By the advance of chemotherapy and aging of the inpatients with leprosy (mean age: 75.7 years), geriatric disease are becoming major problems in Japanese National Leprosarium. Dementia is not diagnosed inpatient with leprosy. After autopsy Alzheimer fibrillary tangle and senile plaques in the brain of aged leprosy is not easy demonstrated by routine stains. However, these is easy demonstrable a different senile plaque with accretion to the Alzheimer fibrillary tangle, if it employed the specific immunohistochemical method on these brain. We employed both tau protein and the divided beta protein, and each of protein is able to divide dementia and non-dementia into aged groups in leprosy. Low prevalence in Japanese leprosy patients is demonstrable in dementia of what happened was accurate in alzheimer disease with subtype of senile plaque.