Results of a comprehensive survey of the literature concerning coronary artery anatomy, embryology, and pathophysiology show the lack of an adequate definition of normal coronary arteries. To fill this gap, the present review considers the available data concerning the embryogenesis of the coronary arteries and proposes a new definition of normality that refers to essential anatomic features. The concepts of normal variant versus anomaly are introduced, based on a statistical definition of the normal range (99% of the presentations observed in a normal, unselected population). Coronary anomalies are defined as those patterns found in less than 1% of the cases. The wide spectrum of coronary abnormalities is then organized according to a comprehensive classification scheme. For clinical purposes the conceptual difference between anatomic and pathophysiologic anomalies is stressed. The current paucity of experimental studies concerning normal and abnormal embryogenesis of the coronary arteries is found to be the major limitation to an understanding of this subject.