Using the 2008 and 2012 American Community Survey and 2011–2012 National Survey of Children’s Health, the authors assessed eligibility for Medicaid/CHIP among uninsured children and the reasons some children are unenrolled. Despite increases in the number eligible for Medicaid/CHIP between 2008 and 2012, participation rose by 6 percentage points nationally. The number of eligible but uninsured declined from 4.9 to 3.7 million, but 68% of uninsured children in 2012 qualified for Medicaid/CHIP. Interest in enrolling uninsured children in Medicaid/CHIP is high, but despite the high rates of prior enrollment, many families had knowledge gaps and perceived difficulties with enrollment.