This study describes a framework for analyzing the formation of political and economic costs in setting pollution taxes aimed to control the contamination of water bodies, in 2006-2011, for the Área Metropolitana del Valle de Aburrá and its regulated community. Through an exploratory analysis and using an inductive approach, this study examines the actual experience of implementing an environmental policy in a specific region. The results of this study suggest that political and economic costs explain not only the supplier's logic and reasoning but also the consumer's level of demands intended to reduce contamination in the Medellín River. © 2010 Universidad de Antioquia. All rights reserved.