We studied first the long term results in a series of 1 139 immediately operable breast cancers, treated by a protocol which gave an important role to extended radical mastectomy (radical mastectomy with internal mammary node dissection). No difference in survival was noted according to the surgical procedure used, and the extended mastectomy does not seem to have demonstrated its superiority. Its value could be judged in a more rigorous manner thanks to the results of an international therapeutic trial, comparing radical mastectomy with extended radical mastectomy. Results were improved by the extended procedure in only one sub-group of patients, whose tumours was located in central or inner quadrants, T1 or T2, with positive axillary nodes: these patients represents 13 per cent of patients with immediately operable tumors. Taking these results into account a new protocol has been adopted at the Institut Gustave-Roussy: T1 cancers will be the object of a therapeutic trial between conservative treatment and modified radical mastectomy. T2 (internal or central) cancers, with axillary nodal involvement will be treated by extended radical mastectomy. T2 tumors (external) and all T3 tumors will be treated by a modified radical mastectomy.