The informal Expert Group on ATT Implementation (EGAI) fourth meeting was held in Costa Rica. The aim of this meeting was to promote clear understandings about how to maximize the operational effectiveness of the Treaty, and facilitate consistent and robust implementation. In this meeting, more than 30 experts on ATT (including diplomats, export control authorities, regional organizations and civil society) discussed how to implement appropriate and effective transit, transshipment and brokering controls and how to mitigate risks associated with arms exports. The meeting was organized with complementary assistance from the Arias Foundation for Peace and Human Progress, Control Arms and the Ministry of Foreign Affairs of Costa Rica.