In the absence of respiratory distress and massive visceral herniation, the diagnosis of blunt diaphragmatic disruption can be difficult. This is particularly true for diaphragmatic injuries confined to the right hemidiaphragm. Because diagnostic delay and strangulation are associated with notable increases in mortality and morbidity, it is important to identify the injury as early as possible. Victims of lateral impact motor vehicle collisions are more likely to experience rupture of the diaphragm than victims of frontal collisions. Occupants exposed to left lateral impacts are at greatest risk. The side of diaphragmatic rupture correlates with the direction of impact. The right hemidiaphragm is more resistant to rupture. Deformation shear is a more plausible mechanism for diaphragmatic rupture after lateral impacts. Knowledge of the mechanisms that produce this injury combined with information regarding the victim's seat position and direction of the impacting force should lead to a high index of clinical suspicion for diaphragmatic rupture. Chest radiography and diagnostic peritoneal lavage will establish the correct diagnosis in almost 90% of the patients with acute diaphragmatic disruption. Additional diagnostic studies are reserved for the remaining 10% of patients. Due to the pressure differential between abdomen and thorax, the natural history of these injuries is one of enlargement, and none can be expected to heal spontaneously. Once the diagnosis has been established, the treatment of every diaphragmatic disruption is surgical repair.