Results of studies reported here show that adsorption could result in considerable accumulation of hormones on hydrophobic hollow fibre membrane surfaces during filtration of trace-hormone containing feed solutions with a linear adsorption isotherm applicable over the majority of the estrone concentration range examined (2.6 to 154 ng/L). Models based on both diffusion and surface reaction limitation were used to describe the kinetics of estrone adsorption to the membranes tested. Results indicate that the rate of adsorption of estrone to the hollow fibre membranes was limited principally by surface reaction rate rather than the rate of diffusive transport to membrane surface sites. Both adsorption and desorption kinetics were satisfactorily described by pseudo-first order expressions. These results are of environmental significance, especially in drinking water applications, where contaminants such as natural and synthetic hormones may accumulate on the membranes and desorb during backwashing and membrane cleaning.