Context. In France, despite the implementation of universal and complementary medical cover reducing financial barriers to accessing health care, difficulties are still encountered for vulnerable patients. Method. A randomized comparative trial with a 3 month follow-up was carried out between June 2009 and December 2010 on two populations of patients, both experiencing difficulties in paying their health care. One was recruited by general practitioners (GPs) and the other by the department of accident and emergency (A&E) in Lapeyronie university hospital, Montpellier, France. After agreement was obtained, patients were offered access to a dedicated social work department. Each population was randomized into two groups, action and information. The professionals organized an appointment with the social workers for the action group and gave an information brochure to the information group. The primary endpoint was the proportion of patients who had obtained a complementary health insurance 3 months after inclusion in the study. Results. 234 patients were included by the GPs and 260 by the department of A&E. After 3 months, 136 of the patients included by the GPs and 93 by the department of A&E had obtained complementary health cover, with no significant difference between the action group and information group. A statistically significant increase in the number of specialized consultations and prescribed molecular biological analyses was found in the population recruited by the GPs. Conclusion. The setting up of a dedicated social work department allowed a number of underprivileged patients to get a better health insurance, and therefore a better access to health care. Organization of the appointment by the health professional was not more effective than information of the patient.