While cementless, porous-coated prosthetic components have shown a high percentage of satisfactory clinical results in short and intermediate term follow-up, there are biologic problems associated with implantation of cementless devices that may predispose to clinical failure at longer term follow-up. Central to the issue of long-term performance is the problem of bone loss secondary either to adaptive bone remodeling processes or to the phenomenon of focal osteolysis. The stiffness of the femoral stem and the relative biologic inertness of the materials used are two properties of critical importance. In the future, continuing developments in the areas of prosthetic design, enhancement of fixation, biocompatibility, and biomaterials research will seek to address and resolve these problems.