The effect of anhydrous cuprous ions on the preparation and properties of polyaniline was investigated. It was observed that the presence of cuprous ions accelerates the formation of polyaniline films. The dry conductivity of the film was also improved. The polyaniline samples of 10 S cm(-1) conductivity were obtained when Cu2+ and H+ ions are electrogenerated concurrently during the electro-oxidation of aniline. A mechanism related to the role of cuprous ions which involves chemical and electrochemical oxidation steps is proposed.