Multidrug resistance (MDR) is widely thought to be a major cause of the failure in cancer chemotherapy. The detection of MDR marker is therefore valuabe in studying the mechanisms of MDR and to predict response to chemotherapy in patient with carcinoma. Previous studies have examined MDR marker in gastric cancer, but the major part of the investigation in patients have focused on a single parameter. The purposes of this study were to detect the expression of glutathione S transferase pi(GST ?), multidrug resistance associated protein(MRP), lung resistance protein(LRP) and multidrug resistance gen 1 (MDR1) in the patients with primary gastric cancer, who had not received prior chemotherapy, and evaluate the correlation between GST ?, MRP, LRP and MDR1. The expression of GST ?, MRP, LRP and MDR1 mRNA in carcinoma tissue and the adjacent non cancerous tissue from 50 patients was examined by semiquantitative reverse transcription polymerase chain reaction (RT PCR). The positive rate of GST ? mRNA, MRP mRNA, LRP mRNA and MDR1 mRNA in gastric cancer tissue were 36.00%, 12.00%, 10.00%, and 10.00% respectively. Their expression in gastric cancer tissue was significantly higher than that in the adjacent non cancerous tissue. The overall positive rate of their expression in gastric tissue was 48.00%. The results indicated that GST ? mRNA, MRP mRNA, LRP mRNA and MDR1 mRNA are overexpressed in various degrees and no co expression exists among the studied genes in gastric cancer,and perhaps intrinsic MDR exists in 46% patients with primary gastric cancer .