Abstract: Objective : To evaluated the expression of multidrug resistant proteins in nasal NK/T cell lymphomas. It may be helpful to detect multidrug resistant proteins for clinicians mak-ing decision when chemotherapy chosen. Methods : Five kinds of multidrug resistant proteins were examined by immunohistochemistry which were glutathions-transferase (GST-π), Topoisomerase Ⅱ (Topo Ⅱ), multidrug resistance (MRP), lung-resistance-related protein (LRP) and Pglycoprotein (P-170). Results : Expression of multidrug resistant proteins was studied in 68 cases of NK/T cell lymphomas, the tumor cells were positive for GST-π in 33/68(48.35%); TopoⅡ, 44/68(64.71%); LRP, 14/68 (20.59%) and negative for both P-170 and MRP. For GST-π positive cases, 16 (23.53%) of them were strongly positive; 17 (25.00%) were positive. For LRP positive cases, 3 (4.41%) of them were strongly positive, 11(16.18%) positive. Among the TopoⅡ positive cases, 24 (35.29%) of them were grade I, 25 (36.76%) gradeⅡ,12(19.12%) grade Ⅲ and 7(10.29%) were grade %. There were no significant difference between the expression of GST-π, TopoⅡ and LRP by statistic analysis. Conclusion : P-170 protein and MRP may have common modulation factors and have no effect for drug resistance on nasal NK/T cell lymphomas. On the other hand, GST-π, Topo Ⅱ and LRP may play an important role in the effect of chemotherapy in nasal NK/T cell lymphoma. It may be helpful to detect multidrug resistance proteins for clinicians making decision when chemotherapy chosen.