The prevalence of epidemic hepatitis at Kumayama-cho, Akayuwa-gun in Okayama prefecture was fully observed for 3 years and the epidemic type was studied. And the ressults were as follows. 1. Studying the prevalence on the 3 parts of the district dividing by the unit of old village distribution, the prevalence progressed slowly, and it was mostly sporadic at the beginning and then it was mostly eruptive. And the epidemic wave could be seen, even mild, in each district. 2. The epidemic state at Kumayama-cho was clarified by the election of the most appro priate cases connecting the prevalence of each part of the district. 3. Studying the epidemic pattern on the village unit at each district, the connective spreading type of the prevalence was a few at the first year, but it was clearly observed on most of the cases at the second year, after obtaining the proof that the occurrence of the patients at the second year was the occurrence of the cases contracting the latent and unsignificant infection at the first year and the cases thought to be the common course infection were extremely a few. 4. The percentage of contraction at each district was 2.36-4.77%.