High-energy electron diffraction has been used to obtain reduceddensity functions from multilayered thin films. Due to the verynature of the experiment, only interatomic correlationsperpendicular to the incoming electron beam are responsible for thescattered intensity. This allows an investigation of the interfaceinterdiffusion of inner surfaces. Since no specimen preparation isneeded, the technique is uninfluenced by preparation artefacts. Wedescribe the theory and the experimental requirements for theapplication of this method and present results obtained for aterbium/iron multilayer film.