Molybdenum nitride coatings were deposited onto high-speed steel (HSS) substrates by the arcPVD technique. It was possible to produce coatings with Mo2N and MoN structure by varying the nitrogen partial pressure between 0.4 and 1.5 Pa. The relationships between hardness, thickness, and crystallographic structure of the coating and the deposition parameters were investigated. Hardness of the coatings increased with the increase of nitrogen content of the coating. Tribological behavior of the coatings was determined by ball-on-disk wear tests. The wear behavior of Mo-N-coated HSS samples against alumina balls was better than that of TiN-coated ones. Electrochemical polarization experiments were conducted in 1 N sulfuric acid. The porosity of the samples was determined by the copper decoration test. The coating with the lowest nitrogen content showed the best corrosion protective properties in the electrochemical rests. (C) 1997 Elsevier Science S.A.