Anomalous origin of the left coronary artery from the pulmonary trunk is associated with high mortality in infancy but in rare cases the condition is diagnosed in adults. The present report describes three adult cases of this anomaly. Two of the patients (age 18 and 34 years) were resuscitated from cardiac arrest, which had occurred in relation to physical exercise. The third patient (20 years) had presented with angina pectoris and signs of ischaemia on exercise ECG. In all patients, coronary arteriography revealed a large right coronary artery with collateral filling of the left coronary artery, which originated from the pulmonary trunk. A successful surgical correction of the anomalous coronary artery was performed in two of the patients.