This study examined whether ischemia-reperfusion injury to skeletal muscle could be reduced by postischemic infusion of phosphoenolpyruvate (PEP) and adenosine triphosphate (ATP). The rectus femoris muscle of 54 rabbits was rendered ischemic for 3.5 hr. Eighteen rabbits received no further treatment. Thirty-six were infused intra-arterially at the end of ischemia, 18 with vehicle alone, and 18 with a mixture of PEP (80 μmol/kg) and ATP (2.6 μmol/kg). Six rabbits from each group were explored after 24 hr reperfusion and the muscles assessed for viability (by nitro blue tetrazolium). ATP (by luciferin-luciferase chemiluminescence), malonyldialdehyde (MDA) (thiobarbituric acid method), and water content. The remaining muscles in each group were examined histologically after either 1 hr or 4 days of reperfusion. At 24 hr the viability of the PEP/ATP infused muscles (789 ± 154 percent) was significantly greater than that of untreated (414 ± 273 percent) or vehicle-infused groups (340 ± 327 percent). ATP stores were significantly higher and MDA (indicative of free radical activity) and water content significantly lower in the PEP/ATP treated group. At 24 hr and 4 days, muscles infused with PEP/ATP showed less necrosis and fewer infiltrating neutrophils than the untreated groups. Studies with isolated rabbit neutrophils showed that ATP alone significantly inhibited superoxide anion production by stimulated neutrophils. However, when combined with PEP at concentrations similar to those achieved in vivo, ATP did not significantly affect superoxide production. The findings indicate that post- ischemic infusion of PEP/ATP significantly reduces ischemia-reperfusion injury in rabbit skeletal muscle. The protective effect of PEP/ATP is more likely to be due to supplementation of intracellular ATP stores than to the inhibition of superoxide production by infiltrating neutrophils.