Gastrointestinal inflammation is a complex series of events involving numerous mediators and cytokines that act to focus and coordinate the immune system. The interactions of various mediators and cytokines appear to be important in the regulation of T-cell responses during inflammation. As well, the actions of certain cytokines can have profound effects on the intestinal epithelium, such as the induction of secretory responses, the expression of adhesion molecules, and in some instances cytokines may promote epithelial cell damage. The expanding list of immune and nonimmune cells that can produce cytokines offers new mechanisms that may be involved in various types of inflammation. Finally, additional mediators such as nitric oxide can be induced by cytokines and may have important pathophysiologic consequences during inflammation.