The incorporation of SO3- groups into a polypyrrole backbone was successfully carried out using FSO3H/acetonitrile medium. The degree of sulfonation (sulfonation or sulfur-to-nitrogen ratio) of polymer was controlled by varying FSO3H concentration while the film was being electrodeposited. The cyclic voltammograms of the electrodeposited films were taken between -1.00 and +2.00 V (versus Ag/AgCl) in blank solution. A substantial effect on the electrical conductivity was observed upon the incorporation of SO3- groups in the polypyrrole polymeric chain. The elemental analysis results of the freshly prepared and reduced films give independent evidence that the SO3- groups are covalently bound to the structure. FTIR, UV-Vis, spectroscopy and SEM techniques were used to characterize the electrosynthesized polypyrrole films. (C) 2004 Wiley Periodicals, Inc.