Thirteen cases of femoral shaft fractures were treated with flexible intramedully nails for 10 months period from May 1981 to March 1982 at the Department of Orthopaedic Surgery, Soon Chun Hyang College Hospital. The results were as follows: l. Of the 13 cases, 7 were males and 6 females, and they were in the age between 18 to 63 years. 2. The fracture sites were accounted that three of the thirteen cases were at the proximal one third of the femur, four at the middle one third, four at the distal one third, and the other two were segmental and five cases being comminuted. 3. Average interval between injury and operation was 13.4 days. 4. Closed nailing was possible in 10 cases; in 3 cases open reduction was inevitably required and cerclage wiring was done in 2 cases in these 3. 5. Average interval between operation and full weight bearing was 10.2 weeks. 6. Primary bone union was achieved in 12 cases and delayed in one case. 7. Many complications were noted including pain around knee in 5, posterior angulation in 4, protrusion of nail in 4, varus deformity, fragmentation, distal migration of nail, shortening, knee stiffness and delayed union in one each. But, despite these numerous complications, functional disturbance such as knee stiffness was observed in one. 8. According to the Denker's functional criteria, 12 were classified as excellent or good, and one were poor. 9. Flexible intramedullary nailing seems to be a good method in treatng the femoral shaft fractures especially for those not suitable for Kuntscher nailing, provided that exact technical and mechanical considerations are born in mind.