The harmonization of national laws is a traditional and prominent instrument for achieving the internal market. This chapter aims at recalibrating the scope, the role and the shape of the programme of legislative harmonization in the EU. It shows that harmonization should be seen as a broad, complex and virtually unlimited process concerned with the removal of barriers to trade as much as with the institutional, social and moral infrastructures of the market. It is a process that looks for effectiveness and uniformity in market integration but is anxious to accommodate social and cultural diversity. It involves the EU legislator, European Court of justice and the Member States as well as a large set of private actors.