PURPOSE: To analyise the effect of degree of force on trauma and degree of osteoporosis in femoral unstable intertrochanteric fracture's result of treatment using compression hip screw. MATERIALS AND METHODS: From January 1993 to December 1997, 55 patients who were operated with compression hip screw and followed up for more than 1 year were devided into high and low energy injured group by the mechanism of the trauma and also devided low(gradeIV,V,VI) and high grade osteoporosis group(gradeI,II,III) by Singh's index. We analize and compare the result of treatment in each groups. RESULTS: The averrage rate of mechanincal complication was 24%. The mechanical complication rate of the high grade osteoporosis group(34%) was higher than low grade osteoporosis group(9%)(p<0.05). The average subsidence of compression screw was 9.9mm and it shows significant difference between low(7.8mm ) and high grade osteoporosis group(11.5mm )(p<0.05). The average increased varus deformity of neckshaft angel during follow up was 3.8degrees and it shows singnificant defference between high energy injuried group(4.6degrees ) and low energy injuried group(2.7degrees)(p<0.05). No difference was seen in each groups for time of bone union(p>0.05). In view of functional recovery by Clawson's method, no difference between pre-injury and postoperative state was seen in 7 cases(22%) in high grade osteoporosis group and 13 cases(57%) in low grade osteoporosis group, thus worse functional recovery was seen in high grade osteoporosis group. CONCLUSIONS: We observed higher mechanical complication rate, more compression screw subsidence and worse functional recovery in high grade osteoporosis group and more varus deformity in high energy injured group. Thus we need more attension to treatment and follow up in high energy injured, severe osteoporotic unstable intertrochanteric fracture.