Although the mechanism of acute appendicitis (AA) is partly understood, the progression following the onset of inflammation has not yet been clarified. To determine oxidative activities in the plasma of patients with AA, superoxide dismutase (SOD) activities and malondialdehyde (MDA) levels were measured in samples from 31 patients diagnosed as having AA and 10 otherwise healthy children with inguinal pathologies. The patients with AA were divided into three subgroups: acute focal (AFA) (n = 8), acute suppurative (ASA) (n = 9), and acute perforated appendicitis (APA) (n = 14), according to the intraoperative findings and histopathologic examination.. SOD and MDA were compared statistically between these subgroups and between them and the control group. Additionally, mean leukocyte counts of each group were determined and the differences between the groups were evaluated. Both SOD and MDA were significantly higher in the ASA and APA groups compared to controls and AFA group. The mean leukocyte numbers of the ASA and APA groups were significantly higher compared to the AFA group. Based to these results, it may be speculated that oxygen free radicals (OFR) may play an important role in the extent of AA. To prevent the hazardous effects of OFR, the organism may increase SOD and other antioxidant enzyme levels and/or activities.