There is controversy about the role of inhaled corticosteroids in chronic obstructive pulmonary disease (COPD). Although they appear to have little impact on airways obstruction or its progression, their use may reduce the frequency and/or severity of exacerbations in a subset of patients. We undertook the following study to determine the impact of inhaled corticosteroid on two noninvasive markers of airways inflammation. We assigned 20 stable nonsmoking patients with COPD in random, double-blind crossover fashion to two 2-wk treatment periods with inhaled beclomethasone 500 microg twice daily or matching placebo, followed by a 2-wk washout period. We measured exhaled nitric oxide (ENO), breath condensate H(2)O(2), and flow volume spirometry at weekly intervals. Median baseline ENO was 26.2 (19.3 to 54.8) ppb and fell significantly following 1 and 2 wk of beclomethasone (-10.6 ppb, p = 0.002, and -6.3 ppb, p = 0.013, respectively) but was unchanged by placebo inhalation. Breath condensate H(2)O(2) levels did not change significantly with inhaled beclomethasone or placebo. Although there were no significant changes in FEV(1) with BDP therapy, there was a moderate inverse correlation between changes in ENO and changes in FEV(1) (r -0.50). We conclude that inhaled beclomethasone reduces ENO levels in stable nonsmoking patients with COPD, a finding compatible with an antiinflammatory mechanism of action.