The treatment of municipal wastewater by membrane separation processes, such as reverse osmosis (RO) requires disinfection of the feed water. Chlorine is typically used to limit the occurrence of membrane biological fouling. The use of chlorine can be deleterious to polyamide membranes, which are subject to chemical attack and degradation. The focus of this study was to investigate intrinsic chemical tolerances of commercially available RO membranes by subjecting them to various species of chlorine (e.g., hypochlorous acid, hypochlorite ion and chloramines) under controlled conditions. Solute transport and water flux were monitored to assess changes in membrane performance to determine the overall rate of membrane degradation. Membrane characterization techniques were then employed to examine changes in the membrane properties resulting from exposure to chlorine. Includes 22 references, table, figures.