Mortality due to cerebral vessel disease, malignant neoplasm, heart disease, pneumonia and bronchitis and accident was recorded from 1971 to 1975 in Okayama Prefecture and death rates adjusted to the Japanese population classified by age in 1950 were determined. The results obtained were as follows. 1) The incidence of cerbral vessel and heart disease was higher in the northern part of Okayama Prefecture than that of in the southern part. The incidence of neoplastic disease was high, and pneumonia and bronchitis was low in the southern area of Okayama Prefecture. Deaths by accident were relatively few in the South. The rate of longevity is higher in the North than the South. 2) The correlation coefficient among the five main causes of death and longevity rates was calculated, and a significant positive correlation was found between longevity rates of the various areas and between cerebral vessel diseases and accidents (P>0.1) significant negative correlation was found between the longevity rate and neoplasm at the 5% level. 3) Corrected death rates of the five main diseases in each district were classified in the 6 groups by cluster analysis.