Abstract An impedance study has been carried out in aqueous acidic and in neutral organic solutions on polyaniline (PAn) films prepared with the cyclic voltammetry technique. Charge transfer resistances are rather low at intermediate PAn oxidation levels in agreement with the metallic behaviour reported at these potentials. The corresponding exchange current densities are therefore very high. For the capacitance associated with the polymer, large values have been found which vary as a function of the film potential and the electrolyte used. Using the limiting capacitances obtained by impedance tests, the capacitive current could be separated from the faradaic one in the PAn charging process. Polymer degradation does not occur at high potentials in organic solutions, this testifying that such a reaction is caused by aqueous electrolytes.