The findings of Berger et al,1 including normal pulmonary compliance, elastic recoil, and lung parenchyma on CT scan, support the attribution to an airways disorder. Another strong indication, bronchial hyperreactivity, was noted both in known patients with asthma1 and in WTC patients with restrictive dysfunction.3 Early in the experience with WTC lung disorder, Prezant et al4 reported “nearly equal” reductions (from pre-September 11, 2001, values) in FVC and FEV1 of at least 0.5 L in > 50% of exposed firefighters. Response to a bronchodilator was seen in 63%, and bronchial hyperreactivity was noted in 24% of these patients. These rates are notable because selection criteria for firefighters rigidly exclude asthma. Bronchodilatation in airways disease presenting as restriction often results in equivalent increases in FVC and FEV1 with little change in FEV1/FVC ratio, and bronchoprovocation brings about equivalent decreases. It is, therefore, surprising that Berger et al1 noted no change in postbronchodilator spirometry and that impulse oscillometry, presumably a more sensitive, if less specific, measure of airways dysfunction, showed only small changes with bronchodilator, leaving persistent abnormality in the majority.