Objective. Oxidative stress may be one of the important complex pathogenetic mechanisms that lead to damage in scleroderma; free radicals may provoke endothelial injury, fibroblast proliferation and fragmentation of autoantigens favouring induction of autoantibodies. The present study investigates the oxidant status in scleroderma patients by measuring the urinary concentration of 8-isoprostaglandin-F2α, an F2-isoprostane, and a product of free radical-mediated peroxidation of arachidonic acid. Methods. Forty-three scleroderma patients (42 women and 1 man, mean age 54.1 yr, mean disease duration 9.0 yr) underwent clinical evaluation and instrumental investigations in order to assess skin, vascular, lung and heart involvement. Von Willebrand factor was evaluated as marker of vascular dysfunction in 36 out of the 43 cases. The urinary level of 8-isoprostaglandin-F2α was measured in all scleroderma patients and in the 43 age- and sex-matched healthy controls. Results. Urinary levels of 8-isoprostaglandin-F2α were higher in scleroderma patients than in the healthy control group (341.7 vs 147.6 pg/mg creatinine; P<0.001). Values of 8-isoprostaglandin-F2α were strongly correlated with the nailfold videocapillaroscopy pattern and lung involvement (P=0.002 and 0.003, respectively), showing increasing levels with the progression of pulmonary severity. Correlation between 8-isoprostaglandin-F2α level and von Willebrand factor narrowly failed to reach statistical significance (P=0.05). There was no correlation between 8-isoprostaglandin-F2α concentration and disease activity, vascular, skin and heart involvement, disease pattern or autoantibody profile. Conclusions. Our study further supports the role of oxidant stress in the pathogenesis of scleroderma, showing a strong correlation between a marker of free radical damage with both the severity of lung involvement and the videocapillaroscopic patterns.