Résumé : The sea star Asterias rubens (L.), a representative species of the North Sea benthic environment, was exposed to a mixture of 10 selected PCB congeners (3 coplanar or c-PCBs, and 7 non-coplanar) via experimentally contaminated sediments. Both the degree of bioaccumulation and subsequent immunotoxic effects of these PCBs were determined. A strong congener-specificity for both bioaccumulation and immunotoxicity was found as well as a probable induction of a congener-specific detoxification mechanism resulting in the dramatic decrease in body levels of the three coplanar congeners tested (PCBs 77, 126 and 169). Moreover, a correlation was found between the bioaccumulation of c-PCBs and their immunotoxic effects. These findings suggest that coplanar congeners should be included in the list of congeners recommended to be analyzed for biological impact-oriented marine monitoring programmes.