Silicosis has progressive, but unpredictable development. There are no markers routinely available to measure the activity and prognosis of silicosis. 8-isoprostane, a marker of oxidative stress and leukotrienes B4, C4, D4, and E4 were measured in exhaled breath condensate in patients with silicosis. Sixty subjects were examined, with mean age 66.7±2.0 yr and mean exposure to silica 23.6±2.5 yr. The control group had 25 subjects, with mean age 64.7±4.8 yr. Exhaled breath was collected using the EcoScreen (Jaeger, Germany); 8-isoprostane and leukotrienes were analyzed by high-performance liquid chromatography/mass spectrometry. Several lung functions parameters were impaired in silicotics in comparisons with the controls; ESR, α1-antitrypsin and proteinuria were higher in the silicotics. Antineutrophilic cytoplasmic antibodies were more frequent in the silicotics (39%) than in the controls (4%), (p=0.0017). The mean level of 8-isoprostane in the patients with silicosis was 73.6±9.9 vs. 43±10 pg/ml (p=0.0001) in the controls. Silica exposure category (high, medium, none) was positively associated with the level of 8-isoprostane. In the patients with complicated silicosis, a high level of 8-isoprostane was found more frequently (p=0.0194). Leukotriene D4 was also increased in the silicotics (21.1±2.7 pg/ml) vs. the controls (14.7±2.7 pg/ml), (p=0.001). No significant effect of smoking or alcohol consumption on the markers examined was seen. This is the first study using exhaled breath condensate analysis in patients with silicosis.