The room temperature doping and auto-dedoping processes of FeCl3 and AuCl3 doped polyalkylthiophenes were studied with X-ray photoelectron spectroscopy. The redox chemistry of both the carbon and sulfur atoms on polymer backbone was revealed with the ESCA data. The reactions of counter anions, FeCl4 -1 and AuCl4 -1 during dedoping were carefully studied. The ESCA data also indicated that no chlorination on polymer backbone occured in either doping or dedoping reactions. (C) 2000 Elsevier Science Ltd. All rights reserved.