Five cases of herniation of the heart are described, of varying aetiology and presentation. In one, the pericardial deficiency is congenital. Two are traumatic—one with severe disruption of the rib cage, and one without. Two are post-operative—one early, and one late. Their aetiology, diagnosis and treatment are discussed. If the possibility of herniation is considered, the diagnosis may often be made from a plain chest radiograph. The treatment is operative, and may give relief from a critical circulatory embarrassment.