Jurisdictions across the country, acting in the context of a federal regulatory void and wide gaps in knowledge about the safety of e-cigarettes, are trying to decide whether and how to regulate the devices. This project is an in-depth, real-time study of policymaking surrounding this issue. The project aims to advance understanding of the policymaking process, particularly with respect to how scientific research evidence is or is not used by decision makers, and to identify the key determinants of policy action on this issue, providing a map of the current policy landscape. This policymaking and mapping study will lay the groundwork for future implementation, intervention, and mechanisms studies, which require a thorough understanding of what outcomes policy makers were anticipating and how they came to believe that policy, law, and regulation would achieve those desired impacts. It will advance understanding of the uses of evidence, the role of precedent in other locales, and the intent of laws and policies meant to control tobacco use with implications for the translation of knowledge into practice.