BACKGROUND: Smoking and high-risk occupation have been known to be the risk factors of lung cancer. The carcinogen-metabolizing enzymes in human body such as glutathione S-transferase M1, T1 and N-acetyltransferase 1 have also been regarded as risk factors in many cancers, because the activities of those enzymes play a role in metabolizing the carcinogen. A case-control study was conducted to evaluate the genetic polymorphism of GSTM1, T1 and NAT1 in lung carcinogenesis in Korean men. METHODS: The histologically proven lung cancer cases were recruited from Seoul National University Hospital. The patients of more than 40-year-old with the nonmalignant urinary tract diseases were recruited as controls from the same hospitals. The informations of demographical characteristics and smoking were obtained by interview or chart review and the genetic polymorphisms of GSTM1, T1 and NAT1 were determined by PCR-based assay. The statistical analyses were performed by linear logistic regression. RESULTS: The number of case-control was 118 and 150, respectively. The smoking history was significantly higher in the lung cancer patients than the controls. The prevalence of GSTM1 null-type was statistically higher(OR=2.25 ; 95% C I=1.12-4.51) in squamous cell carcinoma than other genotypes, but other histologic types were not. The prevalence of GSTT1 null-type were not statistically higher than other genotypes in all histologic types. The fast acetylator of NAT1 was more prevalent than normal(OR-2.13 ; 95% C I=1.04-4.40) in all lung cancer patients. CONCLUSION: The null-type of GSTM1 and fast acetylator of NAT1 are associated with development of lung cancer in Korean men.