A 1:1 matched population-based case-control study was conducted in Xuanwei City, Yunnan Province, where the lung cancer mortality is among China's highest. In this study there were 86 newly diagnosed lung cancer cases and 86 matched control subjects with the same sex, fuel type used, and age(+/- 2 years). Buccal cells were collected from each subject to determine the genotypes of GSTM1 and GSTT1. It was found that the rate of GSTM1 null genotype was higher in the case group than in the control group, and its odds ratio was 2.39(95% CI: 1.25-4.56). The odds ratio became 2.62(95% CI: 1.33-5.15) when other possible confounding factors such as smoking, COPD, and the lifetime exposure to unvented fuel combustion (tons) were adjusted. No association was found between GSTT1 null genotype and lung cancer. The rate of GSTM1 null genotype in Xuanwei City was found to be similar to those of other Chinese populations.