This brief provides new national and state-level information about the uninsured adults with incomes below 138 percent of FPL who could become eligible for Medicaid if states decide to expand Medicaid under the Affordable Care Act (ACA). At present, few states cover non-disabled, non-pregnant parents with incomes up to 138 percent of the Federal Poverty Level (FPL) and even fewer cover such adults without dependent children. This analysis shows that the approximately 15 million uninsured adults who could gain coverage under the ACA Medicaid expansion are a diverse group in terms of their age, gender and race/ethnicity.