Objective：To study the effects of aging on the proximal femur geometry and their clinical significances. Methods：Totally 255 women over the age of 50 were divided into three groups by age：group A（n=156，aged under 65 years old），group B（n=55，aged between 66 and 75 years old），and group C（n=44，aged over 75 years old）. There were 191 women in non-fracture group and 64 women in fracture group. The patients’radiographs of the pelvis were used to measure the geometric parameters of the proximal femur. Results：（1）There was no significant statistical difference in the femoral neck axis length（FNAL） among group A，B and C. （2）There were significant statistical differences in the femoral neck width（FNW） between group A and C. （3）~（4）There were significant sta－tistical differences in femoral medullary cavity width（FMCW） and cortical thickness of femoral neck（FNCT） between group A，B and A，C. （5）There were statistical differences in the ratios of FNCT/FNW and FNW/FNL between group A，B and A，C. （6）There were significant statistical differences in age，FNAL，FNW，FMCW，FNCT，the ratios of FNCT/FNW and FNW/FNL between non-fracture group and fracture group. （7）There was no statistic difference in femoral neck-shaft angle（NSA） among group A，B and C and be－tween non-fracture group and fracture group. Conclusion：The risk of hip fracture is increased with aging due to thinning of cortiex and expansion of medullary cavity of the proximal femur.