Twelve commercial and prototype nanofiltration membranes were evaluated for their stability and performance in aqueous ethanol. Performance was better if membranes were preconditioned by gradual solvent exchange. Flux in ethanol solutions was lower than in water. Viscosity and molar volume of the ethanol Solutions could partly account for differences in solvent flux with some membranes. The molecular weight cut-off (MWCO) of a membrane varies with different solutes and solvents. Rejection studies with sugars, glycols and lipids indicate that the MWCO of the DK membrane is hi-her in aqueous ethanol solutions than in water. (C) 2004 Elsevier B.V. All rights reserved.