This study assesses the importance of enterotoxigenic Escherichia coli (ETEC) as a diarrhoeal agent in developing countries. Odds ratios were calculated for incurring ETEC-associated diarrhoea based on data reported between 1970 and 1999. Carriage of ETEC was associated with diarrhoea in children aged less than five years, except for hospitalized infants aged 0-11 month(s) and children aged 1-4 year(s) at outpatient clinics. Two hundred and eighty million episodes of diarrhoea due to ETEC were seen yearly among those aged less than five years, and close to 50 million children of this age group were asymptomatic carriers of ETEC. Every 7th diarrhoeal episode in children aged less than one year and close to 25% of diarrhoeal cases in children aged 1-4 year(s) were due to ETEC. A child born in a developing country is likely to experience 0.5 diarrhoeal episodes per year caused by ETEC until the age of five years, after which the yearly incidence drops to 0.1. To conclude, ETEC remains an important diarrhoeal pathogen among children in the developing world.