Glutathione serves as an important intracellular defence against reactive oxygen metabolites and has been shown to be depleted from a number of tissues upon oxidative stress. In the present study we have investigated the levels of total glutathione (reduced + oxidized) in skeletal muscle of the rat after prolonged ischema and reperfusion with and without treatment with hyperbaric oxygen (HBO) for the initial 45 minutes immediately following reperfusion. A tourniquet model for temporary, total ischemia was used, in which one hind leg was made ischemic for 3 or 4 hours. Muscle biopsies were taken after 5 hours of reperfusion. In postischemic muscle there was a significant decrease of total glutathione compared to control muscle, but in the 3-hour-ischema-groups the loss of total glutathione was less in HBO treated animals than in untreated. HBO treatment also preserved ATP and PCr and decreased edema formation in the postischemic muscle following 3 hours of ischemia and reperfusion when compared to untreated animals. However, after 4 hours of ischemia, HBO treatment failed to improve any of these parameters in the postischemic muscle. Thus, our results demonstrate that HBO treatment lessens the metabolic, ischemic derangements and improves recovery in postischemic muscle after 3 hours of ischemia followed by reperfusion.