Pyrrole was electropolymerized in aqueous sodium dodecyl sulfate (SDS) solutions and a correlation between the absorbance maximum (lambda(max)) and the effect of micelle formation was found. The redox stability of the film was studied in 0.05 M SDS solution by cyclic spectrovoltammetry. The spectral changes acquired in different potential regions were analyzed by matrix rank analysis (MRA) to determine the number of independent absorbing species necessary for the description of the observations. With the extension of the potential to the more positive region a new oxidation step was obtained, which was connected to structural changes in the film owing to swelling. Spectral changes proved that no degradation processes occur in the potential range covered. In the more extended potential region neutral polymeric segments are required to reach the quasi-metallic state, and the MRA indicated the necessity to assume the presence of extra species which are connected to partially hydrated parts of the film.