A method to calculate the steady-state multicomponent mass transfer in heterogeneous structures is presented. For this, different transport mechanisms represent different regions inside the composite system. The solving scheme allows the calculation of the molar flow rates along the different transport pathways and the estimation of unknown transport parameters based on experimental data. The steady-state mass transfer of hydrogen and sulfur hexafluoride through a sinter metal supported MFI zeolite membrane is examined as a model system. The support is simulated using the dusty gas model, the molecules passing the zeolite layer may follow transport mechanisms like Knudsen diffusion, surface diffusion or activated gas diffusion. The configuration used, with data from single gas experiments, can predict the binary system only at high temperatures. The problems arising at low temperatures are due to the oversimplified assumption that adsorbed and desorbed molecules do not interact on their way through the MFI zeolite micropores. However, because of the modular structure of the approach, it can be easily extended to more advanced transport models to account for interactions between the different molecules. And the method can be applied equally well to other systems, such as palladium composite membranes or membranes with catalytic activity. (c) 2005 Elsevier B.V. All rights reserved.