Ruptures of the diaphram occur in approximately 2% of cases of severe thoraco-abdominal trauma. They are present on the left in 80% of cases. The rupture is cupolar, sagittal or transversal, with peripheral desinsertion (the last always observed on the right), or paravertebral and retropericardiac posterior tears. Movement of the abdominal viscera toward the thorax can be progressive, with signs appearing only after 3 or 4 days or more. Any attempt to evacuate an intrathoracic effusion should be made carefully. In half the cases in polytraumatic patients, the lesion is confirmed by clinical suspicion or by appropriate surgical exploration. The first emergency step is repair. In cases of recent occurrence and for reasons of abdominal safety, coeliotomy is preferred. Mortality ranges from 20 to 30% and depends on the polytraumatic state but also on heart and respiratory failure and on infectious complications.