C KVV Auger electron spectra of highly oriented pyrolytic graphite (HOPG) (at different emission angles) and of quaterphenyl, fullerenes C60, single- and multi-wall carbon nanotubes (MWNT) have been studied. The interpretation of HOPG spectra is based on the angular dependence of the Auger line shape and on the comparison with the related carbon compounds. The Auger spectra of HOPG at normal (S-HOPGn) and grazing (S-HOPGg) emission are quite different at the high-energy side. We interpret the difference between the two spectra in terms of different sampling depth and interlayer interaction. The normal emission spectrum is formed by the top, underlying layers and interlayer interaction. The last is the interaction between π-electrons of the first and second layers. This π-state is closer to the Fermi level than the π-state of the single layer and may be responsible for metallic conductivity. lnformation on this π-state found in these experiments provides a unique method for identification of the interaction between carbon atomic layers or for differentiating between the single and double layer structures of carbon atoms. © 2004 Elsevier B.V. All rights reserved.