Abstract: Objective : To evaluate expression of multidrug resistance gene (MDR1) and multidrug-resistance related protein (MRP) gene in non-small cell lung cancer and their involvment in multidrug -resistance. Methods : Expression of MDR1 and MRP gene mRNA in paraffin -embedded cancer tissues from 113 non-small cell lung cancer patients was determined by in situ hybridization. Results : The positive expression of MDR1 and MRP were observed in 58 (51.3%) cases and 91(80.5%) cases of non-small cell lung cancer respectively. The expression of MDR1 and MRP was not related to histological subtypes, cell differentiation, TNM staging and lymphatic metastasis (P>0.05).The positive expression of both MDR1 and MRP was observed in 55 (48.8%) cases. And there is a significant correlation between expression of MDR1 and MRP in NSCLC (P<0.01). Conclusions : Both of MDR1 and M R P play significant roles in intrinsic multidrug resistance of non-small cell lung cancer. It is important to detect MDR1 and MRP gene expression in directing chemotherapy of lung carcinoma.