Objective To observe the expression of breast cancer resistance protein(BCRP) gene in breast cancer patients,and to explore its value in evaluating the therapeutic effect of chemotherapy for breast cancer.Methods Semi-quantitative reverse-transcription polymerase chain reaction(RT-PCR) was applied for the detection of mammary BCRP gene expression level in 60 female breast cancer patients who have received chemical therapeutic regimen of CEF(cyclophosphamide,epirubicin and 5-fluorouracil).The patients were divided into two groups according to the BCRP gene expression before CEF therapy.After treatment,the therapeutic effect in the two groups was observed and the BCRP gene expression level was also measured.Results In 17(17/60,28.3%) patients with positive BCRP gene expression,11 were relieved,with a relief rate of 64.7%,lower than 93.0% in patients with negative BCRP gene expression(P