The electrochemical properties of polypyrrole tosylate [PPy(TsO-)] in aqueous solutions were investigated by cyclic voltammetry and ac impedance measurements. The cyclic voltammograms (CVs) of PPy(TsO-) show two reduction processes. Two doping sites of the counteranions in PPy(TsO-), site A with the counteranions located between the PPy layers and site B with the counteranions located in the PPy layers, were proposed based on the results of the electrochemical studies, and the partial counteranion exchange occurred when PPy(TsO-) was dipped in a 1 mol/L HNO3 aqueous solution. The reduction of site A is accompanied by the dedoping of counteranions and the reduction of site B is carried out with the insertion of solution cations. The electrochemical kinetics of the redox processes of site A was analyzed based on the ac impedance results.