This study explores the role of ethnicity in the universe of international crises during the period from 1918 to 2001. We begin with three concepts: ethnicity in international crisis, ethnic actors, and ethnic issues. We then develop a typology of international crisis comprised of interstate, ethnic-interstate, and NSA-interstate (nonstate actor-interstate) cases. Our research questions address all three types of crisis focusing specifically on: 1. Who are the ethnic actors that play a part in crises? 2. What are the issues they introduce? 3. Do interstate and ethnic-interstate crises differ? We present findings on the "universe of 434 International Crisis Behavior (ICB) cases, divided by typological category. Then we analyze ethnic actors and issues in the "world of 130 ethnic-interstate crises, and explore crisis outcome. Finally we examine the "universe of ICB crises with regard to the three postulates on crisis outcome and violence . In conclusion we highlight the importance of an actor-based approach to ethnicity in world politics.