When chest pain, pressure, or other thoracic sensations are present, one must exclude angina pectoris and significant coronary artery disease and also discover noncardiac conditions, if present. Again, one should avoid unjustifiably diagnosing coronary artery disease when it does not exist. Not one single feature, hitherto considered characteristic of coronary disease or of a noncardiac lesion, is definitive in differential diagnosis. Physical findings, blood pressure, heart size, heart configuration, heart valves, and resting electrocardiogram are often normal. Hence, negative objective observations must not serve as evidence of the absence of significant interference with the coronary artery circulation. Differentiation by history alone between chest pain or pressure caused by coronary disease and that caused by noncardiac or functional disorders is often impossible. This is true even if the history is obtained in detail by an experienced physician.