Twenty patients with schizophrenia and ten normal control subjects underwent magnetic resonance imaging of the brain. The volumes of several brain structures were measured using a computer image analysing system. The schizophrenic patients had significantly smaller left parahippocampal volume and larger left temporal horn volume than the control subjects. A larger body of the right lateral ventricle could be estimated in the schizophrenics, but this difference was not significant. In the patient group a non-significant negative correlation was established between the presence of positive symptoms and the left temporal horn volume. There was no significant correlation between the temporal horn and temporal lobe or medial temporal structures. Our results indicate that the left medial temporal structure or left temporal lobe may be involved in schizophrenia and that temporal horn enlargement does not simply represent volume loss of the surrounding tissue.