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.