In this chapter we review the existing literature on cross-national comparative studies of terrorism. We first conceptualize and define terrorism and discuss the benefits and limitations of open source databases as sources of terrorism data, as compared to traditional sources of cross-national comparative crime data. We then review quantitative studies that have examined the correlates of country-level domestic and international terrorism. We focus mainly on economic and political predictors of terrorism, and briefly discuss major demographic correlates. Finally, we conclude with a brief discussion of areas for future research for cross-national comparative studies of terrorism.