This chapter provides a description of the Medicaid program, beginning with the definition of the target group: the poor. This chapter begins with how poverty is defined in terms of several human services programs, including Medicaid. Eligibility for coverage under Medicaid is still income-dependent, but there are now other factors that determine who receives services, which is the next topic of this chapter. Financing of Medicaid is very different from that of Medicare, leading to more state-level variations in services, as well as controversies over some of these services. The Medicaid program is centrally involved in the implementation of the Affordable Care Act (ACA), which will be described here. This chapter concludes with an analysis of this program, as well as some of the challenges in dealing with the social problem of poverty and income inequality.