PURPOSE: To evaluate the effectiveness between reamed and unreamed nailing in the treatment of femoral shaft fracture. MATERIALS AND METHODS: Among the patients of femoral shaft fracture who were treated with reamed and unreamed nail, we reviewed 49 patients whose follow-up was possible for more than 1 year. The patients were divided into two groups: the reamed and the unreamed group. We reviewed union time, nonunion rate, complication and operation time and compared the effectiveness. RESULTS: The average union time was 30.6 weeks in unreamed group and 27.8 weeks in reamed group, which was not different statistically. There were 5 cases of nonunion in 22 unreamed cases and 3 cases in 27 reamed cases, which meant no statistical difference. There was no significant difference of complications between the two groups. The mean operation time was 141 minutes in reamed group and 110 minutes in unreamed group, which meant statistical difference. CONCLUSION: There was no significant difference in union time, nonunion rate and comlication between reamed and unremed group. The operation time was shorter in unreamed group, so unreamed nailing can be preferred in the treatment of multiply injured patient.