Current asthma treatments are effective for most but not all patients.Asthma is classified as a complex genetic disease with its pathogenesis and expression (severity) determined by the interaction of many genes and environ mental factors.Asthma is characterized by its heterogeneity in terms of its clinical and inflammatory phenotypes and their responses to therapy.This disease heterogeneity likely has played a role in variable results from clinical trials that evaluate specific inhibitors of inflammatory mediators ( biologics) in asthma.Moreover,although existing treatments are effective and safe in most asthma patients they may be less effective or potentially harmful in others.In addition,if an individual with asthma is less responsive to standard therapies such as corticosteroids because of specific pharmacogenetic interactions then that patient with asthma will be classified as having more severe or diffi cult-to-treat asthma.Pharmacogenetic approaches hold the promise of matching individualized treatments to spe cific genotypes in a way that minimizes side effects while improving therapeutic outcomes.