|There is growing concern among European Union citizens about chemicals that are suspected of disrupting reproduction in aquatic organisms. Natural estrogens and synthetic chemicals with estrogenic activity have adversely affected a variety of fish. A crucial aspect of identifying the causes of endocrine disruption in aquatic systems is to analyse how chemicals implicated as causative agents might act when present as mixtures. This project aims at improving our understanding of the effects of combinations of multiple estrogenic chemicals and other toxicants on aquatic organisms. It brings together expertise from fish biology, endocrinology, biometry, statistics and analytical chemistry. Mixture effects of combinations of multiple estrogenic chemicals will be assessed and predicted at the sub cellular, cellular, and physiological and organism levels by using a variety of estrogenicity assays.