In this Health Affairs Blog, Kenney and colleagues present preliminary findings from their study of six states California, Connecticut, the District of Columbia, Minnesota, New Jersey, and Washington that have already expanded Medicaid to cover some or all of the low-income adults targeted for coverage under the Affordable Care Act. Through in-depth interviews with high-ranking Medicaid officials across all six states, the researchers, led by Ben Sommers gained insights on the impacts of such expansions and identified several key policy lessons that can help elucidate the opportunities and challenges of expanding Medicaid under health reform in other states.