Some new possibilities of using specular neutron reflection in the study of roughness and interdiffusion in thin-film structures have been proposed and tested (the use of polychromators and supermirrors, direct measurement of the thickness of nonmagnetic interdiffusion layers). A statistical roughness growth law was found to be satisfactory in the interpretation of results, the growth rate being dependent on the materials used, film deposition techniques, etc. The use of (lambda/4, lambda/2)-sequences is proposed to increase the sensitivity of the method to the nonmagnetic interdiffusion layer thickness.