This chartbook uses Medicaid Analytic eXtract (MAX) 2008 data to describe the service utilization of Medicaid enrollees in managed care plans. The chartbook extends the analysis of the previous MAX chartbooks, which focused on the service utilization of Medicaid enrollees covered on a fee-for-service basis. This chartbook also supplements recent MAX issue briefs that focused on the quality and completeness of encounter data. This chartbook provides valuable information for the Centers for Medicare & Medicaid Services and researchers on the availability of and uses for encounter data in MAX data.