Abstract : Best practice recommendations, stemming from evidence based medicine, are part of a well versed process aiming to claim medical legitimacy based on science and are used as policy tools in practice. How do they relate to professional values, and to the practice of medicine?This question is examined within the framework of recommendations regarding the treatment, control and prevention of arterial hypertension (AH) in general practice which can be said to exemplify the construction of a public health risk.The first part of this work is centred on the origins of evidence based medicine, and the way in which it brings continuity as well as change to the relationships between: medical professionals; the institution of medicine and the state; doctors and patients.The second part, a microsociological study of GP consultations with hypertensive patients, shows that recommendations are used to reinforce the doctor's efforts to increase patients' awareness of AH and the ensuing cardiovascular risks. However, GPs use their influence over a long time period and, influenced by their patients, they negotiate, compromise and even disregard some of the best practice recommendations, considering that what may not be achievable in the present, may be achievable in the long term. Recommendations are therefore used in practice in hybrid form, where science is merged with an adaptation to each unique situation. The 'average patient' as the basic unit of evidence based medicine is opposed with the social reality of an individual with a certain level of autonomy and resources whose trust the doctor needs to gain and maintain.