The presence of hormonally active chemicals (‘endocrine disruptors’) in the biosphere has become a worldwide environmental concern. In 1999, a report released by the Swiss Federal Office for the Environment (FOEN) concluded that such chemicals have already left their mark on the Swiss landscape and implicated them as a general cause of population changes in wildlife. Some of the chemicals involved, for example polychlorinated biphenyls (PCBs) and dibenzo-p-dioxins (dioxins), have received wide media attention because of their negative health impact on humans. The potential contribution of endocrine disruptors to the increased incidence of a number of diseases and developmental disorders in humans and animals is alarming, but the establishment of solid cause−effect relationships requires further scientific investigation. In Switzerland, the necessity for a coordinated transdisciplinary approach to the environmental and public health problems caused by endocrine disruptors has now been widely recognized. In 2001, the Federal Government implemented a National Research Programme (NRP) on ‘Endocrine Disruptors’ which aimed to develop scientific strategies to assess the risks and hazards that arise when endocrine disruptors are processed through ecosystems and cause human and animal exposure. The present issue of CHIMIA presents a selection of research highlights from this program.