[Extent] The extent to which residents of the United States who are not U.S. citizens should be eligible for federally funded public aid has been a contentious issue since the 1990s. This issue meets at the intersection of two major policy areas: immigration policy and welfare policy. The eligibility of noncitizens for public assistance programs is based on a complex set of rules that are determined largely by the type of noncitizen in question and the nature of services being offered. Over the past 18 years, Congress has enacted significant changes in U.S. immigration policy and welfare policy. Congress has exercised oversight of revisions made by the 1996 welfare reform law (the Personal Responsibility and Work Opportunity Reconciliation Act, P.L. 104-193)—including the rules governing noncitizen eligibility for public assistance that it established—and legislation covering programs with major restrictions on noncitizens’ eligibility (e.g., food stamps/SNAP, Medicaid). This report deals with the four major federal means-tested benefit programs: the Supplemental Nutrition Assistance Program (SNAP, formerly food stamps), the Supplemental Security Income (SSI) program, Temporary Assistance for Needy Families (TANF) cash assistance, and Medicaid. Laws in place for the past 18 years restrict the eligibility of legal permanent residents (LPRs), refugees, asylees, and other noncitizens for most means-tested public aid. Noncitizens’ eligibility for major federal means-tested benefits largely depends on their immigration status; whether they arrived (or were on a program’s rolls) before August 22, 1996, the enactment date of P.L. 104- 193; and how long they have lived and worked in the United States.