Most investigators studying tardive dyskinesia (TD) hypothesize that the condition is due to a neurochemical abnormality of the striatum. Recently, numerous CT studies have been done to verify brain abnormalities in patients with TD; the findings have, however, been conflicting. The present study was designed to detect possible neuropathological abnormalities in the basal ganglia in a young sample of schizophrenic patients with TD as compared with schizophrenic patients without TD and normal controls. Magnetic resonance imaging (MRI) was used to measure the volumes of the caudate, putamen, globus pallidus, lateral ventricle, and intracranium. The volumes of the caudate nuclei of the patients with TD were significantly smaller than the volumes of the caudate nuclei of the patients without TD and normal controls. This abnormality in the caudate may be related to some previous conditions, which may prove a substrate that is necessary for TD to establish itself in association with neuroleptic use. Further studies are necessary to confirm our findings and to determine the pathophysiologic nature of these structural alterations and the role played by neuroleptics, whether primary or secondary.