Purpose: The purpose of these experiments was to test the hypothesis that endurance exercise training will reduce myocardial lipid peroxidation following short-term ischemia and reperfusion (I-R). Methods: Female Sprague-Dawley rats (4 months old) were randomly assigned to either a sedentary control group (N = 13) or to an exercise training group (N = 13). The exercise trained animals ran 4 d . wk(-1) (90 min . d(-1)) at similar to 75% of (V) over dot O-2max. Following a 10-wk training program, animals were anesthetized, mechanically ventilated, and the chest was opened by thoracotomy. Coronary occlusion was achieved by a ligature around the left coronary artery; occlusion was maintained for 5 min followed by a 10-min period of reperfusion. Results: Although training did not alter (P > 0.05) myocardial activities of antioxidant enzymes (superoxide dismutase and glutathione peroxidase); training was associated with significant increases (P < 0.05) in heat shack protein (HSP72) in the left ventricle. Compared with controls, trained animals exhibited significantly lower levels (P < 0.05) of myocardial lipid peroxidation following I-R. Conclusions: These data support the hypothesis that exercise training provides protection against myocardial lipid peroxidation induced by short-term I-R in vivo.