Government regulations influence virtually every interaction between a health care provider and a patient in the United States. Yet researchers have often struggled to capture the systematic role healthcare regulations play in health outcomes. The Healthcare Openness and Access Project (HOAP), launched in 2016 by the Mercatus Center at George Mason University, seeks to fill this gap by measuring the openness and access of healthcare regulations across states. In this paper, we present the evidence-based framework that underpins HOAP’s methodology. Each state is assigned a score on 42 indicators across six categories: professional regulations, healthcare-delivery regulations, patient regulations, payments regulations, institutional regulations, and pharmaceutical regulations.