Scholars are beginning to consider how state campaign finance regulation influences political behavior and elections, but they lack the systematic measure of these regulations needed to do so. This article describes a simple measure of state campaign finance regulation stringency that is based on state statutes in 2002. Further, this article explains the construction of the measure and assesses its validity and reliability. The index generally confirms qualitative assessments of state campaign finance regulation, and it is correlated with measures of related aspects of state campaign finance regulation, campaign spending, and fundraising.