In this work, we report the pH effect on the relaxation phenomenon of polyaniline for the first redox system. The redox peaks of polyaniline are pH dependent over a certain pH range (up to pH approximately I for the first redox system). However, we observed that the relaxation phenomenon is affected by pH only at pH 2. This can be accounted for by a change in the value of the potential at the outer Helmholtz plane (psi(1)), which conditions the magnitude of the local pH. Since it is known that psi(1) depends on the ionic concentration, we measured the ionic concentration inside the polyaniline film by XPS and showed that it is indeed a function of pH.