Context: Breast cancer has an incidence of 6% in women under the age of 40 years. The treatment should be evaluated individually, but many patients undergo chemotherapy. Evaluate reproductive aspects is fundamental since early menopause might occur after the treatment leading to an impairment of reproductive capacity. Objective: To evaluate ovarian function of reproductive age patients after breast cancer treatment. Methods: A cross sectional retrospective study, carried out by reviewing medical records from young patients treated at the Breast Center of São Lucas Hospital (HSL/PUCRS), from 2006 to 2015. A group of patients received neoadjuvant or adjuvant chemotherapy, according to medical doctor indication. The results were analyzed according to the distribution of variables and were presented as percentage. Patients: All patients with no more than 40 years diagnosed and treated for breast cancer at HSL/PUCRS Breast Center. Interventions: There were no interventions in this study. Main Outcome Measure: Maintenance or return of menstrual cycles after breast cancer treatment. Results: During the established period, 70 patients were analyzed. A mean age at cancer diagnosis was 34.8 years. Regarding parity, 10 patients were nulliparous. Forty-five percent of the patients received information regarding ovarian function preservation; 37.5% from Mastologist and 7% carried out fertility preservation treatment (80.0% with Goserelin acetate and 20.0% performed ovarian tissue freezing). At the end of follow-up, 70% of the patients maintained or resumed menstrual cycle, and no difference was observed between neoadjuvant and adjuvant chemotherapy groups. It was not found any correlation between amenorrhea with histological tumor type, immunohistochemistry or tumor grade. Conclusion: The study presented that the majority of patients maintained menstrual cycles after cancer treatment, regardless the moment of chemotherapy treatment. It seems that the ovarian function in young women after breast cancer chemotherapy treatment has been recovered, however, it is not known how long it takes for these cycles to be ovulatory and how the ovaries may have been compromised by chemotherapy.