In March 2000, an international two-day symposium was organized in Noordwijkerhout, The Netherlands, on 'Natural and synthetic organic compounds in the environment'. The emphasis of the symposium was on the following classes of compounds: polycyclic aromatic hydrocarbons, xeno-estrogens, phyto-estrogens, and veterinary drugs. Sources, environmental distribution, uptake, biotransformation and toxic effects from the molecular to the population level were discussed. Other important aspects were the development of biomarkers, analytical methods, bioassays, molecular modelling and other research tools. Finally, the implications of the findings for government policies were discussed. In this paper, a summary is given of the most important facts and views presented at the symposium. © 2001 Elsevier Science B.V. All rights reserved.