Recently, extemal fxation and unreamed intramedullary nailing are largely used for operative treatment for open long bone fractures. Extemal fixation, especially in cases of unstable fractures, blamed for complications, for example, malunion, delayed union, loss of reduction, refracture, pin tract infection. In addition, there are some problems such as long hospital stay and delayed returning to work. Some surgeons tried to treat such problems by secondary intramedullary nailing, but they came to different retults. The purpose of the current study is to evaluate our experience with secondary intramedullary nailing after failed external fixation of 4 cases of open Grade II, 8 cases of open Grade III a, and 4 cases of open Grade III b tibial fractures. The results are as follows ; 1. The external fixation had been maintained for 123 days in average. 2. The mean interval between removal of the external fixation and intramedullary nailing was 16 days except 5 immediate operation. 3. Reamed intramedullary nailing with static interlocking were done in all 16 cases. 4. In 12 cases of 16, bone union was obtained without complications, and the mean union time after intramedullary nailing was 21.7 weeks radiollogically. 5. Deep infections developed in 2 cases, which had in fracture site, and local infections in 2 cases, which had been in previous pin site of external fixator. In conclusion, delayed intramedullary nailing was a method for treatment of problematic external fixation, such as delayed union, nonunion, loss of fixation, and pin site infection, for open fractures of the tibia.