Myocardial reperfusion injury is defined as the adverse effects that ensue upon restoration of the circulation, which allows blood and nutrients to reach cells previously subjected to ischemia. Restoration of blood flow can be accompanied by the release of oxygen free radicals, the appearance of intracellular calcium overload, and alterations in cell metabolism -all situations that can give rise to functional or structural myocardial injury. Clinical signs of injury may appear after circulation is restored or after the use of extracorporeal circulation during heart surgery, and are manifested as stunned or hibernating myocardium after acute coronary syndromes, as the no-reflow phenomenon (microvascular injury) after blood flow is restored during angioplasty or after >, and especially after surgical revascularization. This review examines the pathophysiological substrates, clinical manifestations and current approaches to treatment for each of these entities.