This study examines the effects of prenatal WIC participation and the use of prenatal care on Medicaid costs and birth outcomes in five states--Florida, Minnesota, North Carolina, South Carolina, and Texas. The study period is 1987 for Florida, Minnesota, North Carolina, and South Carolina and January-June 1988 for Texas. Prenatal WIC participation was associated with substantial savings in Medicaid costs during the first 60 days after birth, with estimates ranging from $277 in Minnesota to $598 in North Carolina. For every dollar spent on the prenatal WIC program, the associated savings in Medicaid costs during the first 60 days ranged from $1.77 to $3.13 across the five states. Receiving inadequate levels of prenatal care was associated with increases in Medicaid costs ranging from $210 in Florida to $1,184 in Minnesota. Prenatal WIC participation was associated with higher newborn birthweight, while receiving inadequate prenatal care was associated with lower birthweight.