"With thousands in Arkansas losing their Medicaid benefits under the state's work-requirement demonstration, the importance of evaluating such experiments could not be clearer," say George Washington University's Sara Rosenbaum and colleagues. But as the authors report in a Commonwealth Fund issue brief, the nation's first-ever Medicaid work demonstration is proceeding despite the absence of any federally approved evaluation to test the requirements' impact on people, as called for under Section 1115 of the Social Security Act.