Seven healthy foals (five ponies and two horses) were maintained on grass pasture with their dams. All foals had normal faeces at the time of testing. An oral xylose absorption test was performed on each foal at one, two and three months of age. Following an 8 h fast, 0.5 g/kg D-xylose as a 10 per cent solution was given via a nasogastric tube. Control and 30 min interval plasma samples were collected for 3 h and the plasma was analysed for xylose using the phloroglucinol microassay technique. Maximum xylose concentration levels were reached between 30 and 60 mins for each of the foals. The mean (±sem) peak xylose concentration at one, two and three months of age was 3.14±0.29, 2.19±0.30 and 1.25±0.22 mmol/litre respectively, which were all significantly different from each other. Xylose absorption capacity decreased, therefore, with age, becoming similar to the adult horse by three months of age. The oral xylose absorption test can be used to evaluate small intestinal absorptive capacity in the foal provided that the results are compared with foals of the same age group.