OBJECTIVE. Despite concerted policy efforts, a sizeable percentage of children lack health insurance coverage. This article examines the impact of the health care safety net and health care market structure on the use of health care by uninsured children.METHODS. We used the Medical Expenditure Panel Survey linked with data from multiple sources to analyze health care utilization among uninsured children. We ran analyses separately for children who lived in rural and urban areas and assessed the effects on utilization of the availability of safety net providers, safety net funding, supply of primary care physicians, health maintenance organization penetration, and the percentage of people who are uninsured, controlling for other factors that influence use.RESULTS. Fewer than half of uninsured children had office-based visits to health care providers during the year, 8% of rural and 10% of urban children visited the emergency department at least once, and just over half of children had medical expenditures or charges during the year. Among uninsured children in rural areas, living closer to a safety net provider and living in an area with a higher supply of primary care physicians were positively associated with higher use and medical expenditures. In urban areas, the supply of primary care physicians and the level of safety net funding were positively associated with uninsured children's medical expenditures, whereas the percentage of the population that was uninsured was negatively associated with use of the emergency department.CONCLUSIONS. Uninsured children had low levels of utilization over a range of different health care provider types and settings. The availability of safety net providers in the local area and the safety net's capacity to serve the uninsured influence access to care among children. Possible measures for ensuring access to health care among uninsured children include increasing the density of safety net providers in rural areas, enhancing funding for the safety net, and policies to increase primary care physician supply. Nonetheless, an alarming number of children remain without health insurance coverage, with recent estimates placing the number of uninsured children at between 9 and 10 million, or ϳ12% to 13% of all children. 2,3 That such a substantial number of children remain uninsured reflects restrictions on eligibility for public insurance as well as incomplete uptake of health insurance coverage by children who are eligible for it. By some accounts, as many as two thirds of uninsured children are eligible for but not enrolled in Medicaid or the State Children's Health Insurance Program, despite substantial efforts to strengthen outreach and streamline administrative processes. 2,3 Compared with children who have health insurance coverage, uninsured children are less likely to have a usual source of care, to have any contact with a physician during a given year, to receive care in circumstances in which care seems warranted (eg, for an ear infection), to receive prescriptio...