OBJECTIVE To evaluate the clinical effects of Russell-Taylor interlocking intramedullar nail (RT nail) on humeral shaft fractures. METHODS Twenty six patients with humeral shaft fractures were treated with RT nail, of whom 19 cases were treated with antegrade RT nail and 7 cases with retrograde RT nail. RESULTS With an average of 16 months (range 6-24 months) of follow-up, all cases acquired bony union with mean union time 4.7 months (range 3-8 months). The recovery of shoulder function was excellent in 18 cases, good in 5 cases, and fair in 3 cases. The recovery of elbow function was excellent in 23 cases and good in 3 cases. One case had shoulder impingement caused by proximal locking screw. All cases had no infection, iatrogenic fracture, and peripheral nerve injury. CONCLUSIONS RT nail is an effective method for the treatment of humeral shaft fractures.