Intramedullary nailing was generally accepted as an excellent method in the treatment of femoral shaft fracture to provide rigid fixation of the fracture, to allow early motion of the joint, and to ensure bony union. We analyzed 100 cases of the fractures of the femoral shaft treated with closed and open intramedullary nailing from January 1988 to May 1994, to compare the results of open and closed intramedullary nailing of femoral shaft fractures and to assess complications and technical problems in intramedullary nailing. The results were as follows: 1. Male was predominant and peak incidence was in the third decades. 2. The most common causes of fracture was traffic accident and associated injuries were in 62 cases. 3. Location of fractures was middle one-thirds in most cases, and Winquist-Hansen Classification type II was the most common. 4. In all cases except 3 cases, operations were done within 2 weeks after injury, and open nailing was done in 66 cases and closed nailing in 34 cases. 5. The average union time was 16.1 weeks in closed IM nailing group, and 20.5 weeks in open IM nailing group and 18.7 weeks in average. 6. The complications was delayed union, nonunion, infection, shortening, failure of distal locking screws and femur neck fracture.