Effects of dietary fibers (DFs) on function and morphology of gastrointestinal tract were examined in gastrectomized rats. Animals were gastrectomized and then were given a fiber-free diet er test diets containing 10% wheat bran, 10% solka-floc; cellulose powder or 5% pectin for ten weeks. The following results were obtained: (1) The feeding of pectin prevented the reduction of growth induced by the gastrectomy. (2) The feeding of DFs significantly reduced the apparent digestibility of dietary protein though this reduction did not influence the postoperative growth. (3) The intestinal transit time was significantly shorter in the DF-fed groups than in the control group. (4) The feeding of DFs influenced neither the tissue weight nor the sucrase activities of small intestine. However, the mucosal hyperplasia measured by the increase in DNA content was observed when rats were fed the diet containing solka-floc or pectin. (5) The cecal weight increased only in the pectin-fed group. (6) In the colon, the feeding of DFs caused the elongation of tissues and inhibited the decrease in the muscular weight induced by the operation. Both the solka-floc and the pectin caused the increase in DNA content in the colonic mucosa.