The counter-anion doping states and redox processes of polypyrrole nitrate (PPy(NO3-) were studied by elemental analysis, cyclic voltammetry and spectroelectrochemical measurements. Two counter-anion doping sites, the positively charged conjugated chain of PPy (site 1) and the protonated pyrrole (py) unit (site 2), were distinguished. It was found that the counter-anions in site 2 are removed with the deprotonation of the py unit in a neutral or basic aqueous solution, while those in site 1 are exchanged with OH- in a basic solution. Two redox processes of PPy(NO)in aqueous solutions, corresponding to the two doping sites, were observed. The mechanisms of the redox processes in acidic, neutral and basic solutions are discussed.