PURPOSE: Medical practices in oncology are expected to be multidisciplinary, yet few articles studied how this may be concretely applied. In the present study, we evaluated the organization of two multidisciplinary committees, one for breast cancer and one for sarcoma, in a French Comprehensive Cancer Centre. METHODS: Both tumours were specifically chosen so as to emphasise substantial differences in relation with incidence, histological subtypes, management strategy, and scientific evidence. Between 2003 and 2004, 404 decision processes were observed, 210 for sarcoma (26 meetings) and 194 for breast cancer (10 meetings). The number of physicians who took part in the discussions and their medical specialties were systematically noted as well as the number of contradictory discussions, medical specialties represented in these contradictory discussions and the topics of contradiction. The last measured data was whether the final committee's decision was in conformity with the referent preferences or not. All these measures were related to the referent's medical speciality and working place, to the stage of the disease and to the disease management stage. RESULTS: Committees' specificities concerned their organization, referent's medical specialties, the number of participants in discussions and their medical specialties. Discussions in the sarcoma committee tended to be more multidisciplinary, involving more specialties. Initial strategy proposal for one patient was modified during the discussions for 86 patients out of 210 (41%) and for 62 out of 194 (32%) respectively for sarcoma and breast cancer. However, there was no significant difference in the rate of contradictory discussions between breast cancer and sarcoma committees (32% versus 41% respectively; P = 0.08). The rates of contradictory discussions were similar for localized cancers, local relapse and metastasis disease (37%, 41% and 34% respectively; P = 0.86). CONCLUSIONS: The present study reports more than 30% of changes concerning strategy for patient with cancer due to multidisciplinary discussions. This indicates that, providing tumour committees are adapted to the pathologies' characteristics, they can promote a collective and multidisciplinary approach to oncology.