Membrane compaction effects are well documented in RO, UF, and gas separation, but little attention is paid to compaction effects in microporous membrane processes. This paper examines the effects of compaction on the gas permeability of microporous membranes to be used in MD. Contrary to what is observed in RO and UF systems where membrane permeability is reduced by compaction, limited compaction of microporous membranes can result in enhanced permeability. This enhancement is the result of decreased membrane thickness, which increases the pressure gradient across the membrane. An experimental method is devised to determine the effects of membrane compaction on permeability, and a theory for modifying flux equations to include a parameter for membrane compaction is introduced.