Exposure of healthy subjects to ozone is associated with increases in cellular and biochemical markers of inflammation in bronchoalveolar lavage fluid. To determine if analysis of induced sputum might similarly reveal the pulmonary inflammatory effects of ozone exposure, we performed cellular and biochemical analysis of induced sputum collected 4 hr after air and ozone (0.4 ppm for 2 hr) exposures from 10 healthy subjects (age 30.0 +/- 5.0 years; 5 females) in a randomized crossover study in which exposures were separated by 2 weeks. We found that the total number of nonsquamous cells was significantly higher after ozone exposure than after air exposure (7.4 vs 3.9 x 10(5)/ml, P < 0.05) as was the percentage of the nonsquamous cells that were neutrophils (80.0 +/- 7.0% vs 51.0 +/- 20.0%, P < 0.05) and the levels of myeloperoxidase in the sputum fluid phase (1.6 +/- 0.6 vs 1.3 +/- 0.6 microg/ml, P < 0.05). In addition, IL-6 and IL-8 levels were higher after ozone than after air exposures, but not significantly so (44.5 +/- 32.4 pg/ml vs 26.8 +/- 30.7 pg/ml, P = 0.11; 1.5 +/- 0.5 ng/ml vs 1.1 +/- 0.6 ng/ml, P = 0.09). Mucin-like glycoprotein levels were also not significantly different between exposures (1.6 +/- 0.9 mg/ml vs 1.3 +/- 1.0 mg/ml, P = 0.26). We conclude that analysis of induced sputum is a useful noninvasive method for studying the pulmonary response to ozone exposure in healthy subjects.