A fracture of the shaft of the femur in adults is common after road traffic accidents. Until recently it was not known that a fracture of the femoral neck can occur while fixing the femoral shaft fracture with an intramedullary nail. We report three patients in whom femoral neck fractures occurred during femoral nailing. Fractures of the femoral neck were detected by routine postoperative radiographs of the hip joint. All the three patients were treated non-operatively and the fractures healed without complication. The cause of the femoral neck fracture seems to be forceful use of an awl in the wrong direction or multiple entry points in the trochanteric region which weaken the femoral neck; subsequent hammering of the nail completes the fracture.