As an inflammatory airway disease, asthma is expected to be associated with an increase in airway blood flow. We therefore compared airway mucosal blood flow (Qaw) among normal subjects (n = 11) and patients with stable asthma receiving (n = 13) or not receiving (n = 10) long-term inhaled glucocorticosteroid (GS) therapy. Qaw was calculated from the uptake of dimethyl ether in the anatomic dead space minus the most proximal 50 ml (DS), and expressed as blood flow per ml DS. Mean (+/- SE) Qaw was 38.5 +/- 5. 3 microl . min-1 . ml-1 in normals, 68.2 +/- 7.9 microl . min-1 . ml-1 in GS-naive asthmatics (p < 0.01), and 55.4 +/- 5.3 microl . min-1 . ml-1 in GS-treated asthmatics (p < 0.05). Ten minutes after administration of 180 microg albuterol by metered dose inhaler, mean Qaw increased by 83 +/- 26% in normal subjects (p < 0.01), but did not change significantly in GS-naive (+5 +/- 8%) or GS-treated (+32 +/- 15%) asthmatics. These results demonstrate that Qaw is increased in stable asthmatics and resistant to further increase by a standard inhaled dose of a beta-adrenergic agonist.