The people of the United States is exposed to a large number of chemicals in their daily lives. In order to prioritize chemicals that should be considered for surveillance of and/or research in human milk, criteria were developed at the Technical Workshop on Human Milk Surveillance and Research on Environmental Chemicals in the United States. The criteria include (1) lipid solubility and/or persistence in the environment; (2) extensive exposure (e.g., high-production-volume chemicals and chemicals in personal care products); (3) known or suspected toxicity in a biological system; (4) historical interest, trend information; (5) chemicals of emerging concern; and (6) chemicals for medicinal use and chemicals in occupational settings. A working list of chemicals was developed for each of the criteria. It should be noted that more than one criterion may be applicable to a selected chemical, but the selected chemical should possess at least one of these designated criteria. It is hoped that by following a cohort of nursing women through their lactational cycle for a group of these chemicals, data generated will indicate the extent of infant exposure and may suggest methods for risk management to decrease inadvertent exposure for breast-feeding mothers and infants. While not the focus of this article, certain endogenous chemicals in human milk beneficial to the health of the infant warrant study as well.