Endocrine disruptors are characterized by their influence on animal endocrine systems resulting in reproductive, developmental, neurological, and immune dysfunction. The purpose of this overview is to provide the reader with a sense of the activities within the U.S. Environmental Protection Agency (USEPA), in particular NHEERL, that address the many facets of research on endocrine disrupting chemicals (EDCs) and to highlight the approach being taken at the different organizational levels within the USEPA, including screening, testing and evaluating endocrine disrupting chemicals. As a part of this endeavor, the USEPA continues to evaluate the current research activities in order to better understand and refine the process of risk characterization of EDCs. Thus, the participants in this session were asked to review their research within the framework of a better identification of EDC effects, better characterization of those compounds that have endocrine disrupting activity and how to incorporate this information into the risk assessment paradigm. Specifically, the goals of the ensuing papers were to compare individual vs. population indicators of endocrine disrupting effects, examine comparable and multiple mechanisms of toxicity, and describe the use of effects as indicators to identify toxicants and their sources. Mammalian and fish reproductive endpoints served as models to emphasize commonalities between human and wildlife risks.