Background: Of the 4.8 million uninsured children in America, 62–72% are eligible for but not enrolled in Medicaid or CHIP. Not enough is known, however, about the impact of health insurance on outcomes and costs for previously uninsured children, which has never been examined prospectively. Methods: This prospective observational study of uninsured Medicaid/CHIP-eligible minority children compared children obtaining coverage vs. those remaining uninsured. Subjects were recruited at 97 community sites, and 11 outcomes monitored monthly for 1 year. Results: In this sample of 237 children, those obtaining coverage were significantly (P < .05) less likely than the uninsured to have suboptimal health (27% vs. 46%); no PCP (7% vs. 40%); e...