Drinking water disinfection, mandatory to provide drinking water free of pathogens, is associated with the formation of disinfection by-products (DBPs) that have been linked to public health concerns. Drinking water chlorination produces a wide range of toxic DBPs, only a fraction of which have been identified let alone characterised for their toxic potential. Bioanalytical tools should complement chemical analysis for a comprehensive risk assessment to assure that unidentified DBPs are also captured. In vitro bioassays will enable the detection of mixture effects caused by known and unknown transformation products. However, many DBPs are volatile and polar and thus cannot be evaluated with current methods. After implementation and validation of improved extraction and dosing techniques, my goal in the proposed project is to develop a screening tool that combines cell based bioassays indicative of relevant human health endpoints with chemical analysis to identify toxicologically relevant DBPs. The combination of bioanalytical assessment with sophisticated state-of-the-art chemical analysis will provide a guidance scheme for an effect directed identification of toxicologically relevant transformation products formed during advanced water treatment processes. This aims not exclusively at single compounds but also at substance groups or toxicophores. The establishment of applicable bio-analytical screening tools will enable the toxicological monitoring of advanced treated waters and allow the evaluation of pre- and post-treatments for by-product mitigation.