Massive right atrial (RA) enlargement is certainly more common in children than in adults, owing to rare congenital anomalies. Indeed, the largest description of such chamber enlargement was noted in a child, where the RA volume was reported to be 900 ml. We now report one of the largest descriptions of the RA in an adult, in absence of tricuspid stenosis and other common adult associations of RA abnormality, such as chronic pulmonary disease, severe mitral valvular pathology with pulmonary hypertension, and pulmonary embolism or infarct. The RA volume was estimated to be well over 500 ml and was notably disproportionate to that of the left atrium and either ventricle.