Interlocking nailing has been increasingly used to treat humeral shaft fractures with the improvement in intramedullary device design and surgical technique. We reviewed the clinical results in twenty nine patients who had intramedullary nailing for the treatment of humeral shaft fractures from May, 1992 to July, 1995 in wonkwang university hospital. there were 8 polytrauma patients; 6 were osteoporotic elderly patients; 10 were comminuted fractures; 2 were segmental fractures; 1 was nonunion; 1 was pathologic fracture; 1 was bilateral humeral fractrure. Trueflex, Seidel and Uniflex nail were selected 13, 8 and 8 cases respectively. According to AO classification, simple, wedge and complex fractures were 14, 7 and 8 cases respectively. The result of this study were as follows : sound bony union were observed in twenty three cases, but six nonunions treated by additional operations such as bone graft, modified dual onlay bone graft or OR/IF with bone graft were occurred. Nonunion was occurred mainly in simple and wedge type of AO classification. Distraction of fracture site occurred mainly in simple type of AO classification was related with nonunion. Chronic shoulder symptoms were observed in six cases, and proximal nail protrusion and injury to rotator cuff were considered as its possible cause. Other omplications were one postoperative radial nerve palsy and metal breakage.