Over the past decade, much has been learned concerning the origin and development of the ventricles. However, most, if not all, of the new information has come from study of the mouse heart. Most of this information has yet to be assimilated by those who study ventricular function or diagnose congenitally malformed hearts. Nevertheless, the evidence available from recent studies, particularly if it can be shown relevant to human development, is remarkably pertinent to these topics. For example, knowledge of how each ventricle derives its inlet and outlet components, information available for human development (Lamers et al., Circulation 86:1194-1205, 1992), provides a firm foundation for understanding congenital cardiac malformations, particularly those dependent on a functionally univentricular circulation (Jacobs and Anderson, Cardiol Young 16(Suppl 1):3-8, 2006). Appreciation of ventricle development also is important with regard to understanding the basis of so-called ventricular noncompaction because this knowledge will elucidate whether the compact component of the ventricular walls is produced by consolidation of the initially extensive trabecular zone seen during early development or by defective formation and/or maturation of the compact myocardium (Anderson, Eur Heart J 29:10-11, 2008). Knowledge concerning the mechanism whereby ventricular myocytes are packed within the compact component of the ventricular walls then will help clarify the architectural arrangement of the aggregated myocytes, a topic of considerable recent interest. This review discusses all these topics.