The clinical, electrocardiographic, hemodynamic and arteriographic features of Prinzmetal’s variant form of angina pectoris are discussed, based upon previously reported case material and our own experience with 11 patients. Although the chest pain of Prinzmetal’s angina results from myocardial ischemia, the syndrome differs from the classical form of angina pectoris in many respects. In particular, Prinzmetal’s angina develops at rest or with light activity and is accompanied by S-T segment elevation on the electrocardiogram, while classical angina pectoris is precipitated by increased cardiac work and is frequently accompanied by S-T segment depression. Arteriography in most cases reveals either focal stenosis of a single major coronary artery or anatomically normal vessels. Only rarely are multiple vessel disease or total obstructions seen. There is strong clinical evidence suggesting that Prinzmetal’s angina is produced by transient paroxysmal spasm of a major coronary artery. This has been verified recently by actual angiographic demonstration of spasm while attacks were in progress.