Objective:To evaluate the clinical results of treatment of midshaft tibial fracture with expandable intramedullary nails compared with interlocking intramedullary nails.Methods: From June 2003 to August 2005, 46 patients (27 males and 19 females, aged 20-74 years, mean = 38. 4 years) with midshaft tibial fracture were treated surgically in our department. The causes of fractures were traffic injury in 21 patients, fall injury in 6, tumbling injury in 11 and crushing injury in 8. According to AO/ ASIF classification, Type A fracture was found in 16 patients, Type B in 11, Type C, in 5, and Type C2 in 2. Open fractures were found in 12 patients, according to Gustilo classification, Type Ⅰ in 9 patients and Type Ⅱ in 3 patients. Based on the patients'consent, 24 patients were treated with expandable intramedullary nails (Group A) and 22 with interlocking intramedullary nails (Group B). The operation time, blood loss during operation, X-ray fluoroscopic times, hospitalization time, weight bearing time after operation, healing time of fracture andcomplications of all the patients were recorded. The clinical effects of all the cases were evaluated according to the criteria of Johner-Wruhs.Results: All the patients were followed up for 12-34 months (mean =16.2 months). The time of operation, the blood loss, X-ray fluoroscopic times, hospitalization time and healing time of fracture of Group A significantly decreased (P ＜ 0.05) compared with those of Group B, but the time for weight bearing after operation, the Johner-Wruhs degree of clinical effects and complications had no significant difference between Group A and Group B (P＞0.05).Conclusions: Expandable intramedullary nail can shorten operation time, decrease blood loss and reduce invasion, which is a safe and effective treatment method for tibial midshaft fracture.