For women with steroid receptor-positive breast cancers, endocrine therapy has proven to be a major component of adjuvant therapy reducing the risk of recurrence and death. The selective estrogen-receptor modulator (SERM) tamoxifen has been well established as safe and effective in the adjuvant care of both pre- and postmenopausal women. For premenopausal women, ovarian suppression is an important option to be considered. Additionally, aromatase inhibitors have recently demonstrated further benefits in postmenopausal women. The ideal sequencing of treatment with tamoxifen and/or an aromatase inhibitor is the subject of several ongoing studies.