Abstract : The management of occupational risks is based on its construction put in context, on which elements from political, scientific, social, legal and economical contexts influence.Whether it is formal or informal, it is based, on one hand, on the characteristics of the risks and, on the other hand, on the actors and the inseparability of their knowledge and relationships (Hatchuel). The summoned up knowledge is built during work (real activity of work), or made up out of it (heteronom rule, scientific knowledge ...). Professional relationships have an inflence on the organization and on the forms of construction. Some of them favour the expert contributions and the joint construction of risks, whereas others reduce the recourse to expert evaluation within the firm and tend to develop more often a regulation by the external rule. The work and stakes of the employees constitute the basis of the “ascending” construction. The target risks are concrete and easy to perceive problems, studied from the activity of work. The external prescription (knowledge or rule) constitutes the foundation of the “descending” construction, which the target risks are the hardest to perceive and /or the ones that have an external prescription, or strong “constituted” knowledge, like radioactivity, fire, carcinogenic products... The third system “combines” the ascending and the descending. It requires a joint regulation / construction (Reynaud). The target risks are the ones for which a construction in context is necessary, whether because of the lack of a prescription or because of the necessity of considering the activity, like the accidents with exposure to blood and the mental charge. The CHSCT constitutes a regulating subgroup of the construction. Whatever the way of construction, the quality of the regulation determines the quality of the organized actions which are essential to the learning of the risk management.