A simple technique to study intestinal absorption in vivo, a modification of that of Sols and Ponz, is described. A perfusion pump, with or without recycling of the solution along the intestinal lumen, is used and a series of successive absorption periods with high comparative value on the same intestinal segment can be performed. The technique is applied to sugar absorption in rat and hamster, but it can be extended to other substrates and other animal species. For each concentration of sugar, the intestinal absorption rate of glucose remains constant along a number of 1-min successive periods.