The permeation of gasoline vapor was studied using triethylene glycol (TEG) liquid membranes, which were supported on the surface of a microporous hydrophobic membrane. The vapor permeation experiments were conducted using a flat-type membrane cell under the conditions of atmospheric pressure on the feed side and a vacuum on the permeate side. A hydrocarbon mixed vapor was fed into the membrane cell by a carrier gas. The feed vapor consisted of C5-C8 hydrocarbons, in which 72-87% was aromatic. The vapor that permeated through the TEG liquid membrane was 98-99% aromatic. The TEG liquid membrane showed preferential permeation for aromatic components in the gasoline vapor. The selectivities for C6 and C7 aromatic hydrocarbons over paraffin hydrocarbons were 47 and 15, respectively.