Abstract: A method of evaluating the cross-correlation properties of microroughness present at the interfaces in dielectric stacks is based on a comparison between observed and calculated angular distribution of scattered light. The calculation is based on a first-order perturbation treatment of the interaction of a monochromatic plane wave with a dielectric stack which has microroughness present at each interface. The average deviation of the interface microroughness from the perfectly smooth, ideal, situation is assumed to be much less than the incident wavelength. The theory retains the vector nature of the electromagnetic fields, allows for complex dielectric constants, arbitrary angles of incidence, scattering and polarization. The dielectric stack may have any number of layers of arbitrary optical thickness. In practice, angular scattering data is measured for various incident angles with either p- or s-polarized light. These data are then compared to the calculated distribution of scattered light.