Two epidemics of acute, watery diarrhoea in villages in North Arcot district, India, were investigated. The attack rates were 10·03 and 15·53 per 100 population, the median duration was 5 days and enteric pathogens were present in 56·8% and 60·3% of specimens from the two villages, but no predominant pathogen was identified. Examination of stools from a 20% age-stratified random sample of the population of one of the villages after the epidemic found 22·9% of asymptomatic subjects excreted bacterial enteric pathogens. Despite the high background of enteric pathogen carriage, the isolation rates for shigellae, enteropathogenic Escherichia coli and Shiga-toxin producing E. coli were significantly higher (P < 0·001, P < 0·02, P < 0·05) during the epidemic. The epidemics may have been caused by faecal contamination of well water following rain. Point-of-use techniques for water disinfection may be most effective for preventing such outbreaks, but further research into the development of appropriate technology is required.