The results of many studies suggested possible relationship between polymorphism at codons 16 and 27 and development of tolerance to beta-2 adrenoceptor agonist responses as well as disease severity in asthmatic patients. This study was designed to evaluate the effect of polymorphism of beta2 adrenoceptors on response to salmeterol and fluticasone (as inhaled Seretide).Sixty-four patients with either mild or moderate-severe asthma were evaluated in this study. A four-week therapy with Seretide was conducted in moderate-severe asthmatics. The respiratory parameters and asthma score (based on GINA guidelines) were measured before and after run in period. Blood samples were genotyped at codons 16 and 27.No significant difference was observed in genotypes neither at codon 16 nor at codon 27 between mild and moderate-severe asthma groups. However, Patients in Arg/Arg (n = 8) category showed significant improvement in asthma control parameters and lung function compared with Arg/Gly genotype (n =20).These results suggest that genotyping may be useful in some asthmatic patients in order to better tailor asthma treatment plan.