PURPOSE: The purpose of this study is to know the relationship of tibial nonunion with fibular nonunion in the tibio-fibular shaft fracture. MATERIALS AND METHODS: From March 1998 to February 2004, 98 tibio-fibular shaft fractures which did not involve adjacent joints and were followed up at least 1 year were selected. The characteristics of patients and tibia shaft fracture were analyzed statistically to know the above relationship. RESULTS: The patient's factor and tibia shaft fracture factor were not significant statistically. In patients with the fibular union, there was 1 case (1/68) of tibia nonunion, but in patients with the fibular nonunion, there were 6 cases (6/30) of tibia nonunion. So fibular nonunion was significant statistically associated with tibia nonunion (p=0.003). CONCLUSION: Fibular nonunion was presumed to have a higher risk of tibia nonunion.