The development of persistent pain in the shoulder region in patients who have disease of the coronary arteries is sufficiently common to warrant more comment than it has hitherto received. The mechanism responsible for the pain has not been determined, but the frequency of its occurrence is such as to indicate more than a chance relationship to the attendant heart disease. The pain occurs most commonly as an aftermath of myocardial infarction, but it also develops at times in persons who have frequent and severe attacks of angina pectoris and who present no evidence of having suffered from earlier coronary occlusion. One or both shoulders may be affected, but the left shoulder is more commonly involved than the right. The pain lasts for several weeks or months and is usually increased by movement of the arm but is not influenced by walking. In patients who experience attacks of angina pectoris