Abstract Unstable angina is an important symptom of coronary artery disease. Two general clinical presentations may occur: (1) stable angina with a recent increase in severity or angina of recent onset, or (2) acute coronary insufficiency or angina at rest with chest pain resembling that of acute infarction. The risk of death or infarction is greater in patients who have recurrent chest pain and ST-T wave abnormalities despite hospital treatment. In patients without electrocardiographic or serum enzyme evidence of a completed infarct, coronary arteriography and bypass graft surgery can be performed with an acceptably low mortality rate. Surgical treatment provides better symptomatic relief than medical management in many patients, but the significant incidence of perioperative infarction makes it difficult to determine if surgery prevents infarction. Some studies indicate that surgery improves survival in subgroups, but data from large scale randomized studies will be needed to answer this question securely. Patients with disease of the left main coronary artery should probably have surgical treatment. Medical treatment will relieve symptoms in most patients with unstable angina and on a long-term basis may obviate the need for surgery. A preliminary period of intensive medical treatment before surgery may be advantageous since there is little evidence that survival rates are improved by treating unstable angina as an acute surgical emergency.