PURPOSE: This study was performed to analyze the weight-bearing ambulation time, bony union time and complications after fixation of comminuted subtrochanteric fractures of the femur with compression hip screw and evaluate its effectiveness. MATERIAL & METHODS: From January 1993 to January 2000, 21 cases of S e i n s h e i m e r's Type IV and Type V comminuted subtrochanteric fractures of femur which were treated by compression hip screw and followed for more than 1 year were analyzed by weight-bearing ambulation time, bony union time and complications. RESULTS: We recommended partial weight bearing ambulation from 6 weeks after operation and full weight bearing ambulation from 12 weeks after operation. All of 21 cases, primary bony union was achieved and mean time was 16 weeks(range 13 to 25 weeks). 2 cases of mechanical complications were occurred. Also 4 cases of malunion of lesser trochanter and 2 cases of nonunion of lesser trochanter were occurred, but none of them result in limitation of motion, limping nor pain. CONCLUSIONS: We thought compression hip screw is a good implant for rigid fixation of comminuted subtrochanteric fractures, especially involve intertrochanteric region like Seinsheimer's Type IV and Type V.