In this article I will use the terms "coronary artery disease," "angina pectoris," "coronary insufficiency," and "heart pain" interchangeably and synonymously. Angina pectoris can be manifested by almost any kind of pain and results from a disproportion between the oxygen demand and the oxygen supply of the myocardium. On this basis, many factors may operate in angina pectoris. It may be the result of: 1. Coronary sclerosis, coronary ostial closure, or inflammatory changes in the coronary arteries. 2. Chronic severe anemia or acute anemia, when the blood is unable to carry oxygen to the myocardium, or when the patient is suffering from chronic carbon monoxide poisoning. 3. A severe disease of the mitral or aortic valves, when the minute volume output of the heart cannot be maintained under exertion. Here the stroke volume is so decreased that, no matter how rapidly the rate may increase, the total output of blood