Three to 4 million children and adolescents in the United States live within 1 mile of a federally designated Superfund hazardous waste disposal site and are at risk of exposure to chemical toxicants released from these sites into air, groundwater, surface water, and surrounding communities. Because of their patterns of exposure and their biological vulnerability, children are uniquely susceptible to health injury resulting from exposures to chemical toxicants in the environment. The Superfund Basic Research Program, funded by the U.S. Environmental Protection Agency and directed by the National Institute of Environmental Health Sciences, is extremely well positioned to organize multidisciplinary research that will assess patterns of children's exposures to hazardous chemicals from hazardous waste disposal sites; quantify children's vulnerability to environmental toxicants; assess causal associations between environmental exposures and pediatric disease; and elucidate the mechanisms of environmental disease in children at the cellular and molecular level.