We calculate the mean free path of surface polaritons in tunnel junctions, in the presence of roughness on the surface of the outermost film. When these results are combined with our earlier theory of light emission from roughened junctions subject to a dc bias voltage, we discuss the saturation of the intensity of emitted light with increased roughness amplitude. Also, the probability that the surface polariton emits a photon into the vacuum during its lifetime is estimated and found to be very small for waves in the near infrared and visible frequency range. © 1980 The American Physical Society.211151755184