The surface composition of several thin-film semicrystalline polyolefin blends is quantified using secondary ion mass spectroscopy(SIMS). These experiments indicate that the component having the lower crystallinity migrates to the free surface so that the degree of crystallinity is an important factor along with the local polymer-polymer interaction and chain stiffness in determining the surface segregation in polymer blends. Specifically, a systematic study involving mixtures of amorphous polymers [poly(ethylethylene) (PEE), poly(ethylenepropylene) (PEP), and poly(ethylene-co-(1-dodecene)) (EC12)] with semicrystalline model polyethylenes (PE) having various densities (crystalline content! showed the greatest degree of surface enrichment for the amorphous polymers PEE and EC12 and to a lesser degree PEP. The degree of surface segregation for the E materials, was higher for the lower density materials which have a higher amorphous content. Surface enrichment of amorphous component as high as 50-fold was observed. SIMS measurements thus show a definite heirarchy in the degree of surface enrichment according to the degree of crystallinity as well as the relative chain stiffness of the blend components in these model polymer systems.