Recent expansions in Medicaid coverage for children and state health insurance programs for children mean that the majority of low-income children in the United States now are eligible for health insurance. A new analysis of Census data, presented in this report, finds that 94% of all uninsured children with family incomes below twice the poverty line, currently $28,300 for a family of three, qualify for Medicaid or a separate state child health insurance program supported by State Children's Health Insurance Program (SCHIP) funds. Now the United States faces the challenge of raising enrollment rates among children who are eligible for coverage but remain unenrolled and uninsured. Findings of this analysis suggest that the federal government and the states need to implement simpler, more effective enrollment procedures. At both state and national levels, relatively inexpensive measures could be adopted that would help state agencies ease administrative burdens to enrollment. The federal government could accord states new flexibility to enhance the effectiveness of the "presumptive eligibility" option, and it could make the government easier for families to retain Medicaid when they leave welfare for work. Increasing the coverage of legal immigrant children should be a particular focus. States could also do more to improve their child health outreach efforts. (SLD)