The imbalance between oxidants and antioxidants is known to play an important role in the pathogenesis of chronic obstructive pulmonary disease (COPD). Cigarette smoking is the most frequent factor responsible for development of COPD by leading to oxidant overload in the lower airways, due to presence of its own oxidants and to recruitment and activation of pulmonary phagocytes. We aimed to determine whether (1) patients with stable COPD have higher thiobarbituric acid-reactive substances (TBARs, an end-product of lipid peroxidation) and H2O2 levels in expired breath condensate than healthy subjects who have never smoked; (2) COPD subjects who are current smokers exhale more TBARs and H2O2 than COPD ex-smokers and those who have never smoked; and (3) concentration of TBARs correlates with H2O2 levels in the breath condensate of COPD patients. The TBAR and H2O2 content in expired breath condensate of 17 healthy nonsmoking subjects and 44 patients (11 current smokers, 20 ex-smokers and 13 who had never smoked) with stable COPD [forced expiratory volume in 1 s (FEV1) 63.3 +/- 16.3% and FEV1 reversibility 5.2 +/- 4.3% predicted value] was measured spectrofluorimetrically by the thiobarbituric acid and homovanillic acid methods, respectively. The mean concentrations of TBARs and H2O2 in the expired breath condensate of COPD subjects were 12 (0.48-0.86 microM vs. 0.04 +/- 0.14 microM; P < 0.05) and 10 times (0.48 +/- 0.67 microM vs. 0.05 +/- 0.07 microM; P < 0.005) higher than in healthy controls. Current smokers with COPD did not exhale more H2O2 than COPD ex-smokers and those who had never smoked. TBARs levels shared only a tendency to be higher in the breath condensate of smoking COPD subjects than in that of ex-smokers (0.92 +/- 1.49 microM vs. 0.35 +/- 0.44 microM) and of COPD subjects who had never smoked (0.92 +/- 1.49 microM vs. 0.30 +/- 0.53 microM). No correlation was found between TBAR and H2O2 levels in the whole COPD group. These variables did not correlate with cigarette smoking status and the time from smoking cessation. Subjects with stable COPD exhibit increased lipid peroxidation and H2O2 generation in the airways. Current cigarette smoking does not distinguish COPD subjects with respect to TBARs and H2O2 exhalation.