Environmental organizations in the US engage in a variety of political practices in order to meet their goals. Some organizations consciously pursue more contentious and oppositional actions to match their goals, while others adopt methods that align with conventional institutional practices to achieve their goals. This variation in the terrain of the environmental movement is indicated by the behavior of the environmental organizations that it largely comprises. The following is an investigation of the factors that influence the political advocacy of a sample of environmental organizations and thus the political praxis of the environmental movement proper. By deriving concepts from a 2006 survey of a sample of organizations in the US, three conceptual factors derived from social movement theory are operationalized: ideological identities, strategies of practice and resource structures. Using numerous independent variables, these concepts are then tested in a logistic regression for the effect they have on the odds that the organizations would oppose any of three historical events: the World Trade Organization (WTO), the North American Free Trade Agreement (NAFTA) and/or the Kyoto protocols. A typology of environmental organizations is then constructed, tested, substantiated, problematized, and interpreted. Subsequently, a comparative case analysis of 11 distinct organizations was conducted that revealed the ways in which the leadership constructed meaning around their organizational practices and helped develop the typology further, explaining some of its shortcomings and adding nuance to the model that better explains contemporary environmental advocacy behavior in the US. Directions for future research are assessed, and both the challenging and encouraging implications that this research has for the environmental movement as a whole are extrapolated.