There are increasing evidences that prebiotics can modulate various properties of the immune system. This study was conducted to investigate effects of three kinds of fructans (chicory inulin, chicory inulin oligosaccharide and fructooligosaccharide) and a glucose oligomer(isomaltooligosaccharide) in large bowel mass and innnunoglobulin A (IgA) in rats. Forty five Sprague-Dawley male rats weighing about 1909 were randomly sorted to receive one of the five treatments, which were control diet, control diet+6% isomaltooligosaccharide (IMOS), control diet+6% fructooligosaccharide (FOS), control diet+6% chicory inulin oligosaccharide (CIOS), or control diet + 6% chicory inulin (CI). Rats were pair-fed and received the experimental diets for 5 weeks. Cecal and colonic wall weights were significantly higher in fructan (FOS, CIOS, CI)-fed groups compared with control and IMOS groups, and the length of colon was elevated in FOS and CIOS groups compared with control group. Fecal concentrations of acetic acid and total short-chain fatty acids (SCFAs) were significantly elevated in fructan-fed groups. Plasma and cecal levels and fecal excretion of immunogiobulin A (IgA) in rats were not significantly different among groups. However, fructooligosaccharide tended to increase IgA level in cecum. Cecal IgA level was significantly negatively correlated with pH of cecal content (r=-0.337), positively correlated with acetic acid level (r=0.310). Fecal IgA excretion was positively correlated with total SCFA (r=0.311) and propionic acid (r=0.400) level in feces. These results indicate that fructooligosaccharide and chicory inulin oligosaccharide exerted trophic effects in large bowel wall, increased production of SCFAs and decreased pH, which were conditions positively associated with cecal and colonic IgA secretion.