We have measured the reflection coefficient of 4He atoms from films of super fluid 4He on glass and mica. The measurements were made as a function of the momentum of the atoms and the film thickness. We observed specular reflection from the glass substrate only for a thick (232Å) film, and from the mica for both a thin (34Å) and a thick (232Å) film. No inelastic scattering is observed. The thin film has a much smaller reflection coefficient than the thick film.