This project will develop and evaluate a test methodology for the screening of environmental samples on the presence of endocrine disrupting chemicals. The battery of bioassays used will comprise both in vivo and in vitro test systems and will be applied in a biomonitoring campaign in Flanders and South Africa. Specific extraction and fractionation techniques will be investigated to eliminate interfering compounds from samples taken from drinking water reservoirs, effluents and river sediments. The in vivo tests used will be performed with aquatic vertebrate and invertebrate species. Additionally, a transgene yeast and the E screen will be used as in vitro testsystems and tested on the same environmental samples. The main objective will be the selection of a test battery of bioassys which can be used for the screening of the aquatic environment for endocrine disrupting compounds on a routine basis.