The classification of patients with angina pectoris into various subgroups, which clearly differ in risk based on the patient's characteristics, is difficult. Changes in pain threshold occur frequently. The variation in intensity of the "chest discomfort" makes the history and physical of limited value in making the diagnosis. It may be necessary to use noninvasive testing to demonstrate myocardial ischemia and/or coronary angiography to define stenotic coronary artery stenosis. Within the past 30 years, there have been major advances in the successful medical and invasive treatment of angina pectoris. There are now several forms of effective therapy, which are discussed in detail in this monograph.