Abstract Metallic particles were dispersed in electrically conducting polymer films in order to achieve multi-electron transfer processes in a three-dimensional matrix. Dispersions of Pt in polypyrrole were formed by several electrochemical and chemical methods, and the concentration profiles were determined by Auger Electron Spectroscopy (AES). Films were prepared in which Pt was deposited primarily at the polymer/solution interface, at the metal/polymer interface, or uniformly through the film. The electro-catalytic reduction of oxygen was investigated by rotating disk electrode studies with these films. For the homogeneous film, the catalytic current is limited by the rate of O 2 permeation in the film.