Cyclic voltammetric and electrochemical impedance spectroscopic studies of polypyrrole (PPy)-polyaniline (PANI) bilayer conducting polymers were carried out in aqueous medium. The bilayers were prepared by electrochemical polymerization of the corresponding monomers at a platinum electrode surface in 1 M HCI solution. Cyclic voltammograms show additive properties of the bilayer conducting polymers compared with the individual polymers, Electrochemical impedance spectra revealed that the overall responses were mainly dominated by the inner layers. It was found that the charge transfer resistance of PANI decreased markedly when PPy was the outer layer, which is indicative of mediated oxidation. In contrast, when PANI was used as the outer layer, the impedance spectra were similar to those of single PPy films. The electrochemical impedance responses were also characterized with respect to different polarization potentials and thicknesses of the bilayers.