The closed intramedullary nailing is the best method of treatment in femur shaft fracture, but it is not available in some fracture patten or fracture level, and also need specific technique under specific equipment. conventional closed intramedullary nailing dose not provide adequate fixation if cortical contact of the major fragments is lost due to severe comminution. Open intramedullary nailing with aditional wire fixation or bone graft do not always produce good result and involved and increased risk of infection, delayed union, and also need additional operation. We analysed 80 cases of interlocking intramedullary nailing from September 1994 to September 1997. closed intramedullary nailing was used in 47 cases and open intramedullary nailing in 33 cases. The results were as follows; 1. The average union time was 17.58 weeks in closed Im nailing group, and 27.32weeks in open IM nailing group. 2. In open IM nailing group, complications incluled 10 delayed union, 3 nonunion, two infections, shortening of more than two centimeters, which occurred in 3patients. In closed IM nailing group only one complication is transient peroneal nerve palsy.