A perplexing diagnostic problem confronts the physician when his patient complains of cardiac pain too prolonged to be consistent with a diagnosis of angina pectoris but, on the other hand, not attended by the various recognized features of acute myocardial infarction. The duration of bed rest and other details of treatment, as well as the prognosis, depend on the physician's evaluation of the underlying organic and functional changes. The problem is therefore of considerable practical and theoretical moment. The syndrome of cardiac pain which is intermediate between angina pectoris and acute myocardial infarction has been referred to in previous communications1by the term "coronary failure." The diversity of terms used by various authors to designate this and closely similar syndromes has led to considerable confusion. The purpose of this communication is to describe the typical features of coronary failure and to indicate the spectrum-like gradation of cases between the