Background: Interlocking nailing is a surgical technique in the treatment of patients with humeral shaft fractures that can not be treated by non surgical procedures. There are controversies about benefits of this technique. So we evaluated this technique in patients with humeral shaft fracture during 2000-2004.

Materials and Methods: This case series study was performed on 34 patients who operated by antigrade or retrograde nailing. They are followed up till :::union::: formation. Decreasing range of motion in the shoulder and elbow joints was classified as good (less than 10^o), intermediate (10^o-30^o) and bad (more than 30^o) scale. Data analysis was performed by sign test.

Results: 34 patient (56% male, 44% female) aged between 17 and 68 years were studied. 71% and 29% of patients were operated by antigrade or retrograde nailing, respectively. In the 44.1% of patients, duration of :::union::: was less than 3 months. Good scale in the function of shoulder and elbow joints occurred in 88.2% and 85/3% of cases (P<0.01). The frequency of non :::union::: was 5.9%.

Conclusion : It seems that Interlocking nailing is a safe and reliable technique in the treatment of patients with humeral shaft fractures