After a dominant role for more than 30 years, tamoxifen has been progressively replaced by aromatase inhibitors as adjuvant treatment for breast cancer in the menopaused woman. We present here a recall of the mechanisms of action involved together with a review of clinical trials leading to the current situation. Giving trial results in detail, we discuss the current evidence as well as open questions. The populations concerned and trial methodologies are analyzed. Comparative tolerance is detailed. Several questions remain open, either due to the lack of evidence to be obtained from ongoing trials or sufficient follow-up. The evidence presented is commented in light of the American (ASCO) and European (Saint-Gallen) or French (Saint-Paul) guidelines.