Although many families with low incomes are eligible for various health insurance programs, more than three of five eligible children are not enrolled in Medicaid or the State Children's Health Insurance Program (SCHIP). "Churning" in enrollment is also common: over half of low-income family members who repeatedly experience periods without coverage leave Medicaid and then re-enroll later. Focusing on eight states, this project will examine factors that affect program enrollment and coverage stability, including a new federal rule requiring people to document their citizenship when applying for or renewing Medicaid coverage. In Phase 1, state officials and others convened to discuss the implications of the new citizenship documentation requirements and how these effects might be measured. In Phase 2, the researchers will analyze administrative data to determine the impact of the new Medicaid rule and other factors. Findings will inform debate over extending public coverage to a greater number of children.