We have described the problems of deficient acetabular and femoral bone stock in the Japanese total hip prosthesis patients. From the mechanical viewpoint, coverage of the ultra-high-molecular-weight-polyethylene (UHMWPE) socket with bone graft is a prerequisite for preventing socket loosening. Use of a larger diameter UHMWPE cup in combination with new grafting techniques is highly desirable for reasons of creep reduction and minimal wear. From 1984 on, we reported on about 300 cases of dysplasia, high dislocation, RA and osteonecrosis of the hip. Depending on the severity of the problems, various configurations of femoral-head and neck bone grafts and hydroxyapatite particles (100-300 microns in diameter) in combination with bone cement were used. Bone resorption was seen only in the non-weight bearing regions of the graft. With our interface bioactive bone cement and grafting techniques, some of the problems of radiolucent zones and socket wear common to such difficult cases are believed to have been overcome.