This study reports the effect of a TiN film on the mechanical properties and endothelial compatibility of a Co-Cr substrate. A dense, columnar TiN film with a preferential orientation of the (111) plane was deposited successfully on a Co-Cr substrate by reactive DC sputtering, particularly by applying a negative substrate bias during deposition. Good adhesion between the TiN film and Co-Cr substrate was achieved using a thin Ti film as an intermediate layer. The TiN film improved the mechanical properties of the Co-Cr significantly, such as the surface hardness and elastic modulus. In addition, the attachment and proliferation of endothelial cells were enhanced remarkably, which was attributed mainly to the favorable absorption of proteins on a biocompatible TiN surface. (C) 2011 Elsevier B.V. All rights reserved.