Abstract: Objective To evaluate the expression of CD44^＋/CD24^－/low and the relationship between CD44^＋/CD24^－/low and the response to anthracyclines-based chemotherapy in patients with breast cancer. Methods A total of 91 patients with breast cancer were treated with anthracycline-based neoadjuvant chemotherapy,and the clinical response to the chemotherapy was obtained after 2 to 4 cycles.Double-staining immunohistochemistry was used to detect the expression of CD44^＋/CD24^－/low in paraffin-embedded tissues of pre-chemotherapy and post-chemotherapy.Data was analyzed via t test and Chi-square test. Results The expression rate of CD44^＋/CD24^－/low phenotype was 39.6%(36/91).The proportions of CD44⁺/CD24^-/lowcells were significantly increased after anthracyclines-based chemotherapy (P=0.028).The positive rate of ER in CD44^+/CD24^-/low positive group was lower than that in CD44⁺/CD24 ^-/low negative group(25.0% vs.47.3%,P=0.033).And the expression rate of CD44^＋/CD24^－/low phenotype in triple negative breast cancer was higher than that in non-triple negative breast cancer(61.9% vs. 32.9%,P=0.017).There was no significant correlation between CD44⁺/CD24^-/low phenotype and the other clinicopathological parameters,such as age,tumor size,TNM classification,pathological type,histological grade and so on(P>0.05).The overall response of CD44⁺/CD24^-/lowpositive group was higher but had no difference compared with CD44⁺/CD24^-/low negative group (75% vs.69.1%,P=0.542),and the rate of pathological complete remission (pCR) in CD44+/CD24-/lowpositive group was higher than that in CD44+/CD24^-/lownegative group (38.9% vs.18.2%,P=0.028). Conclusion CD44⁺/CD24^-/low cells are demonstrated in certain breast cancer,CD44^＋/CD24^－/low phenotype is associated with triple negative breast cancer and the responsiveness of breast cancer to anthracycline-based chemotherapy.CD44^＋/CD24 ^－/low phenotype may be used as one of the indicators to evaluate the clinical chemotherapeutic response of the patients with breast cancer.