The treaties on which the EU is founded hardly ever mention the notion of solidarity between citizens. The type of solidarity owed according to the terms of the treaties mostly concerns the relationship between Member States. This also holds true in the chapter providing the legal basis for the EU’s migration policies. The present chapter discusses the concept of solidarity in the Dublin System for determining the state responsible for examining an application for asylum. This case is especially critical because the Dublin System has given rise to sharp conflicts pertaining to interstate solidarity. The Dublin example demonstrates that in EU law the principle of solidarity operates in a field of tension between a high degree of supranational integration and, simultaneously, a high degree of heterogeneity among its Member States. It aims to compensate an asymmetric distribution of burdens generated by further steps on the supranational path of European integration.