Supermaximum ("supermax") security prisons have become a common feature of the corrections landscape. Despite their substantial costs, questions about their constitutionality, growing fiscal and managerial challenges confronting correctional systems, and increased demand for evidence-based, practices, little systematic empirical research about their effectiveness exists. Against this backdrop and a debate often framed in ideological terms, we identify five dimensions that we argue should be taken into account to provide a fair and balanced, assessment of supermax prisons. Our study draws on a comprehensive analysis of existing research, site visits to three states, and interviews with 60 corrections policymakers, officials, and practitioners. We conclude with recommendations for research and policy.