The goal of this project is to provide support of the Division of Translational Toxicology (DTT) 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 isopropylated phenol phosphate (IPP) and triphenyl phosphate (TPHP) in rats, following exposure via dosed feed; exposures occur during gestation and lactation and for three months after weaning. IPP and TPHP are aromatic organo phosphate flame retardants. Increased use is anticipated as this class is replacing other classes of flame retardants. Exposure to IPP and TPHP occurs in the general population via its presence in consumer products and in the environment. The data from this project will be used in the development of sound, scientific conclusions about the potential toxicity of IPP and TPHP and ultimately supports the mission and goals of DTT and risk assessment activities of other federal agencies. Keywords: toxicity, isopropylated phenol phosphate, dosed feed, flame retardant