Pt electrodes filmed with polyanilines were prepared by in situ either chemical or electrochemical deposition. The open circuit potentials of the electrodes were recorded during the chemical polymerization. The observed potential profiles were thought to be closely related to the oxidation states of the films deposited on the electrode. The electrochemical deposition of the films on the Pt electrode was carried out in 1 N HCl solution containing a small amount of aniline monomers. The oxidation states of the PANI films were controlled by the applied DC potential and impedance measurements of the Pt/PANI systems were made. Analyses of the spectra were given by comparison the tendencies of the spectra obtained by the controlled DC potentials.