Two hundred and sixty-two fractures of the femoral shaft were treated with the Grosse-Kempf interlocking nail. Mechanical complications occurred in 26 cases (10%): There were five broken nails (2%), four bent nails (1.5%), four proximal screw failures (1.5%), and thirteen major torsional deformations of the nails (5%). Four of the five broken nails were in previously open fractures and were associated with nonunion of the fracture. Two of the nails broke at the junction of the proximal threaded conical portion and the slot in the nail, one occurred at the nonunion site, and two occurred through the proximal of the two distal screw holes. Eccentric portals of entry led to nail deformation in two patients, and additional trauma led to bending in two other patients. There were four failures of the proximal interlocking screw; three of the four broken screws occurred in comminuted subtrochanteric femur fractures treated with static locked nails. Minor degrees of torsional deformation of the nail were seen in up to 50% of the cases. However, major torsional deformation was seen in only 13 patients (5%). Mechanical complications following locked nailing appear to be acceptably low. Their enormous clinical efficacy appears to justify their continued use.