Objective To analyze and evaluate the efficacy of intramedullary interlocking nail in the treatment of long bone fractures.Methods From July 1997 to October 1999,100 cases of long bone fractures were treated intramedullary interlocking nail,including 25 fractures of tibia and fibula at middle site tibia,35 at middle-lower,31 middle femoral,9 middle-lower of femoral.Results The period from 3 to 19 months with an average of 13 months for followed-up.The average fracture healing time was 14 weeks.According to Johnenand-Wruh evaluation method,98 of 100 patients(98%) were excellent osteosythesis,one case was good and only one case was bad.Conclusions The treatment of long bone fractures with intramedullary interlocking nail is a good way.It has high healing rate,and pathologic rigidity of joint movement is fewer.But the method has some limits for operative indication and its special complications also to be explored further.