Dietary fibers are a necessary part of human nutrition. Inulin is a fermentable fiber that improves bacterial ecology in the large bowel and is also a relevant substrate for short-chain fatty acid (SCFA) production. The aim of the present study was to evaluate the clinical effect of inulin, added as dietary fiber into the fiber-free enteral nutrition (Nutrition Standard). Inulin (30-35 g/d) was administered for 1 wk to a group of patients requiring the nutritional support of a liquid enteral diet. A significant increase in flatulence, an indication of rapid bacterial fermentation, was apparent during its infusion in comparison with a fiber-free enteral diet. Moreover, an increment in ability to dehydrate the cecal stream (stool consistency) was apparent in nearly half of patients. No changes in SCFA concentration in stool and indican output in urine were apparent after 1 wk of inulin administration. Intestinal permeability (51Cr-EDTA absorption test) was not influenced by either enteral nutrition or inulin and enteral nutrition administration. Because of good tolerance inulin seems to be a potential source of dietary fiber in clinical enteral nutrition.