Asthma is primarily an airways inflammatory disease, and the bronchial airways have been shown to be particularly susceptible to oxidant-induced tissue damage. The antioxidant ascorbic acid (AA) plays an essential role in defending against oxidant attack in the airways. Decreased levels of AA have been reported in the plasma and BAL fluid of asthmatics, but not at the site directly proximal to asthma pathology, the bronchial airways. We investigated whether asthmatics have deficient levels of AA in the airways compared to healthy subjects. We performed induced sputum (IS) in a group of mild asthmatics (n = 16) and healthy controls (n = 18) in order to compare constitutive levels of antioxidants in the airways of these two groups. We report that asthmatics had significantly decreased AA in both the cellular (17 +/- 3 ng/10(6) cells vs. 40 +/- 4 ng/10(6) cells) and fluid-phase fraction (616 +/- 152 ng/ml vs. 937 +/- 161 ng/ml) of the IS sample compared to normals. No differences were found with glutathione (GSH) and alpha-tocopherol. These results suggest that AA deficiency may be either an underlying factor in the pathophysiology of asthma or a response to asthmatic airways inflammation.