Very few data exist in France on: (1) nurses’ knowledge and behaviour concerning ethical decisions in clinical practice; and (2) their knowledge of ethical rules in clinical research. This questionnaire-based audit tried mainly to assess these questions in a large French university teaching hospital. Of the 257 questionnaires distributed to nurses in 23 clinical units of the hospital, 206 were returned (80% response rate). When responding to the vignette describing a clinical situation requiring an ethical decision to be made, most (...) nurses acted as the patient’s advocate although they have had no formal training in ethics. Indeed, 66% of nurses responding considered that the patients themselves should be the primary decision makers in situations that relate to their health and medical care. For children or comatose patients, the decision should be left to the relatives according to 72% of the responses. The results indicated that the role of health care professionals in ethical decisions made for a given patient should be marginal. Nurses’ knowledge concerning research protocols, particularly their ethical requirements and consequences, is poor at present and information from and communication with doctors should be improved. (shrink)