For many fractures of the femoral shaft, closed intramedullary nailing will not control rotation or telescoping of the fragments. Locked intramedullary nailing combines closed nailing with the percutaneous insertion of screws that interlock the bone and nail. This method permits static locking that controls rotation and telescoping and subsequently conversion to dynamic locking when weight-bearing is started after approximately twelve weeks. By providing greater stability, this method extends the indications for intramedullary nailing to severely comminuted, oblique, and spiral fractures as well as to fractures complicated by loss of bone and fractures in the proximal and distal ends of the femoral shaft. Of fifty-two patients with forty-nine severely comminuted fractures of the femoral shaft and three fractures that were complicated by loss of bone, forty-seven patients had uneventful consolidation of the fracture, with a mean time of 4.5 months for the severely comminuted fractures and seven months for the fractures that had a loss of bone. At follow-up, all forty-seven patients had normal motion of the hip, and forty-five had normal motion of the knee. Of the remaining five patients, four had a non-union that eventually healed (three after a second locked nailing and one after a third) and one had a septic non-union that eventually healed after removal of the nail and screws, debridement, and immobilization with an external fixator. Based on this experience, we concluded that this form of treatment has many advantages. The risk of infection and non-union is low, the incidence and severity of malunion are reduced, the hospital stay is short, and early mobilization of the patient is possible.