Usually, fractures of the humerus can be expected to unite. Circumstances often predisposing to nonunion are open reduction and internal fixation, infection, soft tissue interposition between fracture fragments and inadequate external immobilization. The effectiveness of various methods of treatment and the complication was discussed. The best results are achieved in cases treated by compression plates and iliac bone graft. Total 21 cases of nonunion of shaft of humeral fractures from Jan., 1980 to Dec., 1986 were treated at the Department of Orthopedic Surgery of Soon Chun Hyang University Hospital. The results were as follows ; 1. Incidence of nonunion of humerus shaft among the 270 cases has 7.8%; rates of non-union was 5.4% with nonoperative treatment of fractures of humeral shaft and 10.5% with operative methods. 2. Of 21 cases, male between 20–40th age group was predominant and mean age was 36 years. The cases of fracture was mainly due to the car and machinary accident. 3. Prevalent type and site was lower 2/3 transverse fractures. 4. There were associated injuries in ipsilateral upper extremity in 12(52%) patients. 5. The probable causes of nonunion were complex; 9 of inadequate internal fixation and fixation metal failure, 7 cases of poor external fixation, 3 cases of soft tissue interpostion between fracture fragments and 2 cases of infection. 6. The treatment performed were somewhat variable to include open reduction and plate (DCP) fixation for 18 cases, open reduction and circlage wiring for 2 cases and open reduction and screw fixation for 1 cases. All were supplemented with autogenous iliac bone graft. 7. Postoperative immobilization was done with shoulder spica cast, abduction splint and long arm cast for average 6.5 weeks. 8. All were united at average 4.7 months. Transient radial nerve palsy in 2 cases, and limitation of motion of shoulder and elbow iri 2 cases, which required considerable time of physical therapy, but postoperative infection was none.