Enzymatic synthesis of polyelectrolyte complex of polyaniline (PANI) and sulfonated polystyrene (SPS) was developed. Royal palm tree peroxidase, which is active and stable under acidic conditions, was used as a biocatalyst. The template polymerization of aniline was carried out in aqueous buffer at pH 3.5. Varying concentrations of aniline, SPS and hydrogen peroxide in feed the favorable conditions for the production of PANI were determined. Contrary to chemical polymerization of aniline, the role of enzymatic reaction is to control kinetically and proceed under environmental friendly ("green") conditions. The production of the electroactive form of PANI-SPS complex was confirmed by Vis spectroscopy and EPR. (C) 2003 Elsevier Inc. All rights reserved.