Fructose absorption was studied by the breath hydrogen test in 114 healthy children aged 0.1-6 years, given either 2 g/kg or 1 g/kg of fructose. All 57 children given 2 g/kg had peak breath hydrogen excretions > or = 20 ppm. At 1 g/kg only 25/57 (44%) showed incomplete absorption and the percentage incompletely absorbing fructose and the peak breath hydrogen value were significantly higher in children aged 1-3 years. Interestingly, this age distribution correlates with that of toddler diarrhoea.