Aneurysmal dilation of the right atrium is described in a four-year-old boy who presented with cardiomegaly and symptoms of congestive heart failure. Echocardiography revealed the aneurysmal dilation of the right atrium, but a definite diagnosis was obtained only after surgical exploration. This had caused compression of the other cardiac chambers resulting in congestive heart failure. Surgical resection was successful and the patient was discharged on the eleventh postoperative day with good results.
