Bronchial asthma is now widely recognized as a heterogeneous clinical syndrome consisting of various disease phenotypes. Each asthma phenotype may have distinct observable molecular, cellular, morphological, functional, and clinical features , all of which can be possibly integrated into specifc biological mechanisms, called as endotypes . Although differentiating asthma into various phenotypes/endotypes remains speculative so far, these concepts of separation may be useful in characterizing and predicting disease severity, progression, and response to general and specifc therapies including biologic medications . This is particularly important for severe asthma patients who are refractory to current standard therapies including inhaled and systemic corticosteroids (CS) and bronchodilators. Because these patients account for a signifcant proportion of health-care expenditure of asthma , recognizing the heterogeneous nature of asthma, especially severe asthma, may enable us to develop safe and effective phenotype-targeted biological therapies.