By screening the 1470 bp 5' to the start codon of the human beta2 adrenergic receptor gene, we have identified a total of eight polymorphisms (-20 T-->C, -47 T-->C, -367 T-->C, -468 C-->G, -654 G-->A, -1023 G-->A, -1343 A-->G and -1429 T-->A c.f. beta2 adrenergic receptor start codon). Transient transfection of 5' flanking deletion luciferase reporter constructs demonstrated the majority of activity of the human beta2 adrenergic gene 5' flanking region to be present within a 549 bp fragment immediately upstream from the start codon. Because of linkage disequilibrium, some combinations of polymorphisms were particularly frequent. We transiently transfected COS-7 cells with luciferase constructs under the control of the 549 bp of 5' flanking DNA containing the two most frequent extended haplotypes in this region. Luciferase activity was significantly reduced in cells transfected with the 'mutant' construct (-20C, -47C, -367C, -468G) c.f. the 'wild-type' construct (-20T, -47T, -367T, -468C). These data suggest that polymorphisms have the potential to alter human beta2 adrenergic receptor gene expression.