The results of treatment of fractures of the femoral shaft with static interlocking nailing were reviewed retrospectively to determine the clinical importance of any stress-riser or stress-shielding properties of the nail. These properties, if relevant, would have been manifested by refracture of the femur, either through a hole used for a locking screw or through the original site of fracture after extraction of the device. Two hundred and fourteen fractures that had been treated with static interlocking nailing and that had healed without conversion to dynamic intramedullary fixation were divided into two groups. In Group I, which comprised 111 fractures, the static interlocking-fixation device was retained and in Group II, which comprised 103 fractures, the static interlocking-fixation device was removed during one operative procedure at an average of fourteen months after the injury. The average duration of follow-up was thirty months from the time of the original fixation in both groups. All patients in Group II were followed for a minimum of six months after removal of the nail. No femur in Group I, in which the static interlocked nail remained in situ, refractured. No femur in either group fractured through the proximal or the distal holes used for the locking screws. No locking screws or nails broke. One patient (1 per cent) in Group II had a refracture of the femoral shaft through the site of the original fracture six weeks after removal of the nail.(ABSTRACT TRUNCATED AT 250 WORDS)