The two opposite fluxes which lead to the build-up of a filtration cake have been studied in the case of the cross-flow microfiltration process. The back transport of particles was estimated according to the mechanism of shear induced diffusion. Mass balancing, associated with the resistance in series model, gave a differential equation which was integrated formally versus time. The result was an expression for the permeate flow that takes into account the operating parameters (transmembrane pressure and tangential flow velocity) and the suspension properties (the radius of particles, the concentration of the solution and the specific resistance of the cake). Experiments have been performed with baker’s yeast suspended in a saline solution in order to validate this model.