Shanghai Institutes for International Studies(SIIS), Pacific Forum of Center for Strategic and International Studies (CSIS), Center for Naval Analyses and Institute for Defense Analyses co-organized Quadrilateral symposium entitled “China, ROK, Japan, and U.S.: Security, Interests, and Identity in the 21st Century”. Scholars of the four countries had discussed the issues of Northeast Asian perception on security, the impacts of national identities and political evolutions on foreign policies in China, Japan and Korea, the Six-Party Talk and regional security, the U.S.-Japan alignment, U.S.-Korea alignments and regional security, as well as the regional security mechanisms.