Due to their function as biofiltrators species of shellfish are also affected by the worldwide contamination of the environment with persitent organic pollutants. In order to study the specific contamination status of bosporus waters, we have taken individuals of Mytilus galloprovincialis (Lamarck, 1819) as samples from the local market and analysed them for organochlorine pesticides, PCB congeners and synthetic compounds of the nitromusc group. In some cases quantified values exceeded the contamination grade of e.g. blue mussels (Mytulis edulis) from the north sea (german bight). Nevertheless the found results remained far below german regulatory limits. Obviously the grade of contamination is saisonally influenced reaching a maximum in the year's middle.