This article explores the empirical significance of the concept of enduring rivalries for the study of international conflict. We examine whether conflict occurring in enduring rivalries was more frequent and severe than international conflict in other contexts, specifically conflict in isolation and protorivalries. Our empirical results indicate that a large portion of militarized disputes take place in the context of rivalries, especially enduring rivalries. Enduring rivalries are also the setting for over half of the interstate wars since 1816; enduring rivalries at the extreme are almost eight times as likely to experience a war as a pair of states in an isolated conflict. Contrary to our expectations, enduring rivalries were not involved in a disproportionate number of territorial changes; yet, when such transfers occurred in enduring rivalries, they were three times more likely to involve military conflict than in isolated disputes. Implications for future research are discussed.