There continue to be disagreements concerning the embryology of the ventric- ular septum and the nomenclature of its various parts, as well as on its phylogenetic derivation. It must be obvious that until such time as these uncertainties have been resolved it will not be possible to understand the pathogenesis of ventricular septal defects and other anomalies involving the ventricular septum. In an effort to clarify some of these difficulties a number of individuals, including anatomists, embryologists, pathologists, cardiologists, and sur- geons, all acknowledged experts in their respective...