Objective. Intramedullary nail system fixation of inter- and subtrochanteric femoral fractures allows early weight-bearing, especially in osteoporotic bone. Restoration of anatomical shape and early return to function of the injured leg. Indications. All inter- and subtrochanteric fractures of AO type 31-A without limitation. Contraindications. Open physes and unsuitable femoral shaft anatomy ( increased anterior bow of femoral shaft or malunion after femoral fracture). Surgical technique. If possible closed, otherwise open fracture reduction on a fracture table and unreamed intramedullary nailing. Fixation of the fracture by insertion of a helical blade via a guide wire in the head-neck fragment of the femur. Option of static or dynamic locking at the femoral diaphysis. Postoperative management. Early mobilization immediately the day after surgery with full weight-bearing and use of assistive device, as tolerated. Thrombosis prophylaxis for 6 weeks with fondaparinux, rivaroxaban or a low molecular weight heparin (LMWH), alternatively oral anticoagulation. Results. Between April 2004 and June 2005, the AO multicenter study at 11 European trauma centers included 313 patients (mean age 80.6 years, 77% women, 23% men) with 315 unstable trochanteric fractures treated with a Peroximal Femoral Nail Antirotation (R) (PFNA (R)) device for consecutive follow-up [24]. In 82%, the fractures were 31-A2, while in 18% the fractures were 31-A3. Average operation time for A2 fractures was 56 min and 66 min for A3 fractures. Average duration of hospital stay in the trauma center was 12 days. Surgical reduction and fracture fixation that permitted full weight-bearing immediately after operation was achieved in 72% of cases. Of 165 complications, 46 were surgery-related with unplanned revision surgery in 28 cases (including 7 femur fractures and 4 acetabular penetrations). Follow-up for more than 1 year was possible in 56% of patients. After 1 year, 89% of the fractures were consolidated. The highest complication rate was found in fractures type 31-A2.3 and in patients older than 90 years. The recorded number of implant-related complications (14.6%) is comparable to the results of other intramedullary and extramedullary implants.