The dose intensity of adjuvant chemotherapy for breast cancer is an important predictor of clinical outcome. Dose-dense chemotherapy increases the dose intensity of the regimen by delivering standard-dose chemotherapy with shorter intervals between the treatment cycles. The rationale for dose-dense therapy stems from the Norton-Simon hypothesis: Sequential, consecutive dosing of chemotherapy using single or a combination of agents increases the dose density over alternating dosing, improving results. Supporting adjuvant studies, such as C9741, and the ensuing clinical experience indicate an improved disease-free and overall survival. Dosedense adjuvant chemotherapy improves clinical outcomes without increasing toxicity.