An unusual radiological feature, not mentioned in the literature, is reported. It has been observed in a patient with traumatic rupture of the diaphragm associated with intra-abdominal bleeding. This injury produced a free pleuroperitoneal movement of liquid demonstrated in the supine and erect chest radiographs. Since there is an associated abdominal injury in most cases of rupture of the diaphragm, this radiological sign might be more common. The importance of supine and erect chest radiography is reinforced in cases of multiple injuries.