Neutron reflectivity measurements were made on electroactive films of [Os(bipy)(2)(PVP)(10)Cl](+) spin coated onto Au electrodes. Solvent content and film swelling were monitored as functions of the solution pH and counterion (perchlorate vs. p-toluenesulfonate). Film swelling was much greater near the polymer/solution interface than within the interior of the film. Furthermore, this spatial variation in film swelling was more pronounced in p-toluenesulfonate media than in perchlorate media. Structural information is presented here in the form of spatial distribution of polymer and solvent within the film; these profiles could not have been obtained directly from purely electrochemical measurements.