Toxicology is the study of adverse effects of chemical agents (xenobiotics) on living organisms. In this course, principles underlying the absorption, distribution, biotransformation, and elimination of foreign chemicals from the body are presented. Experimental methods and animal models used to assess toxic effects of chemicals are discussed. Toxic effects of specific chemicals, i.e., pesticides, metals, solvents and vapors, and radioactive chemicals are also addressed. Major air pollutants and contaminants of soil and water that pose a risk to humans are reviewed. Methods of risk assessment, and governmental legislation and regulations designed to limit exposure to hazardous chemicals are considered.