PURPOSE: To investigate the bone union time of patients treated with interlocking intramedullary nailing in wedged tibial shaft fracture and to evaluate the factors that influence this result. MATERIALS AND METHODS: 32 patients treated with interlocking intramedullary nailing for wedge tibial shaft fracture were reviewed with a follow-up period of more than 1 year. Radiographic results were assessed with diameter (%) and length (mm) of wedge fragment, pre and postoperative displacement (mm) of wedge fragment. We also checked the bone union time of the main fragment and the wedge fragment (paired t-test). We investigated the bone union time acocording to the diameter, length of wedge fragment, pre and postopertvie displacement (correlation analysis). RESULTS: Bone union time of the main fragments averaged 15.3 weeks (6~53 weeks) and that of wedge fragment averaged 24.2 weeks (8~64 weeks) (p=0.005). There was no correspondence between wedge fragment diameter and bone union time (p=0.681), but the bone union time of wedge fragment increased in proportion to its diameter (r2=0.747, p=0.031). There was no correspondence between preoperative displacement of wedge fragment and bone union time (p=0.574), but the bone union time increased in proportion to postoperative displacement of wedge fragment (r2=0.730, p=0.001). CONCLUSION: Wedge fragments need longer time for bone union than main fragments in interlocking intramedullary nailing for wedge tibial shaft fractures. We need to pay attention to the displacemet of fragments in treating tibial shaft fractures with large wedge fragment.