BACKGROUND: Over the last decade, the increasing number of people experiencing difficult social conditions--especially in urban areas--has led to the implementation of free (health and social care) clinics for uninsured and/or poor people. METHODS: In this paper, we give some results of multidisciplinary (sociological and epidemiological) research conducted among patients attending five of these free clinics in the Paris area. RESULTS: The statistical and qualitative analyses revealed the diversity of the studied population, as well as the conditions in which these consultants attended such clinics, what kind of services and help they used and, furthermore, what kind of social ties were strengthened. CONCLUSION: These results lead us to discuss our present knowledge of the determinants of the utilization of the healthcare system, not only among vulnerable people, but perhaps also amongst the general population.