Objective: To investigate the expression of MDR-1 P-glycoprotein(MDR-1 Pgp) in breast cancer and analyze its correlation to the biological behavior and prognosis of the disease. Methods:The expression of MDR-1 Pgp was examined in 75 cases of breast cancer patients by using three different monoclonal antibodies(JSB1, C219 and C494) with S-P immunohistochemisty. These patients were followed up for 5 years, and the correlation between MDR-1 Pgp expression, survival rate and lymph metastasis was analyzed. Results: Positive detection of MDR-1 Pgp by JSB1, C219 and C494 in 75 cases of breast cancer was 86.7%, 48% and 85.3%, respectively. MDR-1 Pgp expression was not related to ages of patients (P > 0.05). JSB1-detected expression of MDR-1 Pgp was related to lymph node metastasis(P < 0.05); while C219 and C494 were not(P > 0.05). The patients with MDR-1 Pgp expression positively detected by either two of the three antibodies, had five-year survival rate that was significantly higher than those positively detected by all the three antibodies(P < 0.05). Conclusion:Three antibodies should be used simultaneously to detect MDR-1 Pgp expression in breast cancer. Positive MDR-1 Pgp expression in breast cancer detected by all the three antibodies may represent a poor prognosis; while positive MDR-1 Pgp detection by JSB1 and C494 is associated with lymph metastasis. Objective: To investigate the expression of MDR-1 P-glycoprotein (MDR-1 Pgp) in breast cancer and analyze its correlation to the biological behavior and prognosis of the disease. Methods: The expression of MDR-1 Pgp was examined in 75 cases of breast cancer patients by using three different monoclonal antibodies (JSB1, C219 and C494) with SP immunohistochemisty. These patients were followed up for 5 years, and the correlation between MDR-1 Pgp expression, survival rate and lymph metastasis was analyzed. Positive detection of MDR-1 Pgp by JSB1, C219 and C494 in 75 cases of breast cancer was 86.7%, 48% and 85.3%, respectively. MDR-1 Pgp expression was not related to ages of patients (P> 0.05). JSB1 While the expression of MDR-1 Pgp was related to lymph node metastasis (P <0.05); while C219 and C494 were not (P> 0.05). The patients with MDR-1 Pgp expression positively detected by either two of the three antibodies, had five-year survival rate that was significantly higher than thos Positive antibodies to the MDR-1 Pgp expression in breast cancer. Positive MDR-1 Pgp expression in breast cancer detected by all the three antibodies may represent a poor prognosis; while positive MDR-1 Pgp detection by JSB1 and C494 is associated with lymph metastasis.