This second Project THRIVE describes the Early and Periodic Screening, Diagnosis, and Treatment (EPSDT) program of Medicaid with a focus on young children ages birth to 5 and offers tips for using the program in state Early Childhood Comprehensive Systems to improve early childhood health and development, state performance rates on child health, and collaborative efforts with other federal and state programs and services. Through EPSDT, Medicaid can finance services that promote child health, child development, and healthy mental development such as regular checkups, interperiodic screenings, and treatment. While in theory EPSDT guarantees children coverage for a full range of services, in practice, screening and referral rates fall short of the 80 percent screening benchmark set in 1989. State ECCS initiatives can use interagency coollaboration to improve EPSDT performance and child health access.