The polarization of light scattered by the surface of a material contains information that can be used to identify the sources of that scatter. In this paper, first order vector perturbation theory for light scattering from interfacial roughness of a dielectric layer is reviewed. In addition, methods for calculating the Stokes vector for scatter from multiple sources and for decomposing a Stokes vector into contributions from two non-depolarizing scattering sources are provided. The polarization of light scattered from interfacial roughness depends upon the relative roughness of the two interfaces and the degree of phase correlation between the two interfaces. Experimental results are presented for three cases: a nominally conformal film, a nominally anticonformal film, and a lateral offset roughness film. The method works well for the nearly conformal film. Difficulties that arise for the other two cases are discussed.© (2003) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.