It is generally recognized that on a chest roentgenogram the pericardial fat pad often produces a shadow at the left apical border of the heart (3). It was our good fortune to observe two interesting autopsies on extremely obese white males. Upon opening the thoracic cage it was noted that the pericardial fat was markedly increased (Fig. 1). More significant was an unusually thick pericardial fat pad which covered the anterior and right lateral surface of the right auricle and superior vena cava. The question then presented itself: Would this fat pad produce a shadow on a postero-anterior roentgenogram of the chest similar to the shadow seen at the left border of the heart? It may be recalled that on routine postero-anterior chest films of obese persons the mid portion of the mediastinum at times appears broadened. This is usually explained by the elevated diaphragm and the transverse position of the heart. It is the purpose of this paper to present findings in gross pathological specimen, and on x-ray fi...