Abstract: Objective To analyze the correlation between the expression of breast cancer resistance protein (BCRP) and effi cacy of neoadjuvant chemotherapy. Methods BCRP expression in 84 patients of primary breast cancer were investigated by MaxVisionTM one step before chemotherapy. Then the efficacy of neoadjuvant chemotherapy and pathological changes of post-chemotherapy surgical specimens was compared. The correlation between the expression of BCRP and efficacy of neoadjuvant chemotherapy was analyzed. Results (1)The positive expression rate of BCRP was 71.43% in patients with primary breast cancer. (2) BCRP expression was associated with the clinical effi cacy of neoadjuvant chemotherapy. BCRP level in patients with acquired cCR after neoadjuvant chemotherapy was lower than that in SD+PD group and cPR group. BCRP expression between the three groups were signifi cantly different (χ2=9.779,P=0.008). (3)BCRP expression was associated with the pathological response after neoadjuvant chemotherapy. BCRP expression in group of major histological response(grade of 4-5) was signifi cantly lower than that in group of non major histological response (grade of 1-3)(χ2=8.649,P=0.003). (4)There was signifi cant positive relevance between BCRP expression and the number of axillary lymph node metastases( r =0.518, P=0.000). Conclusion BCRP expression in primary breast carcinoma tissue could predict the clinical effi cacy of neoadjuvant chemotherapy and histology effects. There is signifi cantly positive relevance between the expression of BCRP and the number of axillary lymph node metastases. BCRP could be index for effi cacy and prognosis judgement after neoadjuvant chemotherapy.