This paper considers four programs--Medicaid and the State Children's Health Insurance Program (SCHIP), food stamps, child care subsidies, and the earned income tax credit (EITC)--that form the core work support system in the United States. It highlights differences in program funding, eligibility, and delivery systems. It describes trends in participation and synthesizes research knowledge about the observed differences in program participation. The paper concludes that these programs do not form an effective system. Each program operates under different rules that many low-income working families find daunting. A few recent state innovations offer potential for improving the system.