Poly(aniline-co-phenetidine)s were synthesized by the copolymerization of aniline and o-phenetidine (o-ethoxyaniline). The molar feed ratio of the starting aniline monomers was varied to result in copolymers with different compositions. The actual composition was deduced by integrated proton NMR spectroscopy. The copolymers exhibit excellent solubility characteristics. It was particularly interesting to find that the 20% ethoxyaniline containing copolymer exhibits excellent solubility and yet retains the high conductivity characteristic of the unsubstituted homopolymer. The conductivity of the hydrochloride salt of this par-ticular copolymer is identical to that of the unsubstituted derivative. However, the copolymer solubility greatly exceeds that of the unsubstituted homopolymer. The copolymer in the base form exhibits very high solubility in NMP and the resulting solutions are exceedingly more stable than those of the unsubstituted derivative. A 10% by weight solution of the 20% ethoxy copolymer in NMP is stable for ? 50 days at room temperature afterwhich a gel is formed as compared to previous reports of ? 3–10 h stability for corresponding solutions of the unsubstituted derivative. © 1995 John Wiley & Sons, Inc.