A global system for tracking illicit arms and ammunition is central to improving accountability in the international arms trade and preventing arms getting into the wrong hands. The United Nations negotiations to establish international Marking and Tracing controls present states with an historic opportunity to take a tough stance against the worldwide proliferation of illicit arms and the use of arms for violations of human rights and international humanitarian law and to make real progress. This will be the first major international agreement to come out of the UN Programme of Action on the Illicit Trade in Small Arms and Light Weapons and represents an acid test of its credibility. People in communities suffering from conflict and armed violence in all parts of the world depend upon the successful outcome of these negotiations. In addition to a marking and tracing treaty, states should also negotiate and agree complementary global instruments to prevent arms proliferation - an international Arms Trade Treaty and a treaty to control arms brokers and transporters.