PURPOSE: To compare functional results between interlocking intramedullary nail with wiring and plate for treating long oblique or spiral diaphyseal fractures of humerus. MATERIALS AND METHODS: From April 1996 to February 1999, 9 long oblique or spiral fractures were treated with antegrade humeral locked nails and wiring after minimal open reduction, and another 9 fractures were fixed with plate and screws. Average age of patients was 45.8 years and average follow-up was 13.5 months. RESULTS: Nail group showed earlier clinical and radiologic union than plate and screw group. All patients with plate and screw group(plate fixation) had clinical union within 5.8±2.5 weeks and radiologic union within 8.5±2.1 weeks. But, all patients with wiring had clinical union within 2.8±0.6 weeks and radiologic union within 5.5 ±1.6 weeks. At last follow-up, average range of shoulder motion in plate group was larger than nailing group, but that was stastically insignificant. Plate fixations had more complications than nailing, for example, deep infection, non-union, implant failure and radial nerve injury. CONCLUSION: Interlocking intramedullary nail with wiring has the advantages of minimal tissue trauma and scar formation, sufficient reduction and fixation, early union and fewer complication. So it can be a worthy alternative for the treatment of long oblique or spiral fractures of humerus.