Multidisciplinary meeting (MDM) in oncology has been institutionalised in France by the Cancer Plan. This study aims to determine the place of MDM in the decision process. From November 2004 to July 2005, we observed 29 meetings at the Tours Hospital and 324 case presentations, 80 in orthopaedics, 151 in gastroenterology and 93 in chest medicine. Forty physicians attending the meetings answered a questionnaire exploring their opinions on MDM and the collegial decision. We found that MDM is mostly the place for technical discussions and that patients' wishes are rarely addressed. The different medical specialities are well represented but we observed that only physicians attend MDM. Decisions for straightforward cases are rapidly validated. For more complex clinical situations (25 to 40% of case presentations), the multidisciplinary approach allows to adapt guidelines or to choose alternative treatments. All the physicians interviewed express that MDM legitimates the medical decision. It occurs that they disagree with the RCP decision. We discuss how MDM impacts on the medical decision as well as the shift from the individual decision to the collective one, particularly in term of responsibility.