The present study was conducted on 33 children (median age at initial cardiac catheterization 0.4 years [0.1 to 11.8]) with anomalous origin of the left coronary artery from the pulmonary artery, without associated hemodynamically significant cardiovascular anomalies, who were treated throughout a period of 18 years in our hospital. A two coronary artery circulation was reestablished in 31 of 33 children. One child died before the intended operation, and in one child the left coronary artery was ligated. There were six operative deaths, five intraoperative and one 12 hours after operation. The purpose of the study was to assess which preoperative clinical and angiographic features were associated with a higher perioperative mortality. The following preoperative factors were associated with a statistically significant higher perioperative mortality: young age at operation (p less than 0.03), left and balanced type of coronary circulation (p less than 0.01), and electrocardiographic signs of extensive acute myocardial infarction, namely, marked ST elevation (greater than or equal to 0.2 mV in at least two leads) (p less than 0.03). Left axis deviation on the electrocardiogram was associated with an extreme right dominant type of coronary circulation (p less than 0.005). The latter was also linked with adequate perfusion of the posterolateral left ventricular wall (p less than 0.005). At autopsy, severe increase of heart weight to two or three times the normal heart weight was established in six of seven children. Thus the perioperative mortality was determined primarily by the extent of myocardial ischemia. This in turn is decisively influenced by the dominant type of coronary circulation and the extent of inter-arterial collateralization. Young age, in addition, proved to be a risk factor for mortality at corrective surgery.