OBJECTIVE: To reveal the pattern of involvement of the peroneal and tibial division in the sciatic nerve injury according to the locations and etiologies. METHOD: Fifty-four patients with sciatic nerve injuries were investigated. The relative involvement of peroneal dominant (PD) and tibial dominant (TD) were determined by needle electromyography, and the locations and etiologies of sciatic nerve injury were evaluated. Fifteen patients were followed up and the prognostic factors were investigated. RESULTS: The peroneal division was more severely affected in thirty-three cases (59.3%), tibial division was more in thirteen cases (24.1%), and there were nine cases (16.7%) equally affected. Fracture was the most common cause of sciatic nerve injury, and TD was common in case of pelvic fracture while PD was common in the lesions below the hip joint. Younger person, responsiveness of sensory nerve conduction and fracture were the factors of better improvement while pattern of involvement (TD/PD) was not. CONCLUSION: The sciatic nerve injuries affected the peroneal division greater than the tibial division, but in case of pelvic fracture it affected the tibial division greater than the peroneal division. The relative fixation and anatomical difference of peroneal nerve was thought to be the cause of those differences.