BACKGROUND: The aim of this study was to investigate the levels of oxidative stress including total oxidant status, total antioxidant status, and paraoxonase activity in patients with a diagnosis of acute appendicitis. METHODS: Seventy-three patients who underwent surgery with a preoperative diagnosis of acute appendicitis (Group I) were included into the study. The control group (Group II) consisted of thirty otherwise healthy subjects. After histopathologic examination, the patients were categorized as follows: 1) Acute focal appendicitis, 2) Acute advanced appendicitis including acute suppurative, phlegmonous and gangrenous appendicitis, 3) Acute perforated appendicitis, 4) Sub-acute appendicitis, and 5) Negative exploration. Blood samples for paraoxonase activities, and total oxidant and antioxidant status levels were obtained preoperatively. RESULTS: Total oxidant and antioxidant status of the patients in the acute appendicitis group were higher than those of the control group. When paraoxonase activities of Group I was compared with Group II, no significant difference was determined. Both total oxidant and antioxidant status levels of acute perforated appendicitis were higher than those of both acute focal appendicitis and acute advanced appendicitis. CONCLUSION: The increase in the oxidative status (total oxidant and antioxidant status) was related with the progression of inflammation to the perforation in acute appendicitis.