Member states of ASEAN - the Association of South-East Asian Nations - have developed a distinctive approach to political and security co-operation, which builds on the principles of sovereign equality, non-intervention and non-interference, quiet diplomacy, mutual respect, and the principle of not involving ASEAN in mediating bilateral disputes among the membership. This book examines the origins of ASEAN's diplomatic and security culture and analyses how over time its key principles have been practised and contested as ASEAN states have responded to regional conflicts as well as challenges posed by the major regional powers, ASEAN's enlargement, and the Asian financial crisis. The book goes on to assess whether ASEAN's diplomatic and security culture is likely to remain salient as the political, economic and security context in which regional leaderships operate is undergoing further change.