This section considers the treatment options for perimenopausal women with breast cancer. The perimenopause period begins in the so-called stage 2 of menopausal transition (early menopausal transition, where the length of the cycles changes by 7 days or more) and ends after 12 months of amenorrhea. It is characterized by an early increase in follicle-stimulating hormone and is associated with the presence of anovulatory cycles, irregular periods, and loss of menstrual cycles. The recommended treatment is tamoxifen (TAM) with or without ovarian ablation for 2 or 3 years followed by a re-evaluation. TAM should be maintained if the patient is premenopausal and aromatase inhibitors (AI) are recommended once the menopausal status is confirmed. Ovarian suppression is an acceptable adjuvant therapy in those patients with hormone-sensitive tumors. AI should only be used in postmenopausal women or in combination with chemical castration in premenopausal women. This supplement paper includes the key points of roundtable presentations and discussions of hormonal therapy in breast cancer.