OBJECTIVE:To evaluate the effect of CD44 on drug resistance of breast cancer patients. METHODS:62 breast cancer patients were selected,and the expression of CD44 was detected by immunohistochemical method. Drug resistance was eval-uated by WHO criteria,and the expression of CD44 in breast tissue was observed after observation. RESULTS:There were 48 pa-tients sensitive to CD44 and 14 patients with drug resistance,with statistical significance(P<0.05). After chemotherapy,the ex-pression of CD44 in caner tissue was higher than before chemotherapy,that of patients with drug resistance was higher than pa-tients sensitive to CD44,with statistical significance(P<0.01). CONCLUSIONS:CD44 antigen is closely related to chemothera-py resistance of breast cancer,and high expression of CD44 can be used as an important indicator for breast cancer chemotherapy.