This paper discusses the adsorption mechanisms involved in the rejection of neutral organic fractions using continuous-flow nanofiltration (NF) and reverse osmosis (RC) membrane experiments. It was found that the trend of membrane rejection curves varied with adsorption significance (sigma). For those cases with a lower initial concentration for hydrophobic neutral (Hpo-N) fraction (except for SP-28 membrane), the adsorbed organics on membrane surface showed a more significant effect (higher sigma) on, thus the rejection trend exhibited a three-stage profile: (I) increase in rejection due to initial adsorption and membrane structure change, (II) decrease in rejection because of decreasing adsorption since breakthrough, and (III) no further change in rejection after the saturation of adsorption. For those cases with lower sigma, a mild Stage I could still be identified. However, the rejection efficiency remained constant subsequently. In contrast, when sigma is even lower, no adsorption effect could be observed throughout the experimental period. (C) 2009 Elsevier B.V. All rights reserved.