A retrospective analysis of 211 consecutive complaints treated at the Direction of Health and Social Assistance of Paris was undertaken in order to specify the nature of the complaints and to evaluate their pertinence as an indicator of quality of care. The majority of complaints concern public and private health establishments, in particular surgery and psychiatric services. Although the study confirms the dysfunctioning of the organisation of services and also of therapeutic methods and medical treatments, the evaluation of iatrogenic risks and their avoidable nature is difficult and requires precise instruction. Complaints seem to be a neglected indicator of quality, yet they concern information that is accessible and could, if used with other information, be a first milestone in the vigilance of medical treatments.