Noninvasive imaging is wellsuited to the assessment of myocardial viability. In PET, preserved metabolic activity in regions with reduced blood flow is an accurate clinical marker, with ˜ 85% accuracy for predicting the efficacy of revascularization. Nevertheless, early after reperfusion therapy, this method may overestimate the presence and extent of viable myocardium. Regions of severely ischemic or hibernating myocardium may also be identified by Tl 201 imaging, using late redistribution imaging, thallium reinjection imaging, or restredistribution protocols. Tc 99m sestamibi has theoretic weaknesses for viability assessment, but recent data suggest that this agent is very satisfactory for clinical viability assessment. Low-dose dobutamine echocardiography is also useful for detection of viable myocardium. Although these methods appear to have similar diagnostic accuracy, large-scale studies comparing PET, Tl 201, and dobutamine echocardiography are required early after reperfusion therapy or revascularization to determine their relative efficacies...