Abstract: During September 7 to December 23,1995,an outbreak of Hepatitis A occurred in Chenji Middele School.The main cause was close contact charcterized by concentration of people,crowded dormitory and mixed use of table ware and dily necess ies.There were 19 classes out of 20 infected.Among 1272 teachers and students,there were 116 cases with the total incidece rate of 9.04%.The most serious was Junior Grade II of 17.91%and Junior Grade I was only second to it with the rate of 11.92%.The male was 9.59%,and the female 7.80%.