In this paper we study the relationship between economic growth and environmental degradation through a discussion of the environmental Kuznets curve. We present the main results of an immense literature and assess its implications. Empirically, we reassess the validity of the environmental Kuznets curve for emissions of carbon dioxide with models robust to the presence of non-stationary variables and dependence among the units of the panel. The results point out the weakness of the concept of an environmental Kuznets curve when the properties of the series are properly taken into account.