Breast cancer in young women is increasing. The objective of this work was to analyze the epidemiological, clinical, therapeutic and prognostic characteristics of breast cancer in young women under 40 years. Through a retrospective study spread over five years from 1 January 2008 to 31 December 2012 and held at the Radiation Oncology Service of the University Hospital Mohammed VI Marrakech, we identified 272 cases of breast cancer in patients aged 40 years and under. The frequency of breast cancer in young women under 40 years was 24.42%. The average age was 35.6 years. The pauciparity and nulliparity were predominant (60.6%). 8 % had a family history of breast cancer. The self-examination of a nodule was predominant (93%). Tumors classified T2 were the most frequent (45%), followed by T4 tumors (29%).17% were metastatic immediately with predominant hepatic localizations (37.6%). It was Invasive breast carcinoma no special type (NST) in 82.3% of cases, with a predominance of SBR grades II and III (96%). Hormone receptors were positive in 68% of cases and HER2 overexpressed in 29 % of cases. 218 patients underwent surgery, which was radical in 68% and conservative in 21%. 149 had a locoregional irradiation. 71% received adjuvant chemotherapy with a predominance of FAC60 protocol (35%). Hormonotherapy was prescribed in 78% of cases with positive hormone receptors and trastuzumab in 73.8 % of patients over expressing HER2. After a median follow-up of 8.1 months, 41.4 % had relapses. Overall survival at three years was 70%, and the relapse free survival was 62%. Our study joins the data in the literature advocating more advanced forms and worse prognosis of breast cancer in young patients.