PURPOSE: The role and safety of aromatase inhibitors (AIs) in young breast cancer patients with chemotherapy-induced amenorrhea (CIA) has not been established. The goal of this study was to investigate the safety and efficacy of AIs in young breast cancer patients with CIA. METHODS: From December 2000 to December 2006, 58 patients with hormone receptor positive breast cancer under the age of 45 were treated with AIs as adjuvant therapy. All patients had amenorrhea for more than three consecutive months at the time of treatment. We evaluated the rates of recovery of ovarian function during the treatment, and analyzed the association of the recovery of ovarian function with age, body mass index (BMI), chemotherapy regimen, radiation therapy, and the use of tamoxifen. RESULTS: Recovery of ovarian function was observed in 16 patients (27.6%). The univariate analysis showed that ovarian function was more frequently recovered in patients younger than 40 yr of age, treated with chemotherapy regimens other than Cyclophosphamide, Methotrexate, 5-Flurouracil (CMF), without a history of tamoxifen therapy, and with a higher BMI. The multivariate analysis confirmed that the type of chemotherapy (p=0.034) and the history of tamoxifen therapy (p=0.043) were independent factors significantly associated with the restoration of ovarian function. CONCLUSION: The results of this study suggest that AIs should be considered, with caution in young women with CIA; these agents may promote the unwanted recovery of ovarian function. Especially, in those patients who were not treated with CMF chemotherapy or tamoxifen, where the rates of recovery of ovarian function were higher.