This article examines the characteristics of recipients of childhood Supplemental Security Income (SSI), using a combination of public-use and administrative data. From the early 1980s through the late 1990s, major changes in disability-related eligibility standards, along with welfare reforms affecting SSI and cash assistance, have altered the characteristics of child recipients. The SSI and AFDC/TANF child and family caseloads have converged with regard to demographic factors and multiple program use. The article also discusses the causes and consequences of post-welfare-reform trends.