Building on a discussion at the April 2009 NGO Leaders Forum at Greentree, this paper explores the distinctive contributions that international NGOs have made in development and humanitarian crises, the characteristics that enable them to make these contributions and the limitations to their effectiveness. Twenty-six interviews – with leaders of international NGOs, scholars of civil society and a few southern NGO leaders and senior foundation staff – provided the fodder for this paper. Rather than synthesizing the views gathered, we have teased out major points of convergence and freestanding nuggets into a concise articulation of what makes international NGOs distinctive.