Haverkamp HC, Kaminsky DA, McPherson SM, et al. - This study was undertaken to explore the association between bronchodilator responsiveness and airway hyper-responsiveness assessed with indirect-acting stimuli. Researchers retrospectively compared the spirometric responses to inhaled bronchodilator and a eucapnic voluntary hyperpnea challenge (EVH) in 39 non-smoking adult subjects with asthma (26 male, 13 female; mean ± SD age 26.9 ± 7.8 y; mean ± SD body mass index 26.3 ± 4.7 kg/m²). These outcomes extend previous observations that illustrate a lack of relationship between bronchodilator responsiveness and methacholine responsiveness. Given the poor concordance between the spirometric response to fast-acting bronchodilator and the EVH challenge, these outcomes imply that the airway response to inhaled β2-agonist must be interpreted with caution and in the context of its determinants and limitations.