The copolymerization of carbazole (CZ) and 3-methylthiophene (3MeT) was successfully performed electrochemically in freshly distilled boron trifluoride diethyl etherate by direct anodic oxidation of the monomer mixtures, although the oxidation potentials of CZ and 3MeT were quite different. The electrochemical properties of the copolymers were studied with cyclic voltammetry. The influence of the applied polymerization potential on the synthesis of the copolymers was investigated. The higher potential favored the incorporation of 3MeT units into the copolymers. The insertion of 3MeT units into polycarbazole (PCZ) was helpful in improving the conductivity of PCZ. The novel copolymers had the advantages of both PCZ and poly(3-methylthiophene), that is, good redox activity, good thermal stability, and high conductivity. The structure and morphology of the copolymers were investigated with ultraviolet-visible, infrared spectroscopy, thermal analysis, and scanning electron microscopy. (c) 2006 Wiley Periodicals, Inc.