Electrochemical oxidative copolymerization of aniline with o-aminobenzonitrile in an aqueous acid solution gave a copolymer film with a polyaniline-like structure in which some of the phenyl rings had a cynanide group. For the copolymerization, the applied potential was cycled between -0.2 and 0.9 V vs. saturated calomel electrode at the rate of 50 mVs-1. The proportions of the two monomer units in the copolymer, which were calculated from their ir spectra, absorbance of -CN of the o-aminobenzonitrile unit, changed as their comonomer feed ratio in the solution changed. Cyclic voltammograms of the resulting copolymer films were quite different from those of either homopolymer. The color of the copolymer films changed from blue, the color for the homopolymer of aniline, to gold, the color for the homopolymer of o-aminobenzonitrile, depending on the composition of the copolymer film.