Preoperative therapy allows for a higher rate of breast conserving surgery and has been shown equivalent to adjuvant therapy. Preoperative therapy provides an opportunity to obtain insights into breast cancer biology and to accelerate the evaluation of new therapies. Clinical trials have shown that women who achieve a pathologic complete response (pCR) have substantially improved outcomes compared with those who do not achieve a pCR. The U.S. Food and Drug Administration (FDA) meta-analysis demonstrated that the association of pCR and long-term outcomes is greater in women with aggressive breast cancer subtypes. In patients with HER2+ breast cancer, the addition of trastuzumab to chemotherapy in the neoadjuvant setting has doubled pCR and correlated with improved outcomes. Clinical trials will evaluate tailoring the use of radiation therapy in patients who have received neoadjuvant therapy. Trials have established neoadjuvant endocrine therapy as a valid treatment and research option for ER-rich breast cancer. The neoadjuvant setting allows for evaluation of endocrine therapies in combination with newer targeted therapies in the appropriate patient populations. The neoadjuvant setting provides opportunity to accelerate the evaluation of new agents, improve pCR rates, and identify predictive biomarkers for response. This setting provides the opportunity for screening new agents in combination with chemotherapy while obtaining serial biopsies to understand biology of response and resistance. Although current standard therapies provide substantial benefits for patients with a pCR, patients with residual disease are at substantial risk for disease recurrence. New agents are being evaluated in patients with high-risk residual disease following standard treatment regimens.