Patients with unstable angina, defined as resting chest pain associated with transient repolarization changes on the electrocardiogram, represent a high risk subset among the clinical manifestations of ischemic heart disease. Pathogenetic mechanisms include coronary spasm and vasoconstriction, coronary thrombosis and platelet aggregation. Early prognosis is related to the degree of activity of the disease while long-term outcome depends on the extent of the coronary disease and the degree of left ventricular dysfunction. Medical treatment should include the combination of beta-blockers, nitrates and calcium antagonists as well as the use of heparin and aspirin. Despite such an aggressive treatment, attacks of resting chest pain persist in almost 30 per cent of patients. In these cases emergency revascularization may be achieved by either coronary angioplasty or bypass surgery. The latter operation may result in improved survival in patients with impaired left ventricular function and triple vessel disease.