The principle of precaution, a fundamental, essentially legalistic, rule underpinning health care legislation in France, basically arose from environmental protection policies. This principle became the topic of a good deal of well-publicized debate following the decree concerning HIV contamination rendered in 1993 by the Conseil d'Etat, the supreme jurisdiction on legislative matters in France. This translation of a fundamental principle from one domain to another is not devoid of significance and could have an unexpected impact on the nature and meaning of health care itself. When applied to medicine, the principle of precaution must be confronted with the notion of risk, inherent in all acts of health care. This risk certainly implies patients' rights and informed consent to medical care, but also, in a reasonable search for an acceptable balance between risk and benefit, the freedom of biomedical research from overly-restrictive regulations. Consequently, in accordance with an ethical approach to medical care, legislative and judicial bodies must take into consideration the practical reality of medicine in order to integrate the scientific, economic, social, and psychological aspects of everyday medical practice into health care laws and regulations. Once faced with the reality of health care, the principle of precaution could appear contradictory to the fundamental principles of medicine. Indeed, every physician, every health care worker, makes daily evidence-based decisions that are never devoid of risk. Unrestricted application of the principle of precaution to a growing number of public domains, including medicine, as advocated by a large number of opinion leaders, could lead to an inextricable situation, in total contradiction with the goal of health care itself. In order to develop new truly ethical and adapted health care regulations, we must break down the barriers confining judges and legal representatives to a purely legalistic vision of health care and equally confining physicians to a purely scientific vision of their mission.