UNEP´s mandate in the international arena has been enlarged by the United Nations General Assembly (UNGA) and its legitimacy increased through the establishment of a new Universal Membership body, the United Nations Environment Assembly (UNEA). It is now time to examine how UNEP can further increase its legitimacy and effectiveness by improving its engagement with civil society. UNEP initially engaged in dialogue with formal, registered environmental NGOs. In 2002 civil society engagement shifted to the nine major groups, and since 2004 has expanded to include major groups and stakeholders. However, while the elaboration of major groups and stakeholders was an improvement on the initial design of NGO engagement, UNEP faced a number of new challenges as this paper illustrates.