Patients, including latent infections, were detected by excuting mass examination for two hamlets of Kumayama-cho, a small town prevailing infectious hepatitis, Akaiwa-gun, Okayama Prefecture. Complete medical treatments of these patients were instructed, and also the cases must be taken care of were adequately leaded. Special efforts were taken to improve sanitary and hygienic practices in the community likewise other intestinal infections. In comparison with other hamlets which did not take adequate treatment, epidemic of infectious hepatitis has been almost protected and remarkable results were obtained after one year. These facts might offer interesting materials to prophylaxis for infectious hepatitis.