The efficiency membrane processes is connected with the transport of separated substances through membranes. The the main goal is development of new transport models in polymeric membranes (dense membranes) and in porous inorganic membranes (with asymmetric porous structures) based on experimental data. A pervaporation transport is associated with the phase change of a substance permeating through a polymeric membrane. The pervaporation process can be considered as a combination of liquid and vapor permeation. We try to estimate the phase change position in a polymeric membrane by the comparison of the transport parameters obtained from pervaporation and vapor permeation experiments. The effects of membrane thickness and experimental temperature on the phase-change position and the influence of the membrane orientation relative to transport on the flux through asymmetric porous membranes will be studied. The results could be used for preparation of new membranes with higher separation efficiency. ME 889