Zirconium dioxide thin films were deposited on 316L-stainless steel type substrates using DC unbalanced magnetron sputtering. The process parameter of this work was the target-to-substrate distance (d(t-s)), which was varied from 60 to 120 mm. The crystal structure and surface topography of zirconium dioxide thin films were characterized by X-ray diffraction (XRD) and atomic force microscopy (AFM). The results demonstrate that all of the ZrO2 thin films are composed monoclinic phase. The film sputtered at short d(t-s) (60 mm) shows a rather heterogeneous, uneven surface. The grain size, roughness, and thickness of thin films were decreased by increasing d(t-s). The bioactivity was assessed by investigating the formation of hydroxyapatite (Ca-10(PO4)(6)(OH)(2)) on the thin film surface soaked in simulated body fluids (SBF) for 7 days. XRD and scanning electron microscopy (SEM) were used to verify the formation of apatite layers on the samples. Bone-like apatites were formed on the surface of the ZrO2 thin film in SBF immersion experiments. A nanocrystalline hydroxyapatite (HA) with a particle size of 2-4 mu m was deposited. Higher crystallinity of HA on the surface was observed when the distance d(t-s) increased to more than 80 mm. Therefore, it seems that a d(t-s) greater than 80 mm is an important sputtering condition for inducing HA on the zirconia film. (C) 2011 Elsevier B. V. All rights reserved.