Dietary fiber defined as nonstarch polysaccharides (NSP) has been added to liquid formula diets in order to approach a more physiological state of nutrition. There are interesting experimental data supporting a role for fiber in artificial enteral feeding: NSP components have been shown to increase fecal bacterial mass, to favor colonic sodium and water absorption, to stimulate colonic crypt proliferation and to delay small intestinal glucose absorption. The number of controlled studies testing the effects of fiber added to liquid formulas is, however, small. Thus, there is no firm basis for the routine use of fiber-enriched formulas although these products are commercially available and in widespread clinical use. Research in this important field of digestive physiology is encouraged as many experimental data are in favor of supplementing formula diets with fiber.