The risk factors predisposing children to ascariasis transmission in a rural community of Osun State, Nigeria were investigated from November 2005 to April 2006. Children below 16 years of age were examined at the household level after information on biodata, access to water supply and sanitation, socio-economic status of their parents and degree of cohabitation with their parents was collected using a questionnaire. Of 440 children examined, overall prevalence was 60% and median intensity was 1548 eggs per gram (epg) (min. 48 epg; max. 55464 epg). Infection patterns were gender comparable and age dependent, with peak prevalence (67.8%) occurring in children aged 5-9 years and peak median intensity (4368 epg) in children aged >or=15 years. Logistic regression analysis revealed that prevalence was influenced by patterns of water supply and sanitation, parents' educational background, number of biological parents living with a child and number of playmates a child has. These findings suggest that socio-environmental risk factors which play a role in disease transmission need to be taken into account when formulating sustainable control strategies for ascariasis and other intestinal parasites in Nigeria and elsewhere.