Abstract This article explores the tension between freedom of movement within the EC/EU and the principle of social solidarity, a tension which has increased in step with the progressive enlargement over the years of the circle of potential beneficiaries of the right to cross-border access to the social and welfare benefits guaranteed by the social protection systems of the Member States. The article aims to re-construct the system of Community rules regarding the free movement of persons within the EU from the point of view of the justifying criteria for the cross-border access to national welfare systems of the different categories of migrants. The focus of the article is on the different degrees and models of solidarity which, at least at the present stage of the European integration process, justify correspondingly graduated and differentiated forms of cross-border access to Member States' social and welfare benefits for the various categories of persons who move about within the EU.