Health care professionals are in contact with patients of all social horizons. Healthcare professionals come into contact with patients from all social backgrounds. Low socio-economic status is a well-known determinant of morbidity and mortality. A mobile community health care unit ("Umsco") was created in Geneva in 1996 with the aim of providing health care to very low-income patients who aren't catered for by the traditional healthcare system in Switzerland. The Mobile Unit's patients are mainly female South American illegal immigrants, but also the city' homeless. This article explains how the Unit functions on a day-to-day basis. We describe socio-demographic characteristics of the patients and their main presenting complaints. We also discuss how health care professionals in general can adapt to the specific needs of socially deprived and vulnerable patients.