107 students of Showe Junior High School (out of 510) suffered from infectious hepatitis in a short period after 24th of May, 1954. Detailed clinical and epidemiological researches were made on them and the following results were obtained. 1. In the epidemic of this school, abortive form (gastro-intestinal form and partly common cold form) was seen in most cases and the epidemic belonged to the slight form of infectious hepatitis. 2. At that time, sporadic epidemie was seen among the people of this district. 3. It was supposed that this epidemie was carried by the contaminated water of the common well and it was the common vehicle epidemie. 4. The fact that many hepatitis patients appeared especially in June, was presumably due to the precipitating factor of interim examination, athletic meetings etc. reducing the physical strength.