The objective of this study was to investigate the design and fixation advantages of Sialon ceramic surface replacements implanted without acrylic bone cement. The biocompatibility and friction and wear properties of Sialon ceramic were compared with more conventional prosthetic materials such as stainless steel and alumina. A functional load-bearing canine hip surface replacement model was established to test Sialon femoral cups designed for fixation by bone ingrowth. The results of the polyethylene wear tests on highly polished ceramic and stainless steel counterfaces were essentially similar. These laboratory data indicated that the in-vivo polyethylene wear performance on metal or ceramic prosthetic surfaces could be expected to be indistinguishable, i.e. the ceramic/polyethylene combination would not offer any improved wear resistance in-vivo. It was found possible to get bone ingrowth into the macrokeying areas of the ceramic femoral cups but not into the microporous surfaces due to the presence of a fibrous membrane lining their internal surfaces. The biocompatability specimens also appeared to be invested with a fibrous membrane. Further studies are under way to determine the relationship between reaming procedures, micro motion at the interfaces and Sialon biocompatibility.