The primary goal of systemic adjuvant therapy for breast cancer is to control the risk of local and distant tumor recurrence and thus improve long-term survival. Tamoxifen has been the standard adjuvant endocrine therapy for pre- and postmenopausal women with hormone receptor-positive breast cancer. In estrogen receptor-positive disease, 5 years of tamoxifen reduces the annual breast cancer death rate by 34% irrespective of the use of chemotherapy, age, or other tumor characteristics. Aromatase inhibitors (AIs) can further improve disease-free survival, reducing distant metastases and, in some cases, extending overall survival. Anastrozole and letrozole are approved as upfront adjuvant treatment, anastrozole and exemestane are approved for use in switching strategies after 2-3 years of tamoxifen, and letrozole is approved as extended therapy following the completion of 5 years of standard adjuvant tamoxifen. Choosing the most appropriate adjuvant AI treatment strategy can be a challenge. Original publications and treatment guidelines can help physicians select the optimal adjuvant treatment for individual patients, according to their risk profile.