The principle of informed consent, aimed at the lawfulness of health assistance, tends to reflect the concept of autonomy and of decisional autodetermination of the person requiring and requesting medical and/or surgical interventions. This legal formula, over the last few years, has gained not only considerable space but also importance in the doctrinal elaboration and approaches, as well as juridical interpretations, thereby influencing the everyday activities of the medical profession. Informed consent is still the object of continuous explorations, not only asfar as concerns the already confirmed theoretical profile but, instead, the ambiguous practical and consequential aspect. Analysing how the concept and role of consensus was born and developed with the more adequate and reasonable excursions to make it valid and obtain it, it is impossible not to take into consideration, on the one hand, the very ancient philosophical origins and, on the other, the fact that it was conditioned by religion with the moral aspects and the accelerated deontological evolution with pathways parallel to the needs and the progress offered by new forms of treatment and novel biotechnological applications. The principle of consent is a relatively new condition. In fact, already in the times of not only the Egyptian civilisation, but also the Greek and Roman, documents have been found which show how the doctor's intervention had, in some way, first to be approved by the patient. Plato (law IV) had already foreseen the problems, the procedures and the modes of information which are, in synthesis, at the root of the principles of the present formula of informed consent and correlated the practice of the information and consensus with the quality and social position of the patient. The only guarantee that the patient might have, derived from a fundamental principle of medicine of all times: "in disease, focus on two aims, to improve and not to cause damage". A figure can be recognised, in the Hippocratic physician, that cared about the patient's suffering, but never neglected looking after his own outcome, endeavouring to avoid becoming involved in lack of success and death of a patient. The concept of consensus is inexistent, albeit, there is an awareness of the presence of precautious and preventive information. In the behaviour of doctors, in ancient times, it is not difficult to recognize the true motives and the real reasons that, already in those days, give rise to the necessary "defensive medicine" particularly as far as concerns the social status of the patient. Already from the early origins, continuing the Hippocratic tradition, the relationship between doctor and patient was consolidated, based upon two very definite criteria, represented, on the one hand, by the professional duty of the physician to do what is bestfor the patient and, on the other, the duty of the patient to completely accept the physician's decisions and intervention. The Hippocratic physician respected a principle of professional responsibility which was more religious and of a moral type, but, from a legal point of view, very weak inasmuch as it depended upon regulations elaborated by human beings. The conviction and certainty that the physician acted, in the interest of his patient's well-being, has been passed down over the centuries endowing the physician with moral authority and a kind of legal impunity, conditions which corresponded, in an almost reflection-likefashion, with the duty of obedience and subjection, on the part of the patient. Christianity was grafted into this consolidated vision of the sacral character of medicine and medical practice, which did not substantially change the Hippocratic type of ethical behaviour. Non only the population but also the Christian physician was aware of the religious importance of his intense activity as a mission and compared to a special kind of priesthood in safe-guarding health, considered as a gift of God. Therefore, invested with this authority which derived from his professional role and from his very work, he felt it his duty to guide the patient, deciding and for him. The patient is an ignorant person who does not have the knowledge, the intellectual capacity or moral authority to oppose or disagree with the wishes and decisions of the physician who, instead, on account of his doctrine, knows exactly what is goodfor him. In this regard, if we were to speak of consensus concerning the physician's intervention, he would be considered useless in as much as obvious and understood when seeking help. The attitude of the patient towards the physician has always tended to one of strong faith and characterized by psychological subjection borne out by traditions thousands of years old. A patient who was sick, again, as an attitude of respect and gratitude, followed the treatment but never asked for any explanations regarding the therapeutic effects and the physician refrained from taking any initiative to inform the patient or his/her family. Each phenomenon, therefore, has a precise origin, a well-defined history and when its importance tends to significantly condition the activities concerning Man, a desire emerges to learn the origin and the history. As is well known, a trial commenced in Nuremberg, on December 19, 1946, of Nazi doctors and a code was defined in which the judges, all Americans, clearly emphasized a view of medical research and technology: science should never transform or consider human beings as an instrument to be employed for scientific purposes. In actual fact, documents exist providing evidence that a few decades before the drawing up of the Nuremberg Code, the need had been expressed, in Germany itself to somehow make medical interventions and actions legal by means of the use and practice of consensus. The moral and ethical principles in those documents, even if not available as bibliographic references in the English literature, certainly merit,...