Five patients who developed an atypical schizophreniform psychosis following right hemisphere stroke are described and compared to five patients matched for lesion size and location who did not develop any psychopathology after stroke. The patients who developed the schizophreniform illness had a larger frontal horn ratio and larger third ventricle ratio on CT head scans than did the comparison group. This finding suggests that preexisting subcortical atrophy and a right hemisphere lesion location are risk factors for developing schizophreniform disorder following stroke.