Both XPS core level and valence band spectra were obtained from Du Pont E-35 pitch-based carbon fiber surface. The XPS data showed that the E-35 fiber had more oxygen on the surface than the higher modulus pitch-based carbon fibers (e.g., Du Pont E-120 and E-75, and Amoco P55X carbon fibers), but less than the PAN-based carbon fibers (Hercules AU4 and AS4). [See Y. Xie and P. M. A. Sherwood, Appl. Spectrosc.43, 1153 (1989); Chem. Mater.1, 427 (1989);2, 293 (1990); Appl. Spectrosc.44, 797 (1990); Chem. Mater.3, 164 (1991); Appl. Spectrosc.44, 1621 (1990);45, 1158 (1991); Y. Xie, T. Wang, O. Franklin, and P. M. A. Sherwood,ibid.46, 645 (1992).] The E-35 fiber also had a fairly good graphitic structure in both the surface and the bulk as evidenced by both XPS and XRD. No nitrogen was found on this E-35 fiber and other pitch-based carbon fiber surfaces, but it was found on PAN-based fibers. Our previously reported work [Y. Xie and P. M. A. Sherwood, Chem. Mater.1, 427 (1989);2, 293 (1990); Appl. Spectrosc.44, 797 (1990); Chem. Mater.3, 164 (1991); Appl. Spectrosc.44, 1621 (1990);45, 1158 (1991); Y. Xie, T. Wang, O. Franklin, and P. M. A. Sherwood,ibid.46, 645 (1992)], showed that XPS valence band spectra were more sensitive to chemical environment on the carbon fiber surface than core level spectra, and could be well interpreted by X–αcalculations with model compounds. In this work, the valence band spectrum showed that there were at least two different types of oxygen species on the E-35 fiber surface. The two well separated O 2sfeatures in the E-35 fiber valence band spectrum were both more significant than those in the E-75 fiber valence band spectrum.