A flail chest with a manubriosternal separation in a man with multiple injuries was treated with an external fixator applied to the sternum and the manubrium. Pain and ventilatory function were improved, permitting immediate postoperative extubation and prompt patient mobilization. The external fixator was removed after fracture union at 2 months. One year after injury, the patient's pulmonary function was normal. External fixation is an alternative to other methods of sternal fracture stabilization.