Studies of the relationship between lead exposure and the physical and neurobehavioral development of children constitute an important part of the scientific foundation for regulatory policies in many countries. The United States Environmental Protection Agency (U.S. EPA) recently evaluated information on these and other health effects of lead in a 1986 document, Air Quality Criteria for Lead, which included an Addendum reviewing newly emerging results from longitudinal studies of various populations of children. The present paper summarizes and updates the information considered by the U.S. EPA in evaluating the effects of lead on child development. In addition, the paper notes some of the policy issues arising out of such evaluations and suggests some future research directions for follow-up. The dose-response relationships for various effects of lead on child development across a wide range of lead exposure levels are discussed, with particular attention to the effects of low-level lead exposure.