Post-mortem study of a heart specimen from a forty-two-year-old man showed an anomalous origin of the left main coronary artery from the right aortic sinus and its course posterior to the aorta. In this case the branches of the left main artery were smaller than usual, being partly supplied by the right coronary artery, which originated in a common point with a right preventricu lar artery. In the case reported myocardial ischemic signs were not noted. © 1994, Sage Publications. All rights reserved.