Risk assessment, an approach for organizing information about hazards to health, safety, and the environment, provides a framework for gauging the threat to child health from environmental pollutants. A qualitative risk assessment has 4 components: hazard identification, dose-response assessment, exposure assessment, and risk characterization. In a risk assessment, consideration can be given to a population group that potentially has increased susceptibility, whether arising from having a high level of exposure or from increased susceptibility to the agent of concern on a biological basis. Children have been proposed as being at increased risk from some environmental agents, and there has long been concern and debate that the current approach of determining acceptable exposure levels or intake for a person may not yield safe intake limits for infants and children, who may be placed at greater risk than adults because of exposure patterns and inherent susceptibility. The persistence of debate on this critical public health issue reflects, in part, the difficulty of developing sufficiently sensitive and validated animal bioassays for critical outcomes. Epidemiologic studies can play only a limited role, given the complexity of establishing cohorts and tracking exposures from conception forward to assess risks across the lifespan. Meeting society's call for healthy environments for children poses an extraordinary challenge to researchers and to the policy makers who seek to develop evidence-based policies to protect children.