Cardiac surgeons, like paediatric cardiologists, consider that knowledge of cardiac development, and morphogenesis, is a major aid to the understanding of the anatomy of both the normal and the congenitally malformed heart. In previous editions of our textbook, we have eschewed the option of including a chapter on development. We had taken the stance that, until recently, accounts of the complex changes occurring during cardiac development were based on speculations, rather than evidence. Since the turn of the century, all that has changed. Evidence now exists not only to underpin accurate descriptions of the changes in morphology that occur during development, but also to reveal the lineages and molecular biology of the multiple tissues found in the definitive structures.1 In this chapter, however, we will confine ourselves to description of the key morphological features of cardiac development.