PURPOSE: The comparative analysis of clinical difference between the use of reamed nail and unreamed nail in treatment of femoral shaft fracture. MATERIALS AND METHODS: In 105 patients with femoral shaft fracture who were treated with reamed nail or unreamed nail between June of 1997 and April of 2000, 95 patients who underwent more than a year of follow-up were selected. Winquist-Hansen criteria was applied for the classification of fracture. Based on the medical records and radiological examinations, conducted a retrospective, statistical analysis of the duration of operation, the amount of bleeding during operation, the first time of callus formation, union time, and complications. RESULTS: The average duration of operation was 107 minutes for reamed nail group, and 94 minutes for unreamed nail group, and the difference was statistically significant (p<0.005). The amount of bleeding during the operation was 400 mL for reamed nail group and 250 mL for unreamed nail group, and the difference was statistically significant (p<0.001). There was no statistical difference in the first time of callus formation and union time between the two groups but, in general union time tend to be long in unreamed nail group. CONCLUSION: In the treatment of femoral shaft fracture, the use of unreamed nail was shown to have an advantage over the use of reamed nail in terms of the duration of operation and the amount of bleeding. We recommend restrictive cases.