The effect of fluorine elimination from the surface of poly(vinylidene fluoride) with the formation of CF-groups during XPS measurements has been confirmed. The XPS analysis shows that the fluorine content values found individually from F1s- and F2s-lines differ markedly due to the difference in kinetic energies of corresponding photoelectrons but decrease monotonically in the same way during the measurements (ca: 970 min) down to almost a half of their original values. The fluorine elimination results in the -CH2-CF2- --> -CH=CF- transformation thus modifying the hybrid state of carbon atoms. The sensitivity of relative intensity of Auger CKVV spectra to the hybridization mode of the carbon valence electrons made it possible to observe the effect in situ: During the exposure time the intensity of a normalized CKVV peak declines by ca. 10%, which is in reasonable accordance with previous semi-quantitative calculations. The possibility of detecting and monitoring the valence transformations of carbon by measuring the XAES/XPS intensity ratio has been demonstrated. (C) 2003 Elsevier Science B.V. All rights reserved.