Intestinal release of inflammatory mediators and permeation of macromolecules were studied in patients suffering from Crohn's disease, celiac disease and food intolerance with the use of a system for segmental intestinal perfusion. Drug absorption and ion and bicarbonate transport were also studied in healthy subjects. Patients with Crohn's disease of the distal ileum revealed an increased release of inflammatory agents into the lumen of the proximal jejunum. Luminal provocation with different antigens in cases of celiac disease and food intolerance not only activated cells in the intestinal mucosa but also increased the leakage from plasma and lymph. Studies of drug absorption elucidated the kinetics of drug transport from intestine to plasma, and basal neurologic effects on ion and bicarbonate transport were determined.