A series of 84 patients with unstable angina, treated surgically by grafting procedures between October 1970 and September 1976, have been reviewed. The study indicates that extensive coronary artery disease is common in these patients, and suggests that operation may favourably influence mortality, both immediate and delayed, but does not reduce the risk of myocardial infarction. Eighty per cent of the patients were relieved of angina and able to lead a reasonably normal existence.