Drawing upon experiences from two medium-sized Swedish cities, this article deals with the role of cities in social sustainable development. As the argument goes, their potentialities are challenged by three interlinked processes exposing them to sincere societal strains. The uneven development of globalization, the transformed character of migration and an increasing speed of urbanization bring several cities into the danger of tearing apart and develop into arenas for social conflicts. The article discusses the area of tension in which most cities find themselves as well as some of the factors that are considered decisive for the direction in which the cities are heading. By highlighting the interrelationship between security, development and justice the paper argues that urban social cohesion requires proventive security based upon enlarged local democracy and strengthened popular participation. Important conceptual gaps and strong mistrust between different stakeholders calls in this regard for a transformative oriented method of dialogue capable to create space for dissenting voices and to deal with asymmetric power relations.