The investigation was carried out from 15 May to 10 June 2006 among diarrhea patients of two schools and periphery residents in Hecun Town, Jiangshan City. Stool samples were examined for Entamoeba histolytica. Water samples were taken for microbial analysis. 31 cases with E. histolytica were found,with 74.2% (23 cases) of students and preschool children. 9 cases were found in Liuyi kindergarten and 8 cases in Hecun central primary school with a prevalence of 7.4% and 0.65%, respectively. Among 594 asymptomatic close contactors, 9 cases (1.5%) were carriers of cysts. Of the 31 cases, 22 were found with no habit of handwashing before eating or after defecation, and 14 cases had a close contact to the patients. No amoebic cysts or trophozoites were found from 12 water samples collected from schools or patient's houses, but the Escherichia coli level exceeded the national standard in 7 samples.