Ileal absorption of 3-oxy-methyl-D-glucose was studied for 30 min in one-day and 1, 2, 4, 5, 10 and 14-week-old fasted chickens using a perfusion technique in vivo. Phloridzin (1 mmol/l) was used as inhibitor of the active transport mechanism. A progressive decrease in ileal absorption was observed from 1-day to 14-week-old animals. The most dramatic decrease was observed between one-day- and 1-week-old chickens.