A brief review of the literature concerning diaphragmatic hernia discloses little information pertaining to the roentgen diagnosis of parasternal hernia. In those cases in which the hernial contents are intestines, the diagnosis is usually obvious, because of the presence of loculated gas shadows or through the introduction of barium. When the contents of the hernia consist of a solid organ, as omentum, the diagnosis is often obscure. The location of shadows of soft tissue density in this area is suggestive of the possibility of anterior mediastinal tumor and this is often foremost in the interpreter's mind. Advance in thoracic surgery makes accurate diagnosis of lesions in the anterior mediastinum of increasing importance. It is the purpose of this paper to describe a roentgenologic sign which indicates the presence of a parasternal omental hernia. As roentgenology has come into greater use, the recognition of diaphragmatic hernia has increased steadily (3) and today it is not considered rare. Its occurrence on the left (1) is much more frequent than on the right (5). Parasternal hernia, however, which is relatively unusual, is seen more often on the right side (2). This right-sided location may be attributed to the protection which the left costosternal triangle receives from the close attachment of the pericardium and the position of the heart. The contents of the hernia are usually colon, omentum, or both. In the three following cases, seen at the Massachusetts General Hospital, parasternal herniae were present which appeared to pass through the right costosternal triangle. In two cases the hernia contained, at one time or another, omentum only; in the third, the hernial contents included large intestine. Case 1 (BM 2074): A 67-year-old white widow entered the hospital complaining of cough of three months' duration. Its onset had been associated with an upper respiratory infection and it had at first been productive. It became non-productive three weeks before admission. There was no pain or dyspnea. The past history revealed a heart attack fifteen years before, at which time dyspnea was present for six weeks. Physical examination, as well as studies of the blood and urine, was negative. The roentgenologic report was as follows: “The left side of the diaphragm, left lung, and upper portion of the right lung are normal. There are apparently calcified nodes at both lung roots. The right cardiophrenic angle is obliterated by a sharply defined, rounded area of density which moves with the diaphragm and appears to change in shape with respiration [Fig. 1]. In the lateral view, the dense area is localized to the extreme anterior portion of the chest, and as the anterior ribs ascend at inspiration the mass appears to descend. The heart is slightly more to the left than normal and does not shift appreciably with respiration.