For most biocides the environmental burdens resulting from the emission of these substances into the environment are not adequately known. A national monitoring programme aiming to investigate biocides in the environment could change this. In the present project, a concept for the implementation of a comprehensive biocides monitoring was prepared. Furthermore, an approach for the prioritisation of biocidal compounds for a compartment-specific monitoring was developed. In an experimental section, exemplary investigations were carried out on the occurrence of relevant biocides in different environmental media (e.g. fish biota, suspended particulate matter, soils and sewage sludge).