Oxidative stress mediates cell injury during ischemia-reperfusion. On the other hand experimental data suggest that reactive oxygen species induce processes leading to ischemic preconditioning. The extent and source of oxidative stress and its effect on antioxidant status in the human liver during intermittent ischemia and reperfusion remains ill-defined. Liver biopsies, arterial and hepatic venous blood samples were taken from 10 patients undergoing hepatectomy with intermittent Pringle manoeuvre. Plasma malondialdehyde and hepatic glutathione disulfide (GSSG) levels were measured as markers of oxidative stress, plasma uric acid as a marker of xanthine oxidase activity. In addition, changes in hepatosplanchnic consumption of plasma antioxidants and hepatic levels of carotenoids and glutathione (GSH) were measured. After ischemia, hepatosplanchnic release of MDA and increased hepatic GSSG levels were found. This was accompanied by release of uric acid, reflecting xanthine oxidase activity. During reperfusion ongoing oxidative stress was evidenced by further increases in hepatic GSSG content and hepatosplanchnic MDA release. Uric acid release was minimal during reperfusion. A gradual decline of plasma antioxidant capacity and net hepatosplanchnic antioxidant uptake was observed upon prolonged cumulative ischemia. Oxidative stress occurs during hepatic ischemia in man mainly due to xanthine oxidase activity. The gradual decline of plasma antioxidant capacity and net hepatosplanchnic antioxidant uptake during prolonged cumulative ischemia, interestingly did preserve both hydrophilic and lipophilic hepatic antioxidant levels. Decreasing plasma levels and net hepatosplanchnic uptake of plasma antioxidants may warrant antioxidant supplementation although it should be clarified to what extent limitation of oxidative stress compromises ROS-dependent pathways of ischemic preconditioning.