Developmental toxicants, insidious in modes of action and effects, strike the very origin of our lives: the developing embryo, fetus, neonate, and child; they cause spontaneous abortions, stillbirths, malformations, early postnatal mortality, reduced birth weight, mental retardation, sensory loss as well as other functional or physical changes, including subclinical effects having far reaching social and economic impacts. The large majority of developmental defects have unknown etiologies. With this uncertainty, EPA and the scientific community world-wide give high priority to finding new approaches for assessing etiology and risks of developmental effects. The United Nations Conference on Environment and Development (UNCED) and Agenda 21 mobilized the international community to focus on risks posed by chemicals in the environment, including developmental risks. The international harmonization of test and risk assessment guidelines for developmental effects are priorities. Lead, persistent organic pollutants (POPs), endocrine disruptors, and the improvement of quantitative risk assessment methodologies, particularly for children, are priorities. EPA reinvented its research agenda of assure wide involvement of the National Science Foundation, other federal agencies, and national experts in research to address the U.S.'s public health and environmental priorities.