Conducting poly(aniline-co-butylaniline) copolymer was studied by cyclic voltammetry and impedance spectroscopy. Its electrochemical properties and impedance behavior were compared with those of the homopolymers polyaniline and poly(N-butylaniline). The electrochemical stability of poly(aniline-co-butyraniline) copolymer was found to be better than that of polyaniline and comparable with that of poly(N-butylaniline). The impedance behavior of the copolymer was interpreted on the basis of an adatom model. The validity of this model for describing this copolymer electrode in both its oxidized and reduced states was demonstrated. A quantitative estimate of the rate of charge transport in this copolymer as a function of potential was obtained.