Breast cancer is one of the most common malignancies of lethal potential for women in the developed world. Over the past two decades, we have witnessed dramatic advances in the treatment of breast cancer. The golden age of adjuvant systemic therapy for breast cancer began in early 1970s. The early results of the initial clinical trials raised both hopes and innumerable controversies. More importantly, they stimulated many physicians to set up further prospective trials to confirm or rule out the validity of different hypotheses. The initial adjuvant therapy trials used chemotherapy to treat women with lymph node positive cancer. These trials clearly demonstrated a disease-free and overall survival benefit for women receiving combination chemotherapy in the adjuvant setting. These benefits were subsequently extended to women with lymph node negative disease and to women with steroid receptor positive breast cancer. More than 100 randomized clinical trials of breast cancer adjuvant therapy have now been completed. Many of these studies have had more than 20 years of patients follow-up, and firm conclusion can be drawn about the value of treatment in different patients subsets. Although many questions remain to be answered regarding the dose intensity of chemotherapy, the appropriate sequencing of chemotherapy agents, and the use of novel chemotherapy agents such as taxanes, sufficient information is available to conclude that appropriately administered adjuvant treatment does improve survival of patients with early-stage disease.