Objective To compare the clinical effect of reamed and nonreamed intramedullary interlocking nails on treating open tibial fractures. Methods From February 2002 to February 2004, 92 cases of open tibial fractures (86 patients) were treated with intramedullary interlocking nails. Of the 86 patients, 65 were male and 21 were female. Their age ranged from 18 to 68 years (36.5 on average). Of the 92 cases, 54 were in the reamed group and 38 in the nonreamed group. Patients moved with the support of crutch after their wounds were healed. Results All patients were followed up regularly for 6 to 24months. Infection rate in the reamed group and nonreamed group was 20.3% and 5.3% respectively, and there was significant difference between them (Ｐlt;0.05). The averagehealing time of the fractures was 22.5 weeks in reamed group and 19 weeks in nonreamed group, and there was no significant difference between them (Ｐ＞0.05). Delayed unions occurred in 8 cases and 3 cases in reamed group and nonreamed group respectively. Conclusion Compared with reamed group, nonreamed intramedullary interlocking nails have lowerinfection rate and fewer delayed unions and ununions.