X-ray photoelectron spectroscopy is used to study the surface segregation of siloxane in dilute blends of poly(methyl methacrylate)/poly(dimethyl siloxane) graft copolymers in poly(vinyl chloride) (PVC). The graft copolymers are found to be extremely efficient surface modifiers, which form, when added in amounts of 0.5% or more, a continuous siloxane overlayer on the surface of PVC.