It is known that the main cause of the bone resorption around the femoral stem in hip replacement arthroplasty is the stress shielding by the rigid femoral stem. Bone resorption around the femoral stem can result in the fracture of femur, failure of stem fixation and fatigue failure of bone cement. In addition, it makes the revision operation very difficult because of the poor bone quality. Because these secondary effects of the bone resorption make the prognosis of hip replacement arthroplasty poor, lots of researches have been performed to prevent it. In order to develop the methods to prevent the bone resorption, it is essential to have accurate knowledges about the changes in the mineral content of the bone around the femoral stem. But, because there had been no accurate tools to analyze the mineral content of the bone around the femoral stem quantitatively in vivo, most of the researches had been indirect studies such as cadaver studies, experimental animal studies and analyses with simple x-ray findings. DEXA (Dual Energy X-ray Absorptiometry), a recently developed method to measure the bone mineral density (BMD), can detect the quantity of the inorganic substance of bone accurately using 2 narrow energy bands among x-ray spectrum excluding the effect of the surrounding soft tissues. There is a special program to detect the bone mineral density around the femoral stem with DEXA. In this study, using one of the analyzing modes of the program, the bone mineral densities in 4 regions of interest (ROI; regin A, B, C, D) around the femoral stem were checked at 2 weeks, 6 weeks, 3 months and 6 months postoperatively in 31 cases of hip replacement arthroplasty. The BMD findings were analyzed with special respect to the kinds of stems (ABG, Landos and Omnifit stems), trochanteric wiring, time seuence and the regions. The results of the study are summarized as followings. 1. The BMD in 4 ROI around the femoral stem showed the pattern of gradual decrease in the first 6 months after operation. There was no significant difference in the change pattern among the 4 regions. 2. BMD changes around the Landos stem were a little different from those around the ABG or Omifit stem (At postoperative 3 months, the BMD in region A around the Landos stem decreased,more than around the ABG stem. At postoperative 6 months in region B and at postoperative 6 weeks in region D, the BMD around the Landos stem decreased more than those around the Omnifit stem). 3. In groups of trochanteric wiring, the BMD in the greater trochanteric area (region A, B) decreased less than that of the groups in which the trochanteric wiring was not performed.