Animal studies have demonstrated that restoration of blood flow to severely ischemic myocardium is a prerequisite for myocardial salvage. However, it has been shown that the restoration of blood flow to ischemic myocardium may be associated with deleterious changes of the myocardium, including arrhythmias, enzyme release, and contractile dysfunction. These changes were considered to be additional injuries to the myocardium manifested at the time of reperfusion. The reperfusion was accompanied by a burst of oxygen free radical generation and their role as main mediators of the reperfusion injury have been well accepted. Reactive oxygen species (ROS) and cellular redox status regulate many important cellular activities. The role of antioxidant as a therapy for reperfusion injury has thus been tried with mixed and mostly negative results. Further studies are needed if the antioxidant therapies for ischemia reperfusion injury were to be effective.