Risk factors associated with diarrhoea, based on the recall of a recent episode were evaluated from a cross-sectional national nutrition and health study in 1,620 Ecuadorian children less than 5 years old. Prevalence of diarrhoea varied with the age of the children; 6- to 23-months-old children showed the highest prevalence. In this age range the prevalence of diarrhoea was significantly associated with hygienic factors (quality of drinking water, sanitation and refuse system), but not with demographic factors (sex, altitude, population density, family size). The nutritional status of the children was determined by anthropometry and blood chemistry. After stratification for sanitation levels, a low weight-for-age Z-score and low serum retinol and zinc concentrations showed a statistically significant (p < or = 0.06) association with diarrhoea prevalence only in children living under better hygienic conditions. Multivariate analysis revealed significant associations between both sanitation levels and nutritional level as defined by anthropometry, but not by blood chemistry, and diarrhoea prevalence.