The use of the interlocking intramedullary nails expand the possibilities for treatment of femoral shaft fractures, as illustrated by consistent and satisfactory clinical results. However, the technique is relatively complex compared to conventional nails and frequently poses technical problems. A retrospective review was undertaken of twenty-eight patients with femoral shaft fractures which had technical problems after undergoing the closed reduction and internal fixation with interlocking intramedullary nail procedure. We studied the types of the problems. Their causes, the frequency of problems with various kinds of nails, and discussed solutions of the problems. There were 21 additional comminutions and intraop erative splinterings, 8 angular deformities, 3 malpositioned nails, 3 loosened distal locked screws, 2 brocken drill bits, and 1 femoral neck fracture. Bone-union was attained in all cases (28 patients), but the period of treatment to attain bone-union was protracted to an average of 6.8 (5-12) months. In 3 cases, the knee joint range of motion was of limited flexion, 70 to 90 degrees, but in all other cases full range of motion was realized. 7 cases required 2 or more operations. The hospitalization period was for an average of 3.6 months. In conclusion, the importance of careful preoperative planning and experienced surgical technique cannot be overemphasized because we could see no significant difference in the occurence of technical problems in several kinds of the nail.