An estuarine food chain of three trophic levels-algae (Platymonas sp.), rotifers (Brachionus plicatilis) and mysids (Neomysis awatschensis Brandt) was set up in laboratory in order to investigate contributions of water and food to the accumulation of butyltins in upper trophic organisms, as well as to evaluate the likelihood of biomagnification of butyltins through the aquatic food chain. Kinetics of bioaccumulation and depuration of butyltins through the food chain were studied. Bioconcentration factors of butyltins in the three organisms were high (103-104). Butyltin burdens in the upper trophic organisms at steady-state of bioaccumulation by the ingestion of tainted food exceeded those observed by exposure to water only. For total butyltins, food chain transfer number was 1.44 for algae to rotifers and 0.59 for rotifers to mysids, respectively. Biomagnification was not confirmed. It is concluded that whether or not biomagnification occurs depends not only on the property of compounds but also on the organisms involved.