Hibernating myocardium is a state of persistently impaired myocardial and left ventricular function at rest due to reduced coronary blood flows. It can be defined as an exquisitely regulated tissue successfully adapting its activity to prevailing circumstances. It has been documented in patients with angina (chronic stable and/or unstable), acute myocardial infarction, heart failure and/or severe left ventricular dysfunction, and anomalous left coronary artery from the pulmonary artery. The diagnosis of hibernating myocardium involves (a) documenting left ventricular dysfunction at rest and (b) documenting that there is viable myocardium in the area of dysfunction. Tests commonly used for the latter are dobutamine echocardiography, 201Tl isotope studies, and positron image tomography. Revascularization, either by surgery or by interventional catheter techniques, has been shown to improve or normalize the abnormal left ventricular function at rest.