Because of its unique ability to demonstrate the metabolic consequences of myocardial ischemia, positron emission tomography (PET) is extremely valuable in assessing myocardial viability. PET imaging can identify the myocardial segments that are likely to improve after revascularization and may be more sensitive and specific for the detection of coronary artery disease compared with thallium perfusion imaging. Adenosine has several advantages over dipyridamole as a pharmacologic stress agent for use with PET. It produces maximal vasodilation in a significantly greater percentage of patients, is a more potent coronary vasodilator, and its very short half-life may be ideal for use with the very short half-life radioactive tracers used in PET. When combined with metabolic studies, adenosine may be useful for the assessment of patients who received thrombolytic therapy for an acute myocardial infarction.