The books and articles devoted to technique in cardiac surgery are legion. This is most appropriate, as the success of cardiac surgery is greatly dependent upon excellent operative technique. But excellence of technique can be dissipated without a firm knowledge of the underlying cardiac morphology. This is just as true for the normal heart as for those hearts with complex congenital lesions. It is the feasibility of operating upon such complex malformations that has highlighted the need for a more detailed understanding of the basic anatomy in itself. Thus, in recent years surgeons have come to appreciate the necessity of avoiding damage to the coronary vessels, often invisible when working within the cardiac chambers, and particularly to avoid the vital conduction tissues, invisible at all times. Although detailed and accurate descriptions of the conduction system have been available since the time of their discovery, only rarely has its position been described with the cardiac surgeon in mind. At the time the first edition of this volume was published, to the best of our knowledge there had been no other books that specifically displayed the anatomy of normal and abnormal hearts as perceived at the time of operation. We tried to satisfy this need in the first volume by combining the experience of a practising cardiac surgeon with that of a professional cardiac anatomist. We added significantly to the illustrations in the second edition, while seeking to retain the overall concept, as feedback from those who had used the first edition was very positive. In the third edition, we sought to expand and improve still further on the changes made in the second edition. In the second edition, we had added an entirely new chapter on cardiac valvar anatomy, and greatly expanded our treatment of coronary vascular anatomy. We retained this format in the third edition, as we were gratified that, as hoped, readers were able to find a particular subject more easily.