Why is the GCC, which is now in its fourth decade, still a weak defensive organization? This paper tries to explain the dilemmas of collective security in the Arab Gulf region. The paper first elucidates the concept of collective security, which forms the theoretical framework for this study. It then reviews the main sources of threat to Gulf security. It then offers a discussion of security dimensions and defense cooperative between the GCC states, and a detailed analysis of the dilemmas of collective security in the GCC, as well as of the features of the proposed collective security system.