The State Children's Health Insurance Program (SCHIP), passed by Congress in 1997, has been implemented by states in many different forms, thus creating many natural experiments about insurance coverage for low-income children. In Georgia, SCHIP children are enrolled in a Medicaid look-alike program, PeachCare for Kids, with nearly the same administrative rules and providers as in the Medicaid program. Comparing the experiences of PeachCare and Medicaid children thus allows us to examine the impact of population differences on utilization and satisfaction. We find that Medicaid children, controlling for many demographic characteristics, report both less use of services and lower satisfaction with services used. Evidence presented here supports three possible explanations for these differences: Medicaid families are less familiar with and supportive of systems requiring use of an assigned primary care physician, the families face more nonprogram barriers to using care, and physicians have different responses to the two programs.