Reperfusion injury following ischemia is thought to be the consequence of reactive oxygen species possibly generated either by xanthine oxidase activity or by processes associated with neutrophil activation in the affected organ or tissue. The conversion of xanthine dehydrogenase to the oxidase as well as the interactions between endothelium and neutrophils in the margination and activation of the latter are all considered to be results of conditions resulting from the ischemic episode. Determination of the redox status of glutathione in an ischemic/reperfused organ is frequently employed as an indicator of oxidative stress created by the production of oxygen free radicals during the reperfusion period. In this procedure, the ratio of oxidized glutathione (GSSG) to total glutathione (GSH + GSSG) is utilized to demonstrate the proportion of glutathione oxidized during reperfusion. We determined this ratio in the rat small intestine during ischemia and reperfusion and found that while the ratio of GSSG/(GSH + GSSG) does increase, this increase was the result of GSH disappearance rather than an increase in GSSG, and that essentially all of this loss occurred during the ischemic episode. We demonstrated that no oxidation of GSH occurred that was attributable to reperfusion per se; nor was there an increase of GSSG during this reoxygenation period.