The authors prepared an experimental animal model of ischemia and reperfusion of the limbs to evaluate in vivo the reactive oxygen species involvement and protective role of coenzyme Q10 in reperfusion injury. A group of male rabbits (untreated group) underwent clamping of abdominal aorta for 3 hr and then declamping; at intervals blood sampling was drawn for coenzyme Q10, vitamin E, lactic acid and creatine kinase assays. Another group of male rabbits (treated group) underwent the same ischemia period but before declamping coenzyme Q10 was administered intra aorta. In untreated group, coenzyme Q10 and vitamin E plasma levels decreased while lactic acid and creatine kinase plasma levels increased during reperfusion. These data demonstrate that, after only 3 hr of ischemia, the extremities show a biochemical reperfusion injury, and this involves an increased consumption of antioxidants such as coenzyme Q10 and vitamin E. In the treated group, the increase of creatine kinase plasma levels during reperfusion was not significant, while the decrease in vitamin E was more marked.