Positron emission tomography of the heart is a physiologic imaging technique that enables both qualitative and quantitative assessment of regional myocardial blood flow and substrate utilization. Exercise or dipyridamole perfusion imaging with PET is both sensitive and specific for detecting coronary disease and may prove clinically useful in assessing the physiologic significance of anatomically defined stenoses and for noninvasively following stenosis progression or regression. PET can be used to localize and quantitate the extent of antecedent myocardial infarction, and frequently identifies viable tissue when routinely utilized clinical tests indicate completed infarction. The tissue characterization afforded by metabolic imaging with PET in coronary heart disease allows non-invasive identification of viable but jeopardized tissue in a variety of clinical ischemic syndromes, thereby permitting the cardiologist to intervene in anticipation of myocardial salvage. As future developments in PET imaging occur, our understanding of the basic biochemical abnormalities characterizing myocardial ischemia will be utilized with increasing frequency to improve the clinical care provided to patients with coronary heart disease.