Widespread occurrences of endocrine-disrupting chemicals (EDCs) in waterways have attracted a great attention of the scientific community. While scientific evidence associated with human health is restricted due to the longterm effects, impacts of EDCs on trout at the common concentration encountered in sewage effluent have been confirmed by both in vitro and in vivo studies. The impacts of steroid estrogens such as estrone, estradiol (natural hormones) and ethinylestradiol (a synthetic hormone) are often more serious than other synthetic EDCs as they have far higher endocrine-disrupting potency, despite of their low concentration. This paper investigates retention and adsorptive behavior of the natural hormones estrone by two commercial reverse osmosis membranes TFC-S and X-20, using dead end stirred cell systems. While an adsorptive process that reaches a breakthrough governs the retention of estrone by the TFC-S membrane; a sieving mechanism is responsible for the high removal of estrone using the X-20 membrane.