Four cases of lipomatous hamartoma of the interatrial septum (LHIAS) were diagnosed at autopsy, three in elderly women, two of whom were morbidly obese. One patient had signs of congestive cardiac failure, without other significant cardiopulmonary disease, which was thought to be a result of the interatrial lipomatous hamartoma, while in the others, the LHIAS was considered an incidental finding. This condition, previously considered a hypertrophic phenomenon, is now best described as hamartomatous, and is being recognized more frequently both by clinicians and pathologists.