The distribution of inclusions in adult-onset type intranuclear inclusion body disease (INIBD) has not been fully described. We analyzed the clinical and pathological changes of three autopsy cases of adult type INIBD and provide a detailed description of the distribution of inclusions in nervous system and visceral organs. Although patients showed cognitive decline and autonomic dysfunction, there were no specific symptoms related to general organs. The neuropathological changes responsible for cognitive decline and autonomic dysfunction were considered to be white matter changes in the cerebral hemispheres and inclusions in the autonomic nervous system, e.g., in the sympathetic ganglia and myenteric plexus. Alterations of spongiosis with both myelin and axon loss in the cerebral white matter seemed to be related to dysfunction of astrocytes with intranuclear inclusions. In visceral organs, the inclusions were much more widely distributed than previously appreciated and included renal mesangial cells, adrenal sustentacular cells, fibrocytes, Kupffer cells, pancreatic centroacinar and ductal epithelial cells. Since skeletal muscle cells, Schwann cells and smooth muscle cells were also inclusion positive, we propose that biopsy of muscle, peripheral nerve or rectum may prove useful for the clinical diagnosis of INIBD.