Abstract: Objective: To evaluate the clinical value of the expression of multidrug resistance （MDR） P-glycoprotein (P₁₇₀ in patients with acute leukaemia. Methods: 104 specimens were analyzed from 86 patients with acute leukaemia by using monoclonal JSB 1 with immunocytochemical staining technique of alkline phosphatase anti alkaline phosphatase（APAAP）. Results: That P₁₇₀-positive cases were 76.9% （10/13） in refractory group, 40.9% （9/22） in relapse group, 27% （10/37） in fresh case group and 18.8% （6/32） in complete remission group, respectvely. The lst induction remission rate （CR） was 81.5%（22/27） in P₁₇₀-negative cases and 40% （4/10） in P₁₇₀-positive cases in fresh case group （P ＜0.05）. The second remission rate （CR₂） was 30.8%（4/13） and 11.9%（1/9） in P₁₇₀-negative and P₁₇₀-positive in relapsed patients respectively. the relapse rate was also different in patients with CR of 25% （11/44） in P₁₇₀-negative and 70% （7/10） in P₁₇₀-positive cases （P ＜0.05）. Conclusion: It is suggested that P₁₇₀ expression is significantly associated with the clinical resistance to chemotherapy. The detection of P₁₇₀ may be a useful method of predicting theraputic response and designing treatment protocols drug resistant in leukaemia patients.