The goal of this project is to provide support of the Division of the National Toxicology Program (DNTP) hazard identification activities targeted toward the prevention of diseases or adverse effects caused by environmental exposure to chemical or physical agents. Toxicity testing is an important aspect of public health research in that it serves to identify chemicals that are hazardous to human health. Proper conduct of toxicology studies is required to ensure that the resulting data are reliable. This project involves the conduct of toxicity studies of aqueous fire-fighting foams in rats, following exposure via gavage. Aqueous film forming foams (AFFFs) are used to rapidly suppress fires, which is critical in military settings. The data from this project will be used in the development of sound, scientific conclusions about the potential toxicity of tungsten metal and suboxide fibers in rats and inform the selection and use of currently available AFFFs but other agencies. This project also supports the mission and goals of DNTP and risk assessment activities of other federal agencies. Keywords: toxicity, aqueous fire-fighting foams, gavage