The first part of this paper deals with the general anatomy of the postero-septal area of the heart, with particular emphasis on the relationships between the mitral and tricuspid anuli and the right fibrous trigone, between the conducting system and the interatrial septum, and between the right atrium and the posterior superior process of the left ventricle. In the second part, we describe the operative procedure that has been developed for dividing right and left posteroseptal Kent bundles. The key to this technique is the opening of the right atrium along the tricuspid anulus down to the orifice of the coronary ostium; this offers an excellent exposure on the posterior aspect of the septal area, and allows dissection of the sulcus fat pad from the muscular portion of the interventricular septum and the adjacent posterior superior process of the left ventricle down to the level of the mitral anulus. This planned dissection increases the likelihood of interrupting the anomalous pathways without injury to the normal conducting system which remains encompassed within the interatrial septum and the right fibrous trigone. © 1986 Springer-Verlag.