This study is involved with the development of total hip joint prostheses capable of functioning without failure for a lifetime of service. The study addresses itself to: 1. Studies of fatigue characteristics of metallic materials in use; 2. Study of biocompatibility of presently used and new potentially used materials; 3. Study of carcinogenesis of prosthetic materials; 4. Studies of wear and development of wear resistant materials; a polyethylene-graphite composite has been developed and is under evaluation at present; 5. Studies of fixation to bone using porous materials; a fiber metal composite has been developed and is evaluated in relation to this application; 6. Evaluation of failed prosthetic devices; 7. Finite element model computer studies of the prosthetic devices to derive the ideal design configurations and materials selection.