Glenn W. Suter II is a retired environmental assessor. During his 20 years at the U.S. Environmental Protection Agency, he served as the Science Advisor to the Director of the National Center for Environmental Assessment in Cincinnati and as Chairman of the Risk Assessment Forum’s Ecological Oversight Committee. Before that, he worked for 23 years in the Environmental Sciences Division of Oak Ridge National Laboratory. He has authored more than 300 publications, including five authored books and four edited books. Among his recognitions, he received the SETAC Founder’s Award, the USEPA’s Level One Scientific Achievement Award (with Susan Cormier and Sue Norton), and the Gold Medal for Exceptional Service. He is a fellow of the AAAS and SETAC. He has worked on the development of toxicity test protocols; environmental impact assessment for nuclear, geothermal, and coal energy technologies; the National Acid Precipitation Assessment Program; recovery of an endangered species; and ecological risk assessments of contaminated sites and of the mining of copper and coal. He participated in the development of guidance for ecological risk assessment, causal assessment, weight of evidence, field‑based water quality criteria, assessment endpoints, ecosystem services, integrated environmental assessment, species sensitivity distributions, read‑across, and other topics.Susan M. Cormier, now retired, has been a university professor and a senior scientist and science advisor in the Office of Research and Development at the U.S. Environmental Protection Agency. Although trained as a cell biologist, she was drawn to championing environmental causes, even in high school, working to address nutrient enrichment in a neighborhood lake. As a university professor, she investigated and exposed epidemic levels of hepatocellular carcinoma in Atlantic tomcod in the Hudson River. She was recruited to join the EPA, and, in a moment of patriotism, she resigned her faculty position and committed herself for the next 33 years to developing effective ways to assess and protect aquatic resources. She developed USEPA methods, guidance, and applications for condition, causal, and criterion research and assessments, all of which depend on weight of evidence. Much of her work was co‑authored with her long‑time colleague and coauthor, Glenn Suter II, with whom she is excited to share this book.