The modern era of neoadjuvant endocrine therapy was developed with tamoxifen in the 1980s. Trials showed useful downstaging to avoid mastectomy, but long term results showed that this could be used before but not instead of surgery. Recently neoadjuvant aromatase inhibitors have been shown to be superior to tamoxifen. Letrozole was significantly superior in terms of clinical response (55% vs. 36%) and breast conservation (45% vs. 35%). Neoadjuvant anastrozole has also been shown to be significantly superior in terms of breast conservation in the combined results from 2 trials, IMPACT and PROACT (43% vs. 31%) although a significant reduction in clinical response was not seen in the IMPACT trial. Both aromatase inhibitors have a particular gain over tamoxifen in tumours which over-express HER2. Data have emerged from the IMPACT trial suggesting that the changes in short term biological parameters such as Ki67 may predict for long term outcome in major adjuvant trials.