PURPOSE: The purpose of this study was to evaluate the change of the angulation deformity according to apposition of medial cortex and sliding mechanism as to the location of the lag screw in the intertrochanteric fracture of the Korean femur which neck-shaft angle is relatively small . MATERIALS AND METHODS: We selected the patients those angulation of femur neck-shaft was within 5 degree in comparison with normal side, and displacement of fracture fragment was within 4mm on the immediate post-operative radiograph. According to Evans classification, all patients were type I fracture. We classified the patients in two groups -stable medial cortex apposition(Group I) was 13 cases, and unstable no apposition(Group II) was 16 cases. RESULTS: In the Group I, the varus-valgus angulation was average 3.3 degrees when lag screw was positioned at the middle of the femur neck, average 3.6 degrees when lag screw was positioned at the inferior to the femur neck. In the Group II, the varus-valgus angulation was average 6.1 degrees when lag screw was middle of the femur neck, average 1.5 degrees when lag screw was inferior to the femur neck. CONCLUSION: There is no difference in angulation deformity when the lag screw is inferior or middle of femur neck if medial cortex is contacted, but the angulation deformity is less when the lag screw is inferior to femur neck if medial cortex is not contacted, in intertrochanteric fracture.