What influences countries' environmental performance? Do structural differences alone affect the level of air pollution? Do economic conditions determine water quality? Might society's dominant ideology and values impact national environmental performance? Are different kinds of environmental-performance indicators affected by the same variables? This paper employs comparative empirical analyses of EPI data to address these questions. Doing so enables us to contribute the following five insights to the research literature. First, we propose a conceptual categorization of EP following their health, ecological and global aspects. Second, we demonstrate that social policy, a previously underexplored factor, affects environmental policy and performance. Third, we provide evidence for the role of international engagement in explaining global-related environmental performance. Fourth, our research extends the sample studied beyond the traditional OECD sample to 68 countries with diverse development status. Finally, we demonstrate that the multiple regression models we employed provide high levels of explanatory power (up to 89%). Collectively, the results demonstrate the important role of social policy in explaining differences in the environmental performance of countries. In addition, the differences in the influence of the explanatory variables on each of the proposed category support our theoretical arguments for differentiating between various categories of environmental performance.