Summary: The 1991 population of young foster care children differs significantly from the 1986 population in the three locations GAO reviewed--California, New York, and Pennsylvania, the states with the largest average foster care populations in 1991. The 1991 population is much larger, more of these children entered foster care due to some form of neglect, these children have more health-related problems and are at high risk for further problems due to prenatal drug exposure, and they are more likely to be eligible for federal payments. Both federal and state expenditures have felt the impact of the rising number of young foster children and the decline in their overall health. Further, two broad service needs overlap foster and health care programs. First, drug abuse treatment programs for biological mothers and pregnant women are needed to reduce the risks associated with prenatal drug exposure and the likelihood that children will be removed from their families. Second, services to address the health and developmental needs of drug-exposed children are needed to treat their problems. Although few alternatives to foster care are now available to these families, meeting these needs should increase the chances for family reunification. However, drug abuse, to the extent that it persists, will remain a hidden contributor to the costs of various federal programs.