Using glycidyl methacrylate (GMA) as a grafting monomer and a porous high density polyethylene film as a substrate, plasma-graft polymerized membranes were prepared by the different plasma treatment manners, namely, homogeneous both-side (HBS) and one side (OS) treatments. The poly(GMA)-grafted membranes displayed two different types of the feed composition dependence of permeation flux and separation factor for pervaporation (PV) of benzene/cyclohexane (Bz/Cx) mixtures, depending on the plasma treatment manner and the graft yield. The membranes prepared by the HBS treatment and under mild polymerization conditions displayed the highest performance with a permeation flux of 0.30-0.37 kg/m(2) h and a separation factor of 19-22 at feed Bz of 60 wt% and 70 degrees C. The membranes exhibited high performance with excellent durability for PV of other aromatic/aliphatic hydrocarbon mixtures.