The effect of electrolyte concentration on the electropolymerization of pyrrole was investigated by studies of conductivity, tensile strength, and absorption spectra, etc., of polypyrrole films prepared from electrolyte aqueous solutions. The electrolyte salts used in the studies include sodium p-toluenesulfonate (TsONa), NaClO4, NaNO3, and KCl. Cyclic voltammetry and elemental analysis were also performed in the studies of the effect of the NaNO3 concentration. The conductivity, tensile strength, and the counteranion doping degree of conducting polypyrrole films increased obviously with increase of the electrolyte concentration of their polymerization solutions from 0.2 to 1 mol L−1. Further increase of the concentration over 1 mol L−1 has a weak effect on the further improvement of the film quality of polypyrrole. So, 1 mol L−1 was recommended for the electrolyte concentration of the polymerization aqueous solutions of pyrrole. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 65: 2739–2744, 1997