PURPOSE: To investigate the factors which influence on the fixation failure after the compression hip screw fixation for unstable intertrochanteric fractures. MATERIALS AND METHODS: Eighty-two patients of unstable intertrochanteric fracture of A2 and A3 type who had underwent operation with compression hip screw were evaluated at least 1 year follow-up in regard to the age, degree of osteoporosis, fracture type, diastasis of fragment, sliding of lag screw, position of lag screw and status of reduction. RESULTS: 73 patients out of 82 patients had the union and 9 patients showed fixation failure. The results of fixation failure were 6 cases of migration of lag screw and 3 cases of cut-out of lag screw. There were statistically significant correlations between fixation failure and A2.3 and A3 type. The fixation failure group showed increased medial migration of medial cortex of proximal and distal fragment, which is significantly correlated with fixation failure. There were little statistical significant correlations between age, degree of osteoporosis, status of reduction, position of lag screw, sliding of lag screw and fixation failure. CONCLUSION: Another alternative fixation method and technique have to be considered for unstable A2-3 or A3 type because compression hip screw fixation only is very insufficient with high failure rate.