From retrospective review of 111 tibial fractures treated by interlocking intramedullary nailing, 38 operative errors in 28 cases(25%) were included in this study. The errors were classified into two categories. The first category included eighteen errors that related to fracture reduction; nine angular malalignments, four failures in closed nailing to open the fracture site, two peroneal nerve palsies, two shortenings of tibial length(more than 1cm), and one rotational malalignment. The second category comprised twenty errors that related to the nailing itself; eight protrusions of proximal nail tip, five overdistractions of fracture gap (more than 3mm), four additional fragmentations, two mistakes in interlocking screw insertion, and one ankle joint injury by the distal nail tip. Functional results of those 28 cases at the last follow-up(average, 17.5 months; range, 9 to 29 months) were excellent or good in only 60.8 per cent, while the control group treated by adequate operative technique showed excellent or good results in 92.8 per cent.