This report examines levels of insurance coverage, Medicaid eligibility, and Medicaid participation among nonelderly adults in 2014, the first year following the implementation of the major coverage provisions of the Affordable Care Act (ACA). Uninsurance among both parents and childless adults fell sharply between 2013 and 2014, especially in states expanding Medicaid under the ACA. An estimated 7 in 10 eligible adults without other coverage were participating in Medicaid in 2014, but with wide variation across states. In 2014, more than a quarter of uninsured adults were found to be eligible for Medicaid, totaling 8.3 million eligible but uninsured adults.