Background\ud The National Epirubicin Adjuvant Trial (NEAT) and the BR9601 trial examined the efficacy of anthracyclines in the adjuvant treatment of early breast cancer.\ud \ud Methods\ud In NEAT, we compared four cycles of epirubicin followed by four cycles of cyclophosphamide, methotrexate, and fluorouracil (CMF) with six cycles of CMF alone. In the BR9601 trial, we compared four cycles of epirubicin followed by four cycles of CMF, with eight cycles of CMF alone every 3 weeks. The primary end points were relapsefree\ud and overall survival. The secondary end points were adverse effects, dose intensity, and quality of life.\ud \ud Results\ud The two trials included 2391 women with early breast cancer; the median follow-up was 48 months. Relapse-free and overall survival rates were significantly higher in the epirubicin–CMF groups than in the CMF-alone groups (2-year relapse-free survival, 91% vs. 85%; 5-year relapse-free survival, 76% vs. 69%; 2-year overall survival, 95% vs. 92%; 5-year overall survival, 82% vs. 75%; P<0.001 by the log-rank test for all comparisons). Hazard ratios for relapse (or death without relapse) (0.69; 95% confidence interval [CI], 0.58 to 0.82; P<0.001) and death from any cause (0.67; 95% CI, 0.55 to\ud 0.82; P<0.001) favored epirubicin plus CMF over CMF alone. Independent prognostic factors were nodal status, tumor grade, tumor size, and estrogen-receptor status (P<0.001 for all four factors) and the presence or absence of vascular or lymphatic\ud invasion (P = 0.01). These factors did not significantly interact with the effect of epirubicin plus CMF. The overall incidence of adverse effects was significantly higher with epirubicin plus CMF than with CMF alone but did not significantly affect the delivered-dose intensity or the quality of life.\ud \ud Conclusions\ud Epirubicin plus CMF is superior to CMF alone as adjuvant treatment for early breast cancer.\ud (ClinicalTrials.gov number, NCT00003577.