During the past year, important studies on various mechanisms of small bowel disease have been reported. The section on enterocyte function evaluates studies on hypoxia and apoptosis. Many of the studies of small intestinal epithelia use as models T84 cells. When these cells are referred to as intestinal cells, it may be in a general sense. This may be of relevance in permeability studies because the transepithelial resistance of T84 cells is on the order of 1000 to 2000 ohm.cm, much higher than the resistance of the small intestine. These studies produce added insights into cellular function. Hypoxia causes changes in epithelial permeability through autocrine pathways. Additional studies methodically detail apoptosis in the small intestinal cell caused by ischemia-reperfusion and the potential mechanisms. Apoptosis is also important in graft-versus-host disease. A number of studies of the mechanism of action of Clostridium difficile toxins are reviewed; these may have therapeutic implications in the future. Finally, the role of mast cells in immunity and in postischemic inflammation is reviewed.