This paper reports rejection of organic solutes with molecular weight (MW) in a range of 180-600 in aqueous and organic solvents through several commercial solvent resistant nanofiltration membranes (SRNF). The organic Solutes investigated include charged and neutral molecules and the selected solvents are water, water-methanol mixture. methanol. ethanol, acetone and ethyl acetate. The higher rejection in water than in organic solvents was observed for Desal-DK, MPF-44 and STARMEM (TM) series membranes. However, MPF-50 showed "uncommon" rejection characteristics of higher rejection in organic solvents (methanol. ethanol and acetone) than in water for neutral molecules compared to charged molecules. The rejection was analysed in accordance with the charge effect and hydration/solvation mechanism. (c) 2006 Elsevier B.V. All rights reserved.