Adjuvant endocrine therapy substantially reduces tumor recurrence and mortality in pre- and post-menopausal women with hormone receptor-positive early breast cancer but is ineffective in women with hormone receptor-negative tumors. Tamoxifen has been the standard adjuvant endocrine therapy for both pre- and post-menopausal women with hormone receptor-positive early breast cancer and remains the standard of care for premenopausal women. In addition to tamoxifen, ovarian ablation by surgery or radiotherapy remains an option for selected premenopausal women and trials are evaluating the role of ovarian function suppression using luteinizing hormone-releasing hormone agonists. For postmenopausal women, aromatase inhibitors are more effective than tamoxifen therapy and aromatase inhibitors and tamoxifen are regarded as standards of care. Prolonging adjuvant endocrine therapy in postmenopausal women by the sequencing of aromatase inhibitors and tamoxifen can improve outcomes further. Adjuvant endocrine therapy will probably be used for longer durations in selected postmenopausal women.