The comple protocol for the treatment of breast cancer at the Institute Gulslave Rousssy, Villejutit, France, is presented. Treatment is carried out by a multidisciplinary committee dealing with nearly one thousand new breast cancer annually. The protocol is based on initial classification by the T.N. M. system and by characteristics indicating “aggressive biological behaviour”. Patients are seprated into three broad groups for which the mainstays of treatment are surgery, radiotherpy, and chemotherapy. The retionals and results of the protocol are presented.