Abstract: Objective 　To detect the expression of serum glutathione S-t ransferase-π ( GST-π) level in patients with NSCLC, and to investigate it s clinical significance. Methods 　GST-π levels in serum of 46 patients with NSCLC, 19 patients with benign lung diseases and 60 health subjects were detected with ELISA. Forty-six NSCLC patients were given 2 cycles of NVB + DDP chemotherapy and clinical response was evaluated. Results 　The mean serum GST-π level was significantly higher in patient s with NSCLC than in those with benign lung disease and health subject s ( P < 0. 05) . Twenty-five of 46 patients with NSCLC (54. 34 %) showed elevated serum GST-π levels above a cutoff value of 166. 14 ng/ml (mean +two standard deviations in 60 healthy control subjects) . The positive rate was significantly higher in patients with NSCLC than in those with benign lung disease 36. 84 % and heavy subjects 3. 33 % ( P <0. 05) . The positive rate of serum GST-π were 57. 14 % in squamous cell carcinoma and 52. 00 % in adenocarcinoma ( P > 0. 05) . No correlation was observed between the GST-πlevel and stage, sex, pathohistology. Of the 46 patient s treated with NVB + DDP chemotherapy, 19 patients responded to chemotherapy (overall response rate, 41. 30 %) . For the 25 patients with positive GST-πexpression, 5 patients responded to chemotherapy, response rate was 20 %. In the 21 patient s with negative GST-πexpression, 14 patients responded to chemotherapy, respone rate was 66. 67 %. This difference was statistically significant ( P < 0. 05) . Conclusion 　The serum GST-π level may be a valuable tumor marker for NSCLC, There was no correlation between expression of serum GST-π and stage, sex, pathohistology. The response rate of NSCLC patients with GST-π-negative expression was higher than those with GST-π-positive. GST-2π may be a useful predictor of chemotherapy response.