In 2004, ten new states entered the European Union. Relative to the pre-2004 member states, these accession states have lower environmental standards, and some worry that it will be too demanding for these new EU members to fully comply with European environmental provisions. In this paper, we assess one rationale for such harmonization. Specifically, we analyze the determinants of environmental policies stringency, and show that differences in corruption levels are more important as explanatory factor when compared to income differentials. Since high levels of corruption characterize some countries in the enlarged EU, we argue that this is a good reason for an upward harmonization of environmental policies at the EU level.