The relationship between microstructure and physical behavior is especially pronounced in synthetic multilayer materials. Insight to the mechanisms responsible for changes in the mechanical properties can be investigated through a careful examination of the multilayer microstructure. A dominant feature of the nultilayer structure is the interface. The population of interlayer boundaries, that is interfaces, is directly proportional to the multilayer period for any given film thickness. In this paper, we will evaluate “TEM” images of multilayer systems. The interface structure will be viewed in cross-section and a range of layer thicknesses will be considered. Variation in the elastic modulus, yield stress, and microhardness have been observed for noble-transition metal systems over a wide range of multilayer periods, from less than 1 nm to greater than 1000 nm. In epitaxial systems, the extent of superlattice perfection (coherency effects) is closely tied with changes in physical behavior. Emphasis will thus be placed on the str'ucture and strain distribution from the interface, and its role in determining the mechanical properties of multilayers.