After World War II, large amounts of chemical weapons stored on German territory were dumped in the Baltic Sea by order of the allied forces . In addition of being a cheap method of disposal, the belief was that the vast amounts of waters in the oceans would neutralize and absorb the dangerous substances. At least 40.000 tonnes of chemical munitions containing an estimated 13.000 tonnes of chemical warfare agents were dumped in the Baltic Sea, primarily in the Bornholm Basin. Other official dumping sites were the Little Belt area and the Gotland Deep. There is evidence, however, that also other areas besides the offical CWA dumpsides are contaminated by chemical warfare agents (CWA). CWA were dumped as artillery shells, aircraft bombs or in containers; partly entire ships loaded with munitions were sunk. Today, munitions are in different stages of decomposition. Metal shells are corroding and contents are leaking into the environment at a rate that has not been measured so far, posing a possible risk for the Baltic Sea ecosystem. In previous studies, several CWAs of major concern for biota, such as inorganic arsenic and organo-arsenic compounds, have been found in the sediments within and around dumpsites (Missiaen et al. 2010). Unaware of this risk, human sea-bottom activities, such as bottom trawling, constructions of pipelines and cables as well as windfarms are increasingly claiming space within the contaminated areas. The aim of the present study was to increase knowledge on the bioavailability and biological effects of CWAs on fish, using a suite of biomarkers in an integrated approach.