In March 2018, Congress directed USDA’s Economic Research Service to report on the economic benefits of breastfeeding, including its potential cost savings for the Special Supplemental Nutrition Program for Women, Infants, and Children (WIC) and Medicaid. As a result of that directive, this study examined the effects of a hypothetical increase in breastfeeding rates among WIC participants from their 2016 levels to medically recommended levels. The study defined medically recommended levels as 90 percent of infants are exclusively breastfed for their first 6 months, followed by continued breastfeeding with the addition of complementary foods—but not infant formula—for the next 6 months. Results indicate that the number of mothers who participated in WIC that year would have increased by an estimated 646,000 per month, an 8-percent increase in the total number of WIC participants. WIC program costs would have risen by an estimated $252.4 million, or 4.2 percent of total costs in 2016. As a result of health benefits associated with breastfeeding, Federal Medicaid costs would have decreased by at least $111.6 million, resulting in an estimated increase of $140.9 million in combined Federal WIC and Medicaid costs. On the other hand, health-related cost savings that accrue to WIC households or their health insurance providers would have totaled $9.0 billion (excluding the savings that accrue to the Federal portion of Medicaid). Holding other factors constant, if the hypothetical increase in breastfeeding rates was sustained for future years, these estimated values for 2016 would represent cost impacts that recur each year.