Most humeral shaft fractures are treated conservatively. However, in the event of failure of closed reduction, pathologic fractures, multiple fracture, multiple associated injury and severe neurologic disorder, operative treatment may be indicated. The purpose of this article is to evaluate the effectiveness of Ender nailing for the humeral shaft fracture of the patients who have multiple fracture, multiple associated injury and pathologic fractures. Authors treated 56 patients with humeral shaft fractures by flexible intramedu-llary stabilization- Ender nail or Ender nail with Rush pin 47 cases were treated closed method, 9 cases were treated by open method. Period of follow-up was average 16 weeks. Fractures were united by an average 12 weeks(range : 9 to 20 weeks). There were no non-union, infection and malunion. No backing out of nails occured. In conclusion, Ender nailing is effective treatment for the humeral shaft fracture to decrease hospital stay, to permit early range of motion of the shoulder and elbow joint.