The goal of this project is to provide chemistry-based services to support National Toxicology Program (NTP) 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 chemical analyses are required to ensure that, in toxicity studies, the test species are exposed to the prescribed chemicals at the specified dose concentrations. This contract contributes to the ability of toxicity studies to provide evidence of heightened cancer risk along with other toxicological outcomes, by providing study chemical characterization, including unequivocal identity and purity of the chemicals studied, confirmation of the dose concentrations in administered formulations, and internal dose determinations in multiple biological matrices or target organs in the test species. Information about the identity and purity of study chemicals and the concentration of study chemicals in dose formulations is critical to proper evaluation of toxicity tests and development of sound, scientific conclusions about the potential toxicity of the study chemical in the test species. Confirmed identity and purity, dose concentrations and the information obtained through the work of this contract relating to internal dose, ultimately supports the risk assessment efforts of National Toxicology Program and other federal agencies. Internal dose information provided by this contract also enables extrapolations to humans to be made so that the public can be adequately informed about risk factors arising from exposure to studied chemicals.