Under what conditions are environmentally protected areas effectively implemented by subnational governments in Brazil? Despite their varying capacities to implement policies, subnational governments in developing countries such as Brazil have assumed greater responsibilities for environmental governance in recent decades. This leads to different rates of implementation in different regions of Brazil and elsewhere, and may reduce the effectiveness of conservation efforts. My study seeks to explain variation across states in Brazil in patterns of implementation of environmentally protected areas. Through a subnational comparative analysis of the adoption of management institutions and procedures to implement protected areas in six Brazilian states, I argue that the interactions between state agencies and non-state interest groups at subnational levels affect if and how these institutions are adopted, and the potential these institutions have to contribute to effective conservation of natural areas. To assess this argument, I will employ data published by the federal Ministry of the Environment and state agencies in Brazil, process tracing data from interviews with key actors and other observations, and original data that I will gather through a survey of protected area managers in all 26 Brazilian states. To carry out the necessary field work, I will live in Brasília from September, 2010, to September, 2011, and travel multiple times to the states of Amazonas, Bahia, Minas Gerais, Pará, Santa Catarina, and São Paulo. Completion of this study will be facilitated by my institutional affiliation with the University of Brasilia and contacts at regional universities.