Periprosthetic osteolysis and aseptic loosening are serious problems affecting the outcome of total joint replacement. Polyethylene particulate debris generated from metal-on-polyethylene bearing surfaces and the resulting biologic response to this debris are thought to be largely responsible. As a result, there has been a renewal of interest in hard bearing surfaces for total joint arthroplasty, including both metal-on-metal and ceramic-on-ceramic components. The new-generation all-ceramic and all-metal prostheses have demonstrated, both clinically and in the laboratory, lower friction and wear rates than metal-on-polyethylene bearing surfaces. Theoretically, lower wear rates result in less particulate debris and decreased inflammatory response. Despite excellent tribologic (lubrication, friction, wear) properties, metal-on-metal bearings raise associated issues of metal sensitivity and toxicity. For ceramic-on-ceramic bearing surfaces, issues of ceramic quality and the possibility of brittle fracture must be considered.