Using a prefabricated brace, we treated 233 patients who had a fracture of the humeral shaft. One hundred and seventy patients were available for follow-up, which ranged from five weeks to forty-eight months. In these patients (forty-three open and 127 closed fractures), the average time to union was 10.6 weeks; the average varus-valgus angulation, 5 degrees; the average anterior-posterior angulation, 3 degrees; and the average shortening, as measured radiographically, four millimeters. All but three of the patients had an excellent or a good functional result with a nearly full range of motion of the extremity. There were a minimum of complications, including three non-unions. Because of the low morbidity and high rate of success, we concluded that the treatment of choice for diaphyseal fractures of the humerus is the prefabricated brace.