Supplemental Security Income is an odd combination of income support for families with disabled children, disabled working-age adults, and elderly persons. The program faces challenges on three fronts. Payments for children bear little relationship to family need or costs. State efforts to promote transition of children and adults from TANF to SSI appear driven by fiscal considerations. Measuring the impact of poverty among the elderly is hampered by underreporting of benefits in survey data. This paper argues that SSI serves important purposes, but that the target populations might be served best by gradual decoupling or improved integration with other programs.