With thousands of chemicals in commercial use in the United States, decision makers rely on toxicity assessment information to examine the risks these substances may pose. Several key federal agencies -- including the Agency for Toxic Substances and Disease Registry (ATSDR), the Environmental Protection Agency (EPA), the National Institute for Occupational Safety and Health (NIOSH), the National Toxicology Program (NTP), and the Occupational Safety and Health Administration (OSHA) -- as well as state agencies, assess the toxicity of chemicals. This book describes the chemical toxicity assessment activities selected federal and state agencies undertake; assesses the extent to which these federal agencies chemical toxicity assessment activities are fragmented, overlapping, or duplicative; and assesses the extent to which these federal and state agencies coordinate their chemical toxicity assessment activities and challenges in doing so.