One hundred patients were treated with arterial counterpulsation over a 52-month period, indications being acute myocardial infarction complicated by cardiogenic shock or refractory cardiac failure, or elective cardiac surgery complicated by continued dependence on cardiopulmonary bypass. Virtually all patients showed initial improvement and 45 were hospital survivors. Serious complications of treatment were relatively infrequent. Long-term results were good, particularly in patients treated early, and in those with infarction who suffered mechanical complications that could be corrected surgically results suggest an important role of arterial counterpulsation in acute coronary artery disease.