`Two kinds of cross-linked quaternized chitosan (q-chito) membranes were used in this study. One was prepared by coating a casting solution of q-chito containing glutaraldehyde (GA) with a HCl catalyst onto a porous polyethersulfone (PES) support (membrane A). The other was membrane A further cross-linked in an aqueous GA solution with a H2SO4 catalyst (membrane B). These membranes were then applied to the dehydration of ethanol/water mixtures for high temperature and high pressure evapomeation (HTPEV). The permeation flux increased with increasing feed vapor pressure, but decreased with an increase in the feed vapor temperature under constant feed vapor pressure. This decrease in the permeation flux could be attributed to a lowering of the vapor density, which is the ratio of the feed vapor pressure over the total pressure (P-1/P-T). The permeation flux derived from the relationship equation, which was driven statistically by the experimental data with a change in the feed vapor temperature under constant feed vapor pressure, agreed closely with that predicted from the equation as a function of the ratio of P-1/P-T The separation characteristics for water permselectivity in the water/ethanol vapor increased with a decrease in the difference between P-T and P-1.