Reperfusion is the definitive treatment to salvage ischemic myocardium from infarction. A primary determinant of infarct size is the duration of ischemia. Early reestablishment of blood flow to ischaemic myocardium limits infarct size and reduces mortality. In a paradoxical manner, the return of blood flow to ischemic myocardium may result in additional injury in the area at risk. This condition is known as reperfusion injury, and the damage is more likely when reperfusion therapy is delayed. Even when the majority of the clinical trials designed to evaluate agents for preventing reperfusion injury have been disappointing, therapies to limit reperfusion injury remain an active area of investigation.