This report examines Medicaid and CHIP risk-based managed care over the first decade of the 21st century. It finds that well-established programs exist in 19 of the 20 study states and that most states are seeking to expand their programs to cover more enrollees. In contrast to the early years of development of Medicaid managed care, there is substantial stability in the number and types of plans participating. Programs that currently exist provide a learning laboratory and important lessons for other states in how to develop an effective risk-based managed care program for Medicaid and CHIP beneficiaries.