PURPOSE : The purpose of this study was to evaluate the incidence and the factors that influence on malalignment following interlocking nailing for tibial fracture. MATERIALS AND METHODS : The authors analysed 59 patients, 60 cases tibial fracture treated with interlocking intramedullary nailing from 1993 to 1997 about nail insertion site, nail entrance angle and fracture type with roentegenogram. Malalignment was defined as 5 degree or more angular deformity in varus-valgus, 10 degree or more angular deformity in anterior-posterior plane. RESULTS : Malalignment was found in 15 cases out of 60(25%). We found malalaignment in 7 cases out of 11(64%)in proximal fracture, 6 cases out of 29(21%) in middle fracture, 2 cases out of 20(10%) in distal fracture(p<0.001). Correlation between nail insertion site or medial entrance angle and angular deformity was higher in proximal fractures. In midshaft wedge fractures, direction of main fragment influenced on the axial alignment. CONCLUSION : Centromedullary nail orientation is required to prevent malalignment after interlocking intramedullary nailing. Precise selection of nail insertion site and nail entrance angle under the C-arm control in proximal tibial fracture is necessary. Fracture type and fragment direction must be considered during tibial nailing in comminuted tibial fracture.