The article analyses the existing gap between the formal dimension of evidence-based medicine (EBM), as constituted by protocols, procedures, and guidelines, and actual professional practices in relation to a specific issue: the admission of patients to an intensive care unit (ICU). The results of a case study, carried out in the ICU of a hospital in the north of Italy between 2006 and 2007 are reported. The study was performed using ethnographic methods: participant observation, ethnographic interviews, and semi-structured interviews. Empirical data have been analysed using a grounded theory approach. The results show how three dimensions (macrosocial, organisational-interactional, and individual) become intertwined with the operational guidelines that have been drafted on the basis of international evidence. The standardisation process that the guidelines presuppose results in the adoption of a variety of different local styles with respect to the approach that individual doctors take in relation to the admission of a patient to an ICU. These styles can range from strict adherence to the international criteria to a greater compliance with medical–legal, organisational, and individual needs. Furthermore, the results of the study demonstrate how relational knowledge, as a form of situated knowledge, can allow the personnel involved to activate local resources (organisational, professional, and personal) in order to incorporate the formal prescriptions of EBM in professional practice. URN: http://nbn-resolving.de/urn:nbn:de:0114-fqs1502261