The present study describe the role of copper zinc superoxide dismutase (CuZnSOD) in the short-term treatment of experimental colitis induced with 8% acetic acid. The colonic mucosa damage index in the group of 10 rats treated intravenously with 30,000 U/kg CuZnSOD was significantly decreased when compared with the control group (10 rats) treated with normal saline (0.4 +/- 0.6 vs 1.5 +/- 0.5 p < 0.01). Assay of SOD in the control group was 0.3 +/- 0.08 and in the SOD treated group, SOD was significantly increased to 0.8 +/- 0.1, glutathione peroxidase was 44.8 +/- 6.3 in the control and 56.4 +/- 9.1 in the treated group (difference not significant). Both myeloperoxidase activity (14.0 +/- 2.5 vs 22.7 +/- 2.5) and lipid peroxidation products (13.8 +/- 2.9 vs 52.9 +/- 9.6) were significantly lower in the colonic mucosa of the SOD treated group in comparison with the control. These results indicate that the anti-inflammatory effects of CuZnSOD were mainly the removal of oxygen free radicals and indirectly the prevention of lipid peroxidation. This study suggests that CuZnSOD may be beneficial in the treatment of patients with ulcerative colitis. However, our experimental data suggest that this treatment will not have strong effects on the control of severe ulcerative colitis.