In view of the complex cardiac anomalies frequently associated with left-sided juxtaposition of the atrial appendages the disposition of the sinus node has been studied in 6 of these hearts. While the sulcus terminalis still provides a landmark to the position of the node, the nodes were in an anterior position in all 5 hearts with complete juxtaposition, 2 being inferior to the crista terminalis. The node was in a more normal, lateral position in the sixth case with partial juxtaposition.