Sprague-Dawley rats (n=32) were fed a diet containing basal (control), cellulose (5%), or alcohol insoluble residue (AIR) (5%) extracted from the stem and root barks of elm (Ulmus davidiana var. japonica Nakai) for 4 weeks. The effects of the diets, on gastrointestinal functions and morphology were evaluated. The weight gains, food intake, and food efficiencies for the cellulose and AIR diet-fed groups were not significantly different from those of the AIR-free (basal) diet. The gastrointestinal transit times of the stem and root bark AIR diets were significantly reduced (p<0.01) compared to the basal diet, and were slower than those of the cellulose diet. The fecal weights of the stem and root bark AIR diets were significantly increased (p<0.01) up to 4-fold compared to those of the basal diet. The height of the mucosal villi, and mucosal and muscle layer thicknesses of the colon were greater and more developed in the stem and root bark AIR diets (p<0.01) than in the basal diet. The villus heights in the jejunum and the colon mucosal goblet cells were more developed in the order of cellulose > stem bark AIR > root bark AIR diets.