The prevalence of carbohydrate intolerance in Egyptian children during an acute episode of gastroenteritis was determined.one hundred children, less than 3 years old, with acute diarrhea were enrolled into the study. Carbohydrate intolerance (diagnostic criteria: >0.5% reducing substances and stool pH less than 5.5) was diagnosed in 16/100 (16%) children, Lactose intolerance was present in 14 (14%) patients, glucose polymer intolerance in 1 (1%) and monosaccharide intolerance in 1 (1%). The most important predisposing factor was rotavirus. In all cases the carbohydrate intolerance was transient, resolving within 5 days.