Ulcerative colitis is a multifactorial inflammatory disease of the colon and rectum with an unknown etiology. The present study was undertaken to investigate the effect of glutamine administration on oxidative damage and apoptosis in 2,4,6-trinitrobenzene sulfonic acid (TNBS)-induced colitis. Rats received 1 g/kg/day glutamine for intragastric gavage for 7 days before TNBS solution administration and 3 days following TNBS solution administration until sacrifice. Then colonic and pancreatic malondialdehyde (MDA) and glutathione (GSH) levels, and colonic caspase-3 activities of the sacrified rats were measured. TNBS-induced colitis caused significantly increased in the caspase-3 activity and colonic and pancreatic MDA levels and decreased colonic and pancreatic GSH levels compared to those in the sham group. Glutamine treatment was associated with decreased MDA levels and caspase-3 activity and increased GSH levels in the colinic and pancreatic tissue. Histopathological examination revealed that the colonic mucosal structure was preserved and pancreatic inflammation decreased in the glutamine-treated group. In conclusion, glutamine appears to have protective effects against TNBS-induced colonic and pancreatic damage. These results imply a reduction in mucosal damage due to anti-inflammatory and antiapoptotic effects of glutamine.