In Sassen’s analysis the city was becoming very important during last twenty years, for economic, political and cultural life of people. The article presented points in evidence some causes of this new central dimension, relating with globalization’s mechanisms. The structural effects of contemporary social transformations have a particular field of application into the city. They bring out a new geography of central (global) and peripheral cities. This ristructuration transforms, furthermore, the configuration of social relations in urban context, bringing out new social subjects, like women and immigrants. In this dinamic context, the social sciences and urban sociology can find new perspectives of analysis and have an important role, to read the urban dimension in the present globalization.