Background. Although many studies have noted that uninsured children have poorer access and quality of health care than do insured children, few studies have been able to demonstrate the direct benefits of providing health insurance to previously uninsured children. The State Children9s Health Insurance Program (SCHIP), enacted as Title XXI of the Social Security Act, was intended to improve insurance coverage and access to health care for low-income, uninsured children. With limited state and federal resources for health care, continued funding of SCHIP requires demonstration of success of the program. As yet, little is known about the effectiveness of SCHIP on improving access and quality of care to enrollees. Objectives. To measure the impact of the New York State (NYS) SCHIP on access, utilization, and quality of health services for enrolled children. Design Setting. NYS, stratified into 4 regions. The NYS SCHIP is modeled on commercial insurance (32 managed care plans) and at the time of the study had 18% of SCHIP enrollees nationwide. Study Design. For the study group, the design used pre/poststudy telephone interviews of parents of children enrolling in the NYS SCHIP, with baseline interviews soon after enrollment and follow-up interviews 1 year after enrollment. Baseline interviews reflected the child9s experience during the 1-year period before enrollment in SCHIP. The follow-up interviews reflected the 1-year period after enrollment in SCHIP. For the comparison group, the design used baseline interviews of a comparison group enrolled 1 year after the study group to test for secular trends; these interviews reflected the 1-year period before enrollment in SCHIP. Subjects. Children ( n = 2644) 0 to 18 years of age who enrolled in the NYS SCHIP for the first time (November 2000 to March 2001), stratified by age (0-5, 6-11, and 12-18 years), race/ethnicity (white non-Hispanic, black non-Hispanic, and Hispanic; others excluded), and region of NYS. The comparison group consisted of 400 children. Telephone interviews were conducted in English or Spanish throughout the day and evening, 7 days per week, to obtain measures. Main Outcome Measures. Demographic and health measures (child and family characteristics, health status, presence of a special health care need, and prior health insurance), access (usual source of care [USC] and unmet needs for health care), utilization (visits for specific health services), and quality (continuity with USC and measures of primary care interactions). Analyses included bivariate tests, comparing the pre-SCHIP period to the 1-year period after enrollment in SCHIP. Multivariate models were computed to generate standardized populations comprised of key characteristics of the sample to test for differences in measures (after SCHIP versus before SCHIP), controlling for demographic characteristics. Results. Of the 2644 study-group children who completed the initial interview, 2290 (87%) completed the follow-up interview. Key measures for the pre-SCHIP period and short-term “postenrollment” measures for the study group were not statistically different from measures for the comparison group, suggesting no major secular trends. Participants were non-Hispanic white (25%), non-Hispanic black (31%), and Hispanic (45%). Fifty-one percent of the parents were single, and 61% had a high school education or less; 81% of families had income The proportion of children who had a USC increased after enrollment in the NYS SCHIP (86% to 97%). Two measures of accessibility (difficulty getting a medical person by telephone and difficulty getting an appointment) improved after enrollment in SCHIP. The proportion of children with any unmet health care needs decreased (31% to 19%). Specific types of unmet need also were reduced after enrollment; for example, among SCHIP enrollees who had a need for specific type of care, unmet needs were significantly lower postenrollment versus pre-SCHIP for specialty care (−15.5% in unmet need), acute care (−10.1%), preventive care (−9.6%), dental care (−13.0%%), and vision care (−13.2%). Emergency and total ambulatory visits did not change, but the proportion of children with a preventive care visit increased (74% to 82%). The proportion of children who used their USC for most or all visits increased (47% to 89%), demonstrating increased continuity of care. Several indicators of health care quality improved, including an overall rating of quality, the 4 indicators of physician-patient interaction used by the Consumer Assessment of Health Plans Survey, and a measure of parental worry about their child9s health. Improvements were noted among major subgroups of children, with the greatest improvements for those with the lowest baseline levels. For example, at baseline, a lower percentage of children living at 160% of the federal poverty level, and these poorer children experienced the greatest gains in having a USC or having continuity with their USC after enrollment in SCHIP. Conclusions. Enrollment in the NYS SCHIP was associated with 1) improved access, continuity, and quality of care and 2) a change in the pattern of health care, with a greater proportion of care taking place within the usual source of primary care.