Patients with caudate lesions can present with content-specific delusions, possibly due to disruption of frontosubcortical circuits connecting the frontal lobes with the basal ganglia. This study included eight patients who presented with content-specific delusions after right caudate stroke and an equal number of matched controls, without stroke or delusions. Compared to controls, patients with caudate lesions performed less well on tests of memory, abstract reasoning, and frontal executive functions, and had significantly reduced metabolism in the inferior prefrontal cortex. These patients suggest an etiological relationship between alterations in inferior prefrontal functions and the development of content-specific delusions.