Polymorphisms in the ADRB2 gene (especially Gly16Arg) have been reported to affect not only the long-term response to ADRB2 agonists but also the risk of asthma in relation to active and passive smoking, and we specifically selected ADRB2 in this study based on previous interaction effects (Israel et al. 2004; Wang et al. 2001; Zhang et al. 2007). This evidence concerns the gene ADRB2 and asthma.