Nanostructured hydroxyapatite (nHA) thin coatings of thickness 0.5 µm have been successfully produced using a radio-frequency magnetron sputtering technique, through careful selection and control of the processing conditions. nHA coatings were immersed in simulated body fluid (SBF) to determine the rate of nucleation and growth of an apatite layer on their surface. A dense, newlyformed apatite layer with similar characteristics to that of the biological bone apatite, was observed after 7 days of immersion in SBF. X-ray diffraction and infrared analyses confirmed this layer to be calcium-deficient nanocrystalline carbonate HA. All these results demonstrated that the novel nHA coatings were highly bioactive, and the time-frame required to form a dense apatite layer was reduced significantly as compared to the micrometer-sized, sintered HA pellets (from 28 days to 7 days).