The beta2-adrenergic receptor (beta2AR) is a positional candidate gene for asthma located on 5q31-33. There are 17 known polymorphisms in this gene. A determination of the functional significance of these polymorphisms is complicated by the lack of haplotypic assessment in most functional assays. The beta2AR gene is not an asthma-susceptibility gene but appears to be a minor determinant for lung function. The gene also has clear pharmacogenetic effects. Further work is needed to fully define the effects of haplotype on function, disease phenotype and pharmacogenetic effect.