The ultimate goal of environmental policy is reducing pollution. Attention to environmental problems in the social sciences has brought some bold generalizations about causes of good results, but almost no systematic cross-national studies that flesh out major theoretical arguments and test those claims with data. This study makes a seminal contribution to that effort in two ways. First, by taking environmental outcomes over the last thirty years as the central dependent variable, it provides a basis for evaluating national performance in reducing environmental problems. Second, by developing a data set including performance in a number of countries and elaborating on major explanations of environmental performance found in the literature, this study provides the most rigorous available analysis of the determinants of environmental performance. In so doing, it challenges what is probably the conventional wisdom in the social sciences.