Backgrounds : Glutathione-s-transferase (GST) is a kind of phase II metabolism enzyme and plays an important role in the detoxification of various toxic chemicals. It was reported that the genetic polymorphism of GSTM1 and GSTT1 genes may be responsible for asthma development and susceptibility to allergy. Traditional oriental medicine uses a unique diagnostic technique. differentiation-syndrome. to analyze signs and symptoms of patients synthetically. Through differentiation-syndrome. asthma patients can be divided into two groups: the deficiency syndrome group (DSG) and the excess syndrome group (ESG). Objectives : The purpose of this study was to investigate the possible association of GST gene polymorphism with clinical phenotype by differentiation-syndrome of bronchial asthma patients. Materials and Methods : One hundred and ten participants were evaluated by pulmonary function test. Patients with 53 DSG and 31 ESG by differentiation-syndrome were assessed for genetic analysis. GSTM1 and GSTT1 deletion polymorphism was performed by polymerase chain reaction (PCR). Results : GSTM1 gene deletion was detected in 43.4% of individuals in the DSG and in 38.71 % in the ESG. The distribution of GSTM1 polymorphism between DSG and ESG was not significantly different [$x^2$=0.1767, p=0.6742; OR(95% CI)=1.2139(0.4915-2.9979)]. The proportion of GSTT1 null genotypes was 41.51% in the DGS and 45.16% in the ESG. The distribution of GSTT1 polymorphism between DSG and ESG was also not significantly different [$x^2$=0.1065, p=0.7442; OR(95% CI)=0.8618(0.3525-2.1065)]. In the combined analysis of GSTM1 and GSTT1 genes, the frequency of both null type of GSTM1/GSTT1 genes was not significantly different from both positive type of GSTM1/GSTT1 genes[$x^2$=0.0768, p=0.7817; OR(95% CI)=1.2000(0.3303-4.3602)] Conclusions : These results indicate that polymorphism of the GST gene might not be associated with the symptomatic classification of DSG and ESG by differentiation-syndrome in Korean asthmatics.