Diarrhea, constipation and subsequent laxative use are chronic problems in long-term enterally fed patients. We have conducted a double-blind randomized crossover study to evaluate the effects of two enteral formulae (Enrich, 12.8 g of dietary fiber per 1000 kcal and Ensure, fiber-free) on stool frequency, fecal weight, laxative use, gastrointestinal tolerance and bowel function in chronic care tube-fed patients. Twenty-eight subjects (24 male, 4 female) completed the study. Mean daily number of stools and mean daily fecal wet weight in Enrich-fed patients were not significantly different from those of patients receiving Ensure. Ensure-fed patients required significantly more laxatives (p = 0.02) than those receiving Enrich. There were 26 reports of diarrhea in the Ensure-fed group as compared to 6 in the Enrich-fed group, and this difference was significant (p = 0.006). Reporting rates for constipation were not significantly different in the two groups. At the end of the study, the bowel function of 57.1% of patients receiving Enrich was improved when compared with that of 14.3% of Ensure-fed patients, and this difference was significant (p = 0.005). These results suggest that the addition of dietary fiber to enteral formulae improves gastrointestinal tolerance and bowel function, and reduces laxative use in long-term enterally fed patients.