Over the last 25 years, conservative forms of treatment have been used for the locoregional treatment of early breast cancer, stages I and II (< 3 cm in diameter). At present, the same carcinological results are obtained with conservative surgery and radiation therapy as with radical surgery, and the aesthetic and functional results have improved. Several parameters should be taken into account, ie tumour volume, breast volume, multifocal nature and histologic type. A number of questions still remain unanswered namely: what is the most appropriate conservative surgery (quadrantectomy, tumourectomy or local excision)? What is the most appropriate total irradiation dose (50 Gy over 5 weeks: or 45 Gy over 4.5 weeks)? What is the value of radiation boost in patients with negative resection margins? What is the value of radiation boost in patients with a high local risk of recurrence? What is the most appropriate radiation technique for boost in the primary tumour bed (electrons or iridium implants)? Does the external irradiation of regional lymph nodes improve survival rate? Is it possible to extend conservative treatment to a 4-cm diameter tumour? What is the impact of adjuvant systemic chemotherapy and/or hormonotherapy on the risk of isolated breast cancer recurrence?