As a part of a project aiming to assess the potential toxicological effects of contaminants in aquatic ecosystems, the objective of this work was to determine the occurrence of several selected endocrine-disrupting compounds in water and sediment and to estimate the estrogenicity of the water. The study consisted of four sampling campaigns at seven sampling points in the lower Llobregat catchment area (NE Spain). Water and sediment samples underwent chemical target analysis for 19 steroid estrogens and alkylphenols, which are known to be endocrine-disrupting compounds. In this study, the only estrogens detected in the water samples were estrone and estrone-sulfate, which were found at low levels (2-5 ng l(-1)). The alkylphenolic compound showing the highest concentrations was nonylphenol di-ether carboxylate (NP2EC), which was found at levels up to 30.62 microg l(-1) in water samples and 535 ng g(-1) in sediment samples. K (d) was determined for several alkylphenolic compounds and showed the expected trend of decreasing K (d) with increasing polarity. The concentrations of nonylphenol and octylphenol only exceeded the annual average of the European Union's environmental quality standards (EQS) in one sampling point. However, the calculated estrogenic potential surpassed the expected effect concentration in several sampling points, indicating a potential risk. Therefore, we recommend that future EQS include short-chain alkylphenol ethoxylates and carboxylates.