This article examines the role ngos have played in placing and controlling the landmine-ban issue on the international arms control agenda, which eventually changed state behavior toward landmines. It develops a framework for agenda setting to examine how and why ngos were successful in this role. More importantly, the article also examines how ngos were able to generate state action toward the support of the Ottawa Treaty banning antipersonnel landmines, which marked the first time a weapon in widespread use has been banned. The article makes two interrelated arguments. First, ngos initiated the landmine ban by placing it on the international arms control agenda, which gained intense media and public attention for the cause. The ngos accomplished their goal by utilizing cognitive attribution strategies to educate the public about the minimal military utility of landmines and the humanitarian problems they pose. Second, ngos changed states' perception toward the legality and use of landmines once the issue was on the agenda by highlighting the horrible effects and disproportionate consequences of landmine use, playing leadership games with influential individuals and states, and claiming that anti-ban states were using incoherent arguments. In comparison, ngos have not been included in the agenda-setting processes of most other major arms control and disarmament treaties, which typically are negotiated at the behest of major powers. These arguments address the broader question of agency in world politics by showing potential conditions of how ngos can instigate governments to address issues in a way that may culminate in international law.