Twenty years after the landmark Rio Earth Summit, governments still struggle to demonstrate improved environmental performance through quantitative metrics across a range of pollution control and natural resource management challenges. With budgetary constraints an issue around the world, governments face increasing pressure to show tangible results from their environmental investments. The 2000 Environmental Sustainability Index (ESI), the predecessor to the Environmental Performance Index (EPI), first responded to the growing need for rigorous, data-driven environmental performance measurement. The 2012 EPI, the seventh iteration of this environmental measurement project, adds to the foundation of empirical support for sound policymaking and breaks further ground, establishing for the first time a basis for tracking changes in performance over time. The EPI and the Pilot Trend Environmental Performance Index (Trend EPI) rank countries on 22 performance indicators spanning ten policy categories reflecting facets of both environmental public health and ecosystem vitality. The methodology facilitates country comparisons and provides a way to assess the global community’s performance over time with respect to established environmental policy goals.