As states make decisions about whether to implement the Medicaid expansion under the Affordable Care Act, this new analysis highlights the implications of these decisions for coverage, state finances, and providers. The results show that the decisions by as many as 27 states not to adopt the Medicaid expansion will leave 6.4 million people who could have been eligible for Medicaid uninsured. States that do not expand Medicaid will forego significant federal funding, which could have had a positive impact on state economies and general revenues. Moreover, hospitals in these states will receive substantially less revenue than they would have had the state expanded coverage while they will still have to serve a large uninsured population. These findings present a strong economic case for Medicaid expansion.