Treatment options for patients with breast cancer have progressively improved over the past 40 years, from an era of no chemotherapy to the introduction of taxanes, hormonal therapy, and biologic therapy. These advances have resulted in substantial, 15%-20% improvements in clinical outcomes. However, progress has yet to be made to improve the prognosis in many breast cancer patients, and research is currently under way to test new tools, or new applications of older tools, to advance breast cancer management. Chemotherapy clearly remains a cornerstone of adjuvant breast cancer treatment, because breast cancer can be very sensitive to the currently available agents. Meanwhile, the era of a one-size-fits-all approach to breast cancer management is over, and the maximum potential of chemotherapy should now be reached by targeting specific populations. Effective biomarkers are therefore needed to optimize chemotherapy, define more selective populations, and clearly tailor treatment. This paper discusses recent data, including new trials that are more fully incorporating current knowledge with respect to molecular markers and the underlying biology of breast cancer.