Neoadjuvant chemotherapy is increasingly used in the treatment of patients with large tumor and locally advanced breast cancer. We evaluated the efficacy of FEC50 (5- fluorouracil 500 mg/m², epirubicin 50 mg/m², cyclophosphamide 500 mg/m²) and FEC100 (same regimen except with epirubicin 100 mg/m²) chemotherapy regimen in neoadjuvant setting. Fifty-one eligible patients with stage II-III invasive breast carcinoma were retrospectively analyzed. FEC50 group included 25, FEC100 group included 26 patients. Mammographic and ultrasonographic determination of tumor size and nodal status at the initial and preoperative stages were considered to evaluate the efficacy of chemotherapy. Both groups were to receive median 4 (3-4) cycle chemotherapy. Pretreatment features of the patients and tumors were similar in both groups. The response rate was 48% (95% CI, 28.4-67.5) in FEC50, and 57.6% (95% CI, 38.4- 76.5) in FEC100 group. Clinical and pathological complete response rate was 4% (95% CI, 0.0-11.6) in FEC50, and 15.3% (95% CI, 1.4-29.1), 7.6% (95% CI, 0.0-17.7) in FEC100. In this retrospective analysis of our own experience, the response rates observed in FEC50 and FEC100 groups are similar after 4 cycles of neoadjuvant chemotherapy. [Turk J Cancer 2005;35(1):19-25].