Concentration profiles of tethered polymer chains in the presence of mobile homopolymer under good solvent conditions have been calculated using self-consistent field (SCF) methods which incorporated the experimental conditions of a recent neutron reflectivity study by Lee et al. [J. Chem. Sec., Faraday Discuss. 1994, 98, 139]. While there is good qualitative agreement between the experimental results and the SCF calculations, the calculations predict a larger decrease in the tethered layer heights than is observed in the experiments. Furthermore, with increasing mobile polymer molecular weight, the calculations predict concentration profile shapes which become more steplike. The feasibility of discerning this effect using either neutron reflectivity or small angle neutron scattering is discussed.