The purpose of this study was to follow up the changes in antioxidative adaptive mechanisms induced by various periods of small intestinal ischemia in Wistar rats. The superior mesenteric artery was occluded for 15, 30, 45, 60 and 90 min. After the respective ischemic intervals, a reperfusion was set for 120 min. Samples of the serum and intestinal mucosa were taken at the end of ischemia or at the end of reperfusion. Total radical-trapping antioxidant parameter (TRAP) of the serum and the oxidative burst of neutrophils were evaluated using luminol-enhanced chemiluminescence. Individual antioxidants in the serum and the concentration of thiobarbituric acid reactive substances (TBARs) in both serum and intestinal mucosa were measured spectrophotometrically. Increased activation of circulating neutrophils was found after the reperfusion irrespective of the duration of ischemia. TRAP of the serum was increased at the end of the ischemia lasting from 30 to 90 min. This effect was further enhanced by the subsequent reperfusion period. Ascorbate and urate contributed considerably to the TRAP value especially after reperfusion following 60 and 90 min of ischemia. On the other hand, no significant changes in albumin and bilirubin serum concentrations were observed. Contrary to the mobilized antioxidative mechanisms, increased lipid peroxidation was observed in both serum and mucosa samples.