Protests at and around climate summits attract media attention, but it has been assumed, rather than demonstrated, that such protests attract similar kinds of actors who share a common "climate justice" agenda. To test such assumptions, we analyze the patterns of participation in demonstrations around the 2009 UN Climate Change Conference in Copenhagen, centered around the Fifteenth Conference of the Parties to the United Nations Framework Convention on Climate Change (COP-15). Attended by 190 national delegations, with over 30,000 registered participants, 1 formal negotiations among political leaders were surrounded by meetings and seminars involving politicians, scientists, and representatives of a wide range of NGOs. The summit also prompted extraordinary mobilizations of demonstrators, both in Copenhagen and elsewhere. Although, as many of the demonstrators expected, the summit ended without agreement on an effective regime to address global climate change, it provided an important opportunity for networking and mobilization with potentially enduring consequences for the development of a transnational climate movement.The events surrounding COP-15 provided an opportunity to explore the demographic characteristics and political goals of demonstrators mobilized around the most compelling transnational environmental issue of our timeclimate change. By surveying different demonstrations related to a single transnational summit, we examine collective action addressing climate change from the perspective of rank-and-ªle participants, and so provide an important complement to the images conveyed by the slogans and rhetoric of the social movement organizations (SMOs) engaged with climate change.We analyze data on participants in the three largest European climate 1. Fisher 2010, 12.