Myocardial hibernation is a state of persistently impaired left ventricular function in patients with coronary artery disease that improves after revascularization. It was thought to be caused by a chronic reduction in resting myocardial blood flow in a segment subtended by a diseased coronary artery. However, recent studies using positron emission tomography have demonstrated that absolute myocardial blood flow (mL/min/g) to hibernating myocardium is within normal limits in most patients. The authors hypothesize that hibernating myocardium may be the result of repetitive myocardial stunning, that is, the reversible contractile dysfunction occurring after an episode of myocardial ischemia despite the return of blood flow to normal. Myocardial stunning has been demonstrated in humans in different clinical settings, and recent studies have provided evidence that repetitive episodes of exercise induced ischemia can lead to cumulative and prolonged left ventricular dysfunction akin to that observed in hibernating myocardium.