Breast cancer is common, affecting one in nine women worldwide. As stipulated by the St Gallen consensus guidelines, hormone therapy is an integral part of treatment for hormone-responsive disease. Previously, this has been with tamoxifen; however, as a result of a number of recent studies, aromatase inhibitors are now competing for use as first-line agents. In addition, there is as yet no firm consensus as to when and how these drugs should be used within the adjuvant setting. This article reviews the use of aromatase inhibitors in early stage hormone-positive breast cancer. It describes the evidence from the studies involving the aromatase inhibitors in an upfront, switch and extended setting. It further discusses the mathematical models proposed to determine the optimum timing of initiation. In light of the ongoing research into predictive biomarkers, this review then concentrates on whether future focus should be on more individualized treatment strategies than the optimum timing of aromatase inhibitors.