Aromatase is an enzyme complex which is assigned in the last step of estrogen biosynthesis; it increases total estrogen levels by converting androgens to estrogens in tissues like breast, ovary, testis, placenta, brain and adipose. Estrogen causes increased proliferation of tumor cells. It has been shown that the increased expression of aromatase is responsible for high estrogen levels in breast cancer. Therefore, in the treatment, aromatase inhibitors are being tested. The purpose of this study is to demonstrate the effects of aromatase inhibitors on breast health by their mechanisms, to compare their effectiveness according to the other agents in the treatment of breast cancer. For this purpose, literature findings about this subject were summarized. In addition, the resistance mechanisms that can develop against the therapy and the ongoing studies about new treatment strategies for preventing the development of reseistance were also mentioned. As a result, it was understood that the reduction of estrogen synthesis via aromatase inhibition provide greater therapeutic benefits with fewer side effects. Nowadays, aromatase inhibitors are the best option especially for the treatment of postmenopausal women's breast cancer.