Asthma is heterogeneous with respect to clinical presentation, underlying disease mechanisms and response to existing drugs making tailored therapy desirable. Pharmacogenetics, the study of the influence of genetic polymorphisms on drug efficacy and/or adverse effects, is relatively advanced in asthma with replicated genetic associations identified in the main drug classes. In the present issue of Clinical Science, Lipworth and co-workers report a proof-of-concept study and demonstrate that, in asthmatic children carrying the β(2)-adrenergic receptor gene Arg(16) polymorphism, a combination of corticosteroid plus leukotriene receptor antagonist provides superior asthma control (e.g. quality of life scores) compared with corticosteroid plus a long-acting β(2)-adrenergic receptor agonist as add-on therapy. The basis of these observations is well founded, as it has been demonstrated previously that the Arg(16) polymorphism may confer an increased risk of exacerbation following prolonged β(2)--adrenergic receptor agonist use. These results suggest Gly16Arg genotyping in Caucasian asthma patients may have a role in the clinical management of asthma by influencing the decision of which add-on therapy to prescribe; however, larger studies are required to provide definitive conclusions regarding the clinical utility of this approach.