The case of a 51-year-old woman with exertional angina pectoris and isolated anomalous origin of the left anterior descending coronary artery from the right coronary artery is reported. This anomalous artery was not narrowed, coursed in front of the pulmonary artery and did not present either anatomical derangement at the take off or intramyocardial course. The mechanism of ischaemia could not be identified.