Mass transport, accompanied by chemical reaction through membrane reactor has been investigated in the case of varying diffusion coefficient and solubility coefficient. In reality, both parameters might depend on the concentration and/or on the inhomogeneity of the membrane layer. General mathematical models were developed to describe the mass transport, taking into account the external mass transfer resistances as well, when the solubility coefficient can vary, e.g. according to the Langmuir-Hinschelwood adsorption theory or when the value of diffusion coefficient depends on the concentration/anisotropy in the membrane. A general solution has been given that can be applied to most of the mathematical functions of the parameters mentioned. The concentration distribution and the mass transfer rate will be given in closed mathematical forms. The value of the mass transfer rates could be strongly altered by the varying diffusion- and/or solubility coefficient. The mathematical model and the effect of the varying parameters have been discussed in this paper. (C) 2008 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.