Electrochemical studies have been conducted to characterize polypyrrole film prepared in indigo carmine solution, PPy(IC). The PPy(IC) film was found to be formed via an adsorbed layer of IC on the substrate electrode surface. No obvious nucleation process was observed during the film deposition. The electrochemical processes of PPy(IC) are mediated by the entrapped IC in the film. It was found that the redox potential of the PPy(IC) film is dependent on the pH of the solution in the pH range of 0-9, and a stable cyclic voltammogram was obtained at pH values lower than 7. In an alkaline medium, however, the film loses its redox response quickly upon potential cycling resulting in a cation permselective membrane. The PPy(IC) membrane with the bulky and multi-charged dopant was found to have cationic sensitivity but the film was nevertheless rather non-selective to cations.