A 54-year-old man with delusional disorder, somatic type (DDST) showed extremely grotesque somatic delusions, i.e., the presence of another lower jaw with teeth and tongue accompanied by annoying sensations. These somatic delusions responded favorably to treatment with risperidone 2-3 mg/day. The single photon emission computed tomography taken when he had marked somatic delusions showed hypoperfusion in the temporal and parietal lobes. The present report suggests that delusion of reduplication of body parts, which has been generally associated with organic brain diseases, is also observed in DDST. This report also supports prior observations on the efficacy of risperidone for DDST and the association between this disorder and hypoperfusion in the temporal and parietal lobes.