There are still uncertainties as to the mechanism of many pathological conditions, among them allergic diseases. It has been suggest that acetylation rate may be a factor that influences the development of allergic diseases. The aim of the present study was to investigate further whether the genetic polymorphism of the NAT2 plays a role in susceptibility to bronchial asthma disease. Ninety-seven patients with bronchial asthma (atopic n= 62; non-atopic n= 35) and 104 healthy individuals were participated in this study. DNA was extracted from the leucocyte by high pure template preparation kit. NAT2*5A, NAT2*6A, NAT2*7A/B and NAT2*14A polymorphisms of NAT2 were detected by using LightCycler-NAT2 mutation detection kit by real time PCR with LightCycler instrument. We found that mutant NAT2*5A (OR= 3.84, 95% CI= 1.08-13.6) and NAT2*6A (OR= 5.27, 95% CI= 1.06-26.05) genotype could be associated with a high risk for the development of bronchial asthma according to the genotype. After grouping phenotype, the risk for bronchial asthma was more than two times higher (OR= 2.7, 95% CI= 1.07-6.97) in individuals with the slow NAT2*5A acetylator phenotype compared to the fast phenotype. Our study suggests that the NAT2 slow acetylators may be a determinant in susceptibility to asthma disease. This finding may have implications for the theories for the pathogenesis of the disease as well as for therapeutic aspects.