Prior to states expanding their Medicaid programs, low income adults without dependent children were typically only eligible for Medicaid insurance coverage through the Supplemental Security Income (SSI) program due to a disability. However, Medicaid expansions create an opportunity for low income childless adults to obtain health insurance coverage without having to complete the intensive SSI application process and thus reduce SSI participation. Prior research has focused on the effects of pre-ACA (Affordable Care Act) and very short-term ACA Medicaid expansions on SSI participation among the nonelderly U.S. population without examining disparities by demographic group or disability status. However, given that uninsured rates have been historically highest among young adults and there are disparities in the coverage gains from the ACA Medicaid expansions by age, race/ethnicity, educational attainment, marital status, and household characteristics, it is important to understand the effects of the ACA Medicaid expansions on SSI participation among young adults across demographic groups and disability status. Using survey data on SSI benefits from the American Community Survey in difference-in-differences analysis, this project will examine the heterogeneous effects of ACA Medicaid expansions on SSI participation among young adults. This analysis can improve our understanding of the value that young adults place on health insurance coverage relative to SSI cash benefits and has implications for cost savings in the SSI program and young adults’ labor market and savings outcomes given SSI income and asset eligibility criteria.