Calcium phosphate-based ceramics are used in medicine and dentistry due to excellent biocompatibility with human tissues. The formation of hydroxyapatite coatings with a porosity gradient on the surface of metal implants can provide a surface suitable for the in growth of connective tissue. A need exists to both protect the metal substrate against corrosion and provide sufficient mechanical adhesion. Hydroxyapatite coatings have been produced by the reactive, radio-frequency sputtering of stoichiometric Ca10(PO4)6(OH)2 targets using planar magnetrons onto titanium-coated silicon substrates. A fully dense and thin initial-coating layer appears to avoid cracking, improves substrate adhesion, and provides corrosion protection (J. Mater. Res. 16, 2001, 3238). The effect of varying the wear rate is now evaluated on the mechanical behavior of sputter deposited hydroxyapatite coatings.