Simulation results for (a) interfacial alloying and (b) the Villain instability are presented. Both phenomena are important for the interface structure of epitaxial heterolayers and involve new scaling laws. For (a) a mechanism is discussed, which in a limiting case leads to a concentration profile decaying like (distance from the interface)−2. In (b) the critical film thickness is estimated, at which the Villain instability becomes important. Its scaling with the diffusion constant and the Schwoebel length can be combined with results on the strain dependence of these parameters in order to predict what kind of strains enhance or suppress the instability.