In this study, the effect of nitriding on some properties of surgical AISI 316L stainless steel was investigated. Nitriding heat treatment was carried out in a fluidized bed reactor at a temperature of 560 C for 16 h. The hardness of nitrogen-rich region just below the coated layer was around 1200 DPN. Nitrides (CrN, Fe4N and Fe2-3N) formed on the surface was confirmed by XRD analysis. Microstructural changes were observed by optical microscopy. The microstructure of nitrided specimens showed a white layer at the top consisting of iron nitride and chromium nitride. The hardness of nitrided specimens decreased with distance from the surface to the interior of the test sample. Scanning electron microscope study combined with energy dispersive X-ray spectroscopy showed the presence of nitrogen in the outer layer and the transition layer, but not in the base metal. (C) 2004 Elsevier Ltd. All rights reserved.