The role of oxygen free radicals (OFR) in the pathogenesis of many diseases is known. This experimental study was planned to investigate the role of OFR in acute abdominal inflammation. In this study, 20 adult rabbits were used. They were divided into two groups with 10 rabbits in each. In the study group, blood samples were taken from peripheral and mesenteric veins and then their appendices were ligated; after 24 h, blood samples were taken again and the appendices were resected, The same procedures were carried out in the control group, except for ligation of the appendices. Superoxide dismutase, catalase and glutathione peroxidase (GPX) activities were measured in all blood samples. The activities of catalase and GPX were increased postoperatively in peripheral and mesenteric blood samples in the experimental group, The catalase activity was increased in the control group. These results suggest that OFR increased sufficiently to activate the enzymatic defense system in acute appendicitis.