The pages of EHP are replete with studies documenting the potential human health and ecosystem impacts of toxic chemicals. Such research is critical to understanding chemical risks and developing prevention strategies to reduce those risks. Intramural research at the National Institute of Environmental Health Sciences (NIEHS) as well as externally funded studies have led to a better understanding of mechanisms by which toxic chemicals may cause illness along with advanced tools to more rapidly assess risks. As knowledge of the potential impacts of specific chemicals increases, so do market and regulatory pressures to replace those chemicals with safer alternatives.