The collapse of communism in Eastern Europe and the drawing down of the Cold War have raised the profile of long-suppressed sources of instability in Central and Eastern Europe, renewing interest in the role of European security institutions in addressing non-East-West conflicts. This Note examines the experience of European institutions, the European Community (EC), Conference on Security and Cooperation in Europe, Western Euorpean Union, and NATO, in the Yugoslavia crisis. It also considers the relationship between these organizations and the United Nations, which began to play a more significant role in the crisis in the autumn of 1991. The author reviews the evolution of the principal elements of Europe's new security architecture, and describes the actions of the various institutions in responding to the Yugoslavia conflict from the declarations of independence by Slovenia and Croatia on June 25, 1991, until January 1, 1992. The author derives five lessons about future European crises: (1) outside military force plays a limited role, (2) economic leverage is important, (3) institutions for collective decisionmaking are valuable and there are limits to consensus, (4) intervention must take place early, and (5) multiple institutions with overlapping responsibilities present both opportunities and risks.