Studies of non-polio enterovirus prevalence and transmissibility in developing countries are limited and few studies have investigated specific risk factors for infection. An epidemiological survey of non-polio enterovirus among families in Mongolia was conducted in the late summer of 2003. Stools of 122 healthy persons were collected weekly for 5 weeks. Eight serotypes of non-polio enteroviruses (echovirus 30, 33, 12, 25, coxsackievirus A10, A2, A4, A24) were isolated from 62 persons, with an overall isolation rate of 51%, and 64% and 35% among children under 10 years and adults over age 21 years. Fifty-four per cent of isolations were due to intrafamilial infection. Analysis of risk factors for infection suggested contamination of indoor kitchen, bathroom, toilet, and waste disposal area. Hand washing after defecation was protective against infection. Our study findings stress the importance of hand washing and cleaning hygienic facilities to prevent infection by enteric viruses in the home environment.