Studies of explanted Charnley hip prostheses have shown damage or scratching of the polished stainless steel femoral heads. This surface damage is probably due to third body wear by bone cement particles. Damaged femoral heads will produce increased wear rates of ultra high molecular weight polyethylene (UHMWPE) acetabular cups. Sliding wear tests carried out in the laboratory have shown that alumina ceramic counterfaces are more resistant to third body damage from bone cement particles than stainless steel counterfaces. The use of the ceramic femoral heads in artificial hip joints will help to preserve the smooth surface finish on the femoral bearing surface, which is necessary to ensure low wear rates of the UHMWPE cup throughout the lifetime of the prosthesis.