This study shows that the nonsteroidal antiinflammatory drug, ketorolac, protects against myocardial damage induced by reperfusion. This effect was analyzed after 5 min of coronary occlusion in rat hearts. The results indicate that ketorolac, at a dose of 1 mg/kg, effectively protects the heart against reperfusion arrhythmias. Furthermore, it protects from the release of lactate dehydrogenase and creatine kinase to the plasma. We propose that the protective effect of the drug might be due to its chelating action on calcium ions, thus preventing the overload of such cation in myocardial cells.