Surfaces of AISI 304 austenitic stainless steel plates nitrided by plasma immersion ion implantation(PIII)technology were studied by means of Auger electron spectroscopy(AES)and X-ray photoelectron spectroscopy(XPS)to determine the effect of the nitriding process on the surface and subjacent layers.Elemental compositions obtained by AES and XPS at varying depths indicate that the saturation of N is relatively constant as a function of depth,indicating the reliability of PIII technology for subsurface saturation.It is concluded that the concentrations of both Cr and O increase with depth,the subjacent oxide is driven by the Ar+sputtering process used to access the lower layers,and then N is bound to Cr. Surfaces of AISI 304 austenitic stainless steel plates nitrided by plasma immersion ion implantation (PIII) technology were studied by means of Auger electron spectroscopy (AES) and X-ray photoelectron spectroscopy (XPS) to determine the effect of the nitriding process on the surface and subjacent layers. Elemental compositions obtained by AES and XPS at varying depths indicate that the saturation of N is relatively constant as a function of depth, indicating the reliability of PIII technology for subsurface saturation. It is concluded that the concentrations of both Cr and O increase with depth, the subjacent oxide is driven by the Ar + sputtering process used to access the lower layers, and then N is bound to Cr.