This study involved 163 patients with penetrating injuries of the diaphragm (knife, 139; bullet, 24). Intra-abdominal injuries were present in 122 patients (75 per cent) and this resulted in early diagnosis and treatment of the associated diaphragmatic injury (mortality 3.2 per cent). In the remaining 41 patients (25 per cent) the injury was confined to the diaphragm, and the diagnosis was missed during the initial admission in 10 patients who returned at a later stage with diaphragmatic hernia. A diaphragmatic hernia was found in 24 cases (14.7 per cent). Fourteen of these were diagnosed during the initial admission (mortality 7.1 per cent) and the remaining ten were diagnosed during a subsequent admission (mortality 30 per cent). The initial chest radiograph was diagnostic of diaphragmatic injury in 13 per cent, abnormal but not diagnostic in 76 per cent, and completely normal in 11 per cent. The importance of early diagnosis in reducing mortality, morbidity and hospital stay is emphasized. A high index of suspicion, careful clinical examination, and serial chest radiographs remain the best way of making the diagnosis.