The healthcare organization mission is to ensure the safety of the patient and the quality of the care related to any medical act. This mission is subjected to more and more increasingly constraints which involves in fact the evolution of these structures. In France the undergone pressures emanate from several sources; they are political (ministry of health, HAS ), social (classification of the hospitals in newspapers, concepts of quality of the care), legal (trial against experts and hospital for errors, faults), medical (continuous improvement, to offer the best care to its patients) and financial (profitability, pressure of the supervisions). An establishment of health is view as a particular service firm regarding the relation with its customers (patients), the responsibilities associated to each health professionals, the necessary synergy between the various services, the obligation of results for some services, and especially with the pregnancy of the human element. The evolution of these organizations, noted these last years, is similar with the industrial production organizations' evolution, which have to operate deep and important changes to face the market constraints. Thus, certain principles and tools used in the industrial company as well as the experience accumulated on problems rather close like flows management, quality or performance improvement appear relevant in respect to the needs of evolution of care units. According to [1-3] the professionals of health wish to see appearing a new culture of organization. However, several works [4-6] show that the transposition of methods and kind of organization from industrial world towards the medical world require an accompaniment and a major adaptation. In order to show the interest of these transpositions, the entirety of the concepts is implemented in the hospital drug circuit, particularly in the CHU of Nice. Indeed, the drug circuit is a process of care transverse and structuring in health establishments. Each step of the circuit can be the cause of potential errors, affecting the patients' safety until the vital risk or to generate drifts of any kind, with financial and socio-technical impacts. Beside the particular characteristics related to its mission which is to guarantee the safety of the patient and to exempt, whatever the configuration of the requesting departments or pressure of the environment, the good drug to the good patient, under the good conditions, and at the good time, the drug circuit involves many actors and constitutes a very sensitive “risk system”, specially the medicinal iatrogenic risk. Certain causes of this type of risk are inevitable because related to the undesirable pharmacological effects of certain molecules. Some are however avoidable. Errors in the realization of procedure or intervention are the most frequent (50% up to 70%). The errors of prevention and monitoring account for 10 up to 30 % of the cases and the one of diagnosis account for finally 5 up to 20% of the cases. The hospital prevalence of the drug iatrogenic events is estimated between 6.3 and 10.3% of the in-patients one day given with a third up to a half of the events considered as low registers, and an incidence rate of 3.2% for the non hospitalized patients. This type of risk can be relate to any stage of the drug circuit and blame any actor. There is no question of finding punitive solutions towards this actor but the aim is to set up solutions of avoidance of risks situations by considering the system as a whole by a systemic approach [7]. The fight against the iatrogenic risk especially in drug is besides one of the 100 priorities defined by the new French law of public health; with for the first time some precise objectives of reduction. The risk management related to the drug circuit is based on the vigilance according to the scale of the institution starting from the information collected by each service. The difficulties rise from the multiplicity of the actors and the situations as well as problems of identification, then of declaration of the incidents. A risk in the drug circuit will induce, in addition to the potential direct impact on the patient, an economic loss of performance in terms of service's quality, constraints respect and customer satisfaction. It is then necessary to provide to these services the means making them possible to mutually understand the system in which they are implied, to detect and communicate without loss of direction, the nature of the causes or the incident, to anticipate and manage these situations and the inherent risks they involve. Unfortunately, today this system is badly controlled by hospitals. The first reports emitted by the HAS for health establishment certification show the drug circuit like an insecure process, insufficiently controlled. The goal of our approach consists in enriching the modelling step by concepts and methods coming from the science of the danger such as the process of danger [8], the cindynic deficits [9] and the risk's situations management [10]. The purpose of the enterprise modelling [11] and system engineering [12] is to develop and promote methods, techniques, models and tools making it possible to control the behaviour of the company in time. The projects in company, and in a more general way in all the organizations, which are based on these approaches, are multiple and can relate several aspects. Technical aspects such as the reduction in the duration of production cycles, the availability of the technical resources (machines, equipment) and the flexibility of the system production ; economic aspects such as the reduction of the production costs, stocks; human aspects such as the improvement of the working conditions, staff training [13].This research task is completed with the professionals of health, while being based on systemic concepts and by integrating various languages of modelling [14]. In parallel of this conceptual aspect, a step of implementation resulting from the engineering of the systems [12] and processes [13] is developed, adapted and applied within the framework of the medical environment [15]. The awaited result is the improvement of the intelligibility of the system, its procedures, its resources, its anticipation or adaptability by taking into account the specific elements of knowledge to each trade and actor (multi view approach) by building a representation deprived of ambiguity and easily exploitable for analysis. Here the analysis of the obtained models consists in using mathematics methods of proof [16] to detect organisation's risks zone and behaviours. This communication aims on the one hand to describe the conceptual aspects of system and risk modelling; on the other hand, it aims to present the practical application via the implemented step for the system “hospital drug circuit”. The result is then presented as a formal framework for system modelling and risk analysis. This research task falls under a systemic and multi-field step by the means of a direct collaboration between Nice University Hospital pharmacies and the engineering and computer science research laboratory (LGI2P) of l'Ecole des Mines d'Alès from the conceptual development to the application development.