We treated 74 fractures of the tibia by Interlocking intramedullary nail from Jan. 1982 to Mar. 1988. 58 of the fractures were fresh, 11 of these were open fractures. The other had 14 delayed union and nonunion and 2 ostetomy for malunion. Mean follow-up was 12.4 month and we analysed as follows: 1. Of 74 fractures, 73 fractures united and then the union rate was 98.5%. 2. Interlocking IM nail could be used to the majority of fractures of the shaft of tibia from 6cm below the knee joint to 5cm above the ankle joint. 3. Interlocking nail had rigid rotational stability and was appropriate for the treatment of severe unstable fractures. 4. Delayed union or nonunion was a good indication for intramedullary nsilling. 5. The major complication was deep infection. When the fixation was rigid with intramedullary nail, bone union was progressed in spite of infection. 6. Interlocking Intramedullary nailing provided rigid fixation of fracture and then it made possible early joint motion exereise and ambulation.