An epidemiological study was performed with respect to Creutzfeldt-Jakob disease in a designated area in Japan. The subjects were observed in a small rural prefecture where the population generally remains within a limited radius throughout their lives. The patients'' life-styles in each area were investigated in detail. Nine cases appeared in 11 years; 6 were definitive and 3 probable. They were all of the subacute type; there were no noteworthy sexual differences, age of onset, course and/or past histories. Three of the nine cases came from two families; the relationship between familial and isolated cases was examined. Revealed facts and time-space clustering were investigated statistically, but no indication of natural transmission was observable.