A growing body of experimental data indicates that reactive oxygen metabolites such as superoxide, hydrogen peroxide, and hydroxyl radicals may mediate the microvascular and parenchymal injury produced by reperfusion of ischemic skeletal muscle. One potential source of these reactive oxygen metabolites is the inflammatory neutrophil. To assess neutrophil accumulation in postischemic skeletal muscle, we measured tissue myeloperoxidase (MPO) activity in skeletal muscle biopsies taken during control, after 4 h of ischemia, and after 1 h of reperfusion. Tissue levels of reduced glutathione (GSH), superoxide dismutase (SOD), and catalase (CAT) were measured in the same samples to identify alterations in tissue free radical defense mechanisms due to ischemia-reperfusion. Reperfusion of ischemic skeletal muscle was associated with a dramatic increase in tissue neutrophil content (as reflected by a 26-fold increase over control in tissue MPO activity after 1 h of reperfusion) and a concurrent 50% decrease in GSH content. Tissue CAT and SOD activities were unaffected by ischemia-reperfusion. These results suggest a possible relationship between ischemia-reperfusion-induced injury, neutrophil infiltration, and the reduction in tissue GSH.