The objective of this work was to study the irreversible deterioration suffered by poly(o-aminophenol) (POAP) films when the upper positive potential limit (E-upl) is extended to values higher than a threshold value of 0.5 V vs. SCE. To this end three techniques were employed: cyclic voltammetry (CV), surface resistance measurements (SR) and rotating disc electrode voltammetry (RDEV). In a first series of experiments the working electrode was a POAP film deposited on a thin gold film whose thickness is of the order of the mean free path of conduction electrons of gold. A pronounced attenuation in both resistometric and voltammetric responses occurs after subjecting the electrode to potential cycling where E-upl > 0.5 V, as compared with those corresponding to POAP films cycled only between -0.2 V < E < 0.5 V. According to the interpretation of SR measurements, a more extended configuration of redox sites appears at the gold-POAP interface after polymer degradation, as compared with that corresponding to a film cycled only between -0.2 V < E < 0.5 V. In a second series of experiments POAP films were deposited on a rotating disc electrode and after being subjected to the same degradation treatment as indicated above, RDEV experiments were performed. Decreasing De values were obtained as the polymer film became more degraded. On the basis of an electron-hopping model, this last tendency can also be ascribed to less compact distributions of redox sites after polymer degradation. (C) 2003 Elsevier B.V. All rights reserved.