The pervaporation performance of heat-treated PVA membranes with varying degrees of saponification was examined for the separation of ethanol from mixtures with n-heptane, which simulates the on-board separation of ethanol from gasoline containing bioethanol. All of the PVA membranes showed high permselectivity for ethanol against n-heptane. The ethanol selectivity decreased slightly, but the permeation flux increased with decreasing degree of saponification. The ethanol weight fraction in the permeate was higher than 98% for all feed compositions studied for PVA-417 membrane with a degree of saponification of 78-81%. High ethanol selectivity was observed irrespective of the heat-treatment time, and a maximum flux was observed at 3 min heat treatment at 75 degrees C. The flux decreased with increasing heat-treatment temperature. The PVA membrane showed high ethanol selectivity (96.8% in the permeate) and flux (12.2 g.m(-2).h(-1)) for commercially available E10 (10 wt % ethanol) gasoline.