increase in caudate nuclei volumes of firstepisode schizophrenic patients taking antipsychotic drugs objective this study examined the pathomorphology of the caudate nuclei in firstepisode schizophrenic patients with minimal previous neuroleptic exposuremethod magnetic resonance imaging mri of the brain was used to examine longitudinally the caudate pathomorphology in 29 firstepisode schizophrenic patients and 10 healthy comparison subjects mri scans were obtained after the subjects entered the study and at 18month followup the patients were treated with standardized neuroleptic regimens during the 18month period volumetric assessments of the cerebral cortex lateral ventricles and caudate nuclei were performed on t1weighted coronal brain sections in addition the patients were systematically evaluated for psychopathology at baseline and during treatmentresults caudate volumes increased 57 in the patients during the 18month treatment interval whereas they decreased 16 in the comparison subjects over the same time period greater amounts of antipsychotic medication received by patients before the first scan and younger age at the time of the first scan were associated with larger increases in caudate volumeconclusions caudate enlargement occurs early in the course of treatment in young firstepisode schizophrenic patients this may be a result of an interaction between neuroleptic treatment and the plasticity of dopaminergic neuronal systems in young patients