With a worrying accidentology (ten fatal accidents per year for approximately 1700 professionals in France), a culture that promotes a high level of performance and a profession based on the crafttype approach, the practice of mountaineering with a guide can be considered as an unsafe system (Amalberti et al., 2005; Morel et al., 2009). This practice has two particular characteristics. Firstly, it is currently undergoing a deep transformation not only in terms of its environmental context (with global warming), but also because of the media, legal and regulatory pressure that weakens the sustainability of the profession, due to low safety standards. Secondly, it belongs to the service situations. The client is present and involved in the production phases (Falzon and Cerf, 2005): they may be a novice or more experienced and may themself be a victim of accidents. For instance, fifteen clients died in 2018 in France. If, for the guide, clients are a variable to be monitored in a dynamic situation (Hoc, 2001), they are also participants, with their own goals, in the interactive process of the service relationship (Falzon and Cerf, 2005). This service situation, where a professional applies specific skills to provide the service requested by the client, should be distinguished from situations of cooperation between two operators (Falzon and Cerf, 2005; Flageul-Caroly, 2001). According to these elements, this study examines the way the guides build safety with their clients, in a hazardous, dynamic environment and in this particular socioprofessional context.