Résumé : The EORTC Breast Cancer Group (EBCG) is a multidisciplinary international group created in 1962 in conjunction with the EORTC. This group has always focused its activities on the development of new cancer treatments and strategies for all categories of breast cancer. It has been active both in drug development, as well as in the development of new radiotherapy and surgical techniques to attempt to improve cure rates and loco-regional control. Over 40 years, the EBCG has performed dozens of clinical studies including several thousands of patients. Many of these studies have contributed to the clinical knowledge on the treatment of breast cancer and have influenced the standard management of this tumour. Beside its clinical research activities, the Group has also been very active in developing guidelines for breast cancer research, promoting high standards of care in conferences, as well as in fellowships and quality assurance programmes. EBCG is a founding member of the Breast InterGroup (BIG).