A new type of liquid membrane was developed and used fur the dehumidification of air. This two-layer membrane was a single laminate of a supported liquid membrane of a hygroscopic liquid, triethylene glycol (TEG) or polyethylene glycol 400 (PEG400), and a highly hydrophobic microporous membrane, Durapel. The liquid membrane was supported on the surface of the microporous membrane by its water-repellency and is stable during vacuum operation. The permeability of water vapor and air were independently measured through the liquid membrane. The observed value of water permeability was comparable to hydrophilic polymer membranes and was a slight function of its partial pressure. The selectivity of water vapor with respect to air was over 2000. A dehumidification experiment was conducted using a small Aat-type membrane cell. The humidity of the feed air was successfully removed under a high vacuum mode of operation. The observed dehumidification performances of the liquid membranes were compared with model calculations of cross-flow conditions using the measured permeabilities.