Polyaniline (PANI) films, formed by potential cycling methods on Au electrodes in sulfuric acid solutions, were anodically degraded with time at ca. 1 V versus RHE. Ellipsometric and cyclic voltammetric data suggest that colored species are formed within the film, perhaps containing quinone endgroups, and the bulk of the film dissolves uniformly creating greater porosity. This model of film degradation has been supported by transmission electron microscopy (TEM) studies of cross-sectional samples of PANI films. Both TEM and ellipsometry also showed that the PANI film is not delaminated, and is very resistant to anodic dissolution/degradation. Concurrent in situ mass measurements suggest that, in the early stages of film degradation, some regions of the film become electrochemically inactive, although the nature of the charge compensation mechanism of the PANI redox reaction remains unaltered. When no further him degradation can be accomplished, the mass data show that a substantial quantity of largely inactive film material is still present on the electrode surface. Furthermore, the change in the redox potential and the invariant charge compensation stoichiometry suggests that, although the final degraded him is a different material from the newly formed PANI film, only those portions of the him that have PANI characteristics are electrochemically active.