Abstract: Objective: To explore the effect of cyclosporin A(CsA) in reversing multidrug resistance(MDR) in patients with acute leukemia(AL).Methods: Twenty-eight cases of acute leukemia were randomly divided into therapeutic group(CsA plus chemotherapy) and control group(chemotherapy alone).The expression of P-glycoprotein(P-gp) was assayed in 16 cases of the therapeutic group.Results: The total effective rate was 68.8% and the complete remission(CR) rate of the patients receiving repetition treatment was(7/10) in the therapeutic group,while the total effective rate was 25.0% and the CR rate of the patients receiving repetition treatment was 1/8 in the control group.The difference was significant(P<0.05).Conclusions: The CsA combined with chemotherapy may reverse MDR in patients with acute leukemia.With the rise of the positive expressing rate of P-gp of the leukemia cells,CsA's reverse effect on MDR is more obvious.