PURPOSE To compare the clinical and pathologic response rates of doxorubicin and cyclophosphamide (AC) with doxorubicin and docetaxel (AD) as primary chemotherapy in women with primary or locally advanced breast cancer. PATIENTS AND METHODS Eligible patients with histologically proven breast cancer with primary tumors >/= 3 cm, inflammatory or locally advanced disease, and no evidence of metastases were randomly assigned to receive a maximum of six cycles of either doxorubicin (60 mg/m(2)) plus cyclophosphamide (600 mg/m(2)) administered intravenously (IV) every 3 weeks or doxorubicin (60 mg/m(2)) plus docetaxel (75 mg/m(2)) IV every 3 weeks, followed by surgery on completion of chemotherapy. Results A total of 363 patients were randomly assigned to AC (n = 180) or AD (n = 183). A complete clinical response was observed in 17% and 20% of patients treated with AC and AD, respectively (P = .42). Overall (complete and partial) clinical response rates for AC and AD were 61% and 70%, respectively (P = .06). There was no significant difference in either the pathologic complete response rates in the breast with AC (24%) and AD (21%; P = .61) or in the number of patients with positive axillary nodes at surgery with AC (61%) and AD (66%; P = .28). At a median follow-up of 32 months, there is no significant difference between the two groups for the number of relapses. CONCLUSION In contrast to the positive results reported for sequential docetaxel after AC as primary chemotherapy of breast cancer, our data do not suggest a benefit for simultaneous AD over AC.