, however, was more pronounced than in schizophrenia patients with good outcome. CONCLUSIONS Excessive ventricular enlargement in the chronic phase of schizophrenia may be specifically associated with poor functional outcome of the illness.