<b>Borrie, J. and Lichter, I. (1974).</b><i>Thorax</i>, <b>29</b>, 329-337. <b>Pericardial rupture from blunt chest trauma.</b> Pericardial rupture may occur in two distinct anatomical sites, namely the diaphragmatic pericardium and the pleuropericardium. They may be combined. The problems in each type are different. In <i>ruptured diaphragmatic pericardium</i> the rent may involve the pericardial cavity alone, or may extend into one or both adjoining pleural cavities. Upward herniation of abdominal viscera can occur, with or without strangulation. The presence of a pericardial rent may be suggested by diagnostic pneumoperitoneum, and chest films showing displaced abdominal viscera; its extent may be fully revealed only by thoracotomy. If the rent involves only the diaphragmatic pericardium without lateral spread into a pleural cavity, the presence of a rent may be revealed only by exploratory thoracotomy with pericardiotomy. In <i>ruptured pleuropericardium</i> the rent is usually vertical and may occur on either side, more usually on the left. It may be recognized on chest films in its early stages by the presence of intrapericardial air arising from associated lung trauma. There is serious risk of heart dislocation with or without strangulation. The defect must be surgically repaired and, because of pericardial retraction, it may require a fabric patch. Teflon fabric has proved to be a long-term satisfactory pericardial substitute. Two cases of each type of pericardial rupture are described and illustrate these points.