film has been applied for medical cutting tools to improve the mechanical properties such as surface hardness and wear resistance, and also to provide the biocompatible property of the surgical tools. TiN film has been deposited by using a plasma-assisted chemical vapor deposition system. Bipolar-pulsed DC discharge has been used for optimal plasma discharge condition, and the gas mixture of TiCl4, N-2, H-2 and Ar has been used. TiN layer enhanced the surface hardness of 2000 kg mm(2) HK0.01 and the corrosion property of the film. The corrosion resistance of TiN films has been estimated using Hank's solution and the corrosion rates of bare stainless steel substrate and the specimen coated with TiN were 1300 and 66 nA/cm(2), respectively. TiN film also shows a good biocompatibility in the standard cytotoxicity test (ISO10993-5: Tests for Cytotoxicity-In Vitro Methods), which is the normal method for ensuring the biocompatibility of a medical tool. In the standard cytotoxicity test, we obtained an excellent characteristic of biocompatibility from the medical tool coated with TiN layer. This means that the TiN-coated specimen is free of harmful extractables or has not much of them to cause any acute effects even under exaggerated conditions with isolated cells. (C) 2003 Elsevier Science B.V. All rights reserved.