The pathological features of 13 cases with juxtaposition of the atrial appendages in the autopsy files of The Johns Hopkins Hospital were studied. The anomaly occurs most frequently in association with transposition of the great vessels, ventricular septal defect, patent foramen ovale, and obstructive lesions of the tricuspid and pulmonic valves. The malformation complex of tricuspid atresia, atrial and ventricular septal communication, and the transposition of the great vessels seems particularly common with juxtaposition of the atrial appendage. A recent case showed a small accessory right atrial appendage lying in juxtaposition to the left atrial appendage. In addition, a normally situated right atrial appendages in addition to well-formed accessory appendages lying in juxtaposition to the left atrial appendages. It seems that juxtaposition of the atrial appendages should be reinterpreted as an accessory appendage or atrial diverticulum.