Abstract: Objective This study was conducted to get an insight into the cause of the outbreak of infectious diarrhea and evaluate the measures for the control of the outbreak of the epidemic．Methods Five hundred and ninety-three cases of diarrhea occurring from Jun．30 to Jul．30. 2003 in a town and 8 villages nearby were investigated with some normal individuals as control population．At the same time biological samples from wamr，the environment and patients were detected for bacteriological indices and free chloride．Results It was found that the incidence of diarrhea in the period was 4055.5/lakh and the diarrhea outbreaks were caused by constant fecal contamination of drinking water sources，lack of measures for purification and disinfection in the tap-water factories in the local areas and contamination of foodstuffs．Aeromonas/enterotoxigenic Escherichia coli were the causative factors．The epidemics were controlled through comprehensive preventive and therapeutic measures such as the control of the contamination sources，disinfecfion of drinking water，standardization of the purification and disinfection in the tap-water factories and promotion and educafton．Conclusion Pond-ditch water that iS used as a source of drinking water in summer in rural areas should be protected against fecal contamination．Water quality surveillance should be reinforced in the simply equipped water factories．