Sixteen out of 293 (5.4%) procedures for percutaneous transluminal coronary angioplasty, performed between 1985 and 1988, were complicated by acute closure and required emergency revascularization surgery. The injured vessel was the left anterior descending artery in 14 cases and the right coronary artery in 2 cases. All patients had persistent chest pain associated with ST-segment elevation in 14 cases and ST-segment depression in 2 cases. Two patients developed cardiogenic shock and were in cardiac arrest at the beginning of operation; one of these died immediately after the operation. Thus the overall mortality rate was 6.2%. Enzyme evidence of myocardial infarction (CPK-MB greater than 40 UI/I) occurred postoperatively in 8 patients (50%), but only the 6 patients (37.5%) with electrocardiographic evidence of myocardial necrosis (new Q-waves or loss of R-wave voltage) showed akinesis of the myocardium perfused by the occluded vessel at the echocardiographic examination performed two weeks after the operation. The occurrence of myocardial infarction was correlated with the degree of preoperative ischemia and hemodynamic deterioration. A collateral flow was present in 3 cases and none of these showed evidence of myocardial necrosis after the operation. Our results show that emergency bypass surgery for failed coronary angioplasty is less satisfactory than elective surgery, and has a higher mortality and myocardial infarction rate. Thus, the risk of emergency operation for complicated dilation must be considered when selecting of candidates for coronary angioplasty.