Objective.In this study

we investigated the hypothesis that tumor necrosis factor（TNF）α-308gene polymorphism might be of the genetic predisposition to asthma and asthma phenotypes.Methods.TNFα-308gene polymorphism was genotyped in221random unrelated Northern Chinese population（comprising125asthmatics and96healthy controls）and52individuals from12asthmatic families with Han ethnic by using polymerase chain reaction（PCR）-restriction fragment length polymor-phism（RFLP）.Methacholine（Mch）broncho-challenge test

bronchial reversibility test and lung function were underwent in all asthmatics.Results.TNFα-3082homozygosity was present at a significantly higher frequency in asthmatics than that in controls（20.8%vs11.4%

P<0.05

OR2.259）

the TNF allele2was also higher in asthmatics compared with controls（0.42vs0.33

P<0.01）.TNFα-3082homozygosity was an weak independent risk factor for asthma etiology（OR0.226

P<0.05）.Moreover

patients carrying TNFα-3082homozy-gosity had less responsive to inhaledβ 2 -agonist in20minutes than patients carrying other two genotypes（24.1%vs29.5%vs38.8%

P<0.05）.Linkage analysis didn’t support that TNFαgene was linked to asthma （Likelihood of odds

LOD<1）based on familial data.Conclusion These results suggest that TNFα-3082homozygosity may be of a component contribut-ing to the genetic predisposition to asthma

and airway responsiveness toβ2 -agonist.