Objective To investigate the genetic predisposing factor of childhood bronchial asthma through a study of the relation of the children's polymorphisms of vitamin D receptor (VDR) genes and bronchial asthma in Hunan province.Methods There were 71 children of the bronchial asthma group and the same number of normal children of the control group.Their polymorphisms of VDR genes including ApaI and BsmI were detected and compared by the use of polymerase chain reaction - restriction fragments length polymorphism(RFLP).The level of vitamin D and interleukin 4 and 12 were detected through enzyme-linked immunoassay. Results There were both statistical differences in the polymorphism of ApaI gene and the frequency of distribution of its allele between two groups (P<0.05),while the difference of them of BsmI gene was no significance (P>0.05);Comparing with the control group,the average levels of serum 25(OH)D₃ and interleukin 12 were significant lower while interleukin 4 was significant higher (P<0.05).Conclusion s Childhood bronchial asthma is correlated with the polymorphisms of VDR-ApaI,but it has no relation to the VDR-BsmI.The VDR-ApaI may be a genetic susceptibility gene.As an immune regulator,vitamin D is closely associated with the occurrence and development of childhood bronchial asthma,increasing the intake of vitamin D perhaps could reduce the incidence of asthma in a certain extent.