Results of mathematical modeling of gas permeation and pressure profiles in a support, and microfiltration and ultrafiltration layers of ceramic membranes are presented. Two orientations of gas flow through membranes were chosen : the ordinary one oriented from the separation layer to the support, and the opposite one known as backflushing. The results obtained are applicable for testing ceramic membranes by the gas permeation method and for a description of backflushing.