The filling-type membrane is composed of grafted polymer and solvent resistant substrate; calculation of solubility, diffusivity and the swelling-suppression effect of a substrate enabled us to predict solvent permeability. This approach, noted as membrane design, has previously been used in estimating permeability of aromatic compounds through rubbery polymeric membranes. In this study, the influence of plasticization on solubility and diffusivity is investigated theoretically and experimentally with poly(methyl methacrylate) (PMMA). Solubilities predicted by a group-contribution lattice-fluid equation of state (GCLF-EOS) model are consistent with the results of vapor sorption. A modified free volume model is proposed for calculating solvent diffusion in glassy polymers by taking into account the compositional dependence of depression on the glass transition temperature. The solvent diffusion coefficient has a clear transformation at an isothermal glass transition concentration, and predictions are consistent with those measured by vapor permeation. Fluxes of benzene and toluene through filling-type PMMA membrane are measured by vapor permeation experiments, and it was found that the predictions agreed with the experiments. (C) 2001 Elsevier Science Ltd. All rights reserved.