To examine volumetric abnormality, the caudate nucleus was measured in patients with schizophrenia and healthy subjects using magnetic resonance imaging. The absolute and relative volumes of white matter in the caudate nucleus were found to be significantly smaller in patients with schizophrenia compared to those in healthy subjects. There were significant correlations between dosages of neuroleptics during the previous year and absolute gray matter volumes of the caudate nucleus as well as relative white matter volumes in patients with schizophrenia. These findings suggest that reduced white matter volume of the caudate nucleus may be a factor affecting the abnormal connectivity of the corticostriatal loop, and that neuroleptic medication would be related to white matter alteration in patients with schizophrenia. Our result replicates a previous study reporting that there is a lack of negative correlation between age and caudate nucleus volume. We also suggest that the disease process of schizophrenia might interfere with normal aging.