The German Environmental Specimen Bank is a long-term project and has the task to collect and store systematically environmental samples for future demand in ecological-chemical research. The essential requirement to keep the samples unchanged concerns their quantitative and qualitative composition, especially of the xenobiotics and thus the chemical contamination of the matrices. Using the eggs of herring gulls (Larus argentatus) from the islands of Trischen and Mellum (wadden sea) chlorinated hydrocarbon (CHC) concentrations from the years 1988-1992 are presented. The CHC concentrations show a decreasing tendency since 1990. The following pesticides were investigated: Hexachlorobenzene (HCB), α-, β-, γ- hexachlorocyclohexane (HCH), Heptachlor (HC), Heptachlorepoxide (HE), Aldrin, Dieldrin, DDE, PCB (congeners: 101, 138, 153, 180).