Abstract We examine previously reported ultraviolet photoelectron, C K electron energy loss, and CKVV Auger spectroscopic data from “carbidic” layers formed at temperatures between 500 and 650 K on Ni(100) and Ni(111). The “carbidic” layers studied were made from either CO or C 2H 4 exposure to the metal surface. These data indicate that significant amounts of carbon-carbon bonding exists on the surface in addition to the carbon-metal bonding with the substrate, revealing the presence of chemisorbed species, such as C 2, and maybe even C 3, etc. Quantitative interpretations of the Auger data indicate that 20 to 30% of the total electron density has carbon-carbon bonding character. Observed changes in the spectra obtained from different surfaces or at different coverages are accounted for by variations in the fraction of carbon-carbon bonding character.