Univentricular heart of left ventricular type is defined as the condition in which the entirety of atrial inputs is committed to a main chamber exhibiting trabecular pattern of left ventricular type, usually in the presence of another chamber in the ventricular mass which has a right ventricular trabecular pattern. This condition can occur with two atrioventricular valves, a common atrioventricular valve, a straddling atrioventricular valve or with absence of the right or left atrioventricular connexions. The hallmark of univentricular heart of left ventricular type is absence of the inlet septum, which normally separates the inlet portions of the two ventricles and which in the normal heart carries the atrioventricular conduction bundle. In univentricular heart of the left ventricular type, as a consequence of its absence, an abnormal disposition of the atrioventricular conduction tissues is found. An anterior or lateral atrioventricular node is present from which the prenetrating bundle descends onto the trabecular septum separating main chamber from rudimentray chamber. The topographical relationship of the bundle particularly with respect to the outflow tract of the posterior great artery from the main chamber, depends on the position of the rudimentary chamber. In atrial situs solitus, a left-sided rudimentary chamber will be associated with a long bundle in close proximity to the ostium of the posterior great artery from the main chamber. In contrast, in the heart with a right-sided rudimentary chamber the bundle will stay remote from the posterior outflow tract. The position of the rudimentary chamber will also alter the site of the ventriculotomy for any proposed corrective surgery and, hence,, alter the relationship of the bundle relative to the outlet foremen, as viewed by the surgeon. The general disposition of the atrioventricular conduction system in univentricular heart of left ventricular type is not altered by the type or mode of the atrioventricular connexion, nor by the type of the arterial connexion.