Ceramics have been increasingly used in orthopaedics during the last 30 years. Their biological inertness, high hardness and good mechanical strength make them excellent candidates for components such as femoral heads and acetabular cup in Total Hip Replacement prostheses. Currently used bio-inert ceramics – alumina and zirconia – give good clinical results, especially compared to metal – polymer couplings. However, they are subjected to severe biological, tribological and mechanical solicitations during more than fifteen years for the most successful prostheses. They answer these solicitations by presenting specific degradation mechanisms. We will thus examine the phenomena that can account for the long-term behaviour of zirconia components (heads and cups) in THR prostheses.