Intramedullary nailing is one of the most popular method of treatment in femoral shaft fractures,which provides relatively stable fixation and preservation of blood supply and early mobilization. But whether open reduction, cerclage wiring and/or bone graft is necessary for the displaced comminuted fragment is still a subject of controversy. To clarify such debate we compared the results of IM nailing between simple, minimal displaced fractures and displaced, comminuted ones treated with closed method. We analyzed 36 cases of the fresh closed fractures of femoral shaft treated by closed intramedullary nailing from December 1992 to January 1996. There were 24 cases of minimal displaced fractures and 12 cases of displaced ones more than 1 cm during operation. The average follow-up period was 12 months(5-48 months). Clinical and radiological fracture union occurred in 97% of cases(35/36). Radiological callus was noticed just around 3 weeks postoperatively in both groups and the average time to radiological union was 23 weeks in minimal displaced group and 24.8 weeks in displaced one. Because there was no significant difference in bone healing time, closed interlocking intramedullary nailing is thought to be also the good method of treatment in femoral fractures regardless of fracture pattern or displacement of fragments.