A Monte Carlo (MC) simulation of surface enrichment in polymer blends is presented. The algorithm introduced by Madden is used in this simulation, in which a compressible blend is condensed against a solid wall, with the surface of the blend forming an interface with holes (or solvent) that is parallel to the wall. Three regimes in the mixture are thus recognized: the interface at the wall, the bulk regime, and the interface with the vacuum (or solvent) at the surface of the mixture. Under certain conditions, enrichment of one of the components is observed, both at the surface and close to the wall. We find that the surface enrichment even in systems with the same cohesive energy in both components is driven byintermacromolecular interaction and asymmetric composition effects. A smaller part of the driving force arises from the difference in coil sizes between components, with the surface layer of the blend containing an excess of the component with the smaller coil size. A difference in coil sizes in a mixture containing polymers of equal chain length occurs in systems of asymmetric composition and with favorable interaction between components: in this case the majority chains act as a favorable solvent for the minority chains. In such asymmetric compositions, the minority chains move from the surface layers into the more favorable bulk regime. The results are compared with recent mean-field (MF) theory predictions and with those of available experiments. An important finding is that this type of segregation in miscible blends can occur well within the one-phase region of the phase diagram aswell asat its more expected location close to the binodal region.