Poly(o-anisidine) films deposited galvanostatically exhibit the formation of different oxidation states of the polymer with varying pH of the solution. The influence of supporting electrolyte on the extent of formation of the conducting phase at pH 2.1 has been investigated with the help of optical, thermal and potential cycling techniques. The optical spectra of the films reveal the proportionate increase in the fraction of the conducting emeraldine salt phase with the amount of supporting electrolyte (NaCl) added to the solution. Similarly, clarity in the decomposition steps of the thermal patterns and redox peaks in the cyclic voltammograms are found to increase as a function of NaCl concentration.